Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
257 PM EDT Monday may 4 2015

Synopsis...

High pressure has moved off the southeast coast. A cold front
over the upper Midwest will push slowly south...stalling across
the middle Atlantic during midweek. High pressure is expected to
return to the region late in the week while low pressure develops
south of Florida and moves slowly up the southeast coast.

&&

Near term /tonight/...

Warmesy day since last sept courtesy of warm air advection around high pressure off the
southeast CST. M80s currently being xprncd over a large portion of the
middle Atlantic. Cumulus have developed over the mountains...but these are not expeceted to
grow into rw/trw.

Tonight will be the closest to "sultry" as we've seen since...well...
sept. The thing that is message is high dewpoints...which will actually be
in the 40s and 50s. Outside of The Highlands lows will range from the
m50s to the m60s.

&&

Short term /Tuesday/...

A frontal boundary extends across Quebec..into Michigan and the Midwest. This will
be sinking into PA tonight...working slowly toward the Mason-Dixon line
during the day. Probability of precipitation will be incrsg during the afternoon...especially across
Maryland/eastern WV. Blv temperatures will still make it into the lm80s over much of
the area.

The wind field aloft is weak Tuesday. This will preclude any cnvctn
that is able to form from developing in severe storms.

&&

Long term /Tuesday night through Monday/...

There is minor disagreement between operational models on timing and
orientation of the weakening cold front as it slips south into the
area Tuesday night and Wednesday. While this could have some
influence on temperatures and where the highest rain chances are
oriented...sensible weather impacts will be rather minimal due to the
weak nature of the front.

By Tuesday evening...the parent low is nearly out of the picture to
the NE...with the surface front stretched between high pressure centers
over the Great Lakes and near Bermuda. There should be a diurnal
downturn in convection...although there will remain a chance of
showers with the front near the northern part of the County Warning Area. Clouds and
elevated dew points will keep lows in the middle 50s to middle 60s.

As the front progresses southward Wednesday...the highest shower
chances will be over southern and western portions of the County Warning Area.
Terrain forcing may play a greater role in shower develop under the
weak forcing regime. Instability remains rather meager...so kept only a
slight chance of thunder. Temperatures will be a touch
cooler...especially toward northern Maryland. Highs range from middle 70s to
lower 80s. Surface high builds toward Long Island Wednesday night...as
middle level ridge axis builds toward Appalachians. Not a particularly
drying influence as moisture will remain in the decaying frontal
zone. However showers should diminish with lows in the middle 50s to
near 60.

Main story during the extended will be continued above normal temperatures
with low chances of precipitation. Thursday likely the coolest day of the
period...although high temperatures will still be u70s as return flow
recommences. High temperatures likely l/M 80s during the remainder of the
period...which is nearly 10 degrees above climatology norms. Dewpoints will
also rise into the l60s...while not oppressive...the increase in low
level moisture will help keep nighttime lows in m60s.

Daily precipitation chances for any one location hard to nail down
precisely...as forcing is rather nebulous and will be primarily
diurnally driven. Regardless...deep layer shear rather weak...so not
expecting organized severe weather. However...instability does increase over
the weekend so there could be a few isolated stronger T-storms
during the afternoon hours.

&&

Aviation /19z Monday through Saturday/...

VFR conds tonight. Clouds should be on the increases Tuesday...especially
BWI/mtn/mrb...although still staying at VFR levels. Rain shower/thunderstorm are possible in
the afternoon.

Chances of showers will lessen Tuesday night but be renewed
Wednesday. Isolated thunderstorm possible Wednesday afternoon.
Coverage of any aviation impacts would be scattered and brief. If a
marine influence is established behind a cold front...subvfr
ceilings/visibilities could be possible Wednesday night.

VFR conds expected through remainder of the period.

&&

Marine...

West/ gusty SW winds have issued an Small Craft Advisory for the majority of the waters.
Upper ptmc seeing gusts into the l20s. Small Craft Advisory in effect through 8 PM
there. Channeling on the Bay expeceted tonight. Small Craft Advisory already in effect
there.

Cold front slips through the waters late Tuesday night/
Wednesday...shifting winds from SW to NE. Could be a higher surge
of winds near the front...but timing is in question and gusts will
be marginal in terms of small craft conditions. Chance of showers
and isolated storms linger into Wednesday. Light NE flow into
Wednesday night.

Not expecting marine concerns through remainder of the period.
&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...Small Craft Advisory until 2 am EDT Tuesday for anz531>533-
538>542.
Small Craft Advisory until noon EDT Tuesday for anz534-543.
Small Craft Advisory until 8 PM EDT this evening for anz535-
536.
Small Craft Advisory until 6 am EDT Tuesday for anz537.

&&

$$
Products...Woody!/Ads/mse

National Weather Service Glossary of Abbreviations