Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
930 PM EDT Monday may 4 2015
high pressure is centered near Bermuda. A cold front over the
Great Lakes will push slowly south...stalling across the middle-
Atlantic Tuesday and Wednesday. High pressure is expected to
return to the region late in the week while low pressure develops
off the Carolina coast.
Near term /until 6 am Tuesday morning/...
high clouds continue to spread in ahead of a cold front over the
Great Lakes. Prefrontal showers over eastern Ohio/western PA will dissipate
over the Potomac Highlands tonight where sprinkles are possible.
Min temperatures limited from south flow and increasing clouds...upper 50s
inland...warmer at elevation due to inversion...and low 60s
Short term /6 am Tuesday morning through 6 PM 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 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
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 /01z Tuesday through Saturday/...
VFR conds through Tuesday morning. High ceilings develop tonight and
lower to 5-10kft range Tuesday...especially BWI/mtn/mrb...although still
staying at VFR levels. Rain shower/thunderstorm likely 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 then expected Thursday through this weekend.
southerly channeling overnight with gusts around 20 knots up the main part
of the Bay into the overnight...continuing for southern Maryland waters rest
of the night.
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
Not expecting marine concerns through remainder of the period.
District of Columbia...none.
Marine...Small Craft Advisory until 2 am EDT Tuesday for anz530>533-
Small Craft Advisory until noon EDT Tuesday for anz534-543.
Small Craft Advisory until 6 am EDT Tuesday for anz537.