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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
203 am EDT Wednesday may 6 2015

Synopsis...
a stationary front will remain stretched across Pennsylvania
through Wednesday. High pressure build over the northern middle-
Atlantic Wednesday night and persist through the weekend.
Meanwhile...low pressure off southern Florida develop as it moves
north to the Carolina coast through Wednesday night...then likely
persists there through the weekend.

&&

Near term /until 6 am this morning/...
dense fog advisory has been issued for portions of the Shenandoah
Valley...with visible currently showing at multiple spots 1/4 mile or
less. Expecting the reduced visible to continue through daybreak with
mostly clear skies and weakening winds remaining in place.

Otherwise...last of the precipitation pushing off to the east. Could see an
isolated shower pop up along the Mason-Dixon closer to the frontal
boundary. Min temperatures tonight generally low 60s with dewpoints also
in the low 60s.

&&

Short term /6 am this morning through 6 PM Thursday/...
similar day Wednesday compared to Tuesday. Light flow...so slow
moving activity that may congeal again. As of now the best chances
are for the northern tier of the County Warning Area which will be closer to the
stationary front over PA.

Maximum temperatures generally low 80s...a couple degrees less than today due
to middle/high cloud cover. Middle 80s like today where sunnier skies
prevail.

&&

Long term /Thursday night through Tuesday/...
frontal zone will still be fairly ill-defined Wednesday evening.
High pressure will be located to the north while a low takes place
off the Georgia coast. For the majority of the synoptic models...a low level
NE flow is evident pushing into NE Maryland...perhaps as far as
District of Columbia...which serves to stabilize the atmosphere. However the 12z NAM
and nmm...as well as the 00z arw depict convection forming along a
convergence zone in PA and dropping south during the
evening...affecting more of the area. Will continue broad brushed
chance probability of precipitation through the evening...although did extend thunder
mention a little longer to account for convective uncertainty. Dew
points will remain elevated overnight so lows will only fall into
the upper 50s to lower 60s.

On Thursday the surface high moves offshore with light return flow
developing. Middle/upper ridge axis will become centered over
Appalachians. Expect this to squash most convection...but did
continue to carry low end probability of precipitation in the mountains where building (but
meager) instability will combine with terrain circulations. Any activity
will diminish with sunset. Elsewhere atmosphere doesn/T totally dry
out...so partly to mostly cloudy at times. Highs in the 70s...and
lows middle 50s to lower 60s.

Ridging main weather feature through the extended with high/low temperatures
generally 10 degrees above climatology norms. However...residual deep
layer moisture will allow for a chance of afternoon rain showers or T-storms
somewhere in the County Warning Area nearly each day. Best precipitation chances on Friday and
Sat in the favored elevated terrain in the west...with very low
chances as you approach the 95 corridor. Low precipitation chances then
spread eastward for sun...and even more so for Monday...as ridging
begins to loosen its grip on the region and a cloud front approaches.
Organized severe chances through the period very low...as deep layer shear
remains rather anemic....and instability is marginal.

&&

Aviation /06z Wednesday through Sunday/...
isolated showers rest of the evening...quiet tonight with calm
winds and high clouds. Any fog looks to be isolated due to clouds.

Wednesday should be fairly similar to today weather wise...M cloudy west/ isolated
rain shower/afternoon thunderstorm. Still...VFR generally prevails.

Chances of showers and perhaps a thunderstorm will linger into Wednesday
evening...but confidence low on coverage. Low level moisture present
early Thursday morning...which may result in fog...especially if a
terminal sees rain during the evening. Isolated shower possible Thursday
afternoon at mrb/cho. Fog possible...mainly at prone
locations...Friday morning. Winds light/vrb Wednesday night-Thursday night.

Expect VFR conditions Friday through sun. However...low level moisture could
allow for some predawn fog at climatology favored locations.

&&

Marine...
southerly flow to 10 to 15kt behind swath of showers/isolate thunderstorms
moving east from southern Maryland this evening. Scattered rain shower/thunderstorm are possible again on
Wednesday afternoon/evening. Gusts into the 30 to 35 knots range possible
again west/ these.

With weak surface pressure pattern...sustained strong winds are not
expected Wednesday night-Thursday night. Surge with high pressure building to
north may bring best chance at near-Small Craft Advisory gusts Wednesday evening. Scattered
showers and storms are also possible through Wednesday evening.

Winds light under high pressure...so not expecting Small Craft Advisory conds Friday
through sun. Low pressure looks to remain stalled over the Carolinas
Thursday through the weekend. May eject northeast past Delaware-Maryland-Virginia on
Monday.

&&

Climate...
the warmest airmass of the 2015 so far has moved over the region
during the early part of this week.

Dca reached a high of 86 degrees on Tuesday may 5th...the warmest
day since September 21st 2014 when the temperature reached 86
degrees.

BWI reached a high of 85 degrees on Tuesday may 5th...the warmest
day since September 11th 2014 when the temperature reached 89
degrees.

Iad reached a high of 85 degrees on Tuesday may 5th...the warmest
day since September 11th 2014 when the temperature reached 86
degrees.

Cho reached a high of 85 degrees on Tuesday may 5th...the warmest
day since September 21st 2014 when the temperature reached 87
degrees.

Dmh reached a high of 86 degrees on Monday may 4th...the warmest day
since September 11th 2014 when the temperature reached 90 degrees.

Hgr reached a high of 85 degrees on Monday may 4th...the warmest day
since September 6th 2014 when the temperature reached 90 degrees.

Mrb reached a high of 85 degrees on Monday may 4th...the warmest day
since September 21st 2014 when the temperature reached 86 degrees.

Dca = Reagan National Airport (washington dc) BWI = Baltimore-
Washington thurgood Marshall international Airport iad = Dulles
international Airport cho = Charlottesville Albemarle Airport dmh =
Maryland science center (baltimore inner harbor) hgr = Hagerstown
regional Airport mrb = Eastern West Virginia Regional Airport
(martinsburg wv)

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...dense fog advisory until 8 am EDT this morning for vaz026-027-
029-038>040-050-051-507.
WV...dense fog advisory until 8 am EDT this morning for wvz055.
Marine...none.

&&

$$

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