Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 191859

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
259 PM EDT Sat May 19 2018

.SYNOPSIS...A slow moving warm front will move through the area
tonight. A cold front will cross the area on Sunday and stall to
the south on Monday before returning north on Tuesday.



Front has been lifting north through southern MD today where
new convection has fired up. New convection is also developing
west of the Appalachians over northern WV and southwest PA. The
area in southern MD should remain the most active through early
this evening with the convection over WV and PA possibly
approaching the Appalachian region mid evening. Southern MD
remains the most vulnerable area to flash flooding because of
all the rain that they had the past two days(6+ inches in some
places in St. Marys county). Rest of the area, the threat of new
or additional flooding has greatly diminished, so will be
cancelling the flood watch for a large part of the fct area
except for areas south of the Capital Beltway and King George
VA. Showers will tend to dissipate after midnight.



Should definitely see clouds break tomorrow with some sunshine
as winds turn from the southwest. Scattered afternoon/early
evening showers and t-storms are anticipated as cdfnt from the
OH valley crosses the area. Southern MD will be again the most
vulnerable area for flash flooding due to saturated soils and is
the area where models show the best moisture convergence. Faster
cell motion and mid-level winds nearly perpendicular to sfc
front should keep cells moving and minimize flash flooding

The front will be returning north again on Monday with
additional showers expected especially west of the Blue Ridge.



A chance of showers and thunderstorms will continue into Tuesday,
with a front draped across our southern zones. Temperatures will be
in the upper 70`s to low 80`s across the region, depending on the
exact location of the front. A chance of showers and thunderstorms
again on Wednesday, as a stronger low pressure system passes by to
our north. A little more agreement in the latest guidance as far as
frontal passage timing. The front should be through the area by
Wednesday night. Temperatures will remain in the low 80`s. Nor a lot
of precipitation expected during these two days, with maybe a
quarter of an inch of additional precipitation. However, higher
amounts are possible in areas that experience thunderstorms.

High pressure builds into the area Thursday, and quickly slides off
the east coast by Friday. Expect dry conditions during this period,
along with seasonable temperatures.



LIFR/IFR conditions tonight improving rapidly to VFR after 14Z
Sun as winds turn from the southwest. A chance of t-storm at all
TAF sites Sun.

Mainly VFR conditions forecast Tuesday and Wednesday, with the only
threat of sub-VFR conditions being a passing shower over the
terminals. Winds will be light and favor a southwesterly trajectory
on Tuesday, turning Westerly on Wednesday.



Winds will strengthen some tonight into Sun morning mainly over
the southern waters and begin to diminish Sun afternoon. SCA
conditions are expected tonight with SCA conditions possible
again Tue afternoon into Wednesday.

Generally sub-SCA conditions expected Tuesday and Wednesday, with
winds remaining light. A frontal boundary will cross the waters on
Wednesday, bringing the chance for some showers and thunderstorms.
This could create periodic gusty winds on the waters.



Water levels are running around 1 to 2 ft above astronomical
predictions on the Bay and lower tidal Potomac. Minor coastal
flooding is possible at Annapolis and Straits Point tonight and

For the upper tidal Potomac around Washington DC and Alexandria,
fresh water piling down from the Potomac River will cause
anomalies to continue increasing tonight. This will affect
Georgetown more than southwest DC or Alexandria.
-For Alexandria: An advisory is in effect through 4 PM Sunday.

-For Washington DC: Georgetown will be the driver due to the
 freshwater contribution, where moderate flooding is forecast
 for five cycles (with levels not dropping below minor through
 Sunday night). At the southwest waterfront, best confidence for
 moderate flooding will be near high tide tonight through
 Sunday; subsequent cycles may only be minor flooding. A Coastal
 Flood Warning is in effect for Washington DC through Sunday
 and it may need to be extended through Monday. A Coastal Flood
 Advisory is in effect for Alexandria through 4PM Sunday, and it
 may need to be extended through Monday as well.


DC...Coastal Flood Warning until 10 PM EDT Sunday for DCZ001.
MD...Flood Watch until 8 PM EDT this evening for MDZ013-014-016>018.
VA...Flood Watch until 8 PM EDT this evening for VAZ055>057.
     Coastal Flood Advisory until 4 PM EDT Sunday for VAZ054.
MARINE...Small Craft Advisory until 6 PM EDT Sunday for ANZ530>543.


TIDES/COASTAL FLOODING...LFR is the U.S. government's official web portal to all federal, state and local government web resources and services.