Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 180226

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
926 PM EST Wed Jan 17 2018

A cold front will move offshore tonight as low pressure off the
Carolina coast moves northeastward over the western Atlantic.
High pressure will build south of the area through the weekend.
A cold front may approach the area early next week.


Temperatures this evening have dropped quickly in to the teens
across our northern and western zones where skies are clear,
winds have slackened a bit, and a snowpack exists. After seeing
some decreasing in cloud coverage earlier this evening, clouds
have filtered back in from the south over the DC metro area
southward, likely in response to the mid to upper level trough
swinging through our area. Low pressure developing off the
Carolina coast overnight will deepen and race off to the east
northeast over the Atlantic as the aforementioned trough moves
east of our region. This will allow skies to clear for the
entire CWA, except along the western Allegheny front, as
temperatures bottom out in the teens for most, and near 20
degrees in the city centers.

With gusty northwest winds overnight, but not as gusty as
earlier today, wind chills will dip in to the single digits to
below zero across the higher elevations and ridgetops. The
ridgetops are expected to see wind chills of -10 to -20 tonight
into Thursday morning, and a Wind Chill Advisory is in effect
for these areas.

Winds turn more westerly as strong warming commences aloft
Thursday (850 mb temperatures rise from -5 to +5 C in about 12
hours). Despite this advection, dry W flow and subsidence
behind an upper low to the east likely keep the region mainly
sunny Thursday. Downsloping winds could push temperatures in the
lowlands well into the 40s.


Undercut most guidance for temperatures Thursday night with clear
skies and light winds and dew points still in the teens. BUFKIT
soundings imply de-coupling at our usual ideal radiational cooling
spots. A shortwave passing to the north could result in a modest
increase in high clouds Friday, but no precipitation is expected.

The moderating trend in temperatures will continue Friday with highs
nearing 50 in many places. We will still be under the influence of
high pressure, though, so with mainly clear skies and light winds
Friday night, temperatures should again drop into the 20s.


High pressure will continue to settle south of the region over the
weekend. A draw of milder air from the south will allow for
temperatures to at least reach the 50s. There could be a couple of
rain showers in the western mountains as a weak front moves west to
east Saturday night into Sunday.

High pressure will move east Monday. A cold front will approach from
the west and bring a chance of rain showers, mainly in the west and
northern areas during the day. By Monday night, the rain shower
threat spreads west to east. High temperatures likely reach the 50s
once again.

Cooler air will move into the region behind the system on Tuesday,
with a decreasing chance of rain as high pressure builds back into
the region. Highs will be in the 30s and 40s.

Wednesday will be even cooler than Tuesday with high pressure
reinforcing itself across the region. Highs will be 40s near the Bay
but colder in the central and western areas.


Predominate VFR conditions forecast through Friday night as high
pressure builds across the Ark-La-Tex region and eastward in to
the southeast U.S. Northwest winds will abate a bit overnight,
but regain their gustiness (17-20kts) Thursday morning, veering
more westerly and diminishing to around 10 knots through

VFR conditions Saturday through Sunday. Sub-VFR possible by Monday
as a cold front approaches from the west. Winds light and
southwesterly Saturday into Monday before increasing.


In the wake of the frontal passage earlier today, gusty
northwest winds have prevailed over our waters, resulting in SCA
headlines. This gustiness will remain over the open waters
overnight, before SCA gusts return for all waters during the day
on Thursday.

Winds should become light through Friday, and even though there
may be a bit of a gradient at times between high pressure to
the south and a shortwave passing to the north, waters will be
cooler than the air and that should preclude mixing/SCA gusts.

No marine hazards expected Saturday through Sunday night. Winds
southwest to west 5 to 10 knots each period.


MD...Wind Chill Advisory until 9 AM EST Thursday for MDZ501.
VA...Wind Chill Advisory until 9 AM EST Thursday for VAZ503-504-507-
WV...Wind Chill Advisory until 9 AM EST Thursday for WVZ501-503-505-
MARINE...Small Craft Advisory until midnight EST tonight for ANZ530-531-
     Small Craft Advisory from 8 AM to 4 PM EST Thursday for ANZ530-
     Small Craft Advisory until 4 PM EST Thursday for ANZ532>534-


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