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Area forecast discussion 
National Weather Service Baltimore Maryland/Washington District of Columbia
1134 am EDT Friday Oct 31 2014


Low pressure is descending from the Great Lakes...and will cross the
Carolinas Saturday before strengthening offshore while heading
towards Cape Cod Sunday. High pressure will return to the area Monday
and Tuesday followed by another cold front during midweek.


Near term /through Saturday/...

West.V. Satellite imgry shows short WV has pushed into WI. This will dive
into SC Sat as upper level pattern undergoes substantial
amplification west/ a ridge over the central part of the country and a
large trough developing offshore as the northern and southern streams

With this southward trajectory...forcing will be focused over the
mountains for the first stage of this system. Some rain showers
are possible this afternoon there but much of central Maryland and Virginia
will be in a squeeze play until tonight or Saturday when the
system winds up and broad scale lift will produce showers area-
wide. However...any heavier precipitation from the coastal low
will likely remain to the east of the area.

In terms of any least through Saturday cold advection
will be very minimal with this occluded system. The 850-1000 tckns
does not go sub 1300m until the low has developed offshore. Snow
is expeceted to be limited to the very highest elevations of WV...and
mostly as a rain/snow mix at that. The snow will be favored during
diurnal minimums in temperature and any slushy accumulations will
be minor.

High temperatures today will range from the upper 40s at higher
elevations to near 60 in The Lowlands. Lows tonight tempered by
cloud cover in ranging from the middle 30s Highlands to middle 40s east.
Precipitation Saturday will be most widespread west of the Blue
Ridge on Saturday and will limit highs a bit more there...well into
the 40s. Near 50 to the east. Northerly winds will also increase
on Saturday as the low strengthens off the coast.


Short term /Saturday night through Sunday night/...

Blv winds may end up being the biggest story from the upcoming system.

By Sat night...shortwave energy would have shifted off the Atlantic CST...inducing
cyclogenesis NE of Cape Hatteras. In terms of precipitation east of the
aplchns...that pretty much will mark the drier air will work
in on the northwest side of the cyclone. Have opted to hold onto more clouds
than GFS indicating...partly due to timing/uncertainty diffs and
the other part due to low 500 mb heights/positive vorticity advection still pivoting across County warning forecast area.
Winds may be the biggest impact...but the nocturnal timing may
prevent the full 30-40 knots available h9-8 from mixing down. Will be keeping
gusts 25-30 miles per hour.

Across the mountains...the air mass will be cooling sufficiently for some snow.
However...the best dynamic cooling will pass S of area. This leaves only
a marginally favorable air mass west/ warm grnd. Snow totals 1-2" in the higher
elevs. It is not out of the qstn that accums could be enough to
reach advisory level...but this is not a slam dunk and will leaving this to
be decided later..

Sunday looks Lake A windy day. 800 mb-5 ridging builds quite quickly
Sunday...shutting off upslope shsn. A tight pressure gradient over area for
much of the day...and better mixing. Have 30-35 miles per hour gusts in grids.

Min-T in the 30s areawide Sat night/Sun morning...and temperatures struggling
to reach 50f Sun afternoon.

Sun night looks quite chilly as ridge builds over area. Clear skies/decoupling
winds/dewpoints in the 20s. Its looking like a hard freeze for most of
the forecast area xcpt for the urban downtowns and communities near the
Bay. That likely will mark the end of the growing season for much of
the area.


Long term /Monday through Thursday/...
the high slides southeast across the Carolinas and near the
southeast coast Monday and Monday night. Temperatures will modify
some during the day but remain a little on the chilly side Monday

High pressure slides offshore Tuesday through Wednesday night to
allow a cold front to gradually slide into the region and bring a
chance for rain showers. Precipitation timing has been pushed back to
Wednesday-Wednesday night. High pressure will build on Thursday.


Aviation /15z Friday through Tuesday/...
a low pressure system will approach from the west today and tonight.
Any precipitation should stay west of the taf sites through most
of this period. A VFR ceiling may be prevalent with very few
breaks with the appraoching system.

Low pressure strengthens off the coast on Saturday. Northerly
winds will gust up to 20-25 knots and MVFR ceilings will be possible
with showers.

Winds will provide primary op impact Sat an elevated core
of 40+ knots winds cross terminals. The low level jet will reside about 2k feet above surface.
Should have 25-30kt gusts in northwest flow at grnd level...maybe a little higher than
that sun mrng-midday. Any ceilings would be MVFR-VFR Sat night and should clear
by/soon aftr sunrise Sun morning.

VFR Sun afternoon into Tuesday.



East to northeast winds under small craft conditions will prevail
today and tonight as a low pressure system passes west and south of
the area.

With the strengthening low moving off the coast on Saturday...small
craft conditions will be met with northerly winds gusting to
around 30 knots.

Gradient increases Sat night. Am not certain if gale conditions will
encompass entire marine area...but it should hit a majority of it.
Conds would continue into sun before the gradient relaxes and winds
subside. Small Craft Advisory conds prognosticated to hold on through Sun night per current

As hipres builds Ely next hazards expected at that time.


Tides/coastal flooding...

A deep area of low pressure will cross the Carolinas Saturday
morning and then track northeast along the middle-Atlantic coast
Saturday night. Positive departures up to a half foot on the
waters at this time...and these may increase a little bit more through
tonight. Tidal flooding issues would only occur if departures
exceeded a foot. At this point...suspect that wont happen.

Blowout conditions are expected Sat afternoon through Sunday.


Lwx watches/warnings/advisories...
District of Columbia...none.
Marine...Small Craft Advisory from 8 am to 8 PM EDT Saturday for



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