Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
853 PM EST Thursday Dec 25 2014
high pressure will build in through Friday...before moving
offshore on Saturday. A weak cold front will push in from the
northwest Sunday with low pressure from the deep South Riding up
along that front and passing just to the south Monday. Colder high
pressure will follow for middle week.
Near term /through Friday/...
surface high pressure building north tonight through Friday as ridging
sets up aloft. Mainly clear skies across the County Warning Area with subsidence
and a drier airmass in place. Only area with cloud coverage still
western Maryland/Allegheny Front region where passing vorticity maximum/weak
trough still producing broken-overcast clouds. Had anticipated temperatures to
drop off quicker in clear areas with radiational cooling...but
enough mixing still on going keeping west-northwest flow 7-8 kts.
However...winds should diminish enough by 04z with pressure
gradient slacking as high nudges further north...with temperatures
quickly dropping off thereafter. Clouds hanging on a bit longer
over the northwest extreme of the County Warning Area will keep temperatures dropping at slower
rate. Overall...low temperatures across the area sub-freezing except right
along the waters holding in the middle 30s.
Dry weather Friday with center of high passing just to the south as it
starts to push east. Few high level clouds possible from system over the
central US. After the quick shot of cold air advection...surge of warm air advection with
southerly flow on the backside of the high under plenty of daytime
heating with mostly sunny skies will push high temperatures into the
50s...almost 10 degrees above normal.
Short term /Friday night through Saturday night/...
temperatures overnight will only touch the freezing mark across the
sheltered valleys/low lands over the Piedmont/shen valley. Higher terrain
will actually have the warmest values in the area west/ the elevated
inversion. Clear/calm conditions even as a weak upper trough passes
overhead and weakens as it approaches the coast - a precursor the
next upper wave.
Much of Saturday will remain clear and quiet...W/ only a few passing
clouds and relatively warm conditions. The center of the high will
be drifting off the Carolina coast and allow for temperatures to reach the
M-u50s across much of the region. Our brief reprieve from active weather
will be interrupted by late Sat night...as the beginnings of the
next wave of low pressure arrive in the form of dense middle-upper
level clouds. The onslaught of dense cloud cover will prevent temperatures
from dropping back toward the freezing mark...unlike the previous
couple of nights. This will also be key in mitigating the potential
for frozen precipitation over the region during the initial stages of the
Long term /Sunday through Thursday/...
a cold front will push across the region Sunday before sliding into
the Carolinas Sunday night. Some stratiform rain will accompany the
front Sunday through Monday. Some light snow could mix with a little
rain in the Potomac Highlands and along portions of the Mason-Dixon
line Sunday night as colder air is expected to push into these areas
first. We'll hang onto a slight chance of some light rain or snow
Monday night...mainly across the south...as there is still some
degree of uncertainty of a low developing along the front to the
south. The 00z Euro tries to form a low along the north and South
Carolina border. The latest 12z GFS wants to form a low 12 hours
earlier and along the Virginia and North Carolina border before
quickly kicking the low out to sea.
High pressure will build into the region Monday night and
Tuesday...thus persisting Wednesday and Thursday. Drier and cooler
air will move into the region...escorted by the high.
Aviation /02z Friday through Tuesday/...
VFR through taf period. Light west-northwest flow becoming light/vrb overnight. Southerly
flow Friday afternoon...5-7 kts. VFR conditions with light southerly flow continue
Friday night-Sat with high pressure in place.
MVFR to IFR conditions may occur with light rain Sunday into Sunday
night. Winds southwest shifting north 5 to 10 knots with frontal
MVFR conditions possible Monday with lingering light rain. Winds
northeast 5 to 10 knots.
sub-Small Craft Advisory conditions through Friday as high pressure builds
in...with weak flow in place at the surface and aloft.
Light winds over the waters to end the week west/ only some minor southerly
channeling Sat night as a surface high moves off the Carolina coast.
klwx 88d will remain out of service until Saturday...when the parts
to repair the radar are expected to arrive.
District of Columbia...none.