Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 121937

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
237 PM EST Sun Nov 12 2017

A weak low pressure system will affect the region tonight into
Monday, followed by high pressure on Tuesday and Wednesday.
Another front will cross the area Wednesday night into Thursday
morning with high pressure moving back in for Friday.


Surface high pressure will continue shifting offshore through
the rest of today, with dry weather and light winds. Plenty of
high clouds are streaming overhead although some breaks of sun
can be found from the metros northward. Otherwise, temperatures
will be milder than yesterday but still below normal with highs
from the mid 40s to around 50F.

A weak low pressure system will track eastward through the Ohio
Valley this afternoon and evening, approaching the Appalachians
during the first of tonight. This primary low will weaken before
it crosses the mountain chain as a secondary low develops

Areas of light precipitation will develop and move into the
region late this evening, tonight, and into Monday morning.
Precipitation will likely be organized into two main batches,
one associated with the primary low that will push into WV and
western MD before weakening, and a second area is expected to
blossom this evening and spread northeastward across portions of
VA, DC, and into MD. While the majority of the area is expected
to receive mainly plain light rain, a few isolated locations
across northwestern VA, eastern WV, and western MD may drop to
32F at the surface due to wet-bulb cooling or some radiative
cooling this evening before precip arrives. Therefore some
spotty light freezing rain is possible, but impact expected to
be too minimal and isolated to warrant an advisory. In addition,
with very dry low levels this evening, as precipitation moves
in, wet-bulb cooling may lead to some sleet mixed in with the
rain across the northern tier of counties in MD and into
eastern WV. No impact with the rain/sleet mix anticipated. Rain
totals will range from a few hundredths in locations that split
the two main batches of precip, to up to a quarter of an inch in
southeast MD. Lows tonight in the 30s for most.


Low will exit the region rapidly on Monday with showers ending
across much of the area early Monday morning. After the rain
ends, low clouds likely to linger through the morning hours,
with breaks of sun by the afternoon. With some northwest flow
developing behind the low pressure system, some light upslope
rain/snow showers will be possible through the afternoon and
evening. Highs will range from the mid 40s to around 50F.

High pressure will begin to move into the area Monday night into
Tuesday, cresting overhead late Tuesday and Tuesday night. This
will lead to dry weather and fair skies. Lows Monday night and
Tuesday night in the 30s with highs Tuesday rising into the low


Two areas of low pressure will pass through the Great Lakes region
and into Canada. The first will bring a couple of cold fronts
through our region on Thu and again Fri with seasonable
temperatures. The second low is stronger and closer, but still NW of
us with its track. That second low will also bring a pair of cold
fronts through the Mid Atlantic over the weekend. Upslope snow
showers are possible over the highlands of the Appalachians as this
last system departs with cold flow out of the northwest Saturday
night into Sunday.


VFR expected for the remainder of the afternoon and evening with
mid/high clouds. Light rain and lowering ceilings will
overspread the region overnight, with MVFR likely developing
during the second half of the night and into Monday morning.
There is the possibility of some IFR at CHO. Winds will be
generally light and locally variable.

Conditions improve back to VFR by Monday afternoon with
north/northwest flow developing. VFR will continue through at
least Tuesday night with high pressure.

Expect mainly VFR conditions Wed thru the weekend. Exception
would be in any rain showers. Those are most likely Fri night
into Saturday.


Light winds will continue through the rest of today and tonight.
Winds will increase out of the north/northwest Monday and Monday
night behind a departing low pressure system, and winds may
approach SCA criteria, but will keep below for now. High
pressure returns Tuesday and Wednesday.

SCA conditions are possible Thursday behind a cold front.




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