Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 190148
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
848 PM EST Thu Jan 18 2018

.SYNOPSIS...
High pressure will build south of the area through the weekend.
A cold front will cross the area early next week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A 1031mb high pressure center resides over the Gulf Coast
states this evening, extending its northeastern flank over our
region. This expansive area of high pressure is responsible for
clear skies for most locations residing east of the Mississippi
River. Winds have been subdued for the last few hours and will
continue to trend light to calm across the much of the area
overnight. Combine this with clear skies, expect prime
radiational cooling conditions tonight. We`ve already seen some
of our favored radiational cooling locations dip in to the mid
to upper 20s early this evening. With dewpoints in the single
digits to low teens across the area, this leaves plenty of room
for temperatures to bottom out in the mid to upper teens for
most, with locations near our city centers holding in the low to
middle 20s. On going forecast is in good shape with no major
changes needed.


&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SATURDAY NIGHT/...
Warm advection should be underway Friday, with little tangible
weather. Aside from perhaps some high clouds, it will largely be a
temperature forecast. Readings should get into the 40s Friday
(without the winds) and 50s Saturday. Lows will drop into the 20s
Friday night and near freezing Saturday night.

As an upper disturbance tracks along the Gulf coast Saturday-
Saturday night, some moisture could spread north with isentropic
lift up the mountains. At this point, there is light qpf (at
best)...so PoPs are subsequently low (chance). Will need to keep an
eye on temperatures though. Believe that there will be enough warm
advection to preclude freezing rain, but a few GEFS ensemble members
do have subfreezing air just east of where the meager PoPs will be.
And deterministic output also depict a close call. PoPs are only for
the western fringe zones, and are only 20-30%, but did introduce
rain or freezing rain overnight...just in case.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
High pressure will be near the South Carolina coast Sunday, with a
warm front lifting northward to our west. An area of low pressure
will develop along the tail-end of this warm front over the central
Plains. The low is expected to move toward the Great Lakes region
Sunday night through Monday night. With that, the warm front will
bring us a chance for a rain showers along the Mason-Dixon region
and the Appalachian Front Sunday night and Monday. The increased
chance for rain showers will be Monday night with a cold front
passage. Temperatures will be above normal Sunday night through
Monday night. High temperatures could reach the 60s Monday ahead
of the cold front.

Rain showers could linger on Tuesday on the back side of the cold
front. Colder and drier air will move in behind the front as well.
Temperatures will be about 10 degrees cooler than the day before due
to frontal passage.

High pressure will regain control of the region with the chilly
January air but plenty of sunshine Wednesday through Thursday.

&&

.AVIATION /01Z FRIDAY THROUGH TUESDAY/...
VFR conditions will dominate heading in to the weekend. Light
winds forecast overnight in to Friday, remaining at 10 knots or
less, residing out of the west to southwest through Saturday
night.

VFR conditions continue Sunday through midday Monday. MVFR to
briefly IFR conditions possible with rain showers late Monday
and Monday night.

&&

.MARINE...
With a ridge of high pressure building over our region, light
winds will prevail overnight with no headlines expected. Wind flow
will back southwest Friday, and will remain there at 10 kt or
less through Monday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...None.

&&

$$
SYNOPSIS...HTS
NEAR TERM...BKF
SHORT TERM...HTS
LONG TERM...KLW
AVIATION...BKF/HTS/KLW
MARINE...BKF/HTS/KLW



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