Area Forecast Discussion
Issued by NWS Sterling, VA-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
FXUS61 KLWX 270049
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
849 PM EDT Wed Oct 26 2016
High pressure will continue to drift east from the area through
tonight. A cold front will cross the area Thursday evening. High
pressure then builds over the area through Friday night. A
secondary cold front crosses the area this weekend with high
pressure then into at least the middle of next week.
.NEAR TERM /UNTIL 8 AM THURSDAY MORNING/...
-- Changed Discussion --Warm frontal zone continues to lift northeastward across the
region, with main surface front still back across WV and into the
Ohio Valley. A few light returns on radar have been noted across
northern Maryland, and while its mainly just mid level clouds, a
few light sprinkles are possible this evening as initial band
moves through. Otherwise, a mostly cloudy night expected for the
region, with low level flow turning easterly and eventually
south/southeasterly by morning. Most areas will remain dry
through the night, however some light rain showers are possible in
northern areas towards morning as precip breaks out in zone of
warm air advection along strengthening warm front, although bulk
of it should remain north across Pennsylvania. Lows will reach the
40s for most.
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.SHORT TERM /8 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/...
Low pressure develops as it moves east across the Upper Midwest
tonight and the eastern Great Lakes Thursday. The associated cold
front crosses the area Thursday evening with prefrontal rain
showers crossing the area from the west from the late morning to
the late afternoon. Likely PoPs were reserved for roughly north of
the Potomac River where greater convergence occurs into the
afternoon. Guidance consensus has activity developing/enhancing
east of I-95 in the late afternoon/early evening. This could
develop into a line with gusty showers for southern Maryland into
the evening hours. Expect generally a quarter inch QPF north of
the Potomac (maybe a tenth south) with perhaps half an inch for
Upslope rain showers look limited with likely PoPs decreasing to
chance from afternoon to evening.
Gusty winds accompany the cold front with an abrupt shift from
south to west. Magnitude is generally 20 mph with gusts to 30 mph.
Higher gusts possible in convective showers, particularly in
Max temps Thursday mid 50s along the Mason-Dixon, then low to mid
60s across the rest of the CWA. However, development of an in-situ
cold air damming tonight would result in lower temperatures,
Gusty NW winds diminish into Friday morning as 1025mb surface high
pressure builds directly overhead Friday evening. Temperatures
near normal with maxima around 60F and minima around 40F (inland).
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Falling heights attempting to descend out of eastern Canada will be
competing with a building ridge over the southeastern United States
over the weekend and into much of next week. At the moment, it
appears the ridge to the south will win out. This will result in a
warmer and drier than normal pattern over the Mid-Atlantic.
Over time, the ridging to the south begins to slowly retreat
westward which may allow for falling heights and increasing
precipitation chances by the second half of next week.
.AVIATION /01Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --Generally VFR expected through the TAF period. However, a warm
front developing over PA tonight and a cold front crossing
Thursday evening brings a risk for showers and low ceilings. A
light onshore flow develops across the area tonight, turning south
and increasing with gusts around 20 knots Thursday. West, then
northwest winds are expected behind the cold front. Showers may be
gusty, around 30 knots particularly east from I-95.
NW winds with gusts 20 knots into Friday morning before easing.
High pressure overhead Friday evening.
Mainly VFR expected over the weekend with southwesterly
flow around 10 knots Saturday becoming westerly behind a frontal
passage Saturday night into Sunday.
-- End Changed Discussion --
High pressure is just east of the area with a light east winds
developing. Wind shifts south overnight and increases ahead of a
cold front that crosses Thursday evening. SCA begins at 7am for
southern MD waters then expands at 10am for all waters with
southerly channeling of 20 to 25 knots. The northward progression
of winds may be slowed depending on the pressure pattern.
Likely showers late Thursday afternoon/evening associated with the
cold front. Strong gusts and special marine warnings possible
with the showers. Wind shifts W then NW behind the cold front
Thursday night with gusts around 25 kt into Friday morning.
Tranquil Friday evening under high pressure.
Southwesterly winds ahead of an approaching cold front
Saturday will likely result in Small Craft Advisory level wind gusts
over the waters. Winds should diminish by Sunday as the front stalls
over or just south of the waters.
Baltimore-Washington International Thurgood Marshall Airport
(BWI) near Baltimore MD dropped to 32 degrees this morning,
marking the first time since April 10th that the temperature has
dropped to freezing (low on April 10 was 26 degrees).
Washington Dulles International Airport (IAD) in northern Virginia
dropped to 30 degrees, which is the first time the temperature has
fallen below freezing there since April 14th (when the low was
Ronald Reagan National Airport near Washington DC (DCA) was 41
degrees this morning. Its last day at or below freezing was 31
degrees on April 10.
MARINE...Small Craft Advisory from 10 AM Thursday to 6 AM EDT Friday
Small Craft Advisory from 7 AM Thursday to 6 AM EDT Friday for