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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
913 PM EDT Wednesday Jul 1 2015

a cold front will stall out over central Virginia and southern
Maryland tonight. The front will linger over the region through
the weekend...with several waves of low pressure moving east along
it. High pressure will return for the first part of next week.


Near term /through Thursday/...
a boundary is slowly pushing through the southern suburbs of District of Columbia
into southern Maryland and central Virginia this evening.
Convection that has developed along this boundary has trained over
the same areas...resulting in heavy rain for a small area just
south of the district...including Alexandria and portions of
Prince Georges and Fairfax counties. The boundary has slowly slid
off to the south so convection will continue to dissipate across
these areas.

The boundary will stall out over southern Maryland into central
Virginia late tonight. Shortwave energy will also pass through
these areas late tonight in the southwest flow aloft. Left probability of precipitation in
for a few showers across these areas...but coverage should remain
isolated to widely scattered due to the loss of daytime heating
and limited instability. Elsewhere...dry conditions are expected

The boundary will remain nearly stationary Thursday. This will
keep a chance for showers/isolated storms especially over central
and southern locales during the day. High temperatures will be
slightly cooler during the afternoon with readings in the upper
70s west to low- middle 80s east.


Short term /Thursday night through Friday night/...
uncertainty remains with regards to weather late Thursday through Sat subtle to considerable (depending on which guidance you
choose) differences exist among guidance with regards to track and
timing of lp systems tracking along frontal boundary. Made no
significant changes to going forecast...with chances for overnight
showers late Thursday and thunderstorm chances Friday afternoon through the evening.
Instability/shear profiles rather anemic...and 500 mb winds at or below 20
kts...suggest any convective activity would be disorganized. Temperatures
appear to remain reasonable with M/u 70s throughout much of County Warning Area.


Long term /Saturday through Wednesday/...
series of shortwaves crossing region over the weekend followed by a
brief period of ridging Monday. On Tuesday an upper low will develop
off the Delaware-Maryland-Virginia coast while a shortwave on the northern track
passes north of the region. Weak to moderate positive vorticity advection will affect the
area Tuesday night. Series of waves will track along quasi-
stationary front laying across the middle Atlantic region through the
period. A cold front will approach the region Tuesday evening.
Additional shower and thunderstorm development may be possible.


Aviation /01z Thursday through Monday/...
mostly VFR through Thursday. There may be a period of MVFR visibilities
late tonight into early Thursday morning from br. Additional
chances for scattered showers/storms on Thursday...mainly during
the afternoon and evening.

Main aviation concerns Thursday night through Friday remain chances for
showers and thunderstorms...with sub-VFR conditions possible. this time it is difficult to determine exact spatiotemporal
extent of this activity. VFR conds expected outside of any
shower/thunderstorm activity.

Potential exists for additional shower and thunderstorm coverage
over the weekend.


winds will remain below Small Craft Advisory criteria into Thursday. A few
showers/isolated thunderstorms may impact the middle portion of
the Bay and lower tidal Potomac River...especially late this
evening. Additional convection is possible Thursday...especially
during the afternoon and evening.

Main marine concerns Thursday night through Friday would be with any thunderstorm winds appear to remain below Small Craft Advisory criteria in the
light (aob 10 kts) and variable flow.

Additional showers and thunderstorms could impact the waters over
the weekend.


Lwx watches/warnings/advisories...
District of Columbia...none.


near term...bjl/krw
short term...mse
long term...cem

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