Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Baltimore Maryland/Washington District of Columbia
335 am EST Sat Feb 28 2015
high pressure will reside over the central middle- Atlantic through
tonight before moving off the coast 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 3 PM this afternoon/...
pressure rises will continue as high pressure resides across the
middle-Atlantic today. A 130kt jet will stay located over the middle-
Atlantic today and middle-high level clouds will move into the
region from the southwest. These clouds coupled with -10 to -15
850 temperatures will lead to a cold day with surface temperatures reaching the
upper 20s today.
Short term /3 PM this afternoon through Monday/...
flow becomes westerly aloft this evening as warm air advection
increases across the Tennessee Valley and southeast US. High pressure will stay
wedged across the region and temperatures are expected to reach the upper teens
and low 20s by late tonight. Temperatures will begin to rise late tonight
and into Sunday morning. A few upper level waves in the westerly
flow aloft will cross the Northern Ohio valley into Sunday morning.
Warm air advection coupled with forcing to the north will result
in snow across the northern Potomac Highlands Sunday morning. Snow
will move north-NE Sunday morning and around an inch to less than an
inch of snow is expected across the northern Potomac Highlands.
A 30kt southerly jet off the southeast US coast will also pump moisture
into the region. Overrunning will result in precipitation to
approach the central foothills and Piedmont Sunday morning . A
hole in between may result across the Blue Ridge and Shenandoah
Valley but eventually fill in. Precipitation is expected to start
as snow as the entire column will be below zero. Snow will move
north and east across the entire middle-Atlantic by Sunday afternoon.
Warmer air aloft will result in snow changing to ice pellets/freezing rain Sunday
afternoon east of the Allegheny Front. The Wedge of high pressure
will slowly move off the coast and temperatures will slowly climb above
freezing from west-SW to east-NE resulting in a changeover to rain.
Areas west of the Blue Ridge will likely rise above freezing
faster than those east. Temperatures will likely stay below freezing
across northeast Maryland and freezing rain as the prominent ptype is
expected by Sunday afternoon in these parts. There are differences
in how much liquid will fall Sunday. Generally expecting less than
a quarter inch with the higher amts across the northern Potomac
Highlands and much of Maryland. At this time...a few hundredths of
ice accumulation are possible across much of Maryland with amts
near a tenth of an inch in far northeast Maryland.
Frontal system pivots across the area Sunday night...with
precipitation likely ending from west to east during the overnight
hours. Expect areas such as northeastern Maryland to remain wedged
in colder air for the majority of the event...so have held onto
rain/freezing rain mention in those areas. Condfidence not quite high enough to
go with a watch yet though due to uncertainties in quantitative precipitation forecast amounts.
Will continue to highlight in severe weather potential statement and monitor latest model trends.
Upslope rain/snow showers become all snow by early Monday
morning...with a period of accumulating snow possible. Models differ
on how quickly cold air is able to move back in but advisory level
snowfall cannot be ruled out during this time so will mention in severe weather potential statement.
Long term /Monday night through Friday/...
active long term period expected with multiple waves of low
pressure riding along a stalled front expected Tuesday-Thursday.
Precipitation starts out overrunning cold air at the surface and
another period of a wintry mix is possible Tuesday night into
Wednesday. Exactly where the front sets up will determine ptype
thereafter but it looks like a mostly rain event Wednesday into
Wednesday evening...before precipitation gradually ends west to
east through Thursday /possibly a mix before ending especially out
Another shot of cold air looks to follow this frontal system by the
end of next week.
Aviation /08z Saturday through Wednesday/...
VFR conditions expected today as high pressure resides
across the mid-Atlantic. Snow is expected to move into the region
Sunday morning before changing to ice pellets/freezing rain by Sunday afternoon.
MVFR/IFR restrictions will be possible Sunday. Precipitation will
change to rain from SW-west to north-NE Sunday.
Sub-VFR expected Sun night into Monday...mainly rain dca south
and west...with freezing rain likely especially during the evening in vicinity of
BWI/mtn. L/v winds.
Rebound to VFR later Monday through early Tuesday.. then sub-VFR possible
in mixed precipitation Tuesday night-Wednesday am. Westerly winds 10-20 kts Monday become
light NE Monday night-Tuesday PM.
high pressure will continue to move over the waters today.
Nearly winds will continue to subside this morning. A Small Craft Advisory will
continue early this morning and will expire by 6am. A wintry mix
is expected Sunday with snow changing to ice pellets/freezing rain by afternoon and
then changing to rain by Sunday evening. Light winds expected
Generally light winds with wedging/weak gradient Sun night.
Westerly surge to Small Craft Advisory levels likely Monday into Monday night...then lightening
up again as wedging re-establishes Tuesday-Tuesday night.
District of Columbia...none.
Marine...Small Craft Advisory until 6 am EST early this morning for