Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Wakefield Virginia
1007 am EST Sat Feb 13 2016
Arctic high pressure builds across the region through tonight...then
moves off the middle Atlantic coast late Sunday. Low pressure over the
deep south Monday...lifts northeast across the middle Atlantic region
Near term /until 6 PM this evening/...
strong low level cold air advection ongoing across local area. Gusty northwest winds to 25-35
miles per hour...and temperatures mainly in the M-u20s producing wind chills in the
upper single digits to teens. Scattered-broken SC in vicinity of Bay/ocn and on the
Eastern Shore and could be scattered flurries. Otherwise...mainly sunny. For rest
of the day...remaining cold and gusty. Mostly sunny inland...vrb clouds-
partly sunny near the CST. Hi temperatures from the M-u20s north and northwest...to the
l30s southeast...W/ wind chills generally remaining from the upper single digits
(esp on the lower Maryland eastern shore) to the teens.
Short term /6 PM this evening through Monday/...
1035 mb Arctic high moves into the Ohio/Tennessee vllys this evening
with the center of the high over West Virginia by 12z sun. Northwest winds
continue as ridge axis remains west of the forecast area. However...the high gets
close enough for winds to diminish across the Piedmont. This allows
for decent radiational cooling to occur under mainly clear skies.
Lows plunge into the single digits to low teens inland to upper
teens near the coast. Wind chill values generally 0 to 5 above
inland and around 5 below Northern Neck to the Eastern Shore. Have issued a
Wind Chill Advisory where readings are expected to drop below zero.
Center of Arctic high moves across the forecast area sun...then off the coast
sun evening. Tsctns show clear skies to start but high level moisture quickly
ovrsprds the region west to east during the afternoon hours ahead of the
next systm apprchg from the west. Highs only warm into the M-u20s
(-2 Standard dev)...except around 30 southwestern most counties but with much less
Surface high shifts toward New England Sun night as the next storm
system develops over the deep south Monday. Northern stream energy lifts
north of the region Sun night/Monday as a middle level trough tracks
across the central Continental U.S. Monday. Southwesterly flow aloft will result in
moisture return into the middle-Atlantic region. Probability of precipitation increase after
midnight (chc probability of precipitation most areas except likely NWR most cntys) late
Sun night as the northern stream system weakens and weak isentropic
lift advects into the region. Air mass cold enough for all snow as
lows Sun night in the upper teens to around 20. Given lght quantitative precipitation forecast amts
(less than .10) snow amts by 12z Monday expected to be less than one
Precipitation chances quickly increase Monday as a coastal trough sharpens
along the coast and the aforementioned deep south low begins to lift
northeastward toward the local area. Chance to likely probability of precipitation will be maintained
during the morning increasing to likely to categorical during the
afternoon. The challenging part of this forecast will be precipitation type as the
entire gambit of precipitation types are expected due to warm air advection aloft and
critical thicknesses indicating a change over from snow to a mix of
snow/ip/fzra late Monday morning across the Piedmont to mainly rain by
00z Tuesday as temperatures rise above freezing. Latest data supports
Louisa/Fluvanna counties hover around freezing well into Monday night.
This would lead to frozen precipitation types there much for a longer
period of time. BUFKIT thermal profiles support any icing
(freezing rain) mainly west of the i95 corridor. Given more ice
potential...snow totals will be held down to 1-2 inches over the
western most counties with an inch or less elsewhere...but the icing
potential will increase. Icing amts expected to range less than
05 along the i95 corridor upwards to .10 from fvx-lku. Precipitation type
becomes mostly liquid between 21z Monday and 00z Tuesday except northwest most
counties. Temperatures challenging as the models are trying to flood warmer
air in at the surface much quicker than previous forecast had. For now
will go with highs near freezing across the northwestern most counties (where
wedge always hangs on the longest) to between 45-50 along coastal areas.
Despite how messy Monday looks...quantitative precipitation forecast forecast through 00z Tuesday before the
changeover to liquid suggests the event would fall into a Winter
Weather Advisory headline vs warning headline. No headlines will be
issued with this forecast given a fourth / fifth period event.
Long term /Monday night through Friday/...
12/12z numerical models depict low pressure tracking NE from the
deep south to the southern Appalachians Monday evening...then rapidly
deepening as it lifts NE into the middle-Atlantic region by midday
Tuesday as a vigorous upper trough digs across the southern/central
Appalachians. Thermal profiles suggest mixed precipitation could continue
into the evening over the Piedmont. Overnight lows should occur in
the evening...with rising temperatures overnight as the low-level
flow becomes south-southeast. Colder temperatures will likely persist the
longest in the far northwest Piedmont counties where some pockets of -fzra
could continue overnight...but generally all rain is expected by
early Tuesday morning. Periods of moderate rain are possible late
Monday night into Tuesday as a band of strong vertical ascent passes
over the region. Strong pressure falls could produce a modestly
strong southerly wind across the eastern third of the area for a 3-6hr
period Tuesday. Temperatures warm to at least the middle/upper 50s
across the eastern half of the area Tuesday...with low 60s possible
along the coast...while the Piedmont struggles to rise above the
upper 40s/low 50s. Generally expecting drier conditions by Tuesday
night...although some 20-30% probability of precipitation will linger across the north as a
secondary trough swings across the northern mid-Atlantic. Dry and mild
Wednesday under west-northwest flow with highs in the upper 40s to middle 50s. A
cold front tracks across the area Wednesday night...followed by
Canadian high pressure Thursday. This should push temperatures below
normal...but within -1 St dev. A moderating trend commences late
week as high pressure moves offshore and low pressure tracks through
the Great Lakes.
Aviation /15z Saturday through Wednesday/...
plenty of cloudiness across the area as low pressure moves well
offshore and the base of an upper trough swings across the region.
Modified Arctic high pressure builds into the Midwest the rest of
tonight into Saturday with a much colder airmass filtering into
the middle Atlantic region during this time. Temperature and pressure
gradients will result in northwest winds becoming breezy from northwest to southeast
the rest of tonight...becoming gusty after 13/1100z and continuing
through the rest of Saturday. Inland winds averaging 15kt with
gusts up to 20-25kt...along the coast winds will average 20-25kt
with gusts up to 30-35kt. Skies remain mostly cloudy and then
start to break up around sunset. Surface high finally builds into the
region by Sun morning...however northwest winds will be slow to diminish
overnight (especially along the immediate coast) due to a very
gradual relaxing of the temperature/pressure gradient.
High pressure dominates on Sunday with dry weather...generally light
winds...and VFR conditions. Next complex weather system begins to
impact the area late Sunday night. Plenty of cold air in place for
precipitation to begin as all snow Sunday night into Monday morning.
However...a deepening low moving in from the SW is expected to
pull warmer air into the region. This will complicate precipitation
forecast...especially across central Virginia where colder air may linger
at the surface. Could see a wintry mix northwest half of forecast area and a
changeover to all rain across the southeast. Regardless of precipitation
type...expect ceiling/visible reductions once precipitation begins Sunday night
and continuing into Tuesday. A break in precipitation and flight
restrictions is anticipated Tuesday night but could be short-
lived. Another weather disturbance may brush across northern Virginia and the
Maryland lower Eastern Shore Wednesday morning but impacts are not
anticipated at local taf sites at the moment.
various marine headlines have been adjusted. Please refer to
specific marine headline information below or within wbcmwwakq.
Northwest winds picking up right on schedule as an Arctic airmass begins
to surge into the region. Initial gusts will be 25-30kt but will
increase rapidly around sunrise from north to south as the
temperature/pressure gradient tightens significantly during the rest of
today. Gale force gusts of 35-40kt should be anticipated over ches
Bay and all coastal waters...gradually ending from late afternoon
through Sunday morning. Currituck Sound and eastern Virginia rivers will
remain within strong Small Craft Advisory conditions through tonight...then slowly
diminish below thresholds by early Sun afternoon. Waves on ches Bay
will build quickly to 4-5ft this morning with the rapidly
increasing winds. Waves may even reach up to 6ft for brief period
of time during middle morning. Seas also expected to build rapidly
once stronger northwest winds and colder air/pressure gradient move over
the coastal waters. Seas should average 5-8ft at their peak this
afternoon. Freezing spray is also expected as temperatures plummet
today and especially tonight/Sun morning. A freezing spray
advisory remains in effect for today into Sunday morning.
Winds will slowly diminish Sun morning and are expected to fall
below 15kt late Sun afternoon/early evening. Although gale warnings end
for northern coastal waters early Sun afternoon...Small Craft Advisory headlines will likely
be needed for seas lingering around 5ft through late afternoon. Winds
stay fairly light through Sun night and early Monday from the east-southeast as
Arctic high pressure over the waters slides offshore. Another low
pressure system approaches from the SW late Monday night and is
expected to track NE across central Virginia on Tuesday. This will allow for a
modestly strong south-southeast wind of 20-30kt to develop with building seas
to 5-9ft and waves to 3-4ft (up to 5ft in the mouth of ches bay).
Small Craft Advisory winds anticipated Monday night through Tuesday...with seas remaining
elevated through at least Wednesday night due to a less potent system
pushing across northern Virginia Wednesday morning.
low water advisory cancelled for Atlantic side of the Maryland/Virginia
Eastern Shore. Water levels are running about 0.5 feet above
previous forecast. Meanwhile...strong northwest flow associated with an
Arctic cold front will produce blow-out tides and may lead to low
water advisories during low tide cycles this evening and Sunday
Maryland...Wind Chill Advisory from midnight tonight to 10 am EST Sunday
Virginia...Wind Chill Advisory from midnight tonight to 10 am EST Sunday
Marine...freezing spray advisory until noon EST Sunday for anz630>632-
Gale Warning until 10 am EST Sunday for anz650-652-654.
Gale Warning until 7 PM EST this evening for anz656-658.
Freezing spray advisory from 7 PM this evening to noon EST
Sunday for anz658.
Small Craft Advisory until noon EST Sunday for anz633-635>638.
Gale Warning until midnight EST tonight for anz630>632-634.