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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
745 PM EST Monday Mar 2 2015

Synopsis...
high pressure will build across the area tonight. A warm front
will push through the area Tuesday night. A cold front will move
into the region Wednesday followed by high pressure for Thursday
lasting into the weekend.

&&

Near term /through Tuesday/...
high pressure will build into the middle Atlantic region onight.
Winds will diminish by sunset and with mostly clear
skies...temperatures will fall off quickly...dropping to the
lower 20s in most locations except teens over the normally colder
areas west of the Blue Ridge.

Clouds will be on the increase from west to east by early Tuesday
morning as the next weather system approaches. Light precipitation
is expected to begin over the western slopes of the Allegheny
Front then spreading east across the remainder of the forecast
area middle to late morning.

Profiles indicate there is enough cold air for precipitation to
start as a mixture of snow and sleet but a fairly quick transition
to sleet and freezing rain is expected by midday to early afternoon.
Snowfall amounts will be light. Light freezing rain/freezing
drizzle will become the main p-type by afternoon with a few
hundredths to one tenth of an inch of ice accretion expected.
Surface temperatures will be cold enough for some slippery travel
to develop for the afternoon and evening commute. A Winter Weather
Advisory is in effect to cover this threat.

Warmer air will gradually filter in from south to north as southerly
winds increase during the late afternoon and early evening. Rain
will become more likely over central and southern locations. Light
freezing rain will likely hold on longer for the far north and west
suburbs of Baltimore and Washington District of Columbia into the evening. High
temperatures tomorrow will only rise into the 30s in most locations.

&&

Short term /Tuesday night through Thursday/...

Cold air may be lingering into the Ely evening north of the ptmc river
Tuesday evening...otherwise warm air advection will make its way to the surface. Should have warming
temperatures throughout the night. Therefore...will be running west/ a ptype of rain...
west/ just a little lingering freezing rain to the north.

The main ptype issue for overnight Tuesday into Wednesday will be rain. A solid
plume of moisture will be channeled eastward from the western Gulf of Mexico ahead of an
approaching cold front. Am going west/ quantitative precipitation forecast around a half inch...closer to
an inch for the mountains more on this in the Hydro section below.

Cold front passage will come lt in the day. We will be starting from a base in the upper
40s north to upper 50s south /blended newer guidance into the ensemble
maxt forecast/ so even after frontal passage...precipitation will still be rain. Problem
is...surface temperatures will keep dropping through the afternoon-evening while the plume
of moisture continues to stream eastward above it. That would support precipitation changing
over to snow /or perhaps sleet/ Wednesday night. Qstns revolve around the
timing of that transition along west/ how much moisture will be available at
that time. An upper jet will be supportive of precipitation generation...as we
will be in the rrq. At this time...it seems apparent that there will
be measureable snow Wednesday night into Thursday morning. It could be more than
just a little. Have this in the severe weather potential statement at this time. Refer to our probablistic
data via our website for the range of possibilities.

Have snow tapering off during the day on Thursday. Doubt there will be much
of a temperature rise.

&&

Long term /Thursday night through Monday/...
after a few busy weather days...high pressure settles into the region
overnight Thursday. Expect light winds with clearing skies...leading
to strong radiational cooling and very cold temperatures...
especially if there is snow cover from the Thursday system. High
temperatures will remain near freezing Friday despite the return
of warm air advection. After another cold night Friday...temperatures begin to
rebound Saturday and even more Sunday. However...they will remain
in the middle/upper 40s...which is below average for this time of
year.

At this point left weekend precipitation free. But...recent model runs
appear to have a system developing in the deep south and perhaps
beginning to impact our area on Sunday. Would like to see more run
to run consistency before introducing probability of precipitation.

&&

Aviation /00z Tuesday through Saturday/...

VFR expected through 12z Tuesday. Light precipitation will move
in from west to east by middle to late morning. Have introduced light
snow/sleet mixture at most terminals around midday but expect
freezing rain to become the main p-type by afternoon and evening.
The precipitation may change to all rain central and south with
light freezing rain/freezing drizzle holding on longer near kbwi.

MVFR to IFR flgt conds should be widespread Tuesday night through Thursday. Mainly
rain Tuesday night and Wednesday. Snow should be the primary ptype Wednesday night into
Thursday. Depending upon timing...LIFR possible.

At this point not expecting any aviation concerns from Thursday
night through Sunday.

&&

Marine...
winds have diminished on the waters. Small craft conditions could
develop Tuesday night. Visibility will be reduced in frozen
precipitation Tuesday afternoon into Tuesday night.

There is the potential for a brief period of Small Craft Advisory Thursday
afternoon and night before winds subside. After this not
expecting marine concerns through Sunday.

&&

Hydrology...
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
expected.

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.

&&

Lwx watches/warnings/advisories...
District of Columbia...Winter Weather Advisory from 9 am to 10 PM EST Tuesday for
dcz001.
Maryland...Winter Weather Advisory from 7 am to 7 PM EST Tuesday for
mdz501-502.
Winter Weather Advisory from 9 am to 10 PM EST Tuesday for
mdz004>006-011-013-014-503>508.
Winter Weather Advisory from 7 am to 10 PM EST Tuesday for
mdz003.
Winter Weather Advisory from 9 am to 7 PM EST Tuesday for
mdz016>018.
Virginia...Winter Weather Advisory from 7 am to 7 PM EST Tuesday for
vaz025>031-503-504-507-508.
Winter Weather Advisory from 9 am to 10 PM EST Tuesday for
vaz053-054-505-506.
Winter Weather Advisory from 9 am to 7 PM EST Tuesday for
vaz036>040-050>052-055>057-501-502.
WV...Winter Weather Advisory from 7 am to 7 PM EST Tuesday for
wvz050-055-501>506.
Winter Weather Advisory from 7 am to 10 PM EST Tuesday for
wvz051>053.
Marine...none.

&&

$$
Update...Woody!
Prvs...krw/hts/je/mse

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