Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 180231

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1031 PM EDT Wed Aug 17 2016

A weak cold front will gradually move south of the area through
Friday before dissipating. Another cold front will cross the
area early next week. High pressure returns for the middle of next


Update at 1030 PM to remove flash flood watch from the region. As
convection shifts eastward over the next couple of hours, rainfall
rates will lessen and no new additional flooding is anticipated
outside of warned areas.

Previous Discussion from 930 PM...
Activity as of the 9 PM hour is pretty much centered around two
distinct cold- pool driven convective systems. Primary system
which tracked across central Virginia now pushing through the I-95
corridor and will continue to push northeastward through the
evening hours. Second system is moving in from the southwest
towards King George County, the Potomac, and southern Maryland.
Severe threat exists with these over the next 1-2 hours before
gradually subsiding as they move northeastward and into a lower
CAPE environment. Flash flood concern remains as well with
multiple training thunderstorms, high rain rates, and high
efficiency rain processes.

Activity should diminish (at least to showers) by later tonight
as the main wave/vort max moves to the east. Lows in the upper 60s
to mid 70s.


Deep moisture will shunt south of most of the area Thursday with
WNW flow establishing. This will lead to slightly drier and cooler
air. However, the washed out boundary will not be far away with
potential for weak disturbances in the flow, so the best chance of
a shower and storm will be across the south.

Had to introduce POPs a little to the north on Friday, as there
are some indications a wave could pass along the front to the
south and result in a chance of showers and storms by afternoon or


High pressure will build to the north Friday night. Drier and
slightly cooler, yet seasonable, air will funnel southward into our
region. We can`t rule out a scattered shower Friday night due to a
few week disturbances that may try to sneak under the building high
pressure. Most of the activity will be across the Virginia Piedmont
or lower Southern Maryland.

The area of high pressure will weaken some over our region Saturday
and Saturday night, allowing for additional weak disturbances to
move in from the west and bring us a chance for additional showers
or perhaps a thunderstorm.

A moderate cold front is expected to move slowly eastward across the
Great Lakes region Sunday. This front could spawn a few
thunderstorms, mainly in the afternoon and along and west of the
Blue Ridge Mountains.

Showers and thunderstorms could linger Sunday night and Monday as the
front moves toward the Chesapeake Bay and possible stalls just east
of the bay.

High pressure will build in behind the front Monday night and linger
through Wednesday. Drier air and slightly cooler temperatures are


Main aviation weather threat of strong to severe thunderstorms
will continue through 04Z at DCA/BWI/MTN. Localized wind gusts up
to about 40 knots and brief reductions to 1SM or less in heavy
rain possible in the stronger thunderstorms. After 04Z, areas of
showers will continue overnight. Conditions improve to mainly VFR.
There may be areas of fog overnight as well, but coverage and
density in question, so left out for now.

A stray storm may cross near CHO both Thursday and Friday, but
otherwise VFR should prevail.

VFR conditions Friday night through Saturday night. Winds light
and variable.


Main threat will be thunderstorms and associated Special Marine
Warnings for gusty/damaging winds through midnight. Winds after
midnight generally westerly 5-15 knots.

W to NW flow will continue through Friday, generally 10 kt or
less. While a stray storm can`t be ruled out on southern waters,
coverage will be much less than today.

No marine hazards expected Friday night through Saturday night.




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