Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 220159
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
859 PM EST Tue Feb 21 2017

.SYNOPSIS...
High pressure will move off the east coast tonight. A weak
disturbance will cross the area late tonight into Wednesday.
High pressure will be located off the southeast coast of the
United States late in the week. A cold front will pass through
the area this weekend.

&&

.NEAR TERM /THROUGH WEDNESDAY/...
The weather this evening features a cutoff low moving across the
southeastern United States and a northern stream disturbance
pulling north into Canada with a trailing trough into the
Northeastern US. The majority of the moisture associated with
the cutoff low will remain well to the south of the region while
the main forcing with the northern stream disturbance is well
to the north. That being said, enough interaction will occur to
bring a few light rain showers to the region late tonight and
into Wednesday morning, mainly south of the DC Metro region.
Otherwise, plenty of high cloud cover with cutoff low pumping
warm, moist air in aloft. Lows tonight generally 40-45F.

The upper-level disturbance will move off to the east by
Wednesday afternoon and subsidence behind this system should
allow for some sunshine, especially north. A southerly flow
around high pressure over the Atlantic along with the sunshine
will cause more unusually warm conditions. Leaned toward the
higher guidance or even above based on temperatures aloft and
mixing potential...but did tweak temps down a few degrees across
central Virginia where cloud cover may hang on a bit longer.
Max temps will be in the mid to upper 60s across most
areas...but much cooler (50`s) along the shore of the Bay and
along the ridge tops of the Potomac Highlands.

&&

.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
High pressure will remain over the Atlantic Wednesday night
through Thursday night while upper-level ridging builds
overhead. A southerly flow along with sunshine will result in
unusually warm condtions for this time of year. Max temps
Thursday are expected to be well into the 70s for most
areas...but cooler (50s-60s) along the shore of the Bay and in
the ridges. Near record warmth is possible during this time. See
the climo section below.

Very mild conditions are expected for both Wednesday night and
Thursday night...but with increased moisture there will likely
be areas of fog. Some fog may be locally dense.

A couple popup showers are possible Thursday afternoon due to
limited instability from daytime heating. However...coverage
will be widely scattered or isolated and much of the time should
be dry.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
Dry conditions expected for Friday with southerly
flow over our region and high temperatures in the 60s and 70s.
Deep  low pressure moves across the Great Lakes and its
associated cold front moves across the Mid-Atlantic on
Saturday... showers and thunderstorms likely. Dry conditions
return Sunday as high pressure builds behind the front.
Shortwave trough could bring showers over our CWA on Sunday
night, followed by dry conditions on Monday. Frontal boundary
could increase PoPs again for Tuesday.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
Predominantly VFR conditions expected for tonight into Wednesday
morning. A few showers are possible...mainly KCHO.

High pressure will build to our south and east for later
Wednesday through Thursday night. Areas of fog are possible
Wednesday night into Thursday and again Thursday night into
Friday. Fog may be locally dense with IFR/sub-IFR conditions
possible.

Dry/VFR conditions expected for later Friday before a cold
front approaches the area on Saturday... with showers and
thunderstorms possible into Saturday. Sub-VFR conditions
possible Friday night into Saturday at moments. Gusty winds
expected Friday night into Sunday.

&&

.MARINE...
High pressure will remain off the coast through Thursday night.
A southerly flow is expected during this time...but wind speeds
should remain below SCA criteria.

Dry conditions expected for Friday before a cold front
moves across the Mid-Atlantic on Saturday. Showers and thunderstorms
possible. Gusty winds expected Friday night into Sunday, with
SCA conditions likely.

&&

.CLIMATE...
Did a check to see how warm it has been both for meteorological
winter and since Feb 1 at the three major airports in terms of
ranking (average temp): The statistics below are from February
1st through February 20th.

        Since Dec 1      Since Feb 1
DCA     5th warmest      2nd warmest
BWI     14th warmest     13th warmest
IAD     2nd warmest      2nd warmest

Unseasonably warm temperatures are expected during the second
half of the week. Below are record daily high maximum and high
minimum temperature values for the 22nd through 24th (Wednesday
through Friday).

February 22nd
DCA    77 (1874)    60 (1874)
BWI    74 (1874)    51 (1874)
IAD    71 (1991)    52 (1981)

February 23rd
DCA    78 (1874)    51 (1922)
BWI    78 (1874)    52 (1874)
IAD    73 (1985)    51 (1975)

February 24th
DCA    78 (1985)    52 (1975)
BWI    79 (1985)    55 (1985)
IAD    79 (1985)    53 (1985)

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...BJL
NEAR TERM...BJL/MM
SHORT TERM...BJL
LONG TERM...IMR
AVIATION...BJL/MM/IMR
MARINE...BJL/MM/IMR
CLIMATE...DFH


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