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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
353 am EDT Thursday Jul 24 2014

a cold front will slowly pass through the area today. High
pressure will build overhead tonight through Friday before moving
off the coast during the weekend. A cold front will pass through
the area early next week.


Near term /through tonight/...
unlike most cold frontal passages...another secondary wave of
moisture is moving through behind the boundary here in the overnight
period. The cold front itself is more of a weak surface wind shift west/
very little airmass chance behind it other than cooler temperatures. The
strength of the colder/drier airmass is in two separate upper waves.
The first is still back across the upper Midwest...and the second is
about a tier of states further back to the north. Each of these will
eventually sweep reinforcing cooler air and subsidence down from the
northwest...but the moist and generally unstable air will remain south of
the Mason-Dixon line over the next several hours.

Scattered showers still lingering over much of the area...though the
County Warning Area has been largely dry behind the convective line late last
evening. The I-95 corridor will be receiving some of this
slow-moving shower activity into the predawn hours. Embedded areas of
moderate to heavy showers will move across the region...but most
locales will just see some light rain in the coming hours. As the
showers move east...the first upper wave will begin to push into the
northern half of the County Warning Area and dry the area out. The southern half...closer to
the leftover surface boundary - will continue to see showers and
isolated weak convection develop throughout the day. Only into the
evening hours will precipitation chances begin to subside along and south of the
I-66 corridor.

A solid northerly breeze will come over the eastern half of the County Warning Area...W/ the
dry and cool flow pushing across the balt/District of Columbia area later this afternoon.
Temperatures will still make it into the l-m80s across the area for daytime
highs...but dewpoints will hover in the m50s or lower this afternoon
which is a noticeably less humid feel to the air than the past
couple of days. The near-10 degree drop in dewpoints will reflect in
the overnight lows as well on Thursday night/Friday morning. Temperatures across the
northern half will drop to the l60s and some u50s...while the I-95
corridor and areas south/east will see lows in the l-m60s.


Short term /Friday through Friday night/...
a weak upper-level trough will remain overhead Friday.
However...surface high pressure will also be overhead so dry
conditions are expected along with sunshine. A scattered/broken cumulus deck
will develop during the afternoon. Maximum temperatures will range from the
upper 60s and lower 70s in the mountains to the lower and middle
80s across most other locations. Dewpoints in the 50s and 60s will
also make it feel noticeably less humid compared to recent days.

High pressure will remain overhead Friday night...bringing dry and
comfortable conditions.


Long term /Saturday through Wednesday/...
high pressure will move off the coast Saturday and a return
southerly flow will usher in warmer and a bit more humid
conditions. The increased heat and humidity may lead to a couple
showers and thunderstorms...but coverage should remain isolated to
widely scattered due to the lack of a strong lifting mechanism.

A potent cold front will move through the Great Lakes Sunday and
this will carve out a trough of low pressure both at the upper-
levels and lower-levels of the atmosphere across our area. A
southerly flow around high pressure off the Atlantic will continue
to usher in warm and humid conditions. The increased forcing along
with the heat and humidity will lead to a better chance for
showers and thunderstorms.

The cold front will pass through the area Monday...bringing the
chance for more showers and thunderstorms. Noticeably cooler and
drier conditions are expected behind the front for the middle
portion of next week.


Aviation /07z Thursday through Monday/...
scattered showers now sliding from west-to-east across the middle Atlantic
and now reaching the District of Columbia/balt metropolitan areas toward the predawn hours.
Only isolated heavier showers and the two main cloud decks are
roughly 5kft and 10kft...W/ the higher one being the predominant
one. Only the kcho area will see the lowered ceilings/visibilities throughout
the day and west/ more precipitation chances until later this evening. A cold
front sagging south across the area will slowly usher-in a stiff
northwest-northerly breeze later this morning. This will affect areas along the I-95
corridor and east west/ a general north wind near 10kt. Precipitation will
decrease throughout the day and into tonight west/ clearing skies and
light winds toward Friday morning.

High pressure will bring VFR conditions for Friday through Friday
evening. Patchy fog is expected late Friday night into Saturday
morning. A southerly flow will develop for Saturday and Sunday as
high pressure moves off the coast. The increased moisture from
the southerly flow will bring the chance for showers and
thunderstorms. Thunderstorms will be more widespread in coverage
Sunday. A cold front front will pass through the terminals
Monday...bringing the chance for more showers and thunderstorms.


behind the convective line...some showers will move in from the west
but winds will remain light into the early morning. A cold front will
precede a several-hour period of northerly flow...pushing a general 10-15kt
wind channeling down the Stem of the Maryland Bay this aftn/eve. A brief
respite and then some more northerly channeling overnight...but expected
to be near but below Small Craft Advisory range.

High pressure will build over the waters Friday into Friday night.
The high will move off the coast Saturday and Sunday...allowing
for a southerly flow to develop. Southerly winds may gust past
Small Craft Advisory criteria for portions of the waters Saturday afternoon through
Sunday morning. A potent cold front will pass through the waters
early next week.

Showers and thunderstorms are possible Saturday through Monday. As
of now it appears that the most widespread coverage in
thunderstorms will be Sunday into Sunday night...but certainty
remains low this far out.


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


near term...gms
short term...bjl
long term...bjl

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