Area Forecast Discussion
Issued by NWS Sterling, VA

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974
FXUS61 KLWX 230152 AAA
AFDLWX

Area Forecast Discussion...UPDATED
National Weather Service Baltimore MD/Washington DC
852 PM EST Sun Jan 22 2017

.SYNOPSIS...
Low pressure will impact the area through Monday before moving
away Tuesday. A cold front will pass through the area Wednesday
into Wednesday night and an upper-level trough may build overhead
for the end of the week.

&&

.NEAR TERM /THROUGH MONDAY/...

Heights will fall during the next 24 hrs as a strong upper air
system deepens as it tracks from the Gulf coast states to near
Cape Hatteras. An accompanying sfc low over north Georgia will
move off of the mid-Atlc coast by midnight Mon night. Increasing
large scale ascent for upward vertical motion will result in
periods of rain tonight into Monday with the heaviest rains
between 12Z-18Z Mon when strongest easterly upslope winds are
expected. 1-1.5 inches of rain are expected with possible higher
totals over the eastern slopes of the Blue Ridge. Rain will also
start to mix with snow at the highest elevations (> 3kft) of the
Potomac highlands as air cools down as upper level low passes to
the south.

In addition to the rain, tightening pressure gradient will result
in strong gusty east winds with strongest winds expected in the
12Z-18Z time frame. A wind advisory is in effect for counties
adjacent to the Chesapeake Bay and as far west as Frederick county
MD.

&&

.SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/...
Marginal temperatures and warmer air aloft will keep snow totals
down across the higher elevations of the Allegheny Front. Around
an inch of snow accumulation is possible.

An upper level low will continue to spin across the region Monday
night into Tuesday and rain showers are expected. Winds will
become northwest Tuesday and rain showers will taper off. Dry air
will move into the region and the sun should come out by Tuesday
afternoon. Gusty winds up to 30 mph expected Tuesday afternoon due
to the pressure gradient.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Dry conditions expected Wednesday as upper ridge axis to our east
continues to move away, before a cold front moves across the
region Wednesday night. Looks like moisture will be limited with
this front, therefore not much precipitation is anticipated.

Extensive upper level trough and westerly/northwesterly flow could
bring persistent upslope precipitation in the form of snow
showers from Thursday and into Sunday... mainly over the Allegheny
Front... with maybe some showers reaching east of the mountains.

Warmest day of this period is Wednesday with high temperatures in
the 50s and 60s... followed by a drop in the temperatures of 10 to
20 degrees for the second half of the week and into Sunday.

&&

.AVIATION /01Z MONDAY THROUGH FRIDAY/...
IFR/Sub-IFR conditions will continue through the next 24-36
hours. RA will increase in intensity tonight and Monday. Although
cigs may flirt with MVFR due RA and stronger winds in the cloud
layer...Vsbys will likely drop to IFR/SUB- IFR during the heavy
rain but due to uncertainty with timing did not add to TAF. Winds
rapidly increase late tonight through Monday afternoon with the
strongest gusts expected Monday morning and at BWI/MTN/DCA. Gusts
may reach 45 kts at times. Further south and east gusts up to
30-35 kts expected.

Flight restrictions will continue Monday-Monday night. Gusty winds
expected Tuesday afternoon.

Dry conditions expected Wednesday before a cold front moves
across Wednesday night... with limited precipitation associated to
it. An upper level disturbance and west/northwest winds will bring
cooler conditions for Thursday and Friday with possible isolated
showers over our area. Mainly VFR conditions expected Wednesday
through Friday, with possible sub-VFR conditions Wednesday night.
Breezy conditions expected over higher elevations through this
period.

&&

.MARINE...
Low pressure will approach the waters through this evening. Winds
will gradually strengthen overnight.

The pressure gradient will rapidly strengthen late tonight into
early Monday morning before gradually dissipating from south to
north later Monday. A Gale Warning is in effect for the waters
from late tonight through Monday. East to northeast winds will
gust around 35 to 40 knots during this time.

A Small Craft Advisory will likely be needed for portions of the
waters Monday night as the low slowly moves away from the area.
Gusty NW winds exceeding SCA criteria remain Tuesday behind
departing low pressure system. Winds slacken late Tuesday as
influence from low wanes. Mostly dry cold front crosses the waters
late Wednesday into Thursday...with gusty winds possibly to SCA
criteria behind it Thursday afternoon.

Dry conditions expected Wednesday before a cold front moves
across Wednesday night... with limited precipitation associated to
it. An upper level disturbance and west/northwest winds will bring
cooler conditions for Thursday and Friday with possible isolated
showers over our area. Breezy conditions expected during this
period, possibly needing a small craft advisory.

&&

.TIDES/COASTAL FLOODING...
Persistent easterly flow will increase the risk for minor tidal
flooding during high tide cycles beginning Monday afternoon and
lasting into early parts of Tuesday morning (especially at
Annapolis, Solomons, and Straits). Developing westerly flow should
allow for some decrease in anamolies later Tuesday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Wind Advisory from 5 AM to 4 PM EST Monday for DCZ001.
MD...Wind Advisory from 5 AM to 4 PM EST Monday for MDZ004>006-011-
     013-014-016>018-503>508.
VA...Wind Advisory from 1 AM to 10 AM EST Monday for VAZ507-508.
     Wind Advisory from 5 AM to 4 PM EST Monday for VAZ053-054.
WV...None.
MARINE...Small Craft Advisory until 1 AM EST Monday for ANZ530>543.
     Gale Warning from 1 AM to 6 PM EST Monday for ANZ530>543.

&&

$$
SYNOPSIS...HSK
NEAR TERM...LFR
SHORT TERM...BJL/HSK
LONG TERM...IMR
AVIATION...BJL/HSK/IMR
MARINE...BJL/HSK/IMR
TIDES/COASTAL FLOODING...HSK



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