Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
337 am EST Friday Feb 12 2016
high pressure builds in across the region today. A strong cold
front will cross the region tonight with Arctic high pressure
building in its wake for the weekend. Low pressure will impact the
area Monday and Tuesday.
Near term /until 6 PM this evening/...
hipres atop County warning forecast area at this time. However...high clouds already streaming eastward. Should
get middle deck soon too...as we enter a brief period of warm air advection. The theme
for the day will be for thickening/lowering clouds...ahead of a northern
stream shortwave and reinforcing cold front. Scattered-numerous shsn should accompany
thelift ahead of the fnt...which may make it to I-81 by the end of
theday temperatures only a pinch higher than yesterday...and still way below average.
Short term /6 PM this evening through Sunday night/...
cold front passage tonight...bringing a host of potl hazards. Issues are winds...
snow... and wind chill.
Snow...parameters looking favorable for a brief period of snow
coincident west/ the fnt tonight. Scale of threat likely finer than
guidance...so am above MOS. Accums would be under an inch...and would be ont
he Eastern Shore before midngt.
In the mountains...the traj favorable for upslope tngt-Sat...and the dry air mass
would lead to a high snow ratio. This will accumulate several inches. However...am
just under advisory criteria...which is somewhat fitting since snow
growth zone low...and not intersecting the best lift.
Winds...atmos will be well mixed in strong cold air advection Post-front. Model soundings
suggest 30-something knots gusts. Wudnt rule out a few 40 kts.
Confidence not quite there for wind advisories. Admittedly its close for
Temperatures...contining temperature forecasts on the low end of guidance...both min-T
tonight and maxt Sat.
Wind chills...combine the previous two bullets...and wind chills will
definitely be a factor. Best chance at advisory in the mountains it falls about 5-
10 degf short elsewhere. Projecting Onward though...the mountains almost
threaten wind chill warning criteria...especially Sat night into sun.
Elsewhere...forecast values flirt west/ advisory criteria Sat ngt-sun. Mindful that
we/re several cycles out...and nothing seems slam-dunk other than wind
chill advisories in the mountains...would rather not make firm warning/advisory
decision yet. Cognizant of the threat though...will be issuing wind chill
watches for the mountains...where values are the lowest. Other counties
will be carried in the severe weather potential statement. Hopefully...later shifts will be able to
make better-informed decisions.
By sun...the ridge will be overhead...and the only hazard left will be
cold temperatures. May have precipitation returning lt Sun night ahead of next system. Have
chances to cover. More in long term dscn.
Long term /Monday through Thursday/...Arctic high pressure will be
retreating quickly on Monday with moisture advancing quickly northward
ahead of a southern stream system for a potential big mess Monday-Tuesday with
heavy precipitation amounts. Potential for 6+ inches of snow appears to be
mainly confined to the Potomac Highlands with significant icing from
there to the Route 15 corridor and light wintry precipitation to mostly
rain east of there. There is general consensus between models to
bring surface temperatures above freezing everywhere by 18z Tuesday with 50s possible
over eastern areas as 850 mb temperatures climb above 5c as strong srly winds
develop. In addition to wintry precipitation concerns...latest 00z European model (ecmwf)
indicates heavy precipitation amounts up to 3.5 inches water equivalent
which could lead to flooding issues. Warmer temperatures...runoff and
snowmelt could lead to ice jam flooding problems especially after
this weekend's frigid air mass.
By middle week...southern stream system merges/phases with a northern stream
disturbance over the northeast with system intensifying rapidly
leading to strong northwest flow and drying conditions.
Aviation /09z Friday through Tuesday/...
primarily VFR through valid taf period. Clouds will be overspreading the
terminals today...first high/middle deck...and should have stcu by evening.
Cold front coming this evening...perhaps accompanied by a few shsn. Areal
covering/confidence in a pt forecast the concern. Thus...these do not appear
in tafs at this time. Would have breif IFR if airfield affected.
Winds become northwest and pick up Post-front...with some gusts in the middle
30s aftr midngt tonight through Sat afternoon.
Hipres builds Sat ngt-sun. Winds gradually diminishing. No other
Sig winter storm to impact the region Monday-Tuesday with heavy wintry
precipitation Monday-Monday night along and west of the Blue Ridge especially at
kcho...kiad and kmrb before it turns to all rain Tuesday afternoon. IFR
conditions likely Mon-Tue.
winds have diminished...and will have a brief period of sub-Small Craft Advisory conds today into
this evening. Cold front coming tonight...producing northwest winds west/ 30-40kt gusts.
Threat would likely begin around/just aftr midngt. For simplicity...have
raised glw tonight...and carried it through Sat night. Small Craft Advisory likely on sun...
which can be addressed later.
Small craft conditions likely much of next week.
District of Columbia...none.
Maryland...wind chill watch from late tonight through Sunday morning for
Virginia...wind chill watch from late tonight through Sunday morning for
WV...wind chill watch from late tonight through Sunday morning for
Marine...Small Craft Advisory until 6 am EST early this morning for
Gale Warning from 6 PM this evening to 6 am EST Sunday for