Scientific Forecaster Discussion
Area forecast discussion...updated
National Weather Service Baltimore Maryland/Washington District of Columbia
1024 am EST Monday Mar 2 2015
a cold front will cross the middle Atlantic region today. High
pressure then will build in through the first part of Tuesday. A
warm front will push through the area Tuesday night. A strong
cold front will approach the region late Wednesday followed by
cold high pressure for Thursday into the weekend.
Near term /through tonight/...
cold front has pushed through much of the forecast area as of 15z.
Winds have backed to the northwest with decent mixing ongoing
across the forecast area. Earlier patchy dense fog across the
metropolitan areas...central Virginia and southern Maryland has mixed out and skies
will continue to show a clearing trend the remainder of this
morning and into the afternoon hours. Out west...clouds will
remain in place due to upslope component with some scattered snow
showers possible over the western slopes of the Allegheny Front.
Temperatures are a bit of a challenge today. Cold front has
crossed the bulk of the region but northwest wind component will
aid in mixing and a downslope direction. Temperatures may warm a
few degrees into this afternoon before they trend downward later
in the day. Northwest winds will remain on the breezy side with
speeds generally in the 10-20 miles per hour range with a few 25-30 miles per hour gusts
possible behind the fro-PA.
Winds will drop off this evening and so will the temperatures.
Overnight lows are expected to drop off into the low 20s in most
locations except a few teens out west.
Short term /Tuesday through Tuesday night/...
clouds will increase from the southwest towards Tuesday morning
as the next systems approaches the region. High pressure will be
locked in place at the surface while warm advection heads towards
the middle- Atlantic. Similar to Sunday...warm air advection will
lead to precipitation to move into the region from the SW.
Precipitation is expected to begin as snow before quickly changing
to ice pellets/freezing rain by Tuesday afternoon. Forecast maximum temperatures for Tuesday range
from the low 30s in NE Maryland to the middle 30s east of the Blue Ridge.
Further west...temperatures should rise above freezing in the Shenandoah
Valley and higher elevations. Less than a tenth inch of ice is
expected Tuesday afternoon for areas east of the Blue Ridge.
Confidence is low for areas across the Piedmont and southern Maryland
where temperatures may reach the middle 30s.
The middle portion of the week will be very active with substantial
swings in the weather. What happens Tuesday evening may be dependent
on how much temperatures can warm on Tuesday. Strong warm air advection will be
taking place aloft...but as usual the question is how much
translates to the surface...especially in areas where the colder air is
wedged in. By Tuesday evening this may only be in the most favored
areas adjacent to the northern Blue Ridge and across northern Maryland.
Left rain-or-fzra wording in these areas for the evening. Current
forecast calls for warm air to win out with rising temperatures
overnight...but this is far from certain in the areas mentioned
above. On the other hand...the higher elevations could be near 50f
or greater by daybreak.
Long term /Wednesday through Sunday/...
area still forecast to remain in the warm sector on Wednesday with highs
into the 50s except N-cntl/NE Maryland. Showers will be likely throughout
the day in a broad area of moist ascent. However it looks like the
greater moisture may remain SW of the area through this time...which
would reduce the threat for any flooding.
Wednesday night/Thursday forecast is quite uncertain as a cold front slowly
slips through the area. It will be nearly parallel to a strong upper
jet...denoting the tight low level baroclinic zone. At least one
wave of low pressure is forecast to track along the front...which
could occur after colder air begins to push into the area. Have
broadbrushed rain/snow wording based on forecast temperatures. A lot of
moisture will be in play in the frontal zone...which could present
accumulating snow. Agree with wpc guidance that the best chance for
snow accumulations will be north/west of District of Columbia...with the highest amounts in
the WV mountains. Certainly a situation to monitor.
Arctic high pressure works in fully by Thursday night...with lows
dropping into the teens and single digits. The high will slowly move
east across the area through Saturday. Expect gradually moderating
temperatures...perhaps pushing climatology by Saturday and Sunday. A
moisture starved cold front may approach late in the weekend.
Aviation /15z Monday through Friday/...
VFR conditions expected at the terminal sites into tonight.
Northwest winds will be gusty today with speeds in the 10-20 knots
range with higher gusts up to 25 kts possible behidn the frontal
passage. Scattered upslope snow showers will be possible over the
western slopes of the Allegheny Front through this afternoon.
Winds will subside tonight and VFR conditions will continue
through tonight. High pressure builds into the region Tuesday but
moisture will move in from the SW. -Snpl becoming freezing rain will impact
the terminals by Tuesday afternoon. Best chance for ice
accumulation will be at BWI-mtn.
Visibility/ceiling reductions will continue Tuesday night through Wednesday
with rain at times. Gusty southerly winds also expected on
Wednesday. Rain may change to snow for portions of the area
Wednesday night-Thursday...which would lead to sub-VFR conditions.
Small Craft Advisory conditions are expected on the waters as a cold front sweeps
through. Wind gusts in the 18-25 knots range will be common through
early evening before diminishing.
Small Craft Advisory conditions will be possible Tuesday night into Wednesday ahead
of an approaching cold front...and again late Wednesday night into
Thursday as cold air pushes in behind the front.
we have been advertising the potential of midweek flooding in the
hazardous weather outlook. Liquid precipitation forecast from wpc puts much of
the forecast area in a minima for amounts...around an inch or less in
many areas. With temperatures expected to rise into the 50s on
Wednesday...there will be some...possibly a lot of...melting of the
existing snowpack...which computer models and observations indicate
contains anywhere from 3/4 inch to 2 inches of snow water
equivalent. This combination may lead to minor flooding as the rain
falls on Wednesday.
Although river ice is not especially thick...it will have to be
monitored for potential role in affecting runoff. Also...plowed snow
is likely covering some of the drains out there...which could cause
more poor drainage flooding than would otherwise usually be
Worth noting...current forecast rain totals are on the lower side of
the ensemble suites of the gefs and sref. Please continue to monitor
the forecast for updates as the event gets closer.
District of Columbia...none.
Marine...Small Craft Advisory until 6 PM EST this evening for