Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 220056 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
856 PM EDT Tue Mar 21 2017

.SYNOPSIS...
A strong cold front will cross the area tonight into early
Wednesday. High pressure will return Wednesday afternoon
through Thursday night. A warm front will cross the region
Friday. Low pressure may affect the area Sunday.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...

Strong southeastward-moving cold front passes through the area
overnight. Limited moisture will keep PoPs/amounts low...with
high-resolution ensemble guidance suggesting any showers would
remain along/south of I-66. Even where it does precipitate
amounts expected to be barely measurable. Primary impact to
sensible weather will be notable increase in northwesterly
winds behind the front...with gusts ~30 mph by morning.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH THURSDAY NIGHT/...
Winter-like conditions return once more for Wednesday and
Thursday with well below normal temperatures and gusty winds.
Despite near full sunshine Wednesday, 850 mb temperatures
dropping to near -10C will keep highs in the low to mid 40s for
most. Exception will be central Virginia where some locations
will near 50F due to later cold frontal passage and slightly
modified air. These are about 10-15 degrees below the
climatological normals. Gusty northwest winds expected as well
with gusts peaking 30-35 mph during the first half of the day.

Strong Canadian surface high pressure will then build in
Wednesday night and crest directly overhead Thursday morning.
This will lead to near ideal radiational cooling conditions with
clear skies and slackening winds. Thus quite a cold night
expected with lows in the teens and 20s.

High pressure will remain in control on Thursday with sunny
skies and light winds. Temperatures will remain below normal
however, with highs in the 40s for most.

The high will then slide offshore Thursday night with southerly
return flow developing. A warm front will also approach the
region from the west, and some light precip is possible after
midnight/towards morning, especially north/west. With cold
surface temperatures and overrunning warmer air, some light
mixed precipitation is possible north/west.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
High pressure will continue shifting offshore Friday and Friday
night, allowing for a return flow and milder air to develop for
the mid- Atlantic. Some light precipitation is possible Friday
morning with initial surge of warm/moist air aloft.

A cold front will sag across the Eastern Great Lakes Saturday before
stalling across our region Saturday night. A chance for rain showers
will develop during this period.

A storm system will develop along the west end of this stalled front
on Sunday, keeping the chance for rain showers in the region. The
storm system will move east along the front toward the East Coast.
The chance for rain showers linger throughout Sunday night.

More rain showers could develop along an associated cold front that
should also stall across our region on Monday. Temperatures will be
more seasonable.

A stalled front will push northward as a warm front Tuesday,
allowing for rain chances to linger into Tuesday night. Temperatures
will become milder.

&&

.AVIATION /01Z WEDNESDAY THROUGH SUNDAY/...
VFR and relatively light winds expected through the first half
of tonight with a mix of lingering scattered-broken cumulus and
increasing mid/high clouds. A strong cold front will then cross
late tonight and early Wednesday morning. An isolated rain
shower is possible ahead of the front. Winds become gusty out of
the northwest behind the front with gusts up to 30 knots
developing Wednesday morning. VFR conditions continue Wednesday
through Thursday with high pressure moving overhead. Gusty winds
diminish Wednesday night.

Some light precipitation is possible late Thursday night as a
warm front moves towards the region, but significant reductions
are not likely.

VFR conditions Friday and Friday night. MVFR to IFR conditions
with rain showers are possible Saturday into Sunday. Winds
becoming south 5 knots Friday. Winds southwest 5 to 10 knots
Friday night and Saturday. Winds southwest 10 to 15 knots
Saturday night.

&&

.MARINE...
Relatively light winds will continue into tonight. A strong
cold front will cross the waters later tonight and early
Wednesday morning. This will bring gusty north to northwest
winds, with gusts up to around 30 knots expected. Thus a SCA is
in effect for all waters beginning at midnight tonight. It is
possible that gale conditions are briefly observed Wednesday
morning. Gusty winds continue into Wednesday night, but a
slackening trend is expected. SCA ends for some locations at 8
PM Wednesday, but continues for the lower tidal Potomac and the
central Chesapeake until 4 AM Thursday.

Relatively light winds expected Thursday into Thursday night as
high pressure builds across the area. Wind direction will
become southerly by Thursday night.

Small craft advisory conditions possible Friday with increasing
southerly winds. Winds mainly sub-SCA Saturday and Sunday.

&&

.FIRE WEATHER...
Dry conditions and gusty winds expected Wednesday following
strong cold frontal passage. Relative humidities will drop into
the 20 to 30 percent range with sustained north to northwest
winds from 15 to 20 mph, gusting 30 to 35 mph. However,
following recent rain and snow, fuel moistures are currently
between 9 and 15 percent.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory from midnight tonight to 8 PM EDT
     Wednesday for ANZ530-531-535-536-538>540.
     Small Craft Advisory from midnight tonight to 4 AM EDT
     Thursday for ANZ532>534-537-541>543.

&&

$$
SYNOPSIS...MM
NEAR TERM...MM/MSE
SHORT TERM...MM
LONG TERM...KLW
AVIATION...MM/KLW
MARINE...MM/KLW
FIRE WEATHER...MM



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