Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 211449

Area Forecast Discussion
National Weather Service Wakefield VA
1049 AM EDT Wed Mar 21 2018

Low pressure off the Virginia Capes early this morning, will
intensify off the Delmarva coast this afternoon, before
gradually pushing well off to the northeast tonight. High
pressure over the midwest will gradually build into the area
Thursday and Friday. Low pressure moves east from the mid
Mississippi Valley on Saturday and tracks through the Carolinas
on Sunday.


Latest analysis indicating ~993mb sfc low pressure intensifying
off the VA Capes. Precip shield is best organized from central
VA to NE MD and sern PA. Accumulating snow is occurring from the
Piedmont across central VA toward the Nrn Neck. Snow
accumulation over these areas have averaged 1-3" through late
morning. Temperatures range from 30-32F well inland to the upper
30s along the coast. Choptank River bridge webcam indicates snow
is mixing in near Cambridge. Rain is prevailing closer to the
coast with perhaps some sleet mixing in with heavier pcpn rates
as 1000-850mb thickness rates are falling.

The surface low will deepen through the day, while shifting NNE
off the Delmarva coast by late morning and aftn. The general
trend in model guidance has been for a little faster shift to
the north of the the deep lift through the DGZ this morning. As
such, expecting bulk of accumulating snow over much of the
advisory zones to occur this morning into early aftn with just
scattered snow showers (or potentially rain/snow showers by
mid to late aftn. The upper level system slides offshore from
18-21Z during the aftn with the overall system becoming stacked
and nearly stationary off the coast during the 18-00z time
period. This will bring the potential for banded pcpn (in the
form of snow) across the Delmarva and perhaps the Nrn Neck back
west to Caroline County.

Likely to categorical PoPs everywhere through through midday
today as the forcing from the upper level system taps into
moisture, and categorical PoPs over the Ern Shore into the aftn.
Thicknesses suggest rain will take longer to mix with snow over
the Ern Shore, mainly not until the aftn (Dorchester may become
all snow for this morning), then becoming all snow by aftn
evening. Farther W (I-95 corridor to the Piedmont) thicknesses
suggest all snow while pcpn occurs, with snow tapering off from
SW-NE during the aftn, and possibly mixing with light rain at
the tail end. A cold rain for SE VA/NE NC could mix with some
snow this aftn/early evening. The current forecast is for 3-5"
for Louisa, Caroline County and the Nrn Neck, and
Somerset/Wicomico/Dorchester MD. These areas have a winter storm
warning. Elsewhere, 1-3" of snow is forecast in a corridor
along a FVX- RIC-WAL line where winter weather advisories are in
effect. The primary impact will be falling snow with conditions
improving once the snow ends. Accumulation on roads will be
dependent on intensity, otherwise, expected accumulation mainly
on the grass and elevated surfaces. Accumulation farther S
should be 1" or less, and little to no accumulation for far SE
VA/coastal NE NC. Highs today will be in the mid 30s where snow
falls to the upper 30s/low 40s where rain prevails. Highs in
south central VA may rise to the lower 40s later in the aftn as
the precip intensity diminishes.

By the evening, mainly just scattered snow showers with the
exception of the ern shore where a more significant additional
snow accumulation is expected after sunset. Drier air look to
finally win out even acrs the eastern shore by around midnight
or shortly thereafter as the sfc low is progged to then shift NE
twds the New england coast. This will bring an end to any
additional accumulating snow. Becoming partly cloudy most areas
after midnight, except staying mostly cloudy on the eastern
shore. Lows range from the mid/upper 20s NW to the low 30s SE.
Some re- freezing is expected to occur early Thursday morning
especially if the (partial) clearing does occur late tonight.


Upper low will be off the New England coast thu, with another
one progged to dive SE from the upper Great Lakes Thu night and
Fri. This will keep temperatures well below normal for late
March. Highs Thursday in the mid to upper 40s north to around
50 F to the lower 50s over southern VA and NE NC (possibly
cooler over the MD Ern Shore depending on snowfall totals). Lows
Thursday night range from the mid 20s to low 30s, with highs
Friday in the mid-upper 40s N to lower 50s S.


Region remains influenced by large scale upper trof through most
of the extended period. Area is between systems Friday night and
most of Saturday. A shortwave trof will be approaching from the
west Saturday night, and move across the area on Sunday. Latest
00Z GFS/ECMWF remain somewhat at odds with regard to how far
north precip gets with this shortwave. Have gone with a blended
solution, which gives a chance of rain/snow across much of the
area. Shortwave moves offshore Sunday night, with ridging
surface and aloft gradually building into the region Monday
through Tuesday. Overall, cold high pressure building in from
the the NW will provide a continuation of below/much below
normal temperatures for much of the forecast period.

For temperatures, Highs Sat mid 40s to around 50 F. Lows Sat
night generally 30-35, with some upper 30s NE NC. Highs Sun in
the 40s to around 50 F, and Mon mid to upper 40s N/DELMARVA to
mid 50s southern portions of interior NE NC. highs Tuesday
around 50 Lower MD Eastern Shore to the upper 50s interior NE
NC. Lows Sunday night/Monday night in the low to mid 30s.


Low pressure is located off the VA Capes as of 11Z, with high
pressure centered N of the Great Lakes ridging swd into northern
VA. IFR/LIFR conditions prevail at all terminals and should
genly stay that way through the aftn/early evening. Area of
precipitation currently advancing from SW to NE across the
region with mainly snow in the NW Piedmont and now at KRIC with
rain at other terminals. Rain will continue to change to snow
from NW to SE across the area through the remainder of the
morning hrs, but will be slow to make it to the coast and
eastern shore. Will probably take until 15-18Z at KSBY/KPHF,
and KORF probably after 18Z. A N/NW wind of 10-15kt with gusts
to around 20kt is expected, especially near the Bay/Ocean.

Accumulating snow potentially lingers at KSBY this evening.
Otherwise, drier conditions arrive later tonight, with dry and
VFR conditions to prevail Thursday and Friday. Low pressure
approaches from the W late Saturday, with the potential for sub-
VFR flying conditions Sat night into Sunday.


Current observations as of 730Z show North winds of 15 to 25 knots
over the waters with gusts to 30-35 knots as low pressure
intensifies off the coast. Seas range from 8 to 13 feet across the
northern coastal waters and 7 to 10 feet across the southern coastal
waters. Waves range from 3 to 5 feet (up to 6 feet at the mouth of
the Bay). A Gale Warning remains in effect for the northern two
coastal water zones and Small Craft Advisories remain in effect the
rest of the waters.

Low pressure will continue to develop off the Mid Atlantic coast
this morning and slowly lift NE off the Delmarva and New England
coasts today into Thursday. Went ahead and dropped the Gale Warning
from Parramore Island to Cape Charles Light as guidance has
continued to back off slightly on the winds today. Could still see an
occasional gust to 35 knots in this zone, especially out 20 nm.
Otherwise, Small Craft Advisories remain in effect for all other
marine zones through Thursday afternoon. Expect N-NW winds of 15 to
25 knots with gusts to 30 knots with elevated seas between 8 and 13
feet north and 7 and 10 feet south.

Low pressure moves away towards the northern Atlantic late Thursday
through Friday allowing for conditions to slowly relax. Small Craft
Advisories may persist into early Friday for the coastal waters due
to seas remaining at or above 5 feet. High pressure finally builds
over the area Saturday before another low pressure system
potentially impacts the waters Sunday.


Coastal Flood Advisories remain in effect along the Atlantic
Coast through late tonight. Increased swell energy in the wake
of a series of developing low pressure areas will allow for
elevated water levels and the potential for some minor flooding.
Guidance continues to indicate tide levels of 1 to 2 feet above
normal through tonight. Stiff north/northwest winds should limit
the flooding threat in the Bay and Rivers, but a few locations
may approach action stage through the next couple of high tide


MD...Coastal Flood Advisory until 4 AM EDT Thursday for MDZ024-025.
     Winter Weather Advisory until midnight EDT tonight for MDZ024-
     High Surf Advisory until 8 PM EDT this evening for MDZ025.
     Winter Storm Warning until midnight EDT tonight for MDZ021>023.
NC...Coastal Flood Advisory until 4 AM EDT Thursday for NCZ102.
VA...Winter Storm Warning until 6 PM EDT this evening for VAZ048-
     Winter Weather Advisory until 6 PM EDT this evening for
     Coastal Flood Advisory until 4 AM EDT Thursday for VAZ098>100.
     Winter Weather Advisory until midnight EDT tonight for VAZ099.
     High Surf Advisory until 8 PM EDT this evening for VAZ099-100.
     Winter Weather Advisory until 9 PM EDT this evening for VAZ078-
     Winter Storm Warning until 9 PM EDT this evening for VAZ064-
MARINE...Small Craft Advisory until 4 PM EDT Thursday for ANZ630>632-
     Gale Warning until 7 PM EDT this evening for ANZ650-652.
     Small Craft Advisory until 1 PM EDT Thursday for ANZ633-


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