Flash Flood Watch 4, NWS Baltimore/Washington

Anne Arundel County, MD, Baltimore County, MD, Calvert County, MD, Carroll County, MD, Cecil County, MD, Charles County, MD, City of Baltimore, MD, Frederick County, MD, Harford County, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Saint Mary's County, MD, Arlington County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Greene County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Rappahannock County, VA, Spotsylvania County, VA, Stafford County, VA

787 
WGUS61 KLWX 010226
FFALWX

Flood Watch
National Weather Service Baltimore MD/Washington DC
1026 PM EDT Wed Jun 30 2021

DCZ001-MDZ004>006-008-011-013-014-016>018-503>508-VAZ037>040-050>057-
501-502-505-506-011030-
/O.CON.KLWX.FF.A.0004.210701T1800Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia-Frederick MD-Carroll-Northern Baltimore-Cecil-
Southern Baltimore-Prince Georges-Anne Arundel-Charles-St. Marys-
Calvert-Northwest Montgomery-Central and Southeast Montgomery-
Northwest Howard-Central and Southeast Howard-Northwest Harford-
Southeast Harford-Albemarle-Greene-Madison-Rappahannock-Orange-
Culpeper-Prince William/Manassas/Manassas Park-Fairfax-
Arlington/Falls Church/Alexandria-Stafford-Spotsylvania-King George-
Northern Fauquier-Southern Fauquier-Western Loudoun-Eastern Loudoun-
Including the cities of Elkton, Charlottesville, South Gate, Bowie, 
Arlington, Annapolis, Manassas, Odenton, Westminster, Damascus, 
Falls Church, Silver Spring, Purcellville, Bethesda, Chantilly, 
Orange, Prince Frederick, Ballenger Creek, Centreville, Culpeper, 
Huntingtown, Sterling, College Park, Reisterstown, Columbia, 
Fredericksburg, Warrenton, Chesapeake Beach, Falmouth, Herndon, 
Dunkirk, Severna Park, California, Greenbelt, Dahlgren, Germantown, 
Leesburg, McLean, Alexandria, St. Charles, Camp Springs, Rockville, 
Jarrettsville, Lexington Park, Frederick, Arnold, North Beach, 
Waldorf, Suitland-Silver Hill, Lake Ridge, Gaithersburg, Severn, 
Lusby, Reston, Montclair, Turnbull, Baltimore, Dale City, Madison, 
Eldersburg, Clinton, Glen Burnie, Ashburn, Ellicott City, 
Woodbridge, Stanardsville, Washington, Annandale, Franconia, 
Cockeysville, Lisbon, Laurel, Gordonsville, and Aberdeen
1026 PM EDT Wed Jun 30 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT FROM THURSDAY AFTERNOON 
THROUGH FRIDAY MORNING...

The Flash Flood Watch continues for

* Portions of DC, Maryland and Virginia, including the following 
  areas: in DC, District of Columbia. In Maryland, Anne Arundel, 
  Calvert, Carroll, Cecil, Central and Southeast Howard, Central and 
  Southeast Montgomery, Charles, Frederick MD, Northern Baltimore, 
  Northwest Harford, Northwest Howard, Northwest Montgomery, Prince 
  Georges, Southeast Harford, Southern Baltimore and St. Marys. In 
  Virginia, Albemarle, Arlington/Falls Church/Alexandria, Culpeper, 
  Eastern Loudoun, Fairfax, Greene, King George, Madison, Northern 
  Fauquier, Orange, Prince William/Manassas/Manassas Park, 
  Rappahannock, Southern Fauquier, Spotsylvania, Stafford and 
  Western Loudoun.

* From Thursday afternoon through Friday morning.

* Several rounds of thunderstorms are expected Thursday afternoon 
  through early Friday morning with localized rainfall rates of up 
  to 1-2 inches per hour possible. Total rainfall amounts of 1-3 
  inches, with locally higher amounts up to 4 inches are possible.

* Heavy rain in short periods of time will cause the potential for 
  streams and creeks to quickly rise out of their banks as well as 
  the potential for flash flooding in urban areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

$$

BJL

375 
WGUS61 KLWX 011015
FFALWX

Flood Watch
National Weather Service Baltimore MD/Washington DC
615 AM EDT Thu Jul 1 2021

DCZ001-MDZ004>006-008-011-013-014-016>018-503>508-VAZ037>040-050>057-
501-502-505-506-012100-
/O.CON.KLWX.FF.A.0004.210701T1800Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia-Frederick MD-Carroll-Northern Baltimore-Cecil-
Southern Baltimore-Prince Georges-Anne Arundel-Charles-St. Marys-
Calvert-Northwest Montgomery-Central and Southeast Montgomery-
Northwest Howard-Central and Southeast Howard-Northwest Harford-
Southeast Harford-Albemarle-Greene-Madison-Rappahannock-Orange-
Culpeper-Prince William/Manassas/Manassas Park-Fairfax-
Arlington/Falls Church/Alexandria-Stafford-Spotsylvania-King George-
Northern Fauquier-Southern Fauquier-Western Loudoun-Eastern Loudoun-
Including the cities of Elkton, Charlottesville, South Gate, Bowie, 
Arlington, Annapolis, Manassas, Odenton, Westminster, Damascus, 
Falls Church, Silver Spring, Purcellville, Bethesda, Chantilly, 
Orange, Prince Frederick, Ballenger Creek, Centreville, Culpeper, 
Huntingtown, Sterling, College Park, Reisterstown, Columbia, 
Fredericksburg, Warrenton, Chesapeake Beach, Falmouth, Herndon, 
Dunkirk, Severna Park, California, Greenbelt, Dahlgren, Germantown, 
Leesburg, McLean, Alexandria, St. Charles, Camp Springs, Rockville, 
Jarrettsville, Lexington Park, Frederick, Arnold, North Beach, 
Waldorf, Suitland-Silver Hill, Lake Ridge, Gaithersburg, Severn, 
Lusby, Reston, Montclair, Turnbull, Baltimore, Dale City, Madison, 
Eldersburg, Clinton, Glen Burnie, Ashburn, Ellicott City, 
Woodbridge, Stanardsville, Washington, Annandale, Franconia, 
Cockeysville, Lisbon, Laurel, Gordonsville, and Aberdeen
615 AM EDT Thu Jul 1 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT FROM 2 PM EDT THIS AFTERNOON 
THROUGH FRIDAY MORNING...

The Flash Flood Watch continues for

* Portions of DC, Maryland and Virginia, including the following 
  areas: in DC, District of Columbia. In Maryland, Anne Arundel, 
  Calvert, Carroll, Cecil, Central and Southeast Howard, Central and 
  Southeast Montgomery, Charles, Frederick MD, Northern Baltimore, 
  Northwest Harford, Northwest Howard, Northwest Montgomery, Prince 
  Georges, Southeast Harford, Southern Baltimore and St. Marys. In 
  Virginia, Albemarle, Arlington/Falls Church/Alexandria, Culpeper, 
  Eastern Loudoun, Fairfax, Greene, King George, Madison, Northern 
  Fauquier, Orange, Prince William/Manassas/Manassas Park, 
  Rappahannock, Southern Fauquier, Spotsylvania, Stafford and 
  Western Loudoun.

* From 2 PM EDT this afternoon through Friday morning.

* Several rounds of thunderstorms are expected this afternoon 
  through early Friday morning with localized rainfall rates of up 
  to 1-2 inches per hour possible. Total rainfall amounts of 1-3 
  inches, with locally higher amounts up to 4 inches are possible.

* Heavy rain in short periods of time will cause the potential for 
  streams and creeks to quickly rise out of their banks as well as 
  the potential for flash flooding in urban areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

$$

JMG

047 
WGUS61 KLWX 011907
FFALWX

Flood Watch
National Weather Service Baltimore MD/Washington DC
307 PM EDT Thu Jul 1 2021

DCZ001-MDZ004>006-008-011-013-014-016>018-503>508-VAZ037>040-050>057-
501-502-505-506-020315-
/O.CON.KLWX.FF.A.0004.000000T0000Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia-Frederick MD-Carroll-Northern Baltimore-Cecil-
Southern Baltimore-Prince Georges-Anne Arundel-Charles-St. Marys-
Calvert-Northwest Montgomery-Central and Southeast Montgomery-
Northwest Howard-Central and Southeast Howard-Northwest Harford-
Southeast Harford-Albemarle-Greene-Madison-Rappahannock-Orange-
Culpeper-Prince William/Manassas/Manassas Park-Fairfax-
Arlington/Falls Church/Alexandria-Stafford-Spotsylvania-King George-
Northern Fauquier-Southern Fauquier-Western Loudoun-Eastern Loudoun-
Including the cities of Elkton, Charlottesville, South Gate, Bowie, 
Arlington, Annapolis, Manassas, Odenton, Westminster, Damascus, 
Falls Church, Silver Spring, Purcellville, Bethesda, Chantilly, 
Orange, Prince Frederick, Ballenger Creek, Centreville, Culpeper, 
Huntingtown, Sterling, College Park, Reisterstown, Columbia, 
Fredericksburg, Warrenton, Chesapeake Beach, Falmouth, Herndon, 
Dunkirk, Severna Park, California, Greenbelt, Dahlgren, Germantown, 
Leesburg, McLean, Alexandria, St. Charles, Camp Springs, Rockville, 
Jarrettsville, Lexington Park, Frederick, Arnold, North Beach, 
Waldorf, Suitland-Silver Hill, Lake Ridge, Gaithersburg, Severn, 
Lusby, Reston, Montclair, Turnbull, Baltimore, Dale City, Madison, 
Eldersburg, Clinton, Glen Burnie, Ashburn, Ellicott City, 
Woodbridge, Stanardsville, Washington, Annandale, Franconia, 
Cockeysville, Lisbon, Laurel, Gordonsville, and Aberdeen
307 PM EDT Thu Jul 1 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH FRIDAY MORNING...

The Flash Flood Watch continues for

* Portions of DC, Maryland and Virginia, including the following 
  areas: in DC, District of Columbia. In Maryland, Anne Arundel, 
  Calvert, Carroll, Cecil, Central and Southeast Howard, Central and 
  Southeast Montgomery, Charles, Frederick MD, Northern Baltimore, 
  Northwest Harford, Northwest Howard, Northwest Montgomery, Prince 
  Georges, Southeast Harford, Southern Baltimore and St. Marys. In 
  Virginia, Albemarle, Arlington/Falls Church/Alexandria, Culpeper, 
  Eastern Loudoun, Fairfax, Greene, King George, Madison, Northern 
  Fauquier, Orange, Prince William/Manassas/Manassas Park, 
  Rappahannock, Southern Fauquier, Spotsylvania, Stafford and 
  Western Loudoun.

* Through Friday morning.

* Several rounds of thunderstorms are expected this afternoon and 
  evening, potentially continuing through the overnight into early 
  Friday morning. Localized rainfall rates of up to 1-2 inches per 
  hour are expected at times. Total rainfall amounts of 1-3 inches, 
  with locally higher amounts up to 4 inches are possible.

* Heavy rain in short periods of time will cause the potential for 
  streams and creeks to quickly rise out of their banks as well as 
  the potential for flash flooding in urban areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

$$

CJL

815 
WGUS61 KLWX 012237
FFALWX

Flood Watch
National Weather Service Baltimore MD/Washington DC
637 PM EDT Thu Jul 1 2021

MDZ004>006-008-011-503>508-VAZ040-501-505-506-012345-
/O.CAN.KLWX.FF.A.0004.000000T0000Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Frederick MD-Carroll-Northern Baltimore-Cecil-Southern Baltimore-
Northwest Montgomery-Central and Southeast Montgomery-Northwest
Howard-Central and Southeast Howard-Northwest Harford-Southeast
Harford-Rappahannock-Northern Fauquier-Western Loudoun-Eastern
Loudoun-
Including the cities of Silver Spring, Jarrettsville, Westminster, 
Damascus, Elkton, Bethesda, Ballenger Creek, Sterling, Ashburn, 
Reisterstown, Columbia, Purcellville, Germantown, Leesburg, 
Rockville, Frederick, Baltimore, Eldersburg, Ellicott City, 
Washington, Warrenton, Cockeysville, Lisbon, Gaithersburg, and 
Aberdeen
637 PM EDT Thu Jul 1 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch has been cancelled for portions of Maryland 
and Virginia, including the following areas: in Maryland, Carroll, 
Cecil, Central and Southeast Howard, Central and Southeast 
Montgomery, Frederick MD, Northern Baltimore, Northwest Harford, 
Northwest Howard, Northwest Montgomery, Southeast Harford and 
Southern Baltimore. In Virginia, Eastern Loudoun, Northern Fauquier, 
Rappahannock and Western Loudoun.

The Flood Watch is cancelled. While showers and a few thunderstorms 
may still occur overnight, flash flooding is no longer anticipated.

$$

DCZ001-MDZ013-014-016>018-VAZ037>039-050>057-502-020645-
/O.CON.KLWX.FF.A.0004.000000T0000Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia-Prince Georges-Anne Arundel-Charles-St. Marys-
Calvert-Albemarle-Greene-Madison-Orange-Culpeper-Prince
William/Manassas/Manassas Park-Fairfax-Arlington/Falls
Church/Alexandria-Stafford-Spotsylvania-King George-Southern
Fauquier-
Including the cities of South Gate, Bowie, Arlington, Annapolis, 
Falls Church, Odenton, Fredericksburg, Charlottesville, Chantilly, 
Orange, Prince Frederick, Dunkirk, Centreville, Culpeper, 
Huntingtown, College Park, Chesapeake Beach, Falmouth, Herndon, 
Severna Park, California, Greenbelt, Dahlgren, McLean, St. Charles, 
Camp Springs, Lexington Park, Arnold, North Beach, Waldorf, 
Suitland-Silver Hill, Lake Ridge, Manassas, Severn, Lusby, Reston, 
Montclair, Turnbull, Dale City, Madison, Alexandria, Clinton, Glen 
Burnie, Woodbridge, Stanardsville, Washington, Annandale, Laurel, 
Gordonsville, and Franconia
637 PM EDT Thu Jul 1 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT THROUGH FRIDAY MORNING...

The Flash Flood Watch continues for

* Portions of DC, Maryland and Virginia, including the following 
  areas: in DC, District of Columbia. In Maryland, Anne Arundel, 
  Calvert, Charles, Prince Georges and St. Marys. In Virginia, 
  Albemarle, Arlington/Falls Church/Alexandria, Culpeper, Fairfax, 
  Greene, King George, Madison, Orange, Prince 
  William/Manassas/Manassas Park, Southern Fauquier, Spotsylvania 
  and Stafford.

* Through Friday morning.

* Several rounds of thunderstorms are expected this afternoon and 
  evening, potentially continuing through the overnight into early 
  Friday morning. Localized rainfall rates of up to 1-2 inches per 
  hour are expected at times. Total rainfall amounts of 1-3 inches, 
  with locally higher amounts up to 4 inches are possible.

* Heavy rain in short periods of time will cause the potential for 
  streams and creeks to quickly rise out of their banks as well as 
  the potential for flash flooding in urban areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

$$

RCM

283 
WGUS61 KLWX 020618
FFALWX

Flood Watch
National Weather Service Baltimore MD/Washington DC
218 AM EDT Fri Jul 2 2021

...Heaviest rainfall has exited the region, with numerous lighter 
showers moving through during the overnight hours...

DCZ001-MDZ013-014-VAZ037>039-050>055-502-020730-
/O.CAN.KLWX.FF.A.0004.000000T0000Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
District of Columbia-Prince Georges-Anne Arundel-Albemarle-Greene-
Madison-Orange-Culpeper-Prince William/Manassas/Manassas Park-
Fairfax-Arlington/Falls Church/Alexandria-Stafford-Southern Fauquier-
Including the cities of South Gate, Bowie, Arlington, Annapolis, 
Falls Church, Odenton, Charlottesville, Chantilly, Orange, Culpeper, 
Centreville, College Park, Falmouth, Herndon, Severna Park, 
Greenbelt, McLean, Camp Springs, Arnold, Dale City, Suitland-Silver 
Hill, Lake Ridge, Manassas, Severn, Reston, Montclair, Turnbull, 
Madison, Alexandria, Clinton, Glen Burnie, Woodbridge, 
Stanardsville, Washington, Annandale, Laurel, Gordonsville, and 
Franconia
218 AM EDT Fri Jul 2 2021

...FLASH FLOOD WATCH IS CANCELLED...

The Flash Flood Watch has been cancelled for portions of DC, central 
Maryland and Virginia, including the following areas: in DC, 
District of Columbia. In central Maryland, Anne Arundel and Prince 
Georges. In Virginia, Albemarle, Arlington/Falls Church/Alexandria, 
Culpeper, Fairfax, Greene, Madison, Orange, Prince 
William/Manassas/Manassas Park, Southern Fauquier and Stafford.

The Flood Watch is cancelled. While showers will still occur 
overnight, flash flooding is no longer anticipated.

$$

MDZ016>018-VAZ056-057-021200-
/O.CON.KLWX.FF.A.0004.000000T0000Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Charles-St. Marys-Calvert-Spotsylvania-King George-
Including the cities of Dahlgren, St. Charles, Chesapeake Beach, 
Lexington Park, Fredericksburg, North Beach, Waldorf, California, 
Lusby, Dunkirk, Prince Frederick, and Huntingtown
218 AM EDT Fri Jul 2 2021

...FLASH FLOOD WATCH REMAINS IN EFFECT UNTIL 8 AM EDT THIS MORNING...

The Flash Flood Watch continues for

* Portions of southern Maryland and Virginia, including the 
  following areas: in southern Maryland, Calvert, Charles and St. 
  Marys. In Virginia, King George and Spotsylvania.

* Until 8 AM EDT this morning.

* Light to moderate rain showers moving through the region overnight 
  may cause some localized flooding issues, particularly those 
  locations which are more susceptible to high water.

* Heavy rain in short periods of time may cause the potential for 
  streams and creeks to quickly rise out of their banks as well as 
  the potential for flash flooding in urban areas.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

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

&&

$$

BRO

063 
WGUS61 KLWX 021152
FFALWX

Flood Watch
National Weather Service Baltimore MD/Washington DC
752 AM EDT Fri Jul 2 2021

MDZ016>018-VAZ056-057-021300-
/O.EXP.KLWX.FF.A.0004.000000T0000Z-210702T1200Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Charles-St. Marys-Calvert-Spotsylvania-King George-
Including the cities of Dahlgren, St. Charles, Chesapeake Beach, 
Lexington Park, Fredericksburg, North Beach, Waldorf, California, 
Lusby, Dunkirk, Prince Frederick, and Huntingtown
752 AM EDT Fri Jul 2 2021

...FLASH FLOOD WATCH WILL EXPIRE AT 8 AM EDT THIS MORNING...

The Flash Flood Watch for portions of southern Maryland and 
Virginia, including the following areas: in southern Maryland, 
Calvert, Charles and St. Marys. In Virginia, King George and 
Spotsylvania will expire at 8 AM EDT this morning.

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

$$

KJP

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
950 AM EDT Wed Jun 30 2021

.SYNOPSIS...
Bermuda high pressure will remain in control today. A cold front
will slowly approach from the Midwest tonight and Thursday,
eventually pushing southeast on Friday. The front may stall just
southeast of the area over the weekend while high pressure builds
over the Ohio Valley.

&&

.NEAR TERM /THROUGH TONIGHT/...
9:45 AM UPDATE: Current satellite imagery and 12z upper air
analyses depict an upper-level trough centered over the
Midwest/Great Lakes regions and an upper-level ridge centered
over the western Atlantic. Both features are gradually moving
east this morning. Expect gradual height falls across western
portions of the forecast area later today into this afternoon,
which could help aid in the development of thunderstorms later
today, as was mentioned in the previous discussion below. One
thing of note is that dew points thus far seem to be running a
degree or two lower in several spots than anticipated. But with
S to SSW flow, could still see those come up a bit. Will
continue to monitor that over the next couple of hours. Either
way, think we get enough instability for storms later, but could
make some minor differences in the heat indices. Either way,
going to be very hot and humid today, and Heat Advisories remain
in effect across the Baltimore metro area down through Anne
Arundel and Calvert counties. Defer to the previous forecast for
more details on the storm/heat threats for today.

PREVIOUS DISCUSSION: Bermuda high pressure will remain in
control today while upper level ridging gradually becomes
suppressed due to troughing digging into the Great Lakes. The
first topic is the heat. Most areas should be similar or
slightly warmer than Tuesday, resulting in widespread high
temperatures in the mid to perhaps upper 90s. Dew points are
trickier, as a southwest/westerly component to the low level
winds may aid in drier air aloft mixing down during peak heating
(not to mention our early morning dew points are in the 60s in
many areas already). However, higher humidity will likely be
present closer to the warm waters of the Chesapeake Bay, which
could push the heat index to near 105. Therefore, have issued a
Heat Advisory for a number of these counties.

The most robust thunderstorm development today should be to our
north and west, closer to a cold front and upper trough.
However, a lee surface trough is likely to form near the I-81
corridor, and most guidance initiates storms in this area around mid-
late afternoon, aided by mid level height falls. While shear will be
relatively weak, moderate instability and favorable downdraft
parameters could lead to a few pulse severe storms with damaging
winds. Some of these storms could drift toward the metro areas
during the evening hours. Some of the showers and storms originating
to our north and west could drift toward the area this evening as
well, and then again late tonight (targeting the Allegheny Front),
but these storms should be in a weakened state. Otherwise, patchy
fog could occur, especially anywhere that sees rain then subsequent
clearing. Lows remain muggy in the upper 60s and 70s.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
The Thursday into Thursday night period is expected to be active as
a surface cold front and deepening upper level trough (perhaps a
closed low by this point) continue to press southeastward to the
area. Clouds, showers, and perhaps a few storms may be ongoing
during the morning hours in a zone of lift that will be drifting
southeastward from the Appalachians. Ahead of the more widespread
precipitation, the atmosphere should destabilize. Meanwhile, shear
will be increasing ahead of the trough. By afternoon, existing
convection could strengthen, or new storms could fire, as lift will
be plentiful. Some of these storms could be strong to severe with
damaging winds as the primary threat. Some guidance supports the
development of a wave of low pressure on the boundary, which could
result in enough low level shear for a brief tornado, but this is
highly uncertain. Another uncertainty is the location of the
greatest threat, since the morning clouds and showers will likely
affect instability. At the moment, this delineation appears to run
through the DC/Baltimore metro areas to the southern Shenandoah
Valley, but could definitely change. Another potentially hazardous
aspect will be locally heavy rain and flooding. High precipitable
water, relatively deep warm cloud layers, and flow nearly parallel
to the forcing could result in some training heavy rainers. With
increasing dynamic lift and potential low pressure waves on the slow
moving boundary, additional showers and storms with heavy rain could
affect some of the same areas into Thursday night.

The speed of the surface front will be important to Friday's
forecast, as it does appear models are becoming increasingly
progressive. At a minimum, the severe thunderstorm threat looks to
diminish, although with the upper low still approaching and the
boundary nearby, it will likely remain unsettled. The threat for
heavy rain will likely shift to southern Maryland, if not entirely
away from our area. Overall, there should be a drying trend during
the afternoon, but especially overnight. However, a few showers may
linger with the upper low nearby. Temperatures will be much cooler,
generally in the 70s for highs and mid 50s-mid 60s for lows.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
The upper level trough axis that will impact our region during the
later parts of this week will start to shift off-shore on Saturday.
The models are starting agree on the positioning of the upper trough
but there remains a slight timing different between the GFS and Euro
models. The Euro is slightly more progressive with the trough
shifting off-shore which means quicker drying out for our region.
The GFS has the upper trough producing some wrap around showers on
Saturday as the trough pulls eastward off the eastern seaboard. The
cooler temperatures that begin on Friday should continue into this
weekend with afternoon highs running in the 70s to lower 80s. The
threat for showers should taper off through the end of the weekend
as high pressure slowly builds in from the midwest.

Weak ridging is forecast to build over our region during the early
parts of next week. A slow heating trend is forecast to return on
Monday with daytime temps trend back up into the mid to upper 80s
and up into the 90s by Tuesday. The models have a weak front
dropping into our region and remaining nearby sometime on Tuesday.
This boundary may help produced some showers but there will be lack
of good forcing along with only modest CAPE.

&&

.AVIATION /14Z WEDNESDAY THROUGH SUNDAY/...
High pressure will remain in control for most of today with light
southwest winds and diurnal cumulus developing. Scattered storms are
expected to form in a lee pressure trough late this afternoon,
possible progressing across the metro areas this evening. Have timed
a VCTS into the TAFs to cover this threat (except CHO, where there
is a lower chance), although the storm coverage and timing is still
a little uncertain. Any direct storm impact could contain very gusty
winds. Patchy fog is possible later tonight, especially in any areas
that see rain and then clearing. Guidance is generally pointing to
MRB and CHO, but will take a closer look for the 12Z TAFs.

An active period is expected Thursday into Thursday night, with
showers and storms quickly increasing in coverage during the midday
hours. Strong to severe storms and heavy rain will be possible.
Additional rounds of showers and storms may continue into the night.
As a cold front pushes through, MVFR to IFR ceilings and possibly
visibility will become more likely through the night. The front will
slowly push to the southeast Friday and Friday night with decreasing
shower chances; however some periods of sub-VFR conditions may
continue.

Drier air should start to filter into our region this weekend
leading to mostly VFR conditions. Winds are expected to be mainly
out of the west to northwest this weekend. A weak southerly flow
will likely return early next week.

&&

.MARINE...
Winds have tapered off over the Chesapeake Bay, but will keep
the current Small Craft Advisory out through 11 AM, as there are
still some gusts up to around 16 knots or so at this time, so
can't rule out a sporadic gust to 20 knots in the middle of the
Bay.

After a break, winds are expected to increase again in this
area by late this afternoon into the evening. Therefore another
SCA has been issued. Scattered storms with gusty winds may reach
the waters this evening as well.

Southwest flow continues into Thursday ahead of a cold front.
Marginal SCA conditions are possible during the afternoon and
overnight, especially near southern Maryland, but confidence is low.
The bigger hazard will be fairly widespread showers and
thunderstorms, some of which could be strong to severe. The front
will be to the southeast by Friday morning, and relatively light
west to northwest flow will prevail.

As the upper trough shifts away from our region, our marine areas
may require Small Craft Advisories on Saturday. SubSCA conditions
likely at this time on Sunday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...Heat Advisory until 8 PM EDT this evening for MDZ006-008-011-
     014-018-507-508.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 11 AM EDT this morning for ANZ533-
     534-537-543.
     Small Craft Advisory from 5 PM this afternoon to 2 AM EDT
     Thursday for ANZ534-537-543.

&&

SYNOPSIS...ADS
NEAR TERM...ADS/CJL
SHORT TERM...ADS
LONG TERM...JMG
AVIATION...ADS/JMG
MARINE...ADS/JMG/CJL

Hazardous Weather Outlook
National Weather Service Baltimore MD/Washington DC
529 AM EDT Wed Jun 30 2021

ANZ530>543-DCZ001-MDZ008-011-013-014-016>018-504-506-508-
VAZ052>057-010930-
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-
529 AM EDT Wed Jun 30 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

A Heat Advisory is in effect from noon to 8 PM for Baltimore,
Cecil, Anne Arundel, Calvert, and Harford Counties.

An isolated severe thunderstorm with damaging wind gusts is
possible late this afternoon and evening, mainly across the
greater Washington and Baltimore Metropolitan Areas.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Thunderstorms are expected across much of the area Thursday into
Thursday night. Isolated severe thunderstorms with damaging winds
are possible, and a brief tornado can't be ruled out. Heavy rain
may also lead to scattered instances of flooding or flash
flooding.

The heavy rain and flooding threat may linger into Friday for
southern Maryland.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening and
also on Thursday.

MDZ003>006-503-505-507-VAZ025>031-036>040-050-051-501-502-505>508-
WVZ050>053-055-010930-
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-
529 AM EDT Wed Jun 30 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

An isolated severe thunderstorm with damaging wind gusts is
possible this afternoon and evening across much of the outlook
area with the exception of central Virginia.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Thunderstorms are expected across portions of the area Thursday
into Thursday night. Isolated severe thunderstorms with damaging
winds are possible, and a brief tornado can't be ruled out. Heavy
rain may also lead to scattered instances of flooding or flash
flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening and
also on Thursday.

MDZ001-501-502-VAZ503-504-WVZ501>506-010930-
Garrett-Extreme Western Allegany-Central and Eastern Allegany-
Western Highland-Eastern Highland-Western Grant-Eastern Grant-
Western Mineral-Eastern Mineral-Western Pendleton-
Eastern Pendleton-
529 AM EDT Wed Jun 30 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

An isolated severe thunderstorm with damaging wind gusts is
possible this afternoon and evening.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday

Thunderstorms are possible across portions of the area Thursday
into Thursday night. An isolated severe thunderstorm with
damaging winds is possible. Heavy rain may also lead to scattered
instances of flooding or flash flooding.

.SPOTTER INFORMATION STATEMENT...

Spotter activation may be needed this afternoon and evening and
also on Thursday.