Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
1150 am EST Friday Jan 30 2015
high pressure will build across the region for the first half of
the weekend. Low pressure will impact the area late Sunday into
Monday. High pressure will return for the first half of next week.
Near term /this afternoon/...
East of the mountains temperatures have been warming faster than expeceted...and have
been adjusted upwards. Satellite shows waves of clouds continue to stream into
the area from the northwest. Steep low level lapse rates on iad 12z sndg - we
have already seen one band of snsh move through the area. Suspect that
we see more this afternoon.
High pressure building into the area - the steep low level temperature gradient will also
help translate gusty winds to surface. Wind Advisory is in effect for
majority of the forecast area. Winter Weather Advisory remains in effect for The
Highlands for upslope snows.
Short term /tonight through Saturday night/...
Surface high pressure pushes east over the region in the wake of the
cold front as ridging builds in aloft. Mainly dry conditions tonight
through Sat night with the exception of any lingering light upsloping
snow showers first half of tonight. Subsidence aloft will result in
mostly clear conditions tonight...and sunny conditions for Sat.
The main concern during this time frame will be the well below
normal temperatures being ushered in as 850mb temperatures dip below -10 degrees
celsius. Using a blend of adjmet/mosguide...temperatures tonight expected
to drop into the teens everywhere except Potomac Highlands...which
should see lows into the single digits. These temperatures combined with
the on going northwest flow will produce wind chills into the single
digits. The potential exists for needing a Wind Chill Advisory over
the far western portions of the Potomac Highlands with wind chills
dropping to around -12 degrees. However...have held off for any
issuance at this time with the values being borderline with the
criteria and it being mainly after 06z tonight. Elsewhere...though
it will be very cold...wind chills values are expected to remain above
By Saturday...will see gradual warming as the high nudges across the
area...with return flow setting up and injecting in warmer air.
Despite the warming...temperatures still expected to remain below normal
through at least Sat night. 00z model suite in pretty good agreement of
any precipitation moving into the region with the next low pressure system
holding off till after 12z Sunday and have thus a dry forecast through
this time period.
Long term /Sunday through Thursday/...
Models are tracking the low pressure area Sun night/Monday across the County Warning Area.
At this time the best chance for acumulating snows looks to be along the M-d line.
Next week will start cold as the coastal low strengthens...dragging
down cold air. 800 mb temperatures should be dropping to -10 to -14c. At that
rate Monday-Tuesday maxt will have trouble rising above freezing...and min-T may
dip below 0 degf across northern Maryland and in the ptmc Highlands.
GFS suggesting that another southern stream low will fllw midweek hipres
for a potl stormy Thursday. Its still tbd if we will receive the low or it
will pass S of County warning forecast area. Will be keeping probability of precipitation low as theres a lot of weather to
get through first.
Aviation /18z Friday through Wednesday/...
VFR conditions through Sat.
Main concern today strong northwest flow. Gusts start time +/- 1-2
hours...generally in the 20s this morning...then increasing 30-40
kts this aftn/evening. Winds will gradually diminish
tonight...with gusts possible though through the night. Kcho could see
gusts ending as early as 06z. Isolated snow shower possible kmrb but too
low confidence to include...especially with little impact to conditions.
Decreasing west-northwest flow Sat with winds becoming west Sat night. Possible lowering
ceilings late Sat night as the next low pressure system approaches.
Flgt restrictions aplenty sun as lopres crosses terminals. The
afternoon-night time hours should be most affected. Ptype issues exist. Its
no longer a clear-cut snow event. The low will be pulling offshore
Monday. Conds will imprv through the day...but should have some strong northwest wind
VFR Tuesday under hipres.
Gale Warning in effect for through tonight. Could see lingering
gales past daybreak Sat morning...but have held at 09z to account
for uncertainty thereafter. High confidence Small Craft Advisory conditions will
set in Sat morning for Chesapeake Bay...and possible over the tidal
Potomac. Sub-Small Craft Advisory conditions everywhere for Sat night.
Lopres apprchs waters sun day and crosses Sun night. Track of low will
permit a mixed bag of ptypes at night before changing back to snow upon
exit Monday. Also on Monday should be stiff northwest winds as the storm
strengthens as it pulls away. At least Small Craft Advisory possible. Wudnt completely
rule out glw...contingent upon details that are still a little murky.
Hipres will return by Tuesday.
Winds turned northwest bhd a cold front. This will support blow out tides.
Therefore...water levels expeceted to return to normal tonight.
District of Columbia...Wind Advisory until midnight EST tonight for dcz001.
Maryland...Wind Advisory until midnight EST tonight for mdz003-501-502.
Wind Advisory until midnight EST tonight for mdz004>006-011-
Winter Weather Advisory until noon EST today for mdz501.
Virginia...Wind Advisory until midnight EST tonight for vaz025>031-503-
Wind Advisory until midnight EST tonight for vaz040-051>055-
Winter Weather Advisory until noon EST today for vaz503.
WV...Wind Advisory until midnight EST tonight for wvz050>053-055-
Winter Weather Advisory until noon EST today for wvz501-503-
Marine...Gale Warning until 4 am EST Saturday for anz530>543.