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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
314 PM EST Sat Feb 28 2015

high pressure will over the area tonight will move offshore Sunday.
A cold front will pass through the area Sunday night. High
pressure briefly builds Monday night...then a warm front then cold
front will cross the area Tuesday and Wednesday. The cold front
looks to stall along the Carolina coast through Thursday.


Near term /until 6 am Sunday morning/...
high pressure over the region has allowed for dry and cold
conditions for this time of year. Maximum temperatures late this afternoon
will range from the lower 20s in the mountains to the upper 20s
and lower 30s across most other locations.

The high will remain over the region this evening...and there will
be a break in the clouds as an upper-level disturbance moves off
to our east. Therefore...radiational cooling will allow for temperatures
to quickly drop after sunset.

Low pressure will track through into the Midwest tonight while the
surface high slowly starts to shift offshore. Shortwave energy in
the southwest flow aloft will also approach the area during this
time. Clouds will increase overnight...and precipitation will move
toward our western and southern areas by Sunday morning. Thermal
profiles will be cold enough for all snow during this time...but
precipitation amounts will be light through tonight.


Short term /6 am Sunday morning through Sunday night/...
low pressure will track into New England Sunday through Sunday
night while the cold front associated with this system approaches
the area Sunday...and passes through Sunday night. A southerly
flow ahead of the cold front will allow for warm and moist air to
overrun the surface cold air in place...causing more precipitation
to overspread the area quickly on Sunday morning. Thermal profiles
support all snow for the County Warning Area through mid-morning...but warmer air
will work its way into the area...causing snow to change to a
wintry mix late Sunday morning through Sunday afternoon. The
highest snow and sleet totals will be closer to the Mason-Dixon
line where snow will last the longest. However...surface temperatures
will stay near or below freezing for much of the day across most
locations...allowing for ice accumulation from freezing rain. Ice
accumulations around one-tenth of an inch are expected. A Winter
Weather Advisory is in effect for the entire County Warning Area.

The cold front will pass through Sunday night. The dry slot should
move in ahead of this system...causing precipitation to end
across most locations Sunday evening. However...low-level moisture
will remain trapped underneath the subsidence inversion and
pockets of drizzle/freezing drizzle may persist. Therefore...the
Winter Weather Advisory continues into late Sunday night for
northern and eastern areas where precipitation may hold on a bit
longer. Surface temperatures will hover near freezing during this time.
Upslope snow will increase behind the cold front overnight for
locations along and west of the Allegheny Front.


Long term /Monday through Saturday/...
cold front is expected to be east of the forecast area by Monday
morning. High pressure will build over the Ohio Valley. The
combination of a strong pressure gradient and cold advection will
lead to gusty winds up to around 20kts. Upslope snow over the
Potomac Highlands will taper off during the day...with minimal
additional accumulation expected. For temperatures...some upslope
component is likely with west-northwest winds...allowing high temperatures to reach
the low 40s over most of the forecast area...with middle 40s possible
over portions of the central foothills...Virginia Piedmont and southern Maryland.

High pressure builds overhead Monday night...with the ridge axis
reaching the I-95 corridor by early Tuesday morning. We should see
at least a period of good radiational cooling conditions with light
winds and clear skies...although higher clouds will be moving in
ahead of the next system. Low temperatures will be in the 20s over most of
the area...with teens likely at higher elevations.

High pressure resides over the area Tuesday morning with morning low
temperatures below normal. Big changes begin middle/late afternoon
Tuesday with strong low-level warm air advection ahead of the next system. Latest
guidance consistent with overall synoptic pattern for this
system...but differences still remain with regards to the timing of
surface features and associated quantitative precipitation forecast. Initial p-type with this system
will largely depend on the timing of initial precipitation and how
quickly the residual cold air is displaced. Not out of the question
for some wintry mixed precipitation late Tuesday/early Wednesday
morning...especially in our northern zones...before thermal profile
warms enough for all rain.

Wednesday will be the warmest day of the workweek...with 850 mb
temperatures near 10c...expect surface temperatures to be at or above 50f over a
large part of the County Warning Area. Wednesday/Wednesday night could be rather wet
with rain showers throughout the day/night. Dewpoints will also
increase substantially on Wednesday...which will be noticeable
considering we have been entrenched in Arctic airmasses for the past
few weeks. Strong cold front moves through Wednesday/early Thursday
with very strong cold air advection. As with the beginning of the storm...wintry p-
type not out of the question by Thursday as the thermal column

Temperatures will plummet Thursday night as high pressure settles
into the region...leading to a very cold morning Friday. Airmass
modification begins Friday...however temperatures still expected to
be below normal through Saturday.


Aviation /20z Saturday through Thursday/...
VFR conditions through tonight. Snow and sleet will overspread the
terminals Sunday morning. Precipitation will change to freezing
rain and rain late Sunday morning into Sunday afternoon from south
to north. IFR and possible subifr conditions are expected during
this time. Precipitation will taper off Sunday night...but low
clouds and patchy fog may persist.

VFR conditions Monday and Monday night. West-northwest winds Monday with gusts
to around 20kt...occasionally higher gusts possible. Winds diminish
Monday night.

VFR conditions expected early Tuesday...sub-VFR possible Tuesday night
through Thursday night. Friday will likely see a return to VFR


high pressure will remain over the waters tonight before moving
offshore Sunday. A southerly flow is expected Sunday into Sunday
night. Winds should remain below Small Craft Advisory criteria. The flow will turn
toward the northwest behind the front by Monday.

Daytime Small Craft Advisory gusts likely with northwest winds over the waters Monday as a
cold front moves east of the waters. Winds may diminish below Small Craft Advisory
criteria by late afternoon as high pressure builds in from the west.
Winds expected to be 10kt or less Monday night.

Winds will pick up prior to cold frontal passage with Small Craft Advisory possible
beginning late Tuesday night and continuing through frontal
passage on Wednesday.


high temperatures will once again be well below normal
this afternoon...on the order of 15 to 20 degrees below normal.
This will threaten some record daily low maximum temperatures
which are listed below.

Site.......record low maxt
dca........27 (1934)
BWI........25 (1934)
iad........28 (2014)


Lwx watches/warnings/advisories...
District of Columbia...Winter Weather Advisory from 7 am Sunday to 3 am EST Monday
for dcz001.
Maryland...Winter Weather Advisory from 4 am Sunday to 6 am EST Monday
for mdz501.
Winter Weather Advisory from 7 am Sunday to 3 am EST Monday
for mdz005-006-011-013-014-016>018-503>508.
Winter Weather Advisory from 4 am Sunday to 3 am EST Monday
for mdz003-004-502.
Virginia...Winter Weather Advisory from 4 am Sunday to 6 am EST Monday
for vaz503.
Winter Weather Advisory from 4 am to 7 PM EST Sunday for
Winter Weather Advisory from 7 am Sunday to 3 am EST Monday
for vaz052>054-506.
Winter Weather Advisory from 4 am Sunday to 3 am EST Monday
for vaz028-031-505.
Winter Weather Advisory from 7 am to 7 PM EST Sunday for
WV...Winter Weather Advisory from 4 am Sunday to 6 am EST Monday
for wvz501-503-505.
Winter Weather Advisory from 4 am to 7 PM EST Sunday for
Winter Weather Advisory from 4 am Sunday to 3 am EST Monday
for wvz050>053-504.


near term...bjl
short term...bjl
long term...KS/ME

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