Area Forecast Discussion
Issued by NWS Sterling, VA
FXUS61 KLWX 270901
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
401 AM EST Sun Nov 27 2016
High pressure will build in gradually from the west through
tonight...then move offshore on Monday. Upper energy from a large
and strong low pressure system over the upper midwest will move
into the region Monday night and Tuesday, followed by a deepening
surface low that moves across the area Wednesday night through
.NEAR TERM /THROUGH TONIGHT/...
At present, the storm system which helped produce a breezy and
partly to mostly cloudy yesterday is heading well out to sea.
Upper level shortwave has hung back and helped keep some high and
mid clouds around, while we remain in enough of a gradient between
the high to the west and storm to the east to keep a few gusts
around through the night. As day breaks, the clouds should
continue heading east and generally diminish as ridging builds
aloft and the surface high nudges towards us from the west. This
will allow the day to turn out fairly sunny, though enough wind
will persist to create a noticeable breeze. Highs will be fairly
similar to yesterday, but the greater sunshine should make it feel
like a somewhat nicer day. All-in-all, really rather typical for
High pressure at the surface will pass to our south tonight but we
will be under the pressure ridge extending north of it, allowing
winds to go calm quickly after sunset. Combined with mostly clear
skies, we should have an ideal radiational night, with temps below
freezing in most spots.
.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
High pressure will slide eastward into the Atlantic on Monday as a
strong low pushes into the upper midwest and pushes a cold front
towards us. Clouds will be on the increase through the day as will
a southerly wind. However, any rain should hold off until the
night, so still not a bad day. Temps will likely nudge upward a
bit with the warm advection taking hold, but clouds will temper
First piece of shortwave energy pushes through late Monday night
into early Tuesday with the first wave of rain. This will be
associated with a warm front which is expected to lift northward
across the area late Monday night and early Tuesday. Guidance
suggests a second push of warmer air may nudge into southern and
eastern portions of the CWA later in the day Tuesday, helped along
by a very powerful low-level jet which is progged to exceed 50
knots and possibly approach 70 knots at 850 mb. These features
combined should result in a decent rain, though exact amounts are
still up in the air with variations remaining among guidance.
Overall it looks like perhaps a general half inch of rain may fall
with the first wave Tuesday with locally higher amounts (or
lower). Definitely a much-needed rainfall given the recent drought
conditions. With so much wind aloft, Tuesday will not only turn
out mild, but rather breezy to perhaps even a little windy, but
right now do not anticipate wind advisory as it should be fairly
stable and that wind aloft will struggle to mix down.
As the front slides just past us on Tuesday night, temps will drop
off a bit and the rain chances will ebb, but not for long.
.LONG TERM /WEDNESDAY THROUGH SATURDAY/...
Deep low pressure system over the upper Mississippi Valley at the
start of the period will finally eject to the Great Lakes region
late Wednesday. This will bring the upper low`s energy into the
region as a complex system develops, with the likely result
cutting a surface low over the mid-Atlantic region in the late
Wednesday/early Thursday timeframe. The 00Z GEFS has about 1-2"
QPF in this timeframe with WPC`s deterministic falling in the 2-3"
range across our entire region. This QPF is expected to be spread
out over a 36-hour timespan, giving our drought region much needed
Behind this system, high pressure will build at the surface,
giving the area a couple strong northwest flow days late Thursday
through Saturday. Upslope snow along the Allegheny Front will
commence late Thursday and continue through Saturday.
.AVIATION /09Z SUNDAY THROUGH THURSDAY/...
VFR through Monday, then MVFR to occasionally IFR Tuesday with a
storm system brigning rain to the area along with a gusty south
wind. A few gusts today may be around 20 knots from the NW.
IFR conditions for CIGS/VSBY at all terminals likely Wednesday
afternoon through early Thursday. Strong northwest winds expected
Friday and Saturday.
SCA today for gust to 20 knots from the NW, diminishing by
tonight. SubSCA tonight. Winds may start picking up ahead of the
system Monday afternoon with SCA likely and gale possible with
strong front moving in on Tuesday.
Deepening low pressure will move across the region on Thursday,
likley giving all the waters a solid small craft. Strong northwest
flow behind the low will also likely create additional small craft
advisories Friday and Saturday.
Tuesday will have strong southerly fetch up the bay coupled with
a new moon, and deepening low pressure. ESTOFS is giving 2-3 feet
of anomaly north of the Bay Bridge, with this being the model of
choice for southerly fetch. Therefore, expecting at least minor
coastal flooding from Anne Arundel northward, with the max values
approaching moderate in Harford County.
MARINE...Small Craft Advisory until 6 PM EST this evening for
Small Craft Advisory until 6 PM EST this evening for ANZ535.