Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 211420

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1020 AM EDT Sat Apr 21 2018

High pressure over the Great Lakes will slowly move east into
the Northeast U.S. by Sunday night. This high will move offshore
Monday. A low pressure system will bring unsettled weather to
the region Monday night through the middle of next week.


Other than a fairly thin veil of cirrus, skies are mostly clear
across the region thanks to broad high pressure over the Great
Lakes region. Winds are light and variable.

Quiet weather conditions expected much of this weekend as high
pressure remains in control and gradually builds to the east
from the Great Lakes to the Northeast U.S. Light winds and below
normal temperatures are expected as a result. Additional middle
and high clouds will move overhead this afternoon and linger
through tonight. High temperatures should reach the lower to
middle 60s this afternoon. With the additional middle level
clouds and increasing low level dewpoint temperatures, we don`t
anticipate freezing temperatures for a third night in a row
tonight, and in fact it looks like this morning may have been
the last freeze of the season for many areas, or at least for
while. Low temperatures will bottom out in the upper 30s to
lower 40s.


High pressure will continue to provide limited sunshine and
tranquil conditions Sunday into Sunday night. High temperatures
Sunday will reach the lower to middle 60s, while low
temperatures will drop down into the middle 40s and near 40 in
the western ridges and along the Mason-Dixon region. There could
be a sprinkle over the mountains, but it should generally be

As the high pressure moves offshore Monday, winds will become
more persistently from the southeast, bringing additional
moisture into the region. A cut-off low pressure system will
work its way up the East Coast from the Southeast U.S. to the
Carolinas Monday and Monday night. Some rain should begin to
overspread the region from southwest to northeast, beginning
with the central Shenandoah Valley. Temperatures Monday could be
just a few degrees below normal.


Unsettled weather conditions expected Tuesday into Wednesday as
low pressure over the southeastern U.S. and an upper level
cutoff low over TN/KY nears our region. Rain chances will be
increasing during the day on Tuesday from southwest to northeast
as low pressure spreads northeastward. Models trending to favor
the latter half of Tuesday before the rain moves in to the
metro areas, with our far southwestern zones seeing activity
pick up early Tuesday morning. Continued rain chances expected
to persist in to the day on Wednesday as weak surface low
pressure hovers near the Carolina coastline and mid level
troughing starts to dampen a bit. This low pressure area will
move off to the northeast during the day on Wednesday, bringing
a downward trend to shower activity across the region.

Another shortwave trough will approach from the west Wednesday
night and Thursday as surface low pressure passes to our west,
bringing additional moisture and isentropic lift across the
area. Some model differences remain with regards to the strength
of these features and ultimately the coverage/amount of rain
during this time period. The stubborn mid to upper level
troughing will hang around on Friday, as surface low pressure
passes to our north, and a cold front looks poised to move
through the Mid Atlantic region Friday night.

Below normal temperatures will be maintained Tuesday and
Wednesday with elevated moisture and increased cloud coverage,
with a return to near normal temperatures Thursday and Friday,
potentially breaking the 70 degree mark for portions of the area
to close out the work week.


VFR conditions expected through Monday with light and variable
winds, becoming southeast 5 to 10 knots by Monday afternoon.
MVFR conditions are possible at the CHO terminal Monday night
with some light rain approaching from the southwest.

Sub-VFR conditions expected Tuesday through Wednesday as a
broad area of low pressure will impact the terminals with
increasing rain chances. Heaviest rain and ultimately greatest
flight restrictions will likely occur Tuesday night into
Wednesday morning, where IFR/LIFR conditions will be possible.
Increasing easterly breezes are forecast Tuesday into Wednesday,
with gusts nearing 20 knots Tuesday. As the main area of low
pressure starts to pull away from the area Wednesday, winds will
abate a bit, backing out of the north northeast and turning
light, with MVFR VIS/CIGs likely persisting into Wednesday


No marine hazards expected through Monday morning. Winds will
be light and variable, becoming southeast around 10 knots by
Monday morning. Small craft advisory conditions may be possible
Monday afternoon and night. Winds southeast becoming east 10 to
15 knots with possible gusts up to 20 knots.

A broad area of low pressure will impact the waters Tuesday
into Wednesday, with SCA conditions likely during this time
period as a strong easterly flow develops across the area. As
low pressure starts to move off to the northeast on Wednesday,
sub-SCA conditions forecast to return for the latter half of the


Persistent onshore flow is expected to result in increased
tidal anomalies and possible coastal flooding during the middle
part of next week.




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