Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 220222 AAA

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
922 PM EST Tue Nov 21 2017

A cold front will pass through tonight into early Wednesday,
while weak low pressure moves up the coast. High pressure will
build back overhead later Wednesday through Thanksgiving Day.
High pressure will be overhead Friday. A front approaches from
the west on Saturday, High pressure builds later on Sunday and
will remain in control through Tuesday.



Light rain is expected to develop closer to midnight as forcing
for ascent increases as weak low moves up the coast. Looking
generally at a quarter inch or less south and east of I-95 with
perhaps just a trace over the nw DC suburbs.

A period of upslope snow showers are expected late tonight into
Wed morning behind the cold front for locations along/west of
the Allegheny Highlands. Accumulations should be half inch or
less since moisture will be limited...but this may cause
slippery conditions by the early morning hours Wednesday.


The cold front will move off to the south and east early
Wednesday morning. Canadian high pressure will approach from the
north and west and a northwest flow ahead of the high will usher
in drier and chillier conditions. Max temps will hold in the 40s
for most locations north and west of Interstate 95 and in the
lower to middle 50s farther south and east.

High pressure will build overhead Wednesday night...bringing dry
and cold conditions. Min temps will drop into the 20s for most
areas, except lower 30s downtown DC/Balt. High pressure will
remain overhead Thanksgiving Day through Thanksgiving
night...bringing more dry and chilly conditions.


High pressure will be overhead Friday, keeping dry conditions
over our region, before it moves offshore late on Friday. A
front approaches from the west on Saturday, as upper trough
deepens over the eastern CONUS. PoPs increases with this
boundary on Saturday, but deterministic guidance and GEFS are
not too aggressive with precipitation over our CWA. At the same
time a low pressure system will develop off of the southeast
Atlantic coast but it is expected to stay offshore with little
to no impacts to our area.

Upslope showers expected on Sunday with the northwest flow and upper
trough axis moving through our area. Surface high pressure builds
later on Sunday and will remain in control through Tuesday.


A cold front will cross late tonight. A few showers cannot be
ruled out (especially for DCA/BWI/MTN)...but any precipitation
amounts will be light. MVFR conditions are expected late tonight
into early Wed, most prolonged for DCA/BWI/MTN. Northwest winds
will develop behind the cold front early Wednesday morning and
gusts around 20 to 25 knots are expected for most of Wednesday
behind the cold front.

VFR conditions expected Wednesday into early Saturday.
Precipitation possible later on Saturday as a cold front moves
trough our area. Dry/VFR conditions return on Sunday.


Winds will decrease overnight as the gradient relaxes. Will
probably be cancelling SCA for tonight soon as winds have
already diminished. A cold front will pass through early
Wednesday morning and northwest winds will increase behind the
boundary with gusts 25 to 30 knots most likely. An SCA is in
effect for the waters.

High pressure will build over the waters for Wednesday night
through Thursday night. An SCA was extended through Wed night
for most of the Bay and lower Potomac.

Winds are expected to stay less than 20 kts Friday into
Saturday night. Winds will increase on Sunday as low pressure
moves NE offshore the Delmarva Peninsula, therefore, a small
craft advisory is anticipated on Sunday.


MARINE...Small Craft Advisory until midnight EST tonight for ANZ530>534-
     Small Craft Advisory from 6 AM Wednesday to 6 AM EST Thursday
     for ANZ531>534-537-539>541-543.
     Small Craft Advisory from 6 AM to 6 PM EST Wednesday for


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