Alert archive / Maryland / Flash Flood Watches in 2021

Flash Flood Watch 9, NWS Baltimore/Washington

August 17, 20215 counties in Maryland

NWS Baltimore/Washington issued this flash flood watch at Aug 17, 2021, 8:54 AM EDT for 5 counties in Maryland. It was in force for 9 hr.

The area

The counties it named.

The facts

Issued
Aug 17, 2021, 8:54 AM EDT (12:54 UTC)
Expired
Aug 17, 2021, 6:00 PM EDT
In force
9 hr
Issued by
NWS Baltimore/Washington
Flood severity
None

Counties Anne Arundel County, MD, Baltimore County, MD, Cecil County, MD, City of Baltimore, MD, Harford County, MD

The radar

The Sterling radar (KLWX), 103 km from the middle of the area, began a volume at 12:54 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 0.9 hours before the alert went out and 97 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-pSkew-T log-p diagram, Washington/Dulle, VA at 12:00Z on 2021-08-17Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 226 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 12:00Z on 2021-08-17The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 83 square meters per square second.1939Sfc1 km3 km6 km9 kmRMLM
The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.
Mixed-layer CAPE
226 J/kg
Mixed-layer CIN
-58 J/kg
Mixed-layer LCL
577 m above ground
0-6 km bulk shear
22 kt
0-1 km storm-relative helicity
83 m²/s²
0-3 km storm-relative helicity
81 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.7

Open this sounding in Storm Lab

The text

As transmitted.

490 
WGUS61 KLWX 171254
FFALWX

URGENT - IMMEDIATE BROADCAST REQUESTED
Flood Watch
National Weather Service Baltimore MD/Washington DC
854 AM EDT Tue Aug 17 2021

MDZ008-011-014-508-172200-
/O.NEW.KLWX.FF.A.0009.210817T1254Z-210817T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cecil-Southern Baltimore-Anne Arundel-Southeast Harford-
Including the cities of Elkton, Glen Burnie, South Gate, Annapolis, 
Odenton, Arnold, Severna Park, Severn, Aberdeen, and Baltimore
854 AM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT UNTIL 6 PM EDT THIS EVENING...

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Watch for portions of central Maryland, northeast 
  Maryland and northern Maryland, including the following areas: in 
  central Maryland, Anne Arundel. In northeast Maryland, Cecil. In 
  northern Maryland, Southeast Harford and Southern Baltimore.

* Until 6 PM EDT this evening.

* Showers and scattered thunderstorms are expected to develop along 
  the central and upper Chesapeake Bay coastal areas and persist 
  into this afternoon. Training thunderstorms may be capable of 
  producing 2 to 4 inches per hour.

* This much rain in a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

JMG
3 follow-up statements
908 
WGUS61 KLWX 171754
FFALWX

URGENT - IMMEDIATE BROADCAST REQUESTED
Flood Watch
National Weather Service Baltimore MD/Washington DC
154 PM EDT Tue Aug 17 2021

MDZ001-003-501-502-VAZ026>028-WVZ050>052-055-501>506-180200-
/O.NEW.KLWX.FF.A.0010.210818T1000Z-210818T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Garrett-Washington-Extreme Western Allegany-Central and Eastern
Allegany-Rockingham-Shenandoah-Frederick VA-Hampshire-Morgan-
Berkeley-Hardy-Western Grant-Eastern Grant-Western Mineral-Eastern
Mineral-Western Pendleton-Eastern Pendleton-
Including the cities of Mount Storm, Cumberland, Winchester, Ruddle, 
Martinsburg, Woodstock, Petersburg, Keyser, Moorefield, 
Harrisonburg, New Market, Antioch, Mount Jackson, Russelldale, 
Grantsville, Riverton, Hagerstown, Mountain Lake Park, Frostburg, 
Franklin, Fort Ashby, Elk Garden, Oak Flat, New Creek, Paw Paw, 
Sugar Grove, Romney, Brandywine, Headsville, Strasburg, Oakland, 
Ridgeville, and Bayard
154 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT FROM WEDNESDAY MORNING THROUGH 
WEDNESDAY AFTERNOON...

The National Weather Service in Sterling Virginia has issued a

* Flash Flood Watch for portions of Maryland, Virginia and West 
  Virginia, including the following areas: in Maryland, Central and 
  Eastern Allegany, Extreme Western Allegany, Garrett and 
  Washington. In Virginia, Frederick VA, Rockingham and Shenandoah. 
  In West Virginia, Berkeley, Eastern Grant, Eastern Mineral, 
  Eastern Pendleton, Hampshire, Hardy, Morgan, Western Grant, 
  Western Mineral and Western Pendleton.

* From Wednesday morning through Wednesday afternoon.

* Moderate to heavy showers along with scattered strong 
  thunderstorms from the remnants of Tropical Storm Fred will impact 
  portions of western Maryland, eastern West Virginia and 
  northwestern Virginia on Wednesday. Tropical moisture will lead to 
  potential precipitation rates of 1 to 2 inches per hour. Localized 
  storm total rain amounts in excess of 3 inches are possible due to 
  tropical banding and enhancement along the Allegheny and Blue 
  Ridge Mountains.


* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

MDZ008-011-014-508-172200-
/O.CON.KLWX.FF.A.0009.000000T0000Z-210817T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cecil-Southern Baltimore-Anne Arundel-Southeast Harford-
Including the cities of Elkton, Glen Burnie, South Gate, Annapolis, 
Odenton, Arnold, Severna Park, Severn, Aberdeen, and Baltimore
154 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 6 PM EDT THIS EVENING...

The Flash Flood Watch continues for

* Portions of central Maryland, northeast Maryland and northern 
  Maryland, including the following areas: in central Maryland, Anne 
  Arundel. In northeast Maryland, Cecil. In northern Maryland, 
  Southeast Harford and Southern Baltimore.

* Until 6 PM EDT this evening.

* Showers and scattered thunderstorms are expected to develop along 
  the central and upper Chesapeake Bay coastal areas and persist 
  into this afternoon. Training thunderstorms may be capable of 
  producing 2 to 4 inches per hour.

* This much rain in a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

JMG
501 
WGUS61 KLWX 172001
FFALWX

URGENT - IMMEDIATE BROADCAST REQUESTED
Flood Watch
National Weather Service Baltimore MD/Washington DC
401 PM EDT Tue Aug 17 2021

MDZ011-508-180415-
/O.CAN.KLWX.FF.A.0009.000000T0000Z-210817T2200Z/
/O.EXB.KLWX.FF.A.0010.210818T0000Z-210819T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Southern Baltimore-Southeast Harford-
Including the cities of Aberdeen and Baltimore
401 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT FROM 8 PM EDT THIS EVENING THROUGH 
WEDNESDAY EVENING...
...FLASH FLOOD WATCH IS CANCELLED...

The National Weather Service in Sterling Virginia has expanded the

* Flash Flood Watch to include a portion of northern Maryland, 
  including the following areas: Southeast Harford and Southern 
  Baltimore.

* From 8 PM EDT this evening through Wednesday evening.

* Multiple rounds of heavy showers and thunderstorms will affect the 
  region from this evening through Wednesday evening. Tropical 
  moisture will lead to potential precipitation rates of 1 to 2 
  inches per hour. Localized storm total rain amounts in excess of 3 
  inches are possible.

* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

The Flash Flood Watch for this afternoon has been cancelled for a 
portion of northern Maryland, including the following areas: 
Southeast Harford and Southern Baltimore.

$$

MDZ014-172115-
/O.CAN.KLWX.FF.A.0009.000000T0000Z-210817T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Anne Arundel-
Including the cities of Glen Burnie, South Gate, Annapolis, Odenton, 
Arnold, Severna Park, and Severn
401 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch has been cancelled for a portion of central 
Maryland, including the following area: Anne Arundel.

The threat of heavy rain has ended for this afternoon.

$$

DCZ001-MDZ004>006-503>507-VAZ025-029>031-036>040-050>056-501-502-
505>508-WVZ053-180415-
/O.EXB.KLWX.FF.A.0010.210818T0000Z-210819T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia-Frederick MD-Carroll-Northern Baltimore-
Northwest Montgomery-Central and Southeast Montgomery-Northwest
Howard-Central and Southeast Howard-Northwest Harford-Augusta-Page-
Warren-Clarke-Nelson-Albemarle-Greene-Madison-Rappahannock-Orange-
Culpeper-Prince William/Manassas/Manassas Park-Fairfax-
Arlington/Falls Church/Alexandria-Stafford-Spotsylvania-Northern
Fauquier-Southern Fauquier-Western Loudoun-Eastern Loudoun-Northern
Virginia Blue Ridge-Central Virginia Blue Ridge-Jefferson-
Including the cities of Shepherdstown, Silver Spring, Charles Town, 
Charlottesville, Herndon, Arlington, Manassas, Jarrettsville, 
Westminster, Damascus, Falls Church, Purcellville, Lovingston, 
Bethesda, Chantilly, Orange, Luray, Ballenger Creek, Centreville, 
Culpeper, Berryville, Sterling, Reisterstown, Columbia, 
Fredericksburg, Staunton, Falmouth, Shenandoah, Ashburn, Waynesboro, 
Front Royal, Stuarts Draft, Leesburg, McLean, Rockville, Frederick, 
Lake Ridge, Dale City, Alexandria, Stanley, Reston, Montclair, 
Turnbull, Big Meadows, Madison, Eldersburg, Ellicott City, 
Germantown, Woodbridge, Stanardsville, Washington, Annandale, 
Warrenton, Cockeysville, Lisbon, Gaithersburg, Gordonsville, 
Franconia, and Wintergreen
401 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT FROM 8 PM EDT THIS EVENING THROUGH 
WEDNESDAY EVENING...

The National Weather Service in Sterling Virginia has expanded the

* Flash Flood Watch to include portions of DC, Maryland, Virginia 
  and panhandle West Virginia, including the following areas: in DC, 
  District of Columbia. In Maryland, Carroll, Central and Southeast 
  Howard, Central and Southeast Montgomery, Frederick MD, Northern 
  Baltimore, Northwest Harford, Northwest Howard and Northwest 
  Montgomery. In Virginia, Albemarle, Arlington/Falls 
  Church/Alexandria, Augusta, Central Virginia Blue Ridge, Clarke, 
  Culpeper, Eastern Loudoun, Fairfax, Greene, Madison, Nelson, 
  Northern Fauquier, Northern Virginia Blue Ridge, Orange, Page, 
  Prince William/Manassas/Manassas Park, Rappahannock, Southern 
  Fauquier, Spotsylvania, Stafford, Warren and Western Loudoun. In 
  panhandle West Virginia, Jefferson.

* From 8 PM EDT this evening through Wednesday evening.

* Multiple rounds of heavy showers and thunderstorms will affect the 
  region from this evening through Wednesday evening. Tropical 
  moisture will lead to potential precipitation rates of 1 to 2 
  inches per hour. Localized storm total rain amounts in excess of 3 
  inches are possible.

* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

VAZ503-504-180415-
/O.EXA.KLWX.FF.A.0010.210818T1000Z-210818T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Western Highland-Eastern Highland-
Including the cities of Hightown and Monterey
401 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH IN EFFECT FROM WEDNESDAY MORNING THROUGH 
WEDNESDAY AFTERNOON...

The National Weather Service in Sterling Virginia has expanded the

* Flash Flood Watch to include a portion of western Virginia, 
  including the following areas: Eastern Highland and Western 
  Highland.

* From Wednesday morning through Wednesday afternoon.

* Moderate to heavy showers along with scattered strong 
  thunderstorms from the remnants of Tropical Storm Fred will impact 
  Highland County on Wednesday. Tropical moisture will lead to 
  potential precipitation rates of 1 to 2 inches per hour. Localized 
  storm total rain amounts in excess of 3 inches are possible due to 
  tropical banding and enhancement along the Allegheny Mountains.

* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

MDZ003-VAZ026>028-WVZ051-052-180415-
/O.EXT.KLWX.FF.A.0010.210818T0000Z-210819T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Washington-Rockingham-Shenandoah-Frederick VA-Morgan-Berkeley-
Including the cities of Harrisonburg, Winchester, Paw Paw, New 
Market, Martinsburg, Woodstock, Hagerstown, Strasburg, and Mount 
Jackson
401 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH NOW IN EFFECT FROM 8 PM EDT THIS EVENING 
THROUGH WEDNESDAY EVENING...

The Flash Flood Watch is now in effect for

* Portions of north central Maryland, Virginia and panhandle West 
  Virginia, including the following areas: in north central 
  Maryland, Washington. In Virginia, Frederick VA, Rockingham and 
  Shenandoah. In panhandle West Virginia, Berkeley and Morgan.

* From 8 PM EDT this evening through Wednesday evening.

* Multiple rounds of heavy showers and thunderstorms will affect the 
  region from this evening through Wednesday evening. Tropical 
  moisture will lead to potential precipitation rates of 1 to 2 
  inches per hour. Localized storm total rain amounts in excess of 3 
  inches are possible.

* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

MDZ008-172200-
/O.CON.KLWX.FF.A.0009.000000T0000Z-210817T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cecil-
Including the cities of Elkton
401 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 6 PM EDT THIS EVENING...

The Flash Flood Watch continues for

* A portion of northeast Maryland, including the following area: 
  Cecil.

* Until 6 PM EDT this evening.

* Showers and isolated thunderstorms with the potential for 
  producing locally heavy rain will continue this afternoon across 
  Cecil County. The repetitive rainfall may lead to flash flooding.

* This much rain in a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

MDZ001-501-502-WVZ050-055-501>506-180415-
/O.CON.KLWX.FF.A.0010.210818T1000Z-210818T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Garrett-Extreme Western Allegany-Central and Eastern Allegany-
Hampshire-Hardy-Western Grant-Eastern Grant-Western Mineral-Eastern
Mineral-Western Pendleton-Eastern Pendleton-
Including the cities of Mount Storm, Cumberland, Ruddle, Bayard, 
Keyser, Moorefield, Antioch, Russelldale, Grantsville, Riverton, 
Mountain Lake Park, Frostburg, Franklin, Fort Ashby, Elk Garden, Oak 
Flat, New Creek, Sugar Grove, Romney, Brandywine, Ridgeville, 
Oakland, Headsville, and Petersburg
401 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING 
THROUGH WEDNESDAY AFTERNOON...

The Flash Flood Watch continues for

* Portions of western Maryland and eastern West Virginia, including 
  the following areas: in western Maryland, Central and Eastern 
  Allegany, Extreme Western Allegany and Garrett. In eastern West 
  Virginia, Eastern Grant, Eastern Mineral, Eastern Pendleton, 
  Hampshire, Hardy, Western Grant, Western Mineral and Western 
  Pendleton.

* From Wednesday morning through Wednesday afternoon.

* Moderate to heavy showers along with scattered strong 
  thunderstorms from the remnants of Tropical Storm Fred will impact 
  portions of western Maryland and eastern West Virginia. Tropical 
  moisture will lead to potential precipitation rates of 1 to 2 
  inches per hour. Localized storm total rain amounts in excess of 3 
  inches are possible due to tropical banding and enhancement along 
  the Allegheny Mountains.

* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

ADS
371 
WGUS61 KLWX 172158
FFALWX

Flood Watch
National Weather Service Baltimore MD/Washington DC
558 PM EDT Tue Aug 17 2021

MDZ008-172300-
/O.EXP.KLWX.FF.A.0009.000000T0000Z-210817T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Cecil-
Including the cities of Elkton
558 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH WILL EXPIRE AT 6 PM EDT THIS EVENING...

The Flash Flood Watch for a portion of northeast Maryland, including 
the following area: Cecil will expire at 6 PM EDT this evening.

The Flood Watch is cancelled. Flooding is no longer expected to pose 
a threat. Please continue to heed remaining road closures.

$$

DCZ001-MDZ003>006-011-503>508-VAZ025>031-036>040-050>056-501-502-
505>508-WVZ051>053-180600-
/O.CON.KLWX.FF.A.0010.210818T0000Z-210819T0200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia-Washington-Frederick MD-Carroll-Northern
Baltimore-Southern Baltimore-Northwest Montgomery-Central and
Southeast Montgomery-Northwest Howard-Central and Southeast Howard-
Northwest Harford-Southeast Harford-Augusta-Rockingham-Shenandoah-
Frederick VA-Page-Warren-Clarke-Nelson-Albemarle-Greene-Madison-
Rappahannock-Orange-Culpeper-Prince William/Manassas/Manassas Park-
Fairfax-Arlington/Falls Church/Alexandria-Stafford-Spotsylvania-
Northern Fauquier-Southern Fauquier-Western Loudoun-Eastern Loudoun-
Northern Virginia Blue Ridge-Central Virginia Blue Ridge-Morgan-
Berkeley-Jefferson-
Including the cities of Shepherdstown, Silver Spring, Charles Town, 
Charlottesville, Winchester, Herndon, Arlington, Manassas, 
Jarrettsville, Martinsburg, Woodstock, Westminster, Damascus, Falls 
Church, Purcellville, Lovingston, Bethesda, Chantilly, Orange, 
Luray, Ballenger Creek, Centreville, Culpeper, Berryville, Sterling, 
Reisterstown, Columbia, Fredericksburg, Staunton, Warrenton, 
Falmouth, New Market, Shenandoah, Ashburn, Waynesboro, Mount 
Jackson, Front Royal, Germantown, Leesburg, McLean, Rockville, 
Frederick, Hagerstown, Dale City, Big Meadows, Alexandria, Lake 
Ridge, Stanley, Harrisonburg, Reston, Montclair, Turnbull, 
Baltimore, Madison, Eldersburg, Ellicott City, Paw Paw, Stuarts 
Draft, Woodbridge, Stanardsville, Washington, Annandale, Franconia, 
Cockeysville, Strasburg, Lisbon, Gaithersburg, Gordonsville, 
Aberdeen, and Wintergreen
558 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH WEDNESDAY EVENING...

The Flash Flood Watch continues for

* Portions of DC, Maryland, Virginia and panhandle West Virginia, 
  including the following areas: in DC, District of Columbia. In 
  Maryland, Carroll, Central and Southeast Howard, Central and 
  Southeast Montgomery, Frederick MD, Northern Baltimore, Northwest 
  Harford, Northwest Howard, Northwest Montgomery, Southeast 
  Harford, Southern Baltimore and Washington. In Virginia, 
  Albemarle, Arlington/Falls Church/Alexandria, Augusta, Central 
  Virginia Blue Ridge, Clarke, Culpeper, Eastern Loudoun, Fairfax, 
  Frederick VA, Greene, Madison, Nelson, Northern Fauquier, Northern 
  Virginia Blue Ridge, Orange, Page, Prince 
  William/Manassas/Manassas Park, Rappahannock, Rockingham, 
  Shenandoah, Southern Fauquier, Spotsylvania, Stafford, Warren and 
  Western Loudoun. In panhandle West Virginia, Berkeley, Jefferson 
  and Morgan.

* Through Wednesday evening.

* Multiple rounds of heavy showers and thunderstorms will affect the 
  region from this evening through Wednesday evening. Tropical 
  moisture will lead to potential precipitation rates of 1 to 2 
  inches per hour. Localized storm total rain amounts in excess of 3 
  inches are possible.

* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

MDZ001-501-502-VAZ503-504-WVZ050-055-501>506-180600-
/O.CON.KLWX.FF.A.0010.210818T1000Z-210818T2200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Garrett-Extreme Western Allegany-Central and Eastern Allegany-
Western Highland-Eastern Highland-Hampshire-Hardy-Western Grant-
Eastern Grant-Western Mineral-Eastern Mineral-Western Pendleton-
Eastern Pendleton-
Including the cities of Mount Storm, Cumberland, Ruddle, Bayard, 
Keyser, Moorefield, Hightown, Antioch, Russelldale, Grantsville, 
Riverton, Mountain Lake Park, Frostburg, Franklin, Fort Ashby, Elk 
Garden, Oak Flat, New Creek, Monterey, Sugar Grove, Romney, 
Brandywine, Ridgeville, Oakland, Headsville, and Petersburg
558 PM EDT Tue Aug 17 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT FROM WEDNESDAY MORNING 
THROUGH WEDNESDAY AFTERNOON...

The Flash Flood Watch continues for

* Portions of western Maryland, western Virginia and eastern West 
  Virginia, including the following areas: in western Maryland, 
  Central and Eastern Allegany, Extreme Western Allegany and 
  Garrett. In western Virginia, Eastern Highland and Western 
  Highland. In eastern West Virginia, Eastern Grant, Eastern 
  Mineral, Eastern Pendleton, Hampshire, Hardy, Western Grant, 
  Western Mineral and Western Pendleton.

* From Wednesday morning through Wednesday afternoon.

* Moderate to heavy showers along with scattered strong 
  thunderstorms from the remnants of Tropical Storm Fred will impact 
  portions of western Maryland and eastern West Virginia. Tropical 
  moisture will lead to potential precipitation rates of 1 to 2 
  inches per hour. Localized storm total rain amounts in excess of 3 
  inches are possible due to tropical banding and enhancement along 
  the Allegheny Mountains.

* Heavy rain over a short amount of time may result in rapid rises 
  on streams and creeks and in urbanized and poor drainage areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

You should monitor later forecasts and be prepared to take action 
should Flash Flood Warnings be issued.

&&

$$

BJL

What forecasters said that day

The local office's own words before this flash flood watch went out, as it sent them, from the Iowa Environmental Mesonet's archive of National Weather Service text.

NWS Baltimore/Washington wrote its last area forecast discussion before this flash flood watch went out at Aug 17, 4:25 AM EDT, 4 hours 29 minutes earlier.

Area forecast discussion, Aug 17, 4:25 AM EDT, 4 hours 29 minutes before
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
425 AM EDT Tue Aug 17 2021

.SYNOPSIS...
A warm front will lift of the area today as high pressure
centers off the New England coast. The remnants of Fred will
push northward through tonight, nearing the Tennessee Valley,
tracking along the Appalachians and into the region Wednesday
into early Thursday. High pressure will remain across the
Southeast for the balance of the week as an upper level
disturbance lingers over the region. A cold front may approach
the area early next week.

&&

.NEAR TERM /TODAY AND TONIGHT/...
A warm front bisects the CWA early this morning with high
pressure centered across the Great Lakes and New England, as
Tropical Storm Fred churns over deep Southeast states. Locally,
skies are mostly cloudy with ongoing shower activity across
central and northern Maryland, pushing off to the east
northeast. This activity will persist the next couple of hours
before pushing away from the area. Temperatures this morning are
in the upper 60s to middle 70s, with dewpoints right on pace
with those values. As such, patchy fog and low clouds are being
observed across the area.

The warm front will lift further northward today as a mid to
upper level ridge tries to push into the region from our
southeast. This will attempt to limit shower and storm chances,
but won't be enough to squelch them completely. Am advertising
middle of the road POPs today as we should be able to build some
instability with some sun, mainly west of the Blue Ridge, and
the low level moisture remains a plenty. Any showers or storms
that do form this afternoon/evening will be capable of producing
heavy rainfall given PWATs hovering between 1.5-2 inches.
Temperatures today will rise into the upper 70s to upper 80s.

Tonight, the remnants of Fred will near the eastern Tennessee
River Valley as it continues tracking northward. As a result,
POPs will increase across our western and southwestern zones
after midnight, but thinking the best moisture will hold for the
second half of the night. PWATs are forecast to surge tonight
between 2 and 2.25, so moderate to heavy rain will be possible
as daybreak nears across the Alleghenies and northwestern
Virginia into the central Shenandoah Valley.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
The remnants of Fred are forecast to track up the western slope
of the Appalachians Wednesday with moderate to heavy rain
spreading mainly along and west of the Blue Ridge Mountains. The
axis of heaviest rainfall will be determined by the exact track
of Fred and speed as it lifts northward, but with the tropical
airmass in place with ample moisture, several inches of rain
will be possible with a threat for flooding. Current thinking is
the western half of our CWA will favor a greater risk of
flooding given the latest forecast track of Fred and the
assistance of terrain along the Alleghenies and Blue Ridge
Mountains. As with many tropical systems, there will be
sufficient wind shear in the atmosphere as it tracks to our
west. The threat for any thunderstorms that develop to the east
of the track will be capable of turning severe, and perhaps
spawn tornadoes. Again, the exact track and evolution of the
system will be key is narrowing down this threat over the next
24 hours. The Storm Prediction Center highlights much of the CWA
in a Marginal Risk for severe storms Wednesday into Wednesday
night, with damaging winds and tornadoes highlighted as the main
threats.

The remnants of Fred will continue to progress northward toward
the Mason Dixon Line and Pennsylvania into Wednesday night,
with a continued heavy rainfall and flooding threat across the
area. Model guidance progresses Fred to our north by Thursday
morning, allowing for decreasing rain chances to emerge in its
wake. We'll remain on the eastern flank of the broad upper
trough, so as instability builds Thursday afternoon/evening,
additional showers and thunderstorms will be possible across the
mountains.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The longwave pattern will feature a retrograding ridge which re-
positions itself from the western Atlantic to the southern tier of
the country. To the north of this anticyclone, models depict a rex
block with a positive height anomaly south of Hudson Bay, while a
slow moving trough sits over the Great Lakes. A strengthening
upstream trough over the Northern Plains should eventually shift
this ridge/trough couplet eastward over time through the weekend.
Ultimately the slow moving upper trough is forecast to push offshore
late in the weekend and into Monday.

At the surface, as usual, summertime gradients are rather weak with
loosely defined boundaries. The guidance depicts a stagnant area of
low pressure sitting over the Mid-Atlantic with a trough axis
extending southward toward the Carolinas. Otherwise, all other
notable features will be more mesoscale in nature. Most notably,
terrain driven circulations and bay/river breezes will be the likely
drivers of the pattern from Friday and into the weekend.

Given the presence of the upper trough gradually drifting across the
region, expect a daily threat for showers and thunderstorms. The
main focus would be during the afternoon to evening hours which
aligns with the period of better instability. While the more
anomalous tropospheric moisture will exit before this period,
residual enhanced moisture content may lead to a non-zero threat for
flooding. As mesoscale details are difficult to discern multiple
days into a forecast, such aspects of the forecast will likely
become more obvious in the days ahead. Daily high temperatures
should run slightly above average, while overnight conditions stay
mild and humid with lows in the upper 60s to low 70s.

&&

.AVIATION /08Z TUESDAY THROUGH SATURDAY/...
IFR to MVFR conditions expected this morning across most of the
terminals with low CIGs and patchy fog given ample low level
moisture. Predominate VFR conditions should win out for much of
the day today and the first half of tonight, but a passing
shower or storm could deliver a brief episode of sub VFR
conditions in a southerly flow wind regime.

Rain chances increase overnight and toward Wednesday morning as
the remnants of Fred track to our west. Periods of sub VFR
conditions look increasingly likely Wednesday through Wednesday
as showers and thunderstorms track through the region. Winds
will remain on a southerly trajectory during this time.
Conditions return to VFR Thursday as Fred lifts north of the
region and rain chances decrease and winds veer out of the west.

While VFR conditions should prevail on Friday and Saturday across
the area terminals, the approaching trough could bring scattered
showers and thunderstorms to the area. This would include periodic
ceiling and visibility reductions each afternoon and evening.

&&

.MARINE...
Sub SCA conditions are expected over the waters today through
the first half of Wednesday as a light south southeasterly flow
prevails. The remnants of Tropical Storm Fred will track up the
Appalachians tonight through Wednesday night, delivering
widespread shower and thunderstorm activity to the area. As
southerly winds increase Wednesday afternoon/evening, SCA gusts
could be realized for portions of our waters. As the system
lifts to our north by Thursday morning, winds will turn light
out of the west and remain below SCA thresholds.

Winds over the waters should stay below SCA levels through the first
half of the weekend. Northwesterly winds on Friday will give way to
more west to southwesterly flow by Saturday. Any developing shower
or thunderstorm could lead to gusty winds each day.

&&

.TIDES/COASTAL FLOODING...
Prolonged southerly winds, particularly as the remnants of Fred
cross to the west, will maintain elevated water levels through
Thursday. During the next couple of days, Annapolis and Baltimore
are likely to reach minor flooding. This is also supported by the
Steven's Ensemble with a vast number of members favoring minor
flooding being reached.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Coastal Flood Advisory until 5 AM EDT early this morning for
     DCZ001.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

SYNOPSIS...BKF
NEAR TERM...BKF
SHORT TERM...BKF
LONG TERM...BRO
AVIATION...BKF/BRO
MARINE...BKF/BRO
TIDES/COASTAL FLOODING...BRO
Hazardous weather outlook, Aug 17, 8:30 AM EDT, 24 minutes before
Hazardous Weather Outlook
National Weather Service Baltimore MD/Washington DC
830 AM EDT Tue Aug 17 2021

ANZ530>543-DCZ001-MDZ008-011-013-014-016>018-504-506-508-
VAZ052>057-181230-
Chesapeake Bay north of Pooles Island MD-
Chesapeake Bay from Pooles Island to Sandy Point MD-
Chesapeake Bay from Sandy Point to North Beach MD-
Chesapeake Bay from North Beach to Drum Point MD-
Chesapeake Bay from Drum Point MD to Smith Point VA-
Tidal Potomac from Key Bridge to Indian Head MD-
Tidal Potomac from Indian Head to Cobb Island MD-
Tidal Potomac from Cobb Island MD to Smith Point VA-
Patapsco River including Baltimore Harbor-
Chester River to Queenstown MD-Eastern Bay-
Choptank River to Cambridge MD and the Little Choptank River-
Patuxent River to Broomes Island MD-
Tangier Sound and the inland waters surrounding Bloodsworth
Island-District of Columbia-Cecil-Southern Baltimore-
Prince Georges-Anne Arundel-Charles-St. Marys-Calvert-
Central and Southeast Montgomery-Central and Southeast Howard-
Southeast Harford-Prince William/Manassas/Manassas Park-Fairfax-
Arlington/Falls Church/Alexandria-Stafford-Spotsylvania-
King George-
830 AM EDT Tue Aug 17 2021

This Hazardous Weather Outlook is for the Maryland portion of the
Chesapeake Bay, Tidal Potomac River, and I-95 corridor through
central Maryland, northern Virginia, and District of Columbia.

.DAY ONE...Today and Tonight

Scattered instances of flooding are possible today as tropical
moisture from the remnants of Fred approaches the region.

Isolated strong thunderstorms will be possible over the Chesapeake
Bay and lower Tidal Potomac today.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Additional periods of heavy rain and flooding are possible from
tropical moisture through Thursday due in part to the remnants of
Fred.

Isolated severe thunderstorms are possible Wednesday and Wednesday
night in association with Fred.

Isolated severe thunderstorms are possible on Saturday as a system
approaches from the Great Lakes.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be necessary over the next several days.

MDZ003>006-503-505-507-VAZ025>031-036>040-050-051-501-502-505>508-
WVZ050>053-055-181230-
Washington-Frederick MD-Carroll-Northern Baltimore-
Northwest Montgomery-Northwest Howard-Northwest Harford-Augusta-
Rockingham-Shenandoah-Frederick VA-Page-Warren-Clarke-Nelson-
Albemarle-Greene-Madison-Rappahannock-Orange-Culpeper-
Northern Fauquier-Southern Fauquier-Western Loudoun-
Eastern Loudoun-Northern Virginia Blue Ridge-
Central Virginia Blue Ridge-Hampshire-Morgan-Berkeley-Jefferson-
Hardy-
830 AM EDT Tue Aug 17 2021

This Hazardous Weather Outlook is for portions of eastern West
Virginia, northern and central Virginia, and central and western
Maryland.

.DAY ONE...Today and Tonight

Scattered instances of flooding are possible today as tropical
moisture from the remnants of Fred approaches the region.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Additional periods of heavy rain and flooding are possible from
tropical moisture through Thursday due in part to the remnants of
Fred.

Isolated severe thunderstorms are possible Wednesday and Wednesday
night in association with Fred.

Isolated severe thunderstorms are possible on Saturday as a system
approaches from the Great Lakes.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be necessary over the next several days.

MDZ001-501-502-VAZ503-504-WVZ501>506-181230-
Garrett-Extreme Western Allegany-Central and Eastern Allegany-
Western Highland-Eastern Highland-Western Grant-Eastern Grant-
Western Mineral-Eastern Mineral-Western Pendleton-
Eastern Pendleton-
830 AM EDT Tue Aug 17 2021

This Hazardous Weather Outlook is for the Allegheny Front
counties in western Maryland, eastern West Virginia, and Highland
County Virginia.

.DAY ONE...Today and Tonight

Scattered instances of flooding are possible today as tropical
moisture from the remnants of Fred approaches the region.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday

Additional periods of heavy rain and flooding are possible from
tropical moisture through Thursday due in part to the remnants of
Fred.

Isolated severe thunderstorms are possible Wednesday and Wednesday
night in association with Fred.

Isolated severe thunderstorms are possible on Saturday as a system
approaches from the Great Lakes.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be necessary over the next several days.

In the hours before

Local storm report, Aug 17, 2:59 AM EDT, 5 hours 55 minutes before
PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
259 AM EDT TUE AUG 17 2021

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0145 AM     FLASH FLOOD      COLESVILLE              39.07N  77.03W
08/17/2021                   MONTGOMERY         MD   MESONET

            RAPID RISE OF NORTHERN BRANCH OF THE ANACOSTIA RIVER TO
            ABOVE MINOR BETWEEN 145-230 AM. MAXIMUM LEVEL REACHED
            9.31' (MINOR: 9.00').

&&

EVENT NUMBER LWX2105532

BRO

The office that day

Everything else NWS Baltimore/Washington issued on the same UTC day.

IssuedProductOfficeCountiesLasted
Aug 16, 8:47 PM EDTFlash Flood Warning Considerable damage threatLWXWashington2 hr
Aug 16, 9:04 PM EDTFlash Flood Warning Considerable damage threatLWXAllegany2 hr
Aug 16, 11:32 PM EDTFlash Flood Warning Considerable damage threatLWXMontgomery3 hr
Aug 17, 12:39 AM EDTCoastal Flood AdvisoryLWXAnne Arundel100 min
Aug 17, 2:17 AM EDTAreal Flood WarningLWXMontgomery4 hr
Aug 17, 1:54 PM EDTFlash Flood WatchLWXAllegany, Baltimore, Carroll, Frederick, Harford, Howard and 3 more27 hr
Aug 17, 6:40 PM EDTCoastal Flood AdvisoryLWXAnne Arundel, Baltimore, City of Baltimore11 hr

Nearby

Flash Flood Watches in Maryland, 2021Every flash flood watch in 2021

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.