Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
253 PM EDT Friday Aug 28 2015


High pressure remains over the region through the weekend...and
then slides offshore early next week.


Near term /tonight/...

Surface high pressure is centered over northern PA this afternoon.
Nearest upper level feature of note is a shortwave trough in the
upper MS valley. Flat cumulus field has formed and think the atmosphere
is stable enough to prevent convection over the higher terrain.

Tonight...some patchy light fog is possible in the typical
valleys/rural areas. Lows will inch up compared to Thursday night
coincident with dew points....with most locations in the 60s.


Short term /Saturday and Saturday night/...

The surface high inches east on Saturday. The trough over the Great
Lakes will get sheared out and will likely have little affect on the
local area. Low/middle level ridging ends up just east of the
area...which will allow southerly flow to be established. There may
be enough moisture return for an isolated shower or storm to develop
over the high terrain and adjacent valleys...but overall atmosphere
still looks fairly stable. Highs will reach the middle to upper 80s in
most locations.

With dew points beginning to rise by Saturday night...patchy fog
will again be possible South/West...although some cirrus could begin
to spill across the area. Lows will also be a little more
mild...with middle 60s common to around 70 in the urban areas.


Long term /Sunday through Thursday/...

Weather looks to remain fairly quiet to end the last weekend in Aug. High
pressure moves offshore..the next cold fnt is hundreds of miles to the
west...and Erika is between the Bahamas and Cuba. This will leaving the middle
Atlantic in a warm air mass. Highs sun u80/l90s...Sun night mu60s xcpt
l70s along the Bay/in cities. No real change expeceted for Monday.

Isolated cnvtcn sun-Monday will be possible west/ incrsg humidity...primarily
over the mountains

Upper level low cutting off over Great Lakes/Ohio Valley Monday will
slowly move east to eastern Pennsylvania and stalling Wednesday.
Surface low center that forms over area Tuesday will stay through
end of the period. Support for convective development meager during
early half of period but will strengthen during latter half.


Aviation /18z Friday through Wednesday/...

High pressure will provide generally tranquil conditions through
Saturday night. Cumulus field at or above 5kft may be broken at times this
afternoon...but generally scattered. Have introduced MVFR br at cho
tonight...although confidence is low...and cannot totally rule out
development at mrb as well. Similar possibilities of br Saturday
night. Light and vrb winds this afternoon and tonight will become
predominantly southerly Saturday...although speeds will be less than
10 knots.

VFR conds expeceted sun/Mon. Light fog possible overnight iad/mrb/cho both
ngts. Isolated afternoon/evening thunderstorms possible both days...primarily over the



High pressure to the north will slide east Saturday and provide dry
weather. Light and variable winds through tonight will become predominantly
southerly on Saturday. This may allow some speeds of up to 15 knots
on the Bay by Saturday evening...but Small Craft Advisory conditions are not
expected at this time.

Winds expeceted to remain below Small Craft Advisory values sun and Monday.


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



National Weather Service Glossary of Abbreviations