Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 190131

Area Forecast Discussion
National Weather Service Wakefield VA
931 PM EDT Sun Mar 18 2018

High pressure moves off the Mid Atlantic coast overnight. A
pair of low pressure systems will impact the region late Monday
through Wednesday. High pressure builds into the area late in
the week.


Sfc hi pres near the coast attm drifts a bit more to the E
overnight. Mainly SKC a bit while longer then increasing clouds
by late in the night (esp W). Lows in the l-m30s.


The high pushes farther off the coast Monday allowing moisture to
overspread the area due to the onshore flow. Lower levels remain dry
thru about 18Z so look for skies to become mstly cldy to cldy. Some
overrunning light rain (a few hundredths at best) progged to develop
across the Piedmont after 18Z. Highest pops (30-50%) west of the I95
corridor. Highs 45-50 near the coast, in the 50s west of the Bay.

A complex weather system will make for an unsettled mid week period.
Will lean toward a GFS solution as it seems the NAM generates to
much cold air in the boundary layer. Inland concerns range from
mdt to lclly hvy rainfall along with sct tstrms across the se
Mon night, rain mixing with or changing to wet snow Tues night/Wed
(with minor accumls). Coastal issues range form gale force wind
gusts Tues to possible coastal flooding thru the mid week period.
Stay tuned.

First event occurs Mon night as a potent shortwave races eastward
from the TN Valley Mon evening, then across the local area Mon
night. Rather impressive lift progged out ahead of the apprchg low
to produce a widespread rain across the fa. Will carry categorical
pops all areas with some moderate to heavy rainfall possible after
midnight. QPF amounts could exceed an inch of some areas. Again,
following the GFS, a triple pt low will track ne across ne NC and
sern late Monday night then out into the Vacapes Tue morning. Thus,
can`t rule thunder across those areas late Mon night. Lows from the
mid 30s north to mid 40s south.

The sfc low deepens as it tracks across the Vacapes Tues morning,
then pushes farther out to sea Tues afternoon as weak high pressure
tries to nudge in from the north. Will carry likely to categorical
PoPs Tues morning (lclly hvy rain erly ovr the lwr Md ern shore),
except chc PoPs far SW, as the best lift shifts east prior to 18Z.
Chc pops north and east with slight chc PoPs SW Tues afternoon.
Chilly with highs 40-45 north, 50-55 se coastal areas.

Still much uncertainity on how the systm evolves Tues night and Wed.
The first low progged to pull away from the coast Tue night with the
next upr level systm crossing the area Wed. This upr level systm
pulls in enuf cold air to allow p-type issues both periods. Chc pops
Tue evening ramp up to like after midnight as the moisture from the
upr lvl systm crosses the mts. Thicknesses suggest a changeover
from a rain/snow mix to mostly snow across the nw, a buffer area
of mixed/ran and snow on a line from OXB-PHF-AKQ-EMP with a cold
rain across the se. Temps drop into the lwr 30s north and west,
mid-upr 30s se.

Wed could be a repeat of last Mon`s event in where it will take pcpn
intensity to dynamically cool the column to get snow to accum with
temps aoa freezing. Despite thicknesses supporting all snow, will
keep chc to low end likely pops and go with a snow to rain/snow
mix across most of the fa except remaining rain along the outer
banks. It very well may stay snow inland, but sfc temps along with
pcpn intensity will determine how much can accumulate. Given the
synoptic situation, went lower than guidance with highs in the mid
30s north, upr 30s to near 40 se.

Accumulation wise, expect that the best snow accumulations Tue night
will be across the nw with up to an inch (from near a FVX-LKU line
by 12Z Wed. Trace to less than an inch as far east as a SBY-PTB-AVC
line. Wed accumls rather problematic. Will generally go with a 1-2
inch event mainly nw of a SBY-RIC-AVC line for now.


Deep/anomalous trough aloft will remain near the E coast Thu-Fri
before slowly shifting E next weekend. Meanwhile...blocking upper
level high will remain invof Hudson Bay. Using a blend of
GFS/WPC/ECMWF through the period. Expecting a continuation of (much)
below temperatures Wed night/Thu-Sun. Lingering clouds/ISOLD-SCT
RA/SN Wed eve (esp toward the coast)...then Dry/cool wx Thu-Fri.
Next lo pres system develops invof nrn Plains by Fri...then tracks E
(undercutting the upper level high N of the Great Lakes) through the
mid-Atlantic/NE CONUS next weekend...bringing increased clouds/PoPs.

Lows Wed night in the u20s W to the m30s right at the coast. Highs
Thu ranging through the 40s. Lows Thu night in the u20s W...m30s at
the coast. Highs Fri around 50F inland...m40s at the coast. Lows Fri
night in the l30s inland...u30s-around 40F at the coast. Highs Sat
in the u40s-l50s inland...m-u40s at the coast. Highs Sun in the 40s
N to m50s S.


VFR conditions prevail across the region as high pressure along
the coast will slowly move offshore tonight. High level clouds
overspread the area Mon morning and afternoon ahead of the next
system approaching from the SW. Any pcpn with this system will
hold off until after 18Z Mon. Rain will overspread the region
Mon night into Tue. Ceilings and visibilities will generally
decrease to MVFR conditions during the overnight.

Outlook: Another window of flight restrictions Mon night thru
Wed as a pair of low pressure systems impact the area. Rain for
the most part may mix with or change to wet snow by Wed at RIC
and SBY. Gusty winds develop along the coast Tue and Wed as a
coastal storm develops.


Winds and seas continue to relax across the region this afternoon as
high pressure builds across the Mid-Atlantic states.  This area of
high pressure will slowly move off the coast and weaken tonight and
early Monday afternoon.  But it will provide benign conditions
across the waters tonight and Monday.

Beginning Late Monday afternoon conditions will begin to
deteriorate as the next storm system ejects out of the Southern
Plains into the Tennessee River Valley.  Initially, will see the
flow turn serly and still remain rather light in the 10 - 15 kt
range.  But by Tuesday morning, will begin to see sfc low
development over the NC Piedmont with that low sliding NE and off
the Virginia Beach Coast by mid day Tuesday.  At this low
intensifies, the winds will increase quickly, especially over the
northern coastal waters were gale conditions are expected.  South
and west of the surface low, the conditions should remain at SCA
levels.  This initially low will head out to see on Tuesday night,
but as the upper level low enters the region on Wednesday, a new
surface low will develop off the Virginia coast and another round of
Gale force conditions are likely across the northern coastal waters
while SCA conditions with 25 to 30 kt winds are likely over the
remainder of the area.  Seas will build pretty quickly as well on
Tuesday into Wednesday with seas getting up to 8 to 12 FT on the
coastal waters.  For now, have maintained the Gale Watch as Gale
conditions are not likely to be reached before Tuesday morning, but
did extended the watch through 00z Wednesday and depending on the
timing of the gap between the two sfc lows may end up with one long
gale through Wednesday.

By Thursday morning, the sfc low will be moving off the coast and be
a could hundred miles SE of Cape Cod.  This will allow conditions to
begin to relax with NW flow continuing into Friday when high
pressure finally moves over the area.


Low pressure approaches from the TN Valley on Monday, and
intensifies just off the coast on Tue before pulling off to the
NE. Secondary area of low pressure lags back off the SE coast
and tracks NE off the mid-Atlc coast Wed/Wed night. This pattern
will allow for a strong and persistent NE flow into much of the
local area from late Mon into Wed, leading to building tidal
departures and the potential for at least minor coastal flooding
over locations adjacent to the lower Bay and the Atlc coast
from Ocean City to Currituck NC. Current forecast projections
give the greatest chance for flooding on Wed as the anomalies
will take awhile to build Mon night through Tue. If the
system(s) were to slow down, there is some potential for
moderate flooding by Wed but that remains rather uncertain at
this time.


MARINE...Gale Watch from late Monday night through Tuesday evening for


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