Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 221951

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

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.


A weak wedge of high pressure is across the Mid-Atlantic region
this afternoon. Low pressure has moved off the east coast. N-NE
winds will continue across the region through tonight. Low clouds
and patchy fog will persist into tonight. Rain is developing
across the region this afternoon and will continue to move
northward tonight. Light amounts are expected through tonight.

Low pressure will deepen across the SE states this evening and the
pressure gradient will become packed by midnight as the
approaching system pushes the wedge of high pressure to the north.
NE-E winds will strengthen across the region tonight becoming
strong by Monday morning. Gusty winds up to 50 mph are expected
across the Blue Ridge Mtns late tonight into Monday morning. A
wind advisory is in effect for the Blue Ridge mtns from 1AM to
10AM. As high pressure stays in place across northern New England
and the surface low migrates E-NE south of the outlook
area...winds will continue to strengthen with the greatest winds
across central Maryland and DC/Fairfax County. A wind advisory is
in effect for these locations including Washington DC and
Baltimore from 6AM to 4PM. The strongest across the metros will be
Monday morning.

As strong moisture advection occurs late tonight into
Monday...moderate to heavy rain is expected across the Mid-
Atlantic. Amounts will range from 1-1.5 inches with higher amounts
on the eastern slope of the Blue Ridge mountains where
enhancements due to upslope are expected. Amounts may reach 2-2.5
inches along the eastern slopes. Most of the soaking rain will
occur between 1AM-1PM Monday. Can not rule out any nuisance
flooding from poor drainage however widespread flooding is not
expected at this time. Please see hydrology section below for more
details. Due to the saturated ground and strong may be
easier for trees to come down.

The dry slot should enter the eastern half of the region by Monday
afternoon. This may cause convective showers and an isolated
thunderstorm to develop across southern Maryland and surrounding
waters. Rain will continue on the back side of the sfc low as it
moves off the east coast. Temperatures will slowly fall along the
Allegheny Front into Monday night and rain will likely change to
snow at higher elevations.


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.


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.

IFR/Sub-IFR conditions will continue through the next 24-36
hours. -RA is expected across the terminals this afternoon and
evening. 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


Low pressure will approach the waters through this evening. Winds
will gradually strengthen this afternoon through this evening. A
Small Craft Advisory is in effect for the Bay and lower Tidal
Potomac River this afternoon. Winds will continue to strengthen
tonight and SCA is in effect for all waters.

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.


Moderate to heavy rain is expected across the Mid-Atlantic region
late tonight into Monday afternoon. Widespread amounts will range
from 1-1.5 inches with locally higher amts along the eastern
slopes of the Blue Ridge Mtns. Rapid rises of rivers and streams
are expected however flooding is not anticipated at this time.

Amounts of 2-2.5 inches are possible and areas across the Central
Foothills such as the western portions of Nelson, Albemarle,
Greene, Madison. These areas should stay tuned to the forecast as
well as any flood outlooks and future watches and/or warnings.
Due to the recent dry stretch the ground should be able to handle
this amount of rain and therefore flood watches were not issued.

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.


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-
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.
MARINE...Small Craft Advisory until 1 AM EST Monday for ANZ530>534-
     Gale Warning from 1 AM to 6 PM EST Monday for ANZ530>543.
     Small Craft Advisory from 6 PM this evening to 1 AM EST Monday
     for ANZ535-536.


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