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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
1031 am EDT Tuesday Sep 1 2015

Synopsis...
high pressure will remain offshore today. An upper-level
disturbance along with its associated surface trough will pass
through the region Wednesday. Weak high pressure will build
overhead Thursday before a backdoor cold front moves into the area
late Friday into the weekend.

&&

Near term /through tonight/...
surface high pressure is centered over the Ohio/Tennessee valleys this morning
with a weak low off Cape Hatteras. Aloft...ridging is centered
along the eastern Seaboard with a cutoff low in the Ohio Valley.
Stratus from this morning has nearly eroded. Scattered cumulus likely to
develop during midday. A few of these could produce a shower or
storm with the help of the higher terrain in the SW County Warning Area...but do
not think there will be much of consequence with the ridging and
poor lapse rates above the bl. Morning sounding and latest
guidance continue to indicate highs at or above 90f for much of the lower
elevations.

Underneath the ridge tonight skies should be mostly clear and winds light. Dewpoints in
the upper 60s. Thus... pttn should favor fog development since theres no
feature that could bring a marine layer inland. Will have patchy fog across
much of the County warning forecast area. Min-T close to guidance.

&&

Short term /Wednesday through Wednesday night/...
the Midwest 500 mb low should be opening up and heading east. This could
provide a mechanism for a slightly more organized and widespread
thunderstorms and rain development. Forecast will feature scattered probability of precipitation across much of the area for
thunderstorms and rain. Metropolitan balt furthest away from this forcing feature and has
only schc probability of precipitation. Emphasis will be on midday-afternoon hours.

The shortwave will be shearing out and heading southeast Wednesday evening. Will be keeping
some lingering probability of precipitation...but gradually tapering chances off overnight. Cape wasnt
high to start with and will be diminishing. Therefore have transitioned
thunderstorms and rain to rain showers. Any addtl precipitation should be minimal.

Temperatures on Wednesday should be fairly simlr to Tuesday...as not much has changed
in the overall pttn between these two days.

&&

Long term /Thursday through Monday/...
an upper level disturbance should be south of the region Thursday
morning. Lingering showers are possible in the morning mainly
across the southern mid-Atlantic. A surface trough should be located
to the south and east Thursday afternoon and winds should become
nearly Thursday. Another upper level disturbance will approach the
region Thursday afternoon and warm conditions with dewpoints in the middle
60s may result in a few showers and thunderstorms mainly west of the
Blue Ridge. Coverage will likely be greater to the north and some
activity may move into the region Thursday night. The disturbance
moves through the region Friday and Friday night. Temperatures in the 90s
with dewpoints in the middle 60s will lead to another chance for
showers and thunderstorms. Temperatures above normal Thursday-Friday.

High pressure builds into the middle-Atlantic from New England Friday
night and into Saturday. A backdoor cold front is expected to move
into the region and bring drier and cooler conditions from
northeast to southwest. Showers and thunderstorms are possible along
and ahead of the front mainly across the SW Saturday. High pressure
builds into the region Sunday before drifting off the coast
Monday.

&&

Aviation /14z Tuesday through Saturday/...
scattered diurnal cumulus should develop by midday...but bases 050-060 will have no
operational impact...nor will light winds.

Anthr fog opportunity comes tonight. Will keep any restrictions at MVFR
until confidence in its occurrence grows.

Shortwave crossing terminals Wednesday will provide a slightly better chance at thunderstorms and rain.
Scattered covering so direct hit/terminal impacts still uncertain. BWI/mountain
seems to be away from path of hiest risk. Brief flgt restrictions
possible west/in any thunderstorms and rain.

Prevailing VFR conditions expected Thu-Sat. Rain showers/thunderstorms in the vicinity possible
Thursday-Friday...mainly in the afternoon.

&&

Marine...
vrb flow at or below 10 knots at this time. Winds shudnt be much higher than that today
or this evening. Anticipate flow becoming onshore during the afternoon.

May be a few thunderstorms and rain crossing waters Wednesday. Light northwesterly flow bhd shortwave.

A surface trough will likely be near the waters Thursday. An upper level
disturbance may bring showers and thunderstorms Friday. High
pressure in control and will likely keep winds below Small Craft Advisory
conditions.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...none.

&&

$$
Synopsis...heights
near term...ads/hts
short term...heights
long term...has
aviation...ads/has/hts
marine...ads/has/hts

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