Flash Flood Warning 40, NWS Baltimore/Washington

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1013 AM EDT Sat Jun 2 2018

.SYNOPSIS...
A cold front will stall near the area this afternoon. Low
pressure will develop along the front off of the Virginia coast
tonight and remain into Sunday. Low pressure will move away
Monday. Another front approaches Tuesday. High pressure builds
behind it through mid week.

&&

.NEAR TERM /THROUGH TONIGHT/...
Moderate to heavy persistent rainfall is occurring over southern
Grant and Hardy Counties, all of Pendleton County and western
Rockingham County. Rain rates are averaging one half to one inch
per hour with a couple locations in Hardy and Rockingham
Counties already receiving over an inch of rain in the last hour
or two.

Other showers, more isolated and less intense, are popping up
in Albemarle County, Augusta County and Orange County. The
airmass across our region remains very juicy with precipitable
water values above 2 inches.

An upper trough axis will be sharpening over the area this
afternoon, and cutting off tonight. Surface low pressure should
be developing southeast of the area during the evening hours.
The attendant positive vorticity from the upper trough and
residual instability will be capable of supporting renewed
showers and thunderstorms as soon as daytime heating is
realized. This support will continue through the night.
Consequently, will be carrying likely or categorical PoPs for
the next 24 hours.

While CAPE won't be as large as previous days, and shear
minimal, it won't take much in this saturated atmosphere for
thunderstorms to develop. These should be heavy rainers due to
PWAT as well as deep warm cloud depths. Short MBE/Corfidi
vectors indicate slow movers, with possible backbuilding. This
will be particularly problematic as recent rainfall has left the
soil saturated, with Flood Guidance values below an inch in
many instances. As a result, have issued a Flash Flood Watch for
the entire area this afternoon and tonight. Anticipated
rainfall (widespread 2-3 inches, locally higher...potentially
much higher) and unusually moist antecedent conditions could be
a bad combination for somewhere in the forecast area. Since fine
details vary...cannot pinpoint precisely where. Thus the Watch
will be for the whole area.

&&

.SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/...
Low level convergence from low pressure will still be present
Sunday. The low will gradually drift east, but likely won't be
offshore until Sunday night. Since flow will be north, even by
Sunday morning, there will be less moisture to work with...and
practically no CAPE. Nonetheless, the ground will be saturated
and support for continued showers present. Rainfall amounts
should be less...but that may be little consolation. Flood (or
Flash Flood) Watches may need to be extended.

Heights will gradually rise Monday. Cannot rule out a few more
showers, but coverage may be scattered.

&&

.LONG TERM /TUESDAY THROUGH FRIDAY/...
Tuesday morning looks dry, but some showers will be possible
during the afternoon hours as a cold front approaches from the
north. The best chances for showers will be across northern portions
of the forecast area.

Behind this front, a relatively cool airmass will move into the
region. Temperatures will drop into the 40s and 50s Tuesday night
and high temperatures on Wednesday will only reach the 60s and 70s.
An area of high pressure moving in from the Great Lakes will
dominate our weather on Wednesday and Thursday. With high
pressure overhead, skies will be mostly sunny, humidity levels will
be low and temperatures will stay below average.

Temperatures will start to moderate again by Friday out ahead of a
cold front approaching from the northwest. Model guidance differs
substantially with strength of this front and the associated rain
chances (Euro keeps us mostly dry, while GFS has some rain).

&&

.AVIATION /14Z SATURDAY THROUGH WEDNESDAY/...
VFR conditions generally expected through Noon. We anticipate
conditions to deteriorate this afternoon, but distribution may
be uneven. Am gradually taking restriction through MVFR this
afternoon and into IFR late tonight. However, numerous
showers/thunderstorms anticipated, many with heavy rain. Local
flight restrictions may be much lower for short periods of time.
Pinpointing details problematic.

Similar conditions (widespread flight conditions to start, with
frequent by spotty MVFR/IFR) will extend into Sunday, and
possibly Monday. VFR conditions are expected to prevail
thereafter.

&&

.MARINE...
Little wind outside of thunderstorms this afternoon. Low
pressure will develop tonight, increasing the pressure gradient
and providing better mixing. Within the mixed layer, 20 kt
present late tonight through Sunday on the Bay/lower Potomac;
Small Craft Advisories have been posted. These may need to be
extended into Sunday night. There is also the potential for a
short fused Small Craft this afternoon due to frequent gusts
associated with showers and storms. Do not have a good feel for
this potential yet, so will forward these thought to the
dayshift.

Winds are expected to stay below SCA criteria Monday-Wednesday.

&&

.HYDROLOGY...
Cut off low pressure will support numerous- widespread showers
and thunderstorms this afternoon into tomorrow. An anomalously
moist airmass (precipitable water aoa 2 inches) will support
copious rainfall, but saturated soils indicate that flooding
will be a concern. Rainfall rates and repeated storms suggest
that rises may be rapid. A Flash FLood Watch has been posted for
the entire area this afternoon and tonight.

Given expected widespread significant rain and runoff, River Flood
Watches have been posted for many area main stem rivers. Anyone
living in or near flood prone areas should be prepared to move to
higher ground quickly this weekend. Main stem rivers will continue
to see significant rises into early next week as water runs off.

&&

.TIDES/COASTAL FLOODING...
Freshwater runoff may result in minor/moderate flooding at
Georgetown in the Monday night-Tuesday time frame. This will be
contingent on forecast rainfall, which may have significant
changes over the next day or two.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Flash Flood Watch through late tonight for DCZ001.
MD...Flash Flood Watch through late tonight for MDZ003>006-011-013-
     014-016>018-501>508.
VA...Flash Flood Watch through late tonight for VAZ025>031-036>040-
     050>057-501>508.
WV...Flash Flood Watch through late tonight for WVZ050>053-055-
     501>506.
MARINE...Small Craft Advisory from 2 AM to 8 PM EDT Sunday for
     ANZ530>534-537>543.

&&

SYNOPSIS...HTS
NEAR TERM...HTS/KLW
SHORT TERM...HTS/KLW
LONG TERM...KJP
AVIATION...KLW/KJP
MARINE...KLW/KJP
HYDROLOGY...KLW
TIDES/COASTAL FLOODING...KLW

Hazardous Weather Outlook
National Weather Service Baltimore MD/Washington DC
505 AM EDT Sat Jun 2 2018

ANZ530>543-DCZ001-MDZ011-013-014-016>018-508-VAZ052>057-030915-
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-Southern Baltimore-Prince Georges-
Anne Arundel-Charles-St. Marys-Calvert-Southeast Harford-
Prince William/Manassas/Manassas Park-Fairfax-
Arlington/Falls Church/Alexandria-Stafford-Spotsylvania-
King George-
505 AM EDT Sat Jun 2 2018

This Hazardous Weather Outlook is for the Maryland portion of the
Chesapeake Bay, Tidal Potomac River, and adjacent counties in
central Maryland and northern Virginia as well as the District of
Columbia.

.DAY ONE...Today and Tonight

A Flash Flood Watch is in effect for the entire area through late
tonight.

In addition, River Flood Watches have been posted for many sites
along main stem rivers.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Multiple rounds of showers will continue into Sunday. These
showers will be slow moving across wet ground and capable of
producing additional localized heavy rainfall. This may result in
additional or worsening flooding.

The River Flood Watches continue until further notice.

.SPOTTER INFORMATION STATEMENT...

Skywarn spotters should report any flooding or precipitation
totals per established protocols.

MDZ003>006-501>507-VAZ025>031-036>040-050-051-501>508-WVZ050>053-
055-501>506-030915-
Washington-Frederick MD-Carroll-Northern Baltimore-
Extreme Western Allegany-Central and Eastern Allegany-
Northwest Montgomery-Central and Southeast Montgomery-
Northwest Howard-Central and Southeast Howard-Northwest Harford-
Augusta-Rockingham-Shenandoah-Frederick VA-Page-Warren-Clarke-
Nelson-Albemarle-Greene-Madison-Rappahannock-Orange-Culpeper-
Northern Fauquier-Southern Fauquier-Western Highland-
Eastern Highland-Western Loudoun-Eastern Loudoun-
Northern Virginia Blue Ridge-Central Virginia Blue Ridge-
Hampshire-Morgan-Berkeley-Jefferson-Hardy-Western Grant-
Eastern Grant-Western Mineral-Eastern Mineral-Western Pendleton-
Eastern Pendleton-
505 AM EDT Sat Jun 2 2018

This Hazardous Weather Outlook is for eastern West Virginia,
northern and central Virginia, and central and western Maryland
with the exception of Garrett County.

.DAY ONE...Today and Tonight

A Flash Flood Watch is in effect for the entire area through late
tonight.

In addition, River Flood Watches have been posted for many sites
along main stem rivers.

.DAYS TWO THROUGH SEVEN...Sunday through Friday

Multiple rounds of showers will continue into Sunday. These
showers will be slow moving across wet ground and capable of
producing additional localized heavy rainfall. This may result in
additional or worsening flooding.

The River Flood Watches continue until further notice.

.SPOTTER INFORMATION STATEMENT...

Skywarn spotters should report any flooding or precipitation
totals per established protocols.

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
840 AM EDT SAT JUN 02 2018

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

0715 AM     FLOOD            5 SE PAW PAW            39.48N  78.38W
06/02/2018                   MORGAN             WV   911 CALL CENTER

            ROUTE 9 REMAINS FLOODED NEAR LARGENT

&&

EVENT NUMBER LWX1800541

ADS

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE BALTIMORE MD/WASHINGTON DC
842 AM EDT SAT JUN 02 2018

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

0842 AM     FLOOD            2 ENE JOHNSONTOWN       39.59N  78.00W
06/02/2018                   BERKELEY           WV   911 CALL CENTER

            ALLENSTOWN ROAD REMAINS FLOODED NEAR BACK CREEK

&&

EVENT NUMBER LWX1800542

ADS

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