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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
832 PM EDT Tue Aug 23 2016

high pressure remains over the region through much of the week
with a cold front moving through on Friday. High pressure returns
for the weekend.


Near term /until 6 am Wednesday morning/...
high pressure will remain overhead tonight...bringing mainly clear
skies along with light winds. Min temps will range from the mid to
upper 50s in the valleys of the Potomac Highlands to the lower and
middle 60s across most other locations. Patchy fog is possible in
the favored river valleys and rural areas...but higher temp/dewpoint
depressions this evening suggest that widespread fog is not


Short term /6 am Wednesday morning through Thursday night/...
surface high pressure will slowly be working offshore Wednesday and
Thursday. As a result, we should embark upon a warming trend. Upper
80s/near 90 for high temps seem likely again by Thursday. Dewpoints
will start to creep upward too, but still at tolerable levels (lower
60s Tue, mid 60s wed).

As humidity increases, instability levels will rise as well on the
back side of the ridge. NAM continues to place more emphasis on the
westerlies across the northern half of the country. Consequently,
more shortwave advection would be affecting area based on this
solution, primarily Wednesday night and Thursday. GFS is far more
reserved, and seems to be the more plausible scenario.

Am keeping all areas dry Wednesday and Wednesday night, but with
added clouds in the mountains. Although temps will be a little bit
warmer, do not believe there will be adequate forcing for
thunderstorms to develop. By Thursday, believe there will be a
ribbon of instability, confined mainly west of the Blue Ridge. Going
forecast has 30-40% chance of showers/thunderstorms in this area,
which should address threat well.


Long term /Friday through Tuesday/...
a weak cool front is expected to stall across the region Friday
and Friday night. A spotty shower cannot be ruled out along the
boundary. Temperatures will be on the warm side too with highs
reaching the lower to middle 90s.

High pressure will build in behind the front Saturday and Saturday
night. Drier and cooler air expected. Temperatures will be closer to

This high will move east and weaken Sunday and Sunday night. Dry
conditions will prevail Sunday. We can't rule out a shower or
thunderstorm in the west Sunday night as the next cold front moves
across the lower Great Lakes. Temperatures remaining near normal.

The cold front will move across the region Monday and Monday night.
A chance of showers and thunderstorms will ensue through the period.
Temperatures normal.


Aviation /01z Wednesday through Sunday/...
there may be patchy fog overnight, but air mass quite
have limited fog in the forecast. Did allow for MVFR vsbys for
kmrb and kcho.

VFR conditions should generally prevail Wednesday and Thursday as
high pressure departs. Fog may be a little more pervasive by
Thursday with added humidity. In addition, a few thunderstorms would
be possible in the afternoon and evening, especially near mrb.

VFR conditions expected Friday through Friday night. A brief
period of MVFR or IFR is possible in any isolated thunderstorms
near cho, mrb, and iad...mainly Friday evening. Winds southwest
around 5 knots Thursday night becoming northwest around 5 knots
Friday and Friday night.


light south to southeast flow is expected overnight with the
center of high pressure just to the south. Flow will become
southerly over the next couple of days as the high pulls offshore.
For the most part winds will be 10 kt or less. However, may have
some gusts up to 15 kt due to channeling Wed and Thu nights.


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


near term...bjl/hts
short term...heights
long term...klw

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