Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 201418
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
1018 AM EDT Tue Jun 20 2017

.SYNOPSIS...
Weak high pressure will build over the area today and hold
through Thursday. The next cold front will move across the area
at the end of the week or early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
High pressure will be building into the area today. Air mass
will be dry behind the cold front, and combined with subsidence
we will be hard- pressed to generate diurnal clouds. Mixing will
be rather deep: Model soundings suggest that momentum transfer
will be supportive of some gusty winds; these have already been
realized at MRB. Have increased wind forecasts through sunset.
The remainder of the forecast on track.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
A shortwave-trough moving around base of upper level trough
over the Great Lakes will swing through the area during peak
heating on Wed. This may be enough to spark a few showers mainly
across nrn and wrn zones along the Pennsylvania border and
along the spine of the Appalachians. Have mainly slight to low
chance PoPs over those areas. Any shra activity will dissipate
quickly with sunset.

Mid-level ridge then builds on Thu promoting a warming trend
with temps likely to climb into the low 90s. Moisture from the
Gulf and from potential Tropical Cyclone 3 will advect
northward into the mid-Atlantic region Thu night into Fri. There
are notable differences between global models on timing of
moisture and thus showers reaching the area. Have slight to low
chance PoPs across the southwest part of the fcst area. Moisture
then gets entrained into a frontal system with risk of showers
increasing for the end of the week.

&&

.LONG TERM /FRIDAY THROUGH MONDAY/...
The end of the week into the weekend is still shaping up to be an
unsettled period as a frontal zone stalls out across the Mid-
Atlantic. Temperatures through this period may depend some on
clouds, precipitation, and frontal position, but overall should be
near to slightly above normal.

While the actual cold front will be north of the region Friday,
a prefrontal trough will be located east of the Appalachians.
At least some scattered showers and storms will be possible.
Instability isn`t progged to be very strong, but shear profiles
may increase with potential mid level jet streak.

Some uncertainty exists for Saturday into Sunday in terms of the
frontal position and what impact moisture (or even remnant low
pressure) of the current disturbance in the Gulf of Mexico will
have. Nevertheless, the environment will be characterized by high
precipitable water and weak instability, so some periods of heavier
rainfall are within the realm of possibility.

A second cold front will drop south in response to a deepening upper
trough over the Great Lakes, crossing the area sometime early next
week. Behind it, below normal temperatures and low humidity will
arrive.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
VFR conditions through Thu night. A slow moving cold front will
result in the potential for showers and thunderstorms Friday
into Saturday.

&&

.MARINE...
Winds have subsided below Small Craft Advisory criteria on the
Bay for the time being. However, momentum transfer suggests some
gusts will exceed Small Craft Advisory criteria this afternoon.
Have raised the flag this afternoon...extending into the evening
on the Bay and through the night for the mid Bay (Drum Point-
Smith Point/Tangier Sound area).

A cold front will approach from the northwest Friday and slip into
the area on Saturday. At a minimum this will result in a better
chance of thunderstorms. Southwest flow may approach SCA levels on
Friday. Wind forecast becomes more uncertain into Saturday depending
on strength of potential low pressure tracking along the front.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 9 PM EDT this evening for
     ANZ530>533-538>542.
     Small Craft Advisory until 6 AM EDT Wednesday for ANZ534-543.
     Small Craft Advisory until 6 PM EDT this evening for
     ANZ535>537.

&&

$$
SYNOPSIS...LFR
NEAR TERM...HTS
SHORT TERM...LFR
LONG TERM...ADS
AVIATION...LFR/ADS
MARINE...HTS/ADS



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