Forecast Discussion for Willowsford Farm and vicinity from the NWS in Sterling, Virginia

FXUS61 KLWX 111439

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
939 AM EST Wed Dec 11 2019

Canadian high pressure will build across the region today
through Thursday. A low pressure system will then develop in
the Gulf of Mexico and push northward across the eastern United
States Friday and Saturday, followed by another low pressure
system that will approach the region Monday into Tuesday.


The radar is now clear across the entire area, with the back
edge of the cloud cover nearly out of the area as well. Any snow
from this morning will quickly melt as mostly sunny skies are
expected today due to Canadian high pressure pushing towards
the area from the northwest. Highs today will be quite chilly,
only reaching the upper 30s to low 40s. With gusty winds also
present behind the front, wind chills will struggle to get above
freezing for much of the area as well.

High pressure will continue to build across the region tonight
into Thursday. The air mass is chilly, but not excessively or
unusually cold for this time of year, with readings perhaps
approaching 10 degrees below normal... a range which is quite
normal this time of year. Lows tonight may reach the teens in
the cold spots, so not even the coldest it has been so far this
year. Highs on Thursday should be a little cooler (mid to upper
30s), with strong high pressure (~1040mb) set up to the
northeast, which will continue to funnel cooler air into the


The Canadian high pressure will slide east off the coast
Thursday night as low pressure develops along the Gulf Coast,
then heads north. A wedge will remain, however, so cold air
damming looks likely, especially Friday morning. Warm advection
precip looks likely to overspread southwestern areas by mid-
morning Friday, with the rest of the region likely seeing at
least a bit of precip by day`s end. The early arrival presents
problems given the cold air mass in place, so freezing rain is a
significant risk along the I-64 and I-81 corridors that we
forecast for, stretching from Charlottesville to Staunton and
perhaps as far north as Martinsburg. Further north and east, it
appears more likely that temps will have a chance to rise above
freezing before precip arrives, resulting in mostly or all plain
rain. That all said, most precip Friday looks light, with the
more significant rain moving in Friday night after temperatures
are solidly above freezing (if only barely) across our entire
area. Below freezing lows Thursday night will lead to highs in
the 40s east of the mountains Friday, but 30s near I-81, with
temps staying fairly steady Friday night with the rain.


Low pressure near the Delmarva Peninsula will lift northward
into New England Saturday. Expect rain showers during the day.
As an associated front makes its way to the East Coast by
Saturday night, rain showers will taper to become more isolated.
Some upslope rain or snow showers will develop in the Potomac
Highlands in relation to the upper level low that is providing
support to the departing surface low.

Upslope snow showers could linger in the Potomac Highlands on
Sunday with a gusty northwest wind. Elsewhere, colder and drier
air will filter into the central and eastern zones in part to
high pressure.

By Sunday night into Monday, a developing warm front to our
southwest could bring us a chance for some light snow or light
rain. As the warm front lifts northward Monday night, this
wintry mix of snow and rain should become plain rain Tuesday
ahead of an approaching cold front and its affiliated surface
low pressure system. Milder air will be short-lived Tuesday
before a cold front brings a rush of colder air into the area
late Tuesday and Tuesday night. Upslope light snow and a chance
of snow showers to the east could evolve with the rush of cold
air Tuesday night.

High pressure will build in across the region on Wednesday.
Expect below average temperatures to develop and continue.


VFR conditions expected through Thursday night. Gusty northwest winds
at times today should relax later tonight. A period of freezing
rain is possible at CHO early Friday, then up towards MRB later
in the morning-midday, but otherwise, mainly rain is expected
Friday and Friday night. Cigs and vsby likely to drop to IFR at
times by Friday night with the rain.

MVFR conditions possible with rain showers Saturday. VFR
conditions Saturday night through Sunday night. A few snow
showers could venture across CHO and MRB terminals Sunday night,
but shouldn`t have any big impacts on the terminals. Winds
light and variable Saturday becoming west 5 to 10 knots Saturday
night. Winds increasing west-northwest 10 to 15 knots gusts 20
knots Sunday and Sunday night.


SCA continuing at times through this morning, and a secondary
boundary may reinvigorate winds tonight for a time. High
pressure then should let winds relax to sub-SCA by Thursday
afternoon. Light winds then should prevail through Friday night.

Small craft advisory conditions possible Sunday into Sunday
evening as high pressure over the Great Lakes interacts with low
pressure over New England.


MARINE...Small Craft Advisory until midnight EST tonight for ANZ531>533-
     Small Craft Advisory until 6 PM EST this evening for ANZ530-
     Small Craft Advisory until noon EST Thursday for ANZ534-537-



NWS LWX Office Area Forecast Discussion