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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
931 am EST Sat Feb 6 2016

Synopsis...
high pressure will remain overhead today. Coastal low pressure
will pass by well to the south and east late tonight through
Sunday. Another low pressure system will dive south into the Ohio
Valley Monday before passing through our area Monday night into
Tuesday. High pressure will slowly build toward our area during
the middle portion of next week.

&&

Near term /through tonight/...

High pressure is across the region this morning. Temperatures will slowly
climb into the 40s today.

Previous discusssion...

Surface high pressure will remain over the region today...bringing
dry and seasonably chilly conditions. A longwave upper-level
trough will build through the Ohio Valley today and upper-level
low pressure in the southern stream will strengthen over the Gulf
Coast states. A potent jetmax around this upper-level low will
move into the southeastern Continental U.S....and our area will end up close
to the left exit region of the jet. A broken deck of high clouds are
likely as a result. Since the cloud deck will be thin there should
be breaks of sunshine...but partly to mostly cloudy skies are
expected. Maximum temperatures will range from the upper 20s and lower 30s
along the ridges to the lower and middle 40s across most other
locations.

Weak surface high pressure will remain over the region tonight. A
broken deck of high clouds will hang around this evening...but clouds
should thin out as the jetmax heads out to sea. The combination
of mainly clear skies late tonight and light winds will allow for
radiational cooling. Min temperatures will be in the 20s across most
locations.

&&

Short term /Sunday through Monday night/...
low pressure in the southern stream will rapidly intensify off the
southeast coast Sunday while another low digs south into the Great
Lakes. Our area should remain in between these two lows and weak
high pressure will persist. This will keep the area dry and
seasonably chilly...despite sunshine. There may be some high
clouds that move into area well north of the low off the southeast
coast...especially across southern Maryland.

The strong low pressure off the southeastern Continental U.S. Will move out
to sea Sunday night while another low tracks through the Great
Lakes into the Ohio Valley and Midwest. Again the area will remain
in between these systems...so it will be dry and seasonably
chilly.

A high amplitude pattern sets up Monday through Monday night. An
upper-level ridge will build over the western Continental U.S. While a potent
trough and upper-level low dig south into the Ohio and Tennessee
valleys. The surface low associated with this system over the
Great Lakes will Transfer its energy into a coastal low later
Monday/Monday night as shortwave energy around the upper-level
low interacts with the baroclinic zone along the middle-Atlantic
coast. A surface trough/occluded front will extend from the low
over the Great Lakes southeast near our area to the low over the
middle-Atlantic coast. At the same time...shortwave energy will be
rotating around the upper-level low passing through our area.
These mechanisms will likely cause precipitation to develop over
our area later Monday through Monday night. However...details of
exactly how much precipitation and how much cold air will be in
place remain uncertain at this time.

There are two scenarios. The first scenario is that the upper-
level low does not dig far enough south for our area to be
influenced by the surface trough/occluded front. In other words
that sets up to our north. If this occurs...then precipitation
amounts will be light and less cold air will filter in from the
north and east...causing the ptype to be rain or a mix of rain and
snow. This would allow for only light snow accumulations if
any...and most of the snow accumulation would occur over the
higher terrain.

The second scenario is that the upper-level low digs farther south
and we are impacted by the surface trough/occluded front. Colder
air is able to filter in from the north and east on the cold side
of the boundary...and Atlantic moisture would also wrap around
into this system due to an easterly component to the low-level
flow. This would cause significant snowfall accumulations across
much of the area late Monday through Monday night.

Confidence in what scenario plays out is still uncertain at this
time. The gefs mean and GFS deterministic lean toward scenario 1
while the European model (ecmwf) ensemble mean and the deterministic European model (ecmwf) lean
toward scenario 2. The NAM is leaning between the two sets and the
individual gefs members are split as well. The latest forecast
blends most of these solutions together...but details will have to
be fine tuned over the next couple days.

&&

Long term /Tuesday through Friday/...
still some uncertainties with the 00z model suite on the handling
of an upper level trough/closed low pivoting through the region
beginning Monday...but impacting the middle- Atlantic for a good
portion of the coming week. Depending on the depth of the trough
will dictate the development of the surface low off the coast that
will bring the precipitation chances to the County Warning Area for Tuesday into Wednesday. The
placement will also determine any enhancement to the precipitation
development from energy aloft. As such...not making too many
changes from the previous forecast aftr 12z Tuesday until the models
come into better agreement. Rain and/or snow will turn to snow
showers in the west Tuesday...and will last through Wednesday with the trough
overhead. As of now the potential exists for the snow showers to
spread east of the Blue Ridge Tuesday night-Wed...drying up by Wednesday
night as the surface low exits the region with high pressure building
in from the west. Northwest flow as the high builds in could potentially
keep snow showers ongoing through the end of the week.

00z model suite trending cooler with the temperatures...with highs each day
in the 30/40s and lows dropping into the teens/20s. Some below zero
wind chills will be possible Potomac Highlands Wednesday night but at this time
not anticipating Wind Chill Advisory criteria to be met.

&&

Aviation /14z Saturday through Wednesday/...
VFR conditions are expected through midday Monday. Low pressure
will impact the terminals later Monday through Monday night.
Details are uncertain...but wintry precipitation may lead to
subvfr ceilings and visibilities.

Sub-VFR conditions possible Tuesday-Wednesday with snow and/or rain.
VFR conditions by Thursday lasting into Friday. Gusty west winds possible Wed-Fri.

&&

Marine...
high pressure will remain over the waters through tonight. Potent
low pressure will pass by well to the south of the waters later
Sunday through Sunday night. The pressure gradient may be strong
enough for winds to approach Small Craft Advisory criteria across the middle
portion of the Bay and lower tidal Potomac River.

Another low coastal low will develop along the middle-Atlantic coast
later Monday through Monday night. Details remain uncertain at
this time...but Small Craft Advisory winds are possible.

Small Craft Advisory conditions possible on Tuesday on the Chesapeake Bay...with
incrsg chances Wednesday through the end of the week on all waters.

&&

Lwx watches/warnings/advisories...
District of Columbia...none.
Maryland...none.
Virginia...none.
WV...none.
Marine...none.

&&

$$
Synopsis...bjl
near term...bjl/has
short term...bjl
long term...bjl/Sears
aviation...bjl/Sears
marine...bjl/Sears

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