Area Forecast Discussion
Issued by NWS Sterling, VA

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000
FXUS61 KLWX 122010
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
310 PM EST Sun Feb 12 2017

.SYNOPSIS...
Low pressure will rapidly strengthen near New England tonight
and Monday. High pressure will briefly return Tuesday. Another
cold front will pass through Wednesday. High pressure will
return for late in the week.

&&

.NEAR TERM /THROUGH MONDAY/...
Current surface analysis shows low pressure over western
Pennsylvania. A warm front extends southeastward from the low
across northern Virginia and southern Maryland, while a cold
front extends southwestward across West Virginia. Another cold
front is located over Michigan, Lake Michigan and Illinois. High
pressure dominates the central Plains, with another low pressure
over the Southwest.

Tonight, the main story is the two systems in the Northeast and
Great Lakes. They will phase near New England, resulting in one
large and explosively deepening low pressure which will result
in very gusty winds across our region. Guidance remains
relatively consistent with the wind threat, showing gusty winds
late this afternoon and this evening concentrated in
southwestern Virginia and eastern West Virginia, then a second
surge with the second cold front late this evening and a third
surge early Monday as winds aloft increase for a final time.
Thus, only a minor adjustment was made to the wind headlines
today, with the addition of several counties in eastern Virginia
and the northern Virginia Piedmont.

Right now, warm front extends across northern Virginia, with 40s
and low 50s north of it and temperatures near 80 south of it.
This front will try to approach DC but looks more likely to get
shunted eastward by the approaching cold front before it has a
chance to reach the district. In the warm sector, there is a
modest amount of instability and storms have developed to the
west in West Virginia, so included a slight risk of thunder
here. Over the next few hours, as the cold front passes, winds
will intesify over the first segment of the high wind warning,
while still not getting too strong further northeast.

Late this evening, the second cold front crosses the region. The
real wind surge across the remainder of the area will start at
this time. Latest short range guidance suggests some showers may
occur with the front as well, so included a slight chance
through the evening. Winds aloft really intensify near or after
midnight and lapse rates increase as well, so this is when the
headlines start for the majority of the metro. Still some
question just how much can mix down in the middle of the night,
but the potential for widespread 50+ kt gusts is certainly
there.

Upslope flow will also result in rain showers changing to snow
showers along the Allegheny Front. Right now, think that
accumulations will likely stay just below advisory levels, so
have not issued any winter weather headlines, but an inch or
two, perhaps an isolated total of 3, is certainly expected
overnight.

Right now, best wind surge across the metro seems to be most
likely during the morning Monday after the sun comes up, when
winds aloft will remain very strong (50-60 kts) and mixing
increases with insolation. As winds slowly diminish during the
day, gusts should start to drop off, but gusts to 40 knots or
more are still likely most of the day especially around the
metros. Otherwise, it should turn out mostly sunny as high
pressure slowly builds in, with cooler temperatures. Highs
mostly in the 40s with colder readings in the mountains.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
High pressure continues building in from the west Monday night
and pushes past the region to our south on Tuesday, so winds
will steadily diminish. Low pressure will then start approaching
from both the southwest and Great Lakes, so clouds will start
to increase later Tuesday. Some showers of rain or snow may
spread into northwestern areas Tuesday night with the Great
Lakes system, while rain could try to push into southern areas.
Right now however, Tuesday night looks dry across most of the
region, with lows mostly in the 30s.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
A cold front associated with low pressure over northern New
England will move through the Mid-Atlantic Wednesday. Rain
showers are possible ahead of the front but will likely be
confined to the south. Cold air advection will move into the
region behind the front and snow showers will be possible across
the Allegheny Front and Potomac Highlands. Breezy and cool
conditions expected Thursday into Thursday night. High pressure
builds into the region briefly Thursday night and winds will
become southerly into Friday causing temperatures to turn mild
Friday-Saturday.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
Warm front has played havoc with TAF`s today with IFR cigs at
BWI, MTN and MRB while VFR has dominated further south. As two
cold front cross the region late this afternoon and this
evening, the IFR should break for VFR conditions and that will
persist through Tuesday night. A stray thunderstorm can`t be
ruled out this afternoon and this evening at CHO. Winds will
quickly become the main story as gusts may reach 50 knots at
most terminals (CHO being the main exception where 35 knots is
more likely). Winds diminish Monday night with light winds
Tuesday.

Ceiling and visibility flight restrictions not expected Wednesday-
Thursday.

&&

.MARINE...
Developing strong low pressure will bring Storm Force Winds to
much of the bay and Gales to the remainder of the waters tonight
and Monday. Winds will begin to diminish Monday afternoon with
sub-SCA looking likely by Tuesday.

A cold front will cross the waters Wednesday leading to a wind
shift. SCA conditions are likely Wednesday-Thursday.

&&

.TIDES/COASTAL FLOODING...
Strong northwest winds will develop behind a cold front late
this evening and these winds will persist through Monday. Tidal
blowout conditions are likely...especially late tonight and
Monday with anomalies around 1 to 2 feet below normal possible.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...High Wind Warning from 11 PM this evening to 6 PM EST Monday
     for DCZ001.
MD...High Wind Warning until 3 PM EST Monday for MDZ501.
     Wind Advisory from 7 PM this evening to 3 PM EST Monday for
     MDZ003-502.
     Wind Advisory from 11 PM this evening to 6 PM EST Monday for
     MDZ016-017.
     High Wind Warning from 11 PM this evening to 6 PM EST Monday
     for MDZ004>006-011-013-014-018-503>508.
VA...High Wind Warning until 3 PM EST Monday for VAZ025-026-503-504-
     507-508.
     Wind Advisory from 7 PM this evening to 3 PM EST Monday for
     VAZ027>031.
     Wind Advisory from 11 PM this evening to 3 PM EST Monday for
     VAZ038>040-051-057.
     Wind Advisory from 11 PM this evening to 6 PM EST Monday for
     VAZ052-055-501-502.
     High Wind Warning from 11 PM this evening to 6 PM EST Monday
     for VAZ053-054-505-506.
WV...High Wind Warning until 3 PM EST Monday for WVZ501>503-505-506.
     Wind Advisory from 7 PM this evening to 3 PM EST Monday for
     WVZ050>053-055-504.
MARINE...Small Craft Advisory until 6 PM EST this evening for
     ANZ532>534-536-537-541-543.
     Storm Warning from 6 PM this evening to 6 PM EST Monday for
     ANZ530>533-535-538>541.
     Gale Warning from 6 PM this evening to 6 PM EST Monday for
     ANZ534-536-537-542-543.

&&

$$
SYNOPSIS...RCM
NEAR TERM...RCM
SHORT TERM...RCM
LONG TERM...HSK
AVIATION...HSK/RCM
MARINE...HSK/RCM
TIDES/COASTAL FLOODING...BJL/MM



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