Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
342 am EDT Tuesday Sep 16 2014
a cold front will pass through the region during the early morning
hours. High pressure will return later today and remain through
Near term /until 6 PM this evening/...
07 UTC surface analy places weak cold front moving east of the the ptmc Highlands
at this time. Positive vorticity advection gnly confined to PA/NY...and thats where a swath of rain showers
can be found on rgnl radar. Lighter rain showers S of pit...but west/o upa
support doubt that moisture can make it over the mountains warm air advection ahead of fnt
responsible for a period of lower clouds. Have had developing rain showers east of the
blurdg in response to this feature. Hrrr modeled this fairly well.
If any place has potl to see some positive vorticity advection/jetmax/waa interaction...
its Maryland NE of the ptmc river. Have chance probability of precipitation there...as well as along
the Allegheny Front for lift from upslope. The rest of the I-95
crrdr /DC to ezf/ covered by schc probability of precipitation due to isolate nature of precipitation.
After sunrise...the cold front should be moving across the Delaware-Maryland-Virginia...marking
clearing skies and the end of any sprinkles/shra. Pressure rises and cold air advection
should promote gusty winds...although they may not be quite as strong as
they were looking like yesterday. Some guidance suggesting there may be a few
more rain showers in the mountains will keep addtl diurnal cumulus...but opportunites
for any addtl precipitation look meager /too limited to include in grid attm/.
Latest guidance in good synch west/ going maxt forecast. Have blended it in...along
west/ bias corrected gids to acct for continued warm bias.
Short term /6 PM this evening through Wednesday night/...
hipres will be building across the County warning forecast area tonight through tmrw night. However...moisture from
the stalled fnt will be across the Carolinas. Further...500 mb height pttn
slightly troffy. Therefore...may not have clear/calm conds throughout. Have
periods of pt-mostly cloudy skies...especially across centrl Virginia. Will be keeping forecast
dry through the period since forcing minimal.
In terms of temperatures...have gnly gone on the cool side supported by cold air advection
and upper trough axis. Where MOS diverged...am closer to mav.
Long term /Thursday through Monday/...
northerly flow will continue Thursday as high pressure moves across
the the northern Great Lakes and Ontario. A upper level disturbance will
cross the middle-Atlantic Thursday and clouds will increase from north
to south throughout the day. Dry northerly flow at the surface will
continue to advect low relative humidity into the region leading to a dry column.
Isolated showers are possible but confidence is low at this time and will
continue the dry forecast Thursday. Forecast maximum temperatures will range
from the upper 60s in the mountains to middle to high 70s along I-95 and
High pressure will strengthen across the area into the weekend as it
wedges down the eastern Seaboard. Onshore flow Saturday may lead to
low stratus as marine air moves into the region. A shortwave trough
will approach the middle-Atlantic Sunday while high pressure weakens.
Showers and thunderstorms will be possible Sunday night through
Aviation /08z Tuesday through Saturday/...
a cold front will pass through the terminals during the predawn hours.
A couple showers cannot be ruled out...but most areas will be dry.
Weather restrictions not in tafs due to widely scattered nature of precipitation.
The bigger concern for the morning push will be ceilings. MVFR conds
advcg eastward ahead of the fnt. Its looking like all terminals will be
affected prior to frontal passage. Taf amend coming. Do not forsee IFR.
Further... ceilings should lift to VFR during the push.
High pressure will reside across the region for the rest of the
valid period. VFR conditions expected. Onshore flow may lead to
reduced ceilings/visibilities Saturday.
a cold front will pass through the waters during the Ely morning hours.
Ahead of the fnt...southerly channeling has brought 20-25 knots gusts to
tplm2. Will have a lull in winds in vicinity of cold front passage...which is where we are now.
Post-fropa...northwesterly flow will mix better in vicinity of pressure rises. Marginal
case of 20 knots gusts. Small Craft Advisory in effect at this time for Main Channel of the
Bay and Tangier Sound. Small Craft Advisory for all waters behind the front...which
will begin at 9am.
High pressure will build across the waters tonight and reside
through the weekend. North-NE flow on the waters is expected.
A cold front will cross the waters early this morning. Should have
northwest winds causing blow out conditions by the time the next high tide
arrives. Water may be slightly elevated with respect to astro norms...but no
problems anticipated at this time.
District of Columbia...none.
Marine...Small Craft Advisory from 9 am this morning to 5 PM EDT this
afternoon for anz530-531-535>542.
Small Craft Advisory until 5 PM EDT this afternoon for