Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 120324
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
1024 PM EST Wed Jan 11 2017

.SYNOPSIS...
High pressure will extend across the region overnight through
Friday morning. A backdoor cold front drops down from the north
Friday afternoon and evening as high pressure builds over New
England. Some unsettled weather is expected during the upcoming
weekend.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Have not seen as much fog/low stratus development this evening
as previously expected, and latest hi-res guidance is not all
the impressed with fog formation overnight. Think that the presence
of mid/high clouds and just enough wind to allow the atmosphere
to remain stirred up will prevent widespread fog formation.
Therefore, have amended forecast to just allow patchy fog
overnight. Current dew pts are sitting in the mid 40s to low 50s
so temperatures overnight will not deviate too much from
current levels and may actually rise a degree or two.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH SATURDAY/...
A weak trough forms well north of the area on Thu and slowly
advances back on the Mid Atlantic Region. Meanwhile, warm air
advection continues, especially as the sfc pressure gradient
begins to tighten with the approaching boundary. S-SW winds
start out breezy with gusts of 15-20 mph then become more SW by
early aftn and gusting up to 25 mph. The MD/VA Eastern Shore
will experience higher gusts (up to 25 mph in the morning; up to
30 mph in the aftn). Bumped up highs by several degrees into
the mid-upper 60s inland (lower 60s immediate coast) based on
enhanced mixing in sw flow/warm air advection, gradually
clearing/thinning of clouds during the day, and temperature
trends over the past several days where observed temps were
several degrees warmer than the forecast. Breezy southwest winds
persist into Thu night as the trough drops into the region from
the north late Thu night. Overnight lows will be warm once
again with readings generally around 50F.

The trough crosses the area from nnw to sse Fri morning and
effectively outruns the backdoor cold front, which will drop
into the region late Fri aftn into the evening. Temperatures
will be slow to cool from north to south, therefore am
anticipating highs in the mid-upper 50s far nrn counties and
60-65F along/south of Interstate 64. However, dewpoints should
begin to fall more rapidly during the aftn. Model data varies in
the strength of shortwave moisture/energy riding being squeezed
btwn a strong sfc high pressure building to the north and an
upper level ridge over the Southeast/Gulf of Mexico, however
they all agree with bringing precipitation into/along the cold
frontal boundary Fri evening into Sat. Overall the temperature
differential behind the cold front is not as significant as the
last few blasts of Arctic air experienced across the region.
However, it will be enough for precip to begin as all rain Fri
evening which is then expected to transition into a wintry mix
of primarily sleet/freezing rain across nrn counties from
Louisa/Fluvanna counties to the Nrn Neck to the MD/VA Eastern
Shore (staying just north of Richmond attm). Remaining srn areas
will see all rain. An in-situ cold air wedge remains firmly in
place during Sat. Although precipitation is expected to taper
off through the day, precip-type across the north should stay a
wintry mix across the north as the wedge struggles to erode in
the beginning stages of weak warm air advection. If any
ice/sleet accumulation occurs, amounts should easily be less
than 0.05 inches. Overall liquid precip totals should be
0.10 inches or less. Lows Fri night in the lower 30s within
aforementioned wintry mix areas, mid-upper 30s SCntrl VA/SE VA/
inland NE NC, and around 40F coastal NE NC.

&&

.LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/...
High pressure slides across New England early next week with a
weakening frontal boundary meandering across the sern US.
Several weak impulses of energy progged to move east across the
region resulting in periodic chcs for pcpn Sunday and Sunday
night. Thermal profiles suggest some mixed pcpn (rain/sleet)
across the lwr MD eastern shore late Saturday night/early Sunday
morning. Otw, cloudy with light rain/drizzle. Lows Saturday
night in the 30s. Highs Sunday in the 40s except lwr 50s srn
most zones. Lows Sunday night in the 30s.

A warm front lifts north across the area Monday as low pressure
tracks NE into the upr Gt Lakes region. The trailing cold front
not progged across the area until next Thursday. Despite the fa
being in the "warm sector" data suggests plenty of moisture at
different levels to keep the skies rather cldy with periodic
chcs for pcpn. Went ahead and changed pcpn type to more of a
convective one Tuesday and Wednesday. Highs Monday mid 40s-lwr
50s. Lows Monday night mid 30s to lwr 40s. Highs Tuesday ranging
from 50-55 eastern shore to the lwr 60s west of the bay. Lows
Tuesday night in the 40s. Highs Wednesday from the lwr-mid 50s
Eastern shore to lwr-mid 60s west of the Bay.

&&

.AVIATION /04Z THURSDAY THROUGH MONDAY/...
VFR conditions prevail at all the taf sites this evening.
Satellite imagery and obs showing mostly low and mid level
clouds with heavy shield of high clouds farther north from Md to
ME. A cold front extends from the upper Great Lakes to OK with a
warm front over the Oh Valley. Lots of ground moisture exists
after the melting snow over the past 24 hours and this will
likely produce some locally dense fog across the region. However
there should be enough gradient wind to prevent the fog from
becoming widespread. Expect generally MVFR cigs with the chance
of some spotty areas of IFR stratus and vsbys. Another concern
is for some low level wind shear ~2000 ft overspreading the
terminals during the overnight hours and persisting through
~12Z. The warm front will lift north of the region on Thursday
with a more breezy SW flow with gusts to 20-25 KT and mainly VFR
conditions developing between 12-15Z/Thu (and LLWS diminishing
as the higher winds mix down to the sfc).

A backdoor cold front drops back into the area Friday, shifting
winds back to the N/NE as strong high pressure builds north of
the region. This has the potential to bring another round of
degraded flight conditions Fri-Sat, with some mixed precipitation
possible by Sat morning over the N and mainly rain elsewhere.
Continued flight restrictions possible into Sunday as a frontal
boundary lingers across southern Va or NC.

&&

.MARINE...
Hoisted SCA headlines for the Ches Bay and northern coastal
waters Thursday into Thursday evening as SW gradient tightens.
Gusts to between 25-30 kts over the coastal waters are possible
with minimal SCA`s in the Bay. Will also be monitoring the
potential for morning fog across the waters Thursday before the
winds increase. Will carry 1-3NM VSBYS for now.

Backdoor cold front moves north to south across the waters
Friday turning the winds back into a NNE direction. Models
continue to indicate a meager gradient over the waters, but with
a 1045+mb surface high tracking across the Great Lakes, SCA
conditions are possible so went ahead and bumped up the
sustained winds a bit. Seas also build Friday night to 4-6 feet.
High pressure slides into New England Saturday, ridging
southward over the waters. Onshore flow persists.

&&

.TIDES/COASTAL FLOODING...
Latest storm surge guidance indicates a period of below normal
tides early Friday morning. Tidal locations along the Atlantic
coast and the mouth of the Chesapeake Bay can expected
departures of -1.0 to -1.25 MLLW. A Low Water Advisory has been
issued to account for this.

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Low Water Advisory until 4 AM EST Thursday for ANZ634-650-652-
     654-656-658.
     Small Craft Advisory from 7 AM to 6 PM EST Thursday for ANZ632-
     634.
     Small Craft Advisory from 7 AM Thursday to midnight EST
     Thursday night for ANZ630-631.
     Small Craft Advisory from 7 AM Thursday to 5 AM EST Friday for
     ANZ650-652.

&&

$$
SYNOPSIS...BMD
NEAR TERM...BMD/JDM
SHORT TERM...BMD
LONG TERM...MPR
AVIATION...LKB/JEF
MARINE...MPR
TIDES/COASTAL FLOODING...AKQ



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