Area Forecast Discussion
Issued by NWS Sterling, VA

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FXUS61 KLWX 210729
AFDLWX

Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
329 AM EDT TUE JUN 21 2016

.SYNOPSIS...

A cold front over the eastern Great Lakes will move through the
Mid Atlantic states this afternoon and evening. High pressure
will pass to the north Wednesday. Low pressure will track to the
north of the region Thursday. High pressure will return for the
weekend.

&&

.NEAR TERM /TODAY/...

03Z surface analysis showed low pressure over Quebec with an
attendant cold front extending from Lake Ontario back across
central IL. This will descend into the northern part of our
forecast area late this afternoon/this evening. Temperatures will
warm to around 90...hence there will be plenty of low level
energy/CAPE. The approaching boundary will provide a focus for
afternoon convection...with DC/Balt areas being the most likely
target. Helicity is marginal. SPC has placed DC...MD south of
Baltimore...the Highlands and almost all of the LWX part of VA in
slight risk. Strong winds and large hail are the most prominent
concerns.

&&

.SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/...

Storms should be exiting the region during the evening as boundary
tracks south and weakens. If areas outside of cities receive rain
these will have a chance of patchy fog. Temperatures outside now
are in the low/mid 70s. The upcoming night should be cooler - lows
in the lower 70s in the cities/along the Bay...60s elsewhere.

We will be "in between systems" Wednesday. Highs expected to reach
the mid/upper 80s - right around climo norms.

The next precip chance will be Wednesday night as an upper level
short wave tracks across OH and into the northern Mid Atlantic.
Low temperatures will be similar to Tuesday nights.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...

After an active weather day Thursday, Friday and into the weekend
will feature improving conditions under summer sunshine.

Low pressure system will push eastward out of the Midwest and across
the Mid-Atlantic states in west-northwest flow between large scale
trough in SE Canada and large upper level ridge across the southern
US Wednesday night and Thursday. Guidance has come into a general
agreement of tracking the surface low across the PA/NJ/NY area
during the day Thursday, placing the region in the warm sector
following a warm frontal passage late Wednesday night/early Thursday
morning. Will likely see an initial surge of some
showers/thunderstorms with the warm frontal feature. Afterward,
evolution becomes a little more tricky. Will likely see a robust
CAPE field develop Thursday afternoon, with strong overlaying wind
field, leading to the potential for strong to severe thunderstorms,
especially along cold frontal boundary as low presses eastward.
However what`s not clear is the role any ongoing potential
convection (MCS) plays in the region`s eventual convective outcome.
Also of note, is presence of deep westerly flow, which promotes
downsloping and low level drying. High temperatures in the warm
sector likely to be in the 80s to near 90F.

Conditions should dry out for Friday, although a few lingering
isolated showers/tstorms possible in the upper trough across the
higher terrain. Heights then begin to buid Saturday and Sunday as
ridge amplifies out ahead of a system ejecting from the central US
and into Canada. Dry weather expected Saturday and Sunday. Next
chance at any showers/storms will be Monday with trailing cold front
from Canada-bound low. High temperatures in the low 80s Friday,
with gradual warming each day, approaching 90F by next Monday.

&&

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...

VFR conditions this morning. Afternoon thunderstorms are
possible...esepcially at the major airports. Strong gusty
winds/hail will be possible...especialy in the 21 to 03Z
timeframe.

No problems expected tonight or Wednesday. Ceilings could drop to
around 030 Wednesday night...and showers/thunderstorms will be
possible.

Showers and thunderstorms likely on Thursday with periodic Sub-IFR
conditions. Some thunderstorms may become strong to locally severe
with gusty winds and hail. Conditions improve to VFR for Friday and
Saturday.

&&

.MARINE...

Marginal SCA currently in effect on the lower Potomac/Bay. Winds
are gusting to around 15 knots. SCA will be in effect for all
waters today ahead of an approaching frontal boundary. Showers and
thunderstorms...some with strong gusty winds...will be possible
from mid afternoon through mid evening.

SCA conditions likely Thursday/Thursday night on increased
south/west flow with low pressure system. Showers/thunderstorms are
also likely, possibly strong to locally severe. Sub-SCA conditions
return for Friday and Saturday.

&&

.LWX WATCHES/WARNINGS/ADVISORIES...
DC...None.
MD...None.
VA...None.
WV...None.
MARINE...Small Craft Advisory until 4 AM EDT early this morning for
     ANZ530>534-537>541-543.
     Small Craft Advisory from 9 AM this morning to 6 PM EDT this
     evening for ANZ530>543.

&&

$$
PRODUCTS...WOODY!/MJM



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