Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
259 PM 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 /tonight/...
Strong pressure gradient persists over the middle Atlantic. Lots of gusts into the
30+ miles per hour level...few above 40...but will leaving the Wind Advisory up and let
the evening shift decide if it should be dropped b4 the mdngt
Received a call from our spotter in western Pendleton - still snowing about
1/2" per hour. 8" on grnd. Expect another 1-2" could fall late this
afternoon/Erly evening b4 snow tapers off.
Skies should remain cloudy through middle evening then clearing should take over as
high moves over the region. Temperatures should drop into the teens over much
of the area...l20s in the cities...single digits in The Highlands.
In adtn wind chill expeceted to fall to around -5 in The Highlands...
single digits over much of the rmdr of the County Warning Area. This is above Wind
Chill Advisory level...but again will ask evening shift to keep an eye on
Short term /Saturday/...
Sat high pressure over the area. East of The Highlands highs should climb
into the 30s.
Long term /Saturday night through Friday/...
Zonal flow will be over the area Saturday night ahead of the next
approaching shortwave trough in the plains...while surface high pressure
slides off the southeast coast. Little of note other than increasing middle
and high level clouds. Lows generally in the 20s.
The low pressure system will take shape over the Ohio Valley on
Sunday. Isentropic lift may allow some light snow to begin to break
out...especially during the afternoon and along the Maryland/PA border.
Column aloft will be cold enough for snow...but surface temperatures will try
to edge above freezing and in fact may rise above 40 degree south of
US-50...so some rain may mix in with southern extent. Quantitative precipitation forecast will
be very light though and where snow does fall...amounts would likely
be less than an inch.
30.12z model suite has held serve with the track of the low pressure
Sunday night...with even the colder Canadian solution now on the
northward trend. Per collab with wpc...this seems to be a stable
trend...and if anything may end up being a bit further north. This
sends the track of the surface low right over The Heart of the County Warning Area and
diminishes the probability of a more significant snow. This also seems
reasonable since there is not a strong blocking high positioned to
the north...rather an extension of a high over the plains.
Temperatures likely hold fairly steady Sunday night. Greatest chance
for accumulating snow will be along the M-d line and in the Potomac
Highlands. Southern County Warning Area may eventually become all rain. In between
the concern would be for a little mix of everything...and will have
to watch out for models trying to keep temperatures too warm on an
overnight precipitation event with in-situ cad/cold air locking in place in
the climatology favored areas. This could result in freezing rain where models
depict it being warm enough for only rain. Do have some minor ice
accums from Shenandoah Valley up to and along the M-d line...where
even they will likely mix some and limit snow totals. District of Columbia/balt metros
are right on the edge...so please keep track of the latest forecasts
as the exact track of the low is fine tuned. Will hold off on
issuing any sort of watch on this forecast issuance due to the low
confidence...long lead time...and only marginal amounts for warning
criteria on the northern tier of the County Warning Area.
A low pressure system near metropolitan d.C. Will quickly move offshore the
East Coast by midday Monday. The threat for a period of accumulating
snow or perhaps a mix of rain and snow exists for the region
throughout the day...especially over the eastern half. High and low
temperatures Monday and Monday night will average 10 to 15 degrees
below normal...especially late Monday through Monday night with lows
bottoming out near zero or single digits. As for precipitation
Monday night...there is a chance for some good upslope snowfall in
the Potomac Highlands.
High pressure will dominate the region Tuesday and Tuesday
night...bringing dry conditions. Temperatures will remain nearly 10
degrees below normal.
A cold front will sag south out of the Great Lakes Wednesday and
Wednesday night before pushing across the region Thursday.
There is a chance of some light snow or a mix of snow and
rain...mainly Wednesday night into Thursday. Temperatures Wednesday
through Thursday will not be as cold as recent days...but will still
Aviation /19z Friday through Wednesday/...
Broken clouds expeceted to continue over much of the area through middle evening...but
remaining in the VFR range. Wind gusts into the m30s at sites xcpt for
cho. Skies clearing overnight...gusts into the 20s on Sat west/ gnrly clear
IFR conditions possible from Sunday afternoon into Sunday night as
low pressure crosses the area. A mix of precipitation types will be
likely at all terminals.
IFR or LIFR conditions could start the day Monday with periods of
light snow across the terminals. There could be a little rain mix in
near cho. Conditions should become MVFR by the afternoon before
improving to VFR late in the day. Winds SW becoming northwest less than 10
knots early Monday then increasing northwest 15 knots with gusts 20 to 30
knots midday Monday and Monday afternoon.
VFR conditions Monday night and Tuesday. Winds continuing northwest 15
knots gusts 20 to 30 knots Monday before diminishing north becoming S at
5 to 10 knots Tuesday.
Receiving gusts into the 30-35 knots range at several sites on the ptmc/Bay.
Gale Warning in effect through 4 am. This may need to be extend...or
lowered to an Small Craft Advisory. It is likely that an Small Craft Advisory will be needed for waters
into the afternoon hours Sat...then dropping off in late afternoon as high
pressure builds over the area.
Winds are forecast to remain below Small Craft Advisory criteria from Saturday night
through Sunday night. Low pressure will bring mixed
precipitation...especially the upper Potomac and Northern
Bay...Sunday afternoon into Sunday night.
Small craft advisories are likely Monday afternoon through Monday
No marine hazards expected Tuesday.
Nwrly winds have caused water levels to drop below normal on the
Bay/ptmc...but at this time these are not at such a critical level that any
kind of stmt needs to be issued. Again evening shift will be asked to keep
an eye of water levels...which should remain below normal through middle afternoon
District of Columbia...Wind Advisory until midnight EST tonight for dcz001.
Maryland...Wind Advisory until midnight EST tonight for mdz003>006-011-
Virginia...Wind Advisory until midnight EST tonight for vaz025>031-040-
WV...Wind Advisory until midnight EST tonight for wvz050>053-055-
Marine...Gale Warning until 4 am EST Saturday for anz530>543.