Forecast Discussion
092
FXUS61 KLWX 220217
AFDLWX
Area Forecast Discussion
National Weather Service Baltimore MD/Washington DC
917 PM EST Tue Jan 21 2025
.SYNOPSIS...
Arctic high pressure will maintain control leading to well below
normal temperatures and very cold wind chills through Thursday
morning. Temperatures will begin to moderate late this week as
high pressure begins to lift away. A system may approach the
region late in the weekend.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Mid-evening update: Most of the area remains dry, but cold this
evening. The primary exception to this is in St. Mary`s and
southern Calvert counties, where very light snow is ongoing on
the northern periphery of the precipitation shield associated
with a system passing well to our south. Some light snow showers
are also ongoing within upslope flow over the Alleghenies.
Accumulations of less than an inch may be possible in either of
these areas before snow comes to an end later this evening. Dry
conditions are expected for all during the second half of the
night. Previous discussion follows...
Mid and high level clouds will expand across the Mid-
Atlantic through this evening as an upper wave approaches from
the west. Ascent attendant to this wave coupled with just enough
moisture may result in a few flurries or a snow shower or two,
particularly (1) along and west of the Allegheny Front late this
afternoon into this evening (aided by upslope flow), and (2) in
the vicinity of southern MD this evening (on the northern edge
of the precip shield as low pressure passes well to the south).
Elsewhere, flurries are possible and a light snow shower can`t
be ruled out. Any amounts should be light (i.e. less than an
inch), but given the very cold temperatures, slick travel could
result.
Clouds will clear through the overnight as the trough and
surface low pull away. A pressure surge will bring a steady
light wind late during the overnight. Temperatures will fall
into the single digits above zero east of the Blue Ridge, and
single digits below zero to the west of the Blue Ridge. Areas
along and east of I-95 (including DC/Baltimore) look to hold in
the lower teens. Meanwhile, the higher terrain will drop well
below zero, perhaps approaching -10 in spots. A northwest wind
of 5-15 mph (perhaps slightly higher over the mountains and near
the wider waterways) will drive wind chills to near or several
degrees below zero for much of the area late tonight, with the
coldest readings of -10 to -25 over northern MD and along/west
of the Blue Ridge Mountains (coldest at the highest peaks -
perhaps as low as -30 early Wednesday morning).
&&
.SHORT TERM /WEDNESDAY NIGHT THROUGH THURSDAY NIGHT/...
Well below normal temperatures will continue Wednesday into
Wednesday night. Winds will become lighter during this time as
high pressure moves overhead. Still, bitter cold is expected as
high temperatures are unlikely to escape the teens and lower
20s. With high pressure drifting overhead during the evening,
temperatures may fall quickly across the Piedmont. As the high
drifts east overnight, a light south/southeast wind may kick in.
This, coupled with some increasing cloud cover, could keep
temperatures from falling too much further. The generally light
winds and potentially less than ideal radiational cooling later
Wednesday night into early Thursday morning should keep most
areas above Cold Weather Advisory criteria (with a minimal wind
chill factor outside the higher terrain).
Another wave will approach from the west Thursday, then cross
the region Thursday night. This may result in a few mountain
snow showers, with some passing clouds east of the mountains.
Temperatures will moderate a bit heading into Thursday with
highs likely eclipsing freezing for much of the lower terrain.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
A progressive shortwave is primed to track across the Mid-South
toward the Carolinas on Friday. This is expected to have little to
no impact over the Mid-Atlantic region as any precipitation remains
well off the southeastern U.S. coast. Surface high pressure centered
over the area will allow for a very cold night with low temperatures
in the mid single digits to teens. Once the earlier system exits
into the Atlantic, mid/upper heights begin to relax as the flow
turns more quasi-zonal in nature for this weekend. This building of
heights will allow for the continued trend toward milder
temperatures. By Sunday, forecast highs are actually a tad above
late January climatology which would yield mainly 40s across the
region (upper 20s to 30s in the mountains). Although this may not
seem very mild, it will certainly be in stark contrast from earlier
in the week.
Looking into early next week, there still remains a non-zero winter
precipitation threat. While details are unclear, a longwave trough
begins to dip across the Great Lakes region on Monday. Depending on
timing of the warm advection precipitation, some mixed wintry
precipitation is possible as low-level cold air may be stubborn to
erode. Whatever threat that shows up at the onset would gradually
shift over to rain as the boundary layer warms. In terms of
probabilities, the threat remains low, generally around 15 to 25
percent. This is due to quite a bit of model uncertainty and degree
of forcing overspreading the area. Overall temperatures should stay
near average as noted by global ensemble systems.
&&
.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
VFR conditions are expected through Thursday night. Mid-level
ceilings will move across (FL050-FL100) through this evening as
a wave crosses. A few flurries or a light snow shower can`t be
ruled out, but any accumulation or restrictions should be
minimal. Still, with very cold temps, any snow that does fall
will stick to untreated surfaces. Light NW winds will become SW
this evening, then NW and increase a bit overnight into
Wednesday morning with a few gusts around 15 kts possible. Winds
will become light then switch around to the south/southeast
through Thursday.
VFR conditions are expected for Friday and into the weekend. Behind
a cold front off the Atlantic coast, northwesterly winds gusting to
around 15 to 20 knots are possible on Friday. Winds diminish early
in the weekend as high pressure settles over the region. As high
pressure exits, a shift to southwesterly flow is anticipated for the
latter half of the weekend.
&&
.MARINE...
Light northwest winds are expected through this evening. Then, a
front/wave will move through tonight leading to an increase in
winds. Gusts of 20-25 kts out of the northwest are anticipated
late tonight through Wednesday morning before winds diminish.
Winds will become light, then south to southeast through
Thursday night.
Sub-advisory level winds are expected on Friday and Saturday.
Northwesterly winds could push to around 15 knots or so on Friday,
but winds diminish quickly into Friday night and Saturday as high
pressure settles over the waters.
&&
.LWX WATCHES/WARNINGS/ADVISORIES...
DC...Cold Weather Advisory until 11 AM EST Wednesday for DCZ001.
MD...Cold Weather Advisory until 11 AM EST Wednesday for MDZ003>006-
008-011-013-014-016>018-502>508.
Small Craft Advisory from 2 AM to 10 AM EST Wednesday for
MDZ008.
Extreme Cold Warning until 10 AM EST Thursday for MDZ001-501.
VA...Cold Weather Advisory until 11 AM EST Wednesday for VAZ025>031-
036>040-050-051-053>057-501-502-505-506-526-527.
Extreme Cold Warning until 10 AM EST Thursday for VAZ503-504-
507-508.
Cold Weather Advisory from 9 PM Wednesday to 10 AM EST
Thursday for VAZ025-026.
WV...Cold Weather Advisory until 11 AM EST Wednesday for WVZ050>053-
055-502-504.
Extreme Cold Warning until 10 AM EST Thursday for WVZ501-503-
505-506.
MARINE...Cold Weather Advisory until 11 AM EST Wednesday for ANZ530.
Small Craft Advisory from 2 AM to 10 AM EST Wednesday for
ANZ530>543.
Freezing Spray Advisory from 2 AM to 10 AM EST Wednesday for
ANZ531>534-537-539>541-543.
&&
$$
SYNOPSIS...DHOF
NEAR TERM...DHOF/KJP/CAS
SHORT TERM...DHOF/CAS
LONG TERM...BRO
AVIATION...BRO/DHOF/CAS
MARINE...BRO/DHOF/CAS
