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

FXUS61 KLWX 182008

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
308 PM EST Mon Feb 18 2019

High pressure will build into the region tonight through
Tuesday. Low pressure will track through the Midwest into the
Great Lakes Wednesday through Wednesday night. Coastal low
pressure will develop along the Mid-Atlantic Coast Wednesday
night before moving off to our northeast Thursday. Both lows
will impact the area during this time. High pressure will
briefly return late week, but another low may impact the area
for next weekend.


Cold front has cleared the CWA and cooler air is enveloping the
region at present. Gusty northwest winds will gradually decline
thru tonight as high pressure builds towards us and the pressure
gradient relaxes slowly. Upslope snow showers are expected along
the Allegheny Front, but accumulations should be minimal. The
high will pass to the north on Tuesday, with some sun starting
to get filtered by high clouds late. Highs will be notably
chillier than today, but not really unseasonable for mid-late
February. Winds will be much lighter as well. Lows tonight will
be in the 20s for the most part, with highs in the 30s to around
40 on Tuesday.


Fairly classic pattern with a potent low moving into the Great
Lakes and coastal redevelopment taking place with a pretty
significant cold air wedge lingering over the region as high
pressure pulls away on Wednesday. Cold, dry air mass with slowly
moisten up as strong warm advection develops overhead Tuesday
night. Snow will overspread the region from southwest to
northeast late Tuesday night, with snow likely falling CWA wide,
at least briefly, by mid-morning Wednesday. The snow may be
heavy at times thanks to the strong low level jet and
frontogenesis in the 850-700 mb levels, and this could put down
a quick 4-8 inch snowfall thanks to the copious Gulf moisture
available. After that, the warm air aloft will overwhelm the
region, with snow change to sleet and freezing rain from south
to north during the midday and afternoon hours. Overall expect
the warm air aloft to be a bit stronger than earlier guidance
suggested, so cut snow amounts a bit, while increasing ice
amounts a bit, but there are still details to be worked out. If
the snow lingers longer, it could be quite heavy, so amounts
could be several inches low. If, conversely, the warm advection
aloft proves stronger than modeled (not an atypical situation),
our snow amounts could prove too high across much of the region.
That said, think our current forecast is in the ball park, with
a genaral 4-8 inch snowfall across the region within the watch,
and lesser amounts in southern Maryland. Ice accumulation is
always tough, but hedged towards colder meso guidance and
increased longevity and amount of ice. That said, a lot (not
all) of the guidance wants to taper precip off at night to a
large degree, which might save us from true warning level ice
amounts. Either way, however, expect an impactful winter storm.

Temps will settle into the 20s Tuesday night, rise slowly
Wednesday, and settle in the 30s Wednesday night, with areas
northwest of I-95 likely to struggle to rise above freezing
while locations closer to the coast have better luck.


A cold front will move south out of our region on Thursday.
Precipitation may linger into early Thursday afternoon with
mainly rain expected as temperatures at the surface and aloft
are both expected to remain above freezing. A wintry mix may be
possible early Thursday over Northwestern Maryland and the
higher elevations. High pressure will build into our area from
the Great Lakes region through Friday. Winds will become west to
northwesterly leading to drier and cooler conditions through

Saturday into Sunday, a low pressure system is forecast to move
from the Midwest into the Great Lakes region and continue
northeastward into Canada. A warm front associated with the low
over the Midwest is expected to lift northward into our region
Saturday morning and into Pennsylvania by Sunday morning.
Overrunning precipitation will affect our region starting
Saturday morning and transition further northward through
Sunday. As the precipitation moves into our region, temperatures
at the surface and a loft are expected to remain above
freezing. The region will move into the warm sector by Saturday
afternoon. This will lead to winds becoming southerly and
temperatures slowly rising through Sunday. The warm front is
expected to stall to our north and linger through Sunday.
Precipitation will be possible through Sunday with temperatures
possibly climbing up into the 60s by Sunday afternoon.


VFR thru Tuesday evening, with the current gusty winds
diminishing later tonight. IFR expected late Tuesday
night/Wednesday morning with snow, possibly heavy at times, then
transitioning to sleet/freezing rain and eventually rain, though
low cigs/vis may linger thanks to low clouds and mist/fog.

On Thursday, skies will remain overcast with rain possible
through the early afternoon periods. Winds will be strong a loft
with winds at the surface west to northwesterly. SubVFR
conditions will be possible

Friday, skies will become mostly clear with winds light out of
the north. VFR conditions expected at this time.


Gales gradually wind down late this afternoon, with SCA slowly
ending later tonight into early Tuesday as high pressure
gradually builds in. Winds likely stay sub SCA most of
Wednesday, but may pick up as a coastal low develops nearby
Wednesday night.

On Thursday, winds a loft will be strong but mixing will be
limited. Small Craft advisories may be need due to the potential
for gust over 18 knots.

Friday, winds will become light out of the north. No Small
Craft Advisories are expected at this time.


Tidal anomalies are running between 1-1.5 feet above normal, but
should fall under northwest winds. The trend has been slow,
however, so will need to watch sensitive sites, particularly SW
Waterfront, over the next few hours.


DC...Winter Storm Watch from Tuesday evening through Wednesday
     evening for DCZ001.
MD...Winter Storm Watch from Tuesday evening through Wednesday
     evening for MDZ003>006-011-013-014-016-501>508.
VA...Winter Storm Watch from Tuesday evening through Wednesday
     evening for VAZ025>031-036>040-050>056-501>508.
WV...Winter Storm Watch from Tuesday evening through Wednesday
     evening for WVZ050>053-055-501>506.
MARINE...Small Craft Advisory from 6 PM this evening to 6 AM EST
     Tuesday for ANZ531-532-539-540.
     Gale Warning until 6 PM EST this evening for ANZ530>532-535-
     Small Craft Advisory from 6 PM this evening to midnight EST
     tonight for ANZ530-535-538.
     Small Craft Advisory until 6 AM EST Tuesday for ANZ533-534-537-
     Small Craft Advisory until midnight EST tonight for ANZ536-542.



NWS LWX Office Area Forecast Discussion