Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 112053

Area Forecast Discussion
National Weather Service Wakefield VA
353 PM EST Tue Dec 11 2018

High pressure builds over the area tonight through Thursday.
Low pressure approaches from the southwest Thursday night into


As of 355 PM EST Tuesday...

Latest WV/VIS satellite imagery showing northern stream upper
trough diving across the eastern Great Lakes into New England
this afternoon. At the surface, a surface wave continues to
deepen as it slides farther offshore of the lower Mid-
Atlantic/Carolina coast, in response to a departing southern
stream trough. Temperatures have been slow to warm inland with
snowpack over the piedmont into central VA/Nrn neck of VA.
Even with a mostly sunny/sunny sky this afternoon, temperatures
have topped out largely around 40 out west, to middle and upper
40s along the SE coastal plain. Temperatures will quickly
plummet into the 20s and 30s early this evening, setting up
areas of black ice once again tonight. Will note this in the HWO
once again, with an SPS to follow.

High pressure will build from the Gulf coast across the
southeast tonight, bringing a mainly clear, cold night across
the local area. Early morning lows in the teens to around 20
inland...upper 20s to low 30s along the coast.


As of 355 PM EST Tuesday...


High pressure moves offshore on Wednesday. A weak trough clips
the nrn Mid-Atlantic Thursday, with high pressure building
across New England in the wake of this system. Temperatures will
be slow to moderate through midweek given snow cover. Remaining
dry through the period as high pressure prevails under a partly
to mostly sunny/clear sky.

Low temperatures tonight range from the low 20s in the Piedmont, to
the upper 20s/around 30F toward the coast. Highs Wednesday range
from the low/mid 40s inland to the mid/upper 40s at the coast. Highs
Thursday range from the low 40s NW to the low 50s SE, after morning
lows in the mid 20s to low 30s.

Friday/Friday night...

After a quiet mid-week, the pattern will become more active on
Friday into the first half of the weekend. Good model agreement
continues that a strong southern stream shortwave will carve
out a broad upper trough over the southern plains on Thursday,
with that feature eventually closing off and pushing across the
southeast on Friday into Saturday. The associated surface low
will then develop over the TexArkana region late Thursday,
lifting across the mid-south Thursday night, before approaching
our area Friday into Saturday, as the surface high slips farther
offshore Thursday night and Friday.

Overall, model timing is a bit faster with the 12z/Tue suite of
models. ECMWF/NAM and Fv3 all depict overrunning moisture
pushing across the western half of the region Friday morning,
reaching the remainder of the CWA by late Friday afternoon. Rain
then continues across the area Friday evening with the steadiest
rainfall/highest likelihood of PoPs coming Friday night into
Saturday morning. Rain may be moderate to heavy at times. Rain
chances continue into the Saturday afternoon, especially across
the NE. At this time, left any thunder message just south of our
area where models currently indicate better instability. Ahead
of this system, a deep southerly flow will transport abundant
moisture into the region allowing for PWAT values to climb in
excess of 1.5" Friday afternoon into Saturday morning. Model
output shows anywhere from 1 to 2 inches of QPF over the local
area with this system, with ECMWF once again a bit wetter than
the remaining guidance. High QPF values in addition to the
melted snowfall from the previous winter storm will set the
stage for potential flooding issues. Cursory look at MMEFS shows
at least 50-60% probability for minor to moderate river flood
event across each of our river forecast points. A Flood Watch
will certainly be worth consideration with later forecast
packages if current setup remains in place in modeled data, and
will make a mention in HWO, given POPs already in likely to low
end categorical range for Friday afternoon and night.


As of 355 PM EST Tuesday...

Saturday`s low pressure system departs offshore by Sunday morning
with residual showers possible across far southern VA and northeast
NC as the upper level low swings across the region. Still some
disagreement between the models on this feature, decided to go
closer to the ECM/Fv3. ECM is still consistent with showing low
pressure redevelop off the NC coast Sunday night into Monday.
This would allow for rain showers to linger across the east into
Monday morning. The operational GFS is more progressive with
the upper level low, thus has dry weather by Sunday afternoon.
Introduced chance PoPs across the south and southeast Sunday
afternoon into Monday morning to take into account both model
solutions. Dry weather Monday and Tuesday as high pressure
builds back across the region. Temperatures moderate by this
weekend with southerly flow ahead of the next low pressure
system, currently have highs in the lower 50s NW to the low/mid
60s across the SE for Saturday. Sunday will feature highs in the
low to mid 50s across the region. Temperatures trend cooler
early next week as cool high pressure builds across the area.


As of 1205 PM EST Tuesday...

Low pressure is slowly moving farther off the Outer Banks at
midday. Sct-Bkn mid-level clouds have pushed offshore, leaving
mainly clear sky across terminals at 18z TAF time. Remaining
mainly sunny/clear sky through the TAF period this
aftn/tonight, with VFR conditions to prevail through the period.
A NNW wind of 5-10kt this aftn will become W 5kt or less by
tonight as high pressure slides across the Southeast.

Outlook: High pressure prevails Wednesday and Thursday. Low
pressure approaches from the SW Thursday night and Friday, and
tracks across the region Friday night and Saturday.


As of 345 PM EST Tuesday...

Conditions across the marine area continue to improve today as the
secondary area of low pressure off the Carolina coast pulls away
from the region. Winds have been decreasing from north to south
today with 10-15 knots prevalent across the northern Bay and ocean
zones and 15-25 knots from Cape Henry and points to the south. A
weak shortwave trough aloft and surface reflection will clip
northern zones late tonight and Wednesday morning bringing a short
lived stint of renewed cold advection and increased winds. Guidance
differs in the magnitude of cold advection/wind with the WRF
guidance showing the potential for a brief period of SCA conditions
for our northern Bay and ocean zones (north of Cape Charles). The
3km NAM is less robust with winds staying below SCA thresholds.
Given the lack of agreement and marginal wind magnitude will hold
off on introducing new headlines for the Bay with this package.
Waves are slowly decreasing as well with generally 1-2 feet in the
Bay, slightly higher at 2-3 near the Mouth of the Bay. Offshore is a
different story, seas 5-6 feet across the northern zones and 6-8
feet south of Cape Charles. Guidance has trended slower regarding
the reduction in wave amplitude offshore with 5 foot seas indicated
across all ocean zones through Wednesday morning. Therefore, will
extend SCAs for all ocean zones through 15Z tomorrow.

Tranquil marine conditions are in store for the mid week period as
high pressure builds into the area from the west. Longer term model
guidance shows a closed low aloft and surface low pressure
approaching for the end of the week. However, the timing, placement,
and magnitude of depicted low pressure vary substantially among the
GFS/ECMWF/GEM. Will show increasing winds/seas beginning Friday with
the potential for SCA conditions across the Bay and offshore zones
through Sunday.


MARINE...Small Craft Advisory until 4 AM EST Wednesday for
ANZ658-656-658. Small Craft Advisory until 7 PM EST this
evening for ANZ650-652.


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