Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
925 PM EST sun Feb 1 2015
low pressure over the Midwest moves along the Mason-Dixon line
late tonight into Monday morning. High pressure builds through
Tuesday...then a cold front enters the region Wednesday night.
Near term /until 6 am Monday morning/...
Winter Weather Advisory addition of western portions of Grant/
Pendleton/Highland counties for accumulating snow over 3000 feet and
an expected change over to sleet and freezing rain.
As of 02z...1001mb surface low on in/Ohio border...on track to move
along the Mason-Dixon line late tonight to middle-morning Monday.
After a couple initial waves of mainly rain/sleet over the area in
the afternoon...a larger swath of precipitation is crossing the
area...particularly over the southern portions of the County Warning Area. The column
is slowly moistening with rain at ezf...the first few snow flakes
lazily falling at lwx and sleet at cjr. Farther west is snow with
generally less than half inch accumulation and above normal
temperatures in the Shenandoah Valley...two inches reported in
extreme SW Pendleton.
Warm nose is spreading north from southern Virginia. South winds of 10 to 15
knots on ridge lines should allow temperatures to rise above freezing over
the next couple hours. Snow will change to sleet and rain before
all rain for most of the County Warning Area. Will need to watch for a brief
freezing rain bout...but the southerly flow is strong and will be
advection 4 to 5c 850mb temperatures soon. Winter Weather Advisory
holding tight for northern two tiers of counties until 8am. Wintry mix
up there changing over to freezing rain. However...the southerly flow
will only aide the self defeating process of freezing rain
(freezing is exothermic). Min temperatures about now for southwestern areas that
have already wetbulbed...later through the night NE from there.
Short term /6 am Monday morning through 6 PM Monday/...
cold fnt moves through the area Monday morning. Precipitation will taper off quickly
east of the alleghenies...so the story of the day will probably be
wind - strong pressure gradient developing Monday afternoon. A Wind Advisory is expected
for the higher elevs and at least the northern part of the forecast area.
We'll leaving that for later shifts to Ponder. It is mentioned in the
severe weather potential statement.
Models have a wide range of high forecasted for Monday - met and Euro
colder...GFS has many sites into the 50s. As omuch time has spent
on the today/tonight forecast little has been committed to this. We have
afternoon temperatures ranging from the m30s in western Maryland to a50 in lower southern Maryland.
Long term /Monday night through Sunday/...
by Monday evening...low pressure will be located near Cape Cod
with high pressure along the MS valley. Pressure gradient will
still be strong so gusts above 30 miles per hour will linger into the
evening...but be on an overall diminishing trend overnight. Under
the progressive upper flow...the high will be building quickly
from the west. Any lingering upslope snow showers will end during
the evening with little to no accumulation. Kept low temperatures
on the cooler side of guidance as Arctic air rushes in...generally
in the teens with wind chills in the single digits.
The surface high will move across the area on Tuesday and offshore
Tuesday night. A middle level disturbance will increase clouds Tuesday
morning but below that a dry atmosphere will be in place. Return
flow does not commence until late...so highs will still be chilly
ranging from upper 20s north to near 40 south.
A weak area of low pressure will move into the lower Great Lakes
late Tuesday night...but think moisture will remain well northwest of the
area. Some clouds will increase though...with low temperatures not
quite as cold.
A cold front will slide across the region late Wednesday and
Wednesday night. There is a chance of light snow or snow showers
along and behind the front...mainly Wednesday night in the western
third of the region. Temperatures will be close to normal.
The chance of light snow or snow showers lingers Thursday...mainly
across the eastern two thirds of the region. The GFS model is faster
than the Euro model with moving the front eastward. We took an
average of the two models but then leaned slightly toward the slower
of the models since most of the energy will be moving north and the
trough axis is positively tilted. Temperatures Thursday and Thursday
night will be about 15 to 20 degrees colder than Wednesday with a
cold dome of high pressure building behind the front.
High pressure will remain in control Friday and Friday
night...allowing for dry conditions and below normal temperatures.
A cold front tries to slide southward toward the region Saturday but
may not make it until Saturday night. Saturday should remain dry and
temperatures should not be as cold as we may look at high
temperatures reaching near 40 in the central and eastern areas.
Aviation /02z Monday through Friday/...
ceilings continue to diminish this evening..eventually into IFR Cat. On
Monday strong nwrly winds will be possible during the afternoon.
VFR conditions Monday night through Tuesday night. Strong northwest winds
will gradually diminish Monday night...becoming light southerly late
VFR conditions Wednesday. Winds S to SW 5 to 10 knots. VFR to MVFR
conditions Wednesday night with exception to any brief snow showers
at the terminals where there could be brief IFR conditions. Winds SW
veering northwest and increasing 10 to 20 knots with gusts to 30 knots.
VFR or MVFR conditions Thursday with exception to brief snow showers
where IFR conditions could be brief. Winds northwest to north 10 to 20 knots
gusting 25 knots then diminishing late.
Small Craft Advisory for southeasterly flow gusting to around 20 knots for southern Maryland
waters...expanding to most waters for the morning...then Gale
Warning for the afternoon through Monday evening.
A diminishing trend will take place Monday night...Small Craft Advisory conditions
may linger into early Tuesday morning over portions of the waters.
With some uncertainty on how quickly winds diminish...will not
Post a Small Craft Advisory on the back end of the Gale Warning at this time.
Southerly winds develop by late Tuesday...but are forecast to
remain around 15 knots or less.
Small craft advisories possible Wednesday. No marine hazards
expected Wednesday night. Small craft advisories likely Thursday.
District of Columbia...none.
Maryland...Winter Weather Advisory until 8 am EST Monday for mdz003>006-
Virginia...Winter Weather Advisory until 8 am EST Monday for vaz503.
WV...Winter Weather Advisory until 8 am EST Monday for wvz050>053-
Marine...Small Craft Advisory from midnight tonight to noon EST Monday
Gale Warning from noon Monday to 1 am EST Tuesday for
Small Craft Advisory until noon EST Monday for anz533-534-537-