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

FXUS61 KLWX 280909

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
409 AM EST Tue Jan 28 2020

A pair of weak disturbances will cross the region in northwest flow
through Wednesday morning. High pressure will build over the
northern Great Lakes during the middle of the week as a cold front
drops south from New England and low pressure passes well to the
south near Georgia. A larger area of low pressure may approach
from the Southeast U.S. Friday night into Saturday.


A weak shortwave aloft has progressed off to our southeast
overnight. A stubborn low-mid level cloud deck has held strong,
even within the zone of subsidence behind the shortwave. With
the clouds still in place and a light westerly wind, temperatures
have stayed warmer than originally forecast. Have bumped up the
low temperatures, as well as the sky cover forecast.

Despite model guidance indicating that there will be ample
breaks of sunshine today, current thinking is that the cloud
deck in place now will hold strong through the day. Solid
overcast is expected west of the Blue Ridge, with only a few
breaks to the east of the Blue Ridge. Feel relatively confident
in this solution given that the same guidance had clearing skies
overnight, while a solid cloud deck is still in place. With the
strongest subsidence passing further south through the day, if
anything, the synoptic scale pattern would favor an uptick in
clouds. Temperatures won`t climb much from where they are now
with overcast skies in place, with highs in the low-mid 40s.

A shortwave embedded in northwesterly flow will pass off to our
northeast overnight tonight. This should maintain the clouds
cover initially, but the cloud deck may begin to break up toward
morning as the shortwave progresses further to the east and weak
subsidence moves overhead in the wake of the disturbance. Lows
tonight will be in the 20s to low 30s.


The flow pattern across the eastern CONUS will remain devoid of
any high amplitude disturbances over the next couple days. The
flow pattern will be rather convoluted, with several weak
shortwaves progressing from west to east. On Wednesday, we`ll
find ourselves between a shortwave departing off the Northeast
Coast and another shortwave over the Mississippi Valley. We may
finally get a break from the clouds in the zone of weak
subsidence between these two features, but wouldn`t be shocked
if the clouds hold on given what occurred tonight. For now will
maintain the forecast of mostly sunny, but may eventually need
to introduce more clouds. Highs on Wednesday will be in the
upper 30s and low 40s.

The aforementioned shortwave will approach from the west
Wednesday Night and eventually pass overhead by Thursday
afternoon. We will see an uptick in cloud cover Wednesday Night
in advance of the shortwave. During the morning hours on
Thursday, a few rain or snow showers can`t be ruled out over
southwestern portions of the forecast area. However, most of the
area should remain dry. Don`t expect much, if any accumulation
for the areas that do see snow shower activity. Any precipitation
should wind down Thursday afternoon as the shortwave progresses
off to the east and subsidence aloft moves in.


A Gulf of Mexico/Southeast U.S. low development is shown by
global models Fri-Fri night with models indicating both nrn and
srn streams remaining separate and not phasing until system
reaches Atlantic Canada Sunday. During the past 24 hrs, the Euro
has shown the least amount of variability indicating a weak
system remaining just offshore with some precip skirting
southern MD. The GFS, on the other hand, has shown the most
variability from its previous run and it shows a track just
inland from the coast and a deeper system resulting in
widespread significant precipitation to parts of the area. Given
lack of cold air in place/strong surface high to the north and
unfavorable teleconnections pattern, this does not appear to be
a favorable setup for heavy snow for our area at this time,
although can`t completely rule out some light wintry
precipitation just yet especially in our higher elevation areas
like Appalachian Mountains where it is typically cold enough to
snow anyway this time of the year.

After another trof passage early on Sun and a chance of some
light precip, longwave ridge pattern builds from the west
leading to a big warmup for early next week.


There`s a low-end chance that MVFR ceilings could move into MRB
this morning. Otherwise VFR and precipitation-free conditions
are expected at the terminals over the next several days. Winds
today will be out of the northwest, with gusts up to 20 kt

No sig weather expected Fri- Sat.


Anticipate widespread/frequent gusts in excess of 20 knots
through this morning in the wake of a departing shortwave. The
more sheltered waters of the middle and upper tidal Potomac
River, Baltimore Harbor and the northern tip of the Chesapeake
Bay may not have gusts quite as high or frequent due to narrower
trajectories over water, so have opted to leave them out of the
advisory for now. Winds may see a brief uptick over all marine
zones right after daybreak today before the wind field
diminishes this afternoon.

A second weak disturbance will cross over the waters tonight.
Although the attendant wind field will be weaker, more of a
northerly channeling component to the low-level flow could
result in gusts in excess of 20 knots over the wider waters of
the Chesapeake Bay.

Sub-SCA conditions are expected Wednesday through Friday night.

MARINE...Small Craft Advisory until noon EST today for ANZ531-532-539-
     Small Craft Advisory until noon EST today for ANZ533-534-537-



NWS LWX Office Area Forecast Discussion