Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 192000

Area Forecast Discussion
National Weather Service Wakefield VA
400 PM EDT Mon Mar 19 2018

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


Current wv imagery depicts a potent low pressure system
traversing the mid-Mississippi Valley this aftn. Locally, partly to
mostly cloudy conditions are occurring as high clouds stream across
the region. Mild with temperatures ranging from the low 50s NW to
the upper 50s/low 60s elsewhere. This system will result in
unsettled conditions beginning later tonight and continuing through
Wednesday, with two primary events.

The first event occurs tonight as a potent shortwave races ewd from
the TN Valley late this evening, with a surface low tracking across
NC late tonight/Tues morning before emerging off the mid-Atlantic
coast on Tuesday. Rather impressive lift progged with and north of
the sfc low to produce a widespread rain across the FA. Categorical
PoPs prevail for all areas with some moderate to heavy rainfall
possible late tonight into midday Tuesday. QPF amounts could exceed
an inch in some areas. Following a blend of the models, a triple
point low should track NE across NE NC and sern VA late tonight then
out into the VA Capes Tuesday morning. Thus, can`t rule out thunder
across those areas early Tues morning. Lows from the mid 30s north
to mid-upr 40s SE.

The sfc low deepens as it tracks across the VA Capes Tuesday
morning. This will result in windy conditions (NE wind) along the
Atlantic coast of the VA/MD Ern Shore where a wind advisory in in
effect mainly for areas from Chincoteague to Ocean City. The low
then lingers off the coast Tuesday aftn as weak high pressure tries
to nudge in from the north. This will result in the wind becoming
more northerly during the aftn. Likely to categorical PoPs Tues
morning (locally heavy rain early over the Eastern Shore), then
likely pops north and NE with chc PoPs south Tuesday aftn. Chilly
with highs nr 40/low 40s north to 55-60 se coastal areas.


The complex system will continue to impact the region
Tuesday night into Wednesday. There is still much uncertainty on how
the system evolves Tuesday night into Wednesday. However, the 19/12z
GFS/NAM/ECMWF have trended toward a deepening of the surface low
closer to the coast and the potential for frontogenetic banding over
the Delmarva. The upper level system pulls in enough cold air to
allow a transition to snow late Tuesday night into Wednesday. Chc
to likely PoPs Tuesday evening ramp up to likely to categorical
everywhere after midnight through midday Wednesday as the forcing
from the upper level system taps into moisture. Thicknesses suggest
a mixed/rain and snow event across the Piedmont Tuesday night
changing to all snow, and rain/snow Tuesday night changing to all
snow around daybreak Wednesday for central VA. A cold rain over the
Delmarva will change to snow Wednesday morning, and a cold rain for
SE VA/NE NC could mix with some snow Wednesday aftn. The current
forecast is for 1-3" of snow from the NW piedmont across central VA
to the Nrn Neck and the VA Ern Shore, with the potential for 3-5"
over the MD Ern Shore, with possibly 4-6" over Dorchester MD.
Elsewhere, expect an inch or less with no accumulation for far SE
VA/coastal NE NC. This is close to the WPC forecast. Have opted to
issue a Winter Storm Watch for the MD Ern Shore 10z Wed to 03z Thu.
Lows Tuesday night range from 30-32F NW to the upper 30s SE,
followed by highs Wednesday in the low/mid 30s where snow falls to
the upper 30s/low 40s where rain prevails.

Drier air arrives Wednesday night into Thursday as the system pulls
to the northeast. Partly to occasionally mostly cloudy under the
upper trough. Lows Wednesday night range from the mid 20s NW to the
low 30s SE, with highs Thursday in the mid to upper 40s, possible
cooler over the MD Ern Shore depending on snowfall Wednesday.


Remained close to WPC grids for the late week into early next week.
Overall, cold high pressure building to the NW will provide a
continuation of (much) below temperatures for much of the forecast
period. After a cool, dry day on Friday, rain chances increase once
again ahead of next system, which develops across the central plains
on Fri/Friday night...then tracks east, undercutting the omega block
in place over the northern tier of states through the weekend.
Remaining partly to mostly cloudy through the weekend, with rain
chances to increase later Sat into Sat night before becoming more
widespread on Sunday.

For temperatures, Highs Fri/Sat around 50F inland...m40s at the
coast. Lows Fri night in the l30s inland...u30s-around 40F at the
coast. Highs Sun/Mon in the 40s N to m50s S.


VFR conditions continue for the region with mostly mid and high
cloud ceilings. High pressure along the coast will gradually
move east and low pressure over the TN Valley will move towards
the Mid Atlantic coast over the next 24 hours. Clouds will
increase and thicken through the TAF period and rain will
overspread the through the evening and into the overnight. Rain
could be heavy at times and ceilings and visibilities may become
IFR during the overnight into Tue.

Outlook: Another window of flight restrictions late Tues thru
Wed. Rain for the most part may mix with or change to wet snow
by Wed at RIC and SBY. There could be some accumulations of an
inch or two. Gusty winds buffet the coast Tue and Wed as a
coastal storm develops.


This evening the area remains sub-SCA conditions as the sfc
high pressure slides offshore. Flow has become E to SE is
response to the low over the TN river valley which will jump to
the coast by Tuesday morning. E/SE persist this evening at 5 to
10 kt then increase overnight.

Through the overnight hour tonight the pressure gradient
tightens in between the approaching sfc low from the W, and
sfc high centered over ontario. The dilemma for the lower Bay
and Capes is models develop and deepen the surface flow
somewhere between Cape Henry to Oregon Inlet. With the low
forecast to develop right over the Capes this could limit the
wind speeds for a time until the low pulls off the coast. If
the low tracks south across NC then winds over the Bay and Capes
will be stronger. This will all be a matter of timing and storm
track. North of Cape Charles winds will st Gale Force no matter
the storm track.

Have continued Gale Warning N of Cape Charles and SCA headlines
for the remainder of the marine area. NE winds will ramp up
significantly by daybreak, as the initial sfc low stalls over
eastern KY and transfers energy to a developing sfc low across
the NC coastal Plain. Again the exact position of this will be
critical as to how strong the winds get in southern portions of
the marine area from the Capes south. For now, the consensus
has been to rapidly intensify the sfc low in the vicinity of the
VA/NC border Tue morning, then lift it NE and this would
support Gales staying a little farther north. Did add a mention
of gusts to 40 to 45 kt from Chincoteague north and gusts to 35
kt for portions of the Bay.

This initial low will track off the VA coast and then perhaps
stall off the DELMARVA Tue aftn/Tue evening. As the upper level
low enters the region late Tue night/Wed, a new surface low
will develop along/off the Carolina coast and lift it NE off the
Virginia coast during the day Wed. models merge this second low
with the initial low stalled off the coast. 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.

By Wed night/Thu morning, the sfc low will be moving well off
the coast and this will allow conditions to begin to relax with
NW flow continuing into Friday when high pressure finally moves
over the area. Seas likely to remain elevated for the coastal
waters such that SCA headlines will continue through at least
Thu aftn.

Seas will build rapidly Tuesday and due to the nature and
longevity of the event will remain high into Thursday.


Low pressure approaches from the TN Valley later today, and
intensifies just off the coast on Tue before pulling off to the
NE. Secondary area of low pressure lags back off the Carolina
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 tonight into Tue night, then winds
shift more to the NNW on Wed. 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 Late Tue night into midday Wed as the
anomalies will take awhile to build tonight through Tue.


MD...Wind Advisory from 8 AM to 8 PM EDT Tuesday for MDZ024-025.
     Winter Storm Watch from Wednesday morning through Wednesday
     evening for MDZ021>025.
VA...Wind Advisory from 8 AM to 8 PM EDT Tuesday for VAZ099.
MARINE...Small Craft Advisory from 1 AM Tuesday to 8 PM EDT Wednesday
     for ANZ630>632-634>638.
     Small Craft Advisory from 4 AM Tuesday to 8 PM EDT Wednesday
     for ANZ633-656-658.
     Gale Warning from 4 AM Tuesday to 2 PM EDT Wednesday for


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