Area Forecast Discussion
Issued by NWS Wakefield, VA

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FXUS61 KAKQ 231153
AFDAKQ

Area Forecast Discussion
National Weather Service Wakefield VA
653 AM EST Tue Jan 23 2018

.SYNOPSIS...
A trough crosses the region this morning...with the cold front
lagging behind and moving through the region by late afternoon.
The front pushes well off the coast tonight. High pressure
becomes centered over the south central states Wednesday and
builds east into the local area by Thursday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Sfc lo pres found invof north central MI attm will be tracking
ENE into SE Canada today. Its accompanying cold front was the
approaching the mtns attm...and will be crossing the FA midday-
afternoon. Moisture continuing to increase ahead of the FA along
the E coast on S winds (becoming gusty). Area of SHRAs now
moving through west central NC and SW VA will be spreading into
at least wrn/central portions of the FA before sunrise.

Maintaining hi PoPs (60-90%) this morning as cold front
enters/begins to cross (wrn/central portions of) the FA. Will
have widespread SHRAs w/ possible ISOLD tstms (despite minimal
instability/CAPE). Model SHERB values are from +1 to +1.5
between 12-18Z/23...though this parameter does have some
limitations and the synoptic pattern (sfc low into Great
Lakes)/composites (lack of a sharp-digging upper level system
just W of the immediate region/dissimilar upper level jet
structure) do not portray a high prob for tstms/strong-severe
threat for the local area (substantially different from event
earlier this month (eve of the 12th)). SPC maintains a marginal
risk for severe...and if a distinct line or some discrete cells
do develop Tue morning...they will need to be monitored closely
(given strength of low level SSW jet). Will maintain mention in
HWO. Models remain in good general agreement wrt timing and
point to PoPs tapering off W-E quickly by aftn...w/ pcpn moving
out of the entire area by 21Z/23-00Z/24. VRB clouds-partly sunny
by afternoon...deep mixing and a downslope SW flow...highs will
be 70-75F across much of central/SE VA and NE NC...w/ 65-70F on
the eastern shore and over the W/NW sections of the FA (record
highs noted in CLIMATE section below).

&&

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY/...
Dry cooler tonight/Wed w/ lows mainly in the 30s (around 40 F
SE). Mostly sunny with highs Wed u40s on the ern shore to 50-55
F elsewhere. Partly cloudy as an upper trough swings through Wed
night with lows in the u20s-l30s. Mostly sunny and seasonable
Thu w/ highs from the l40s NE to around 50 F south central VA.

&&

.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/...
Overall pattern continues to show the long term period beginning
with a shortwave ridge building eastward from the Mississippi
Valley into the Southeastern US and Mid-Atlantic states on
Friday into Saturday. This is followed by a full latitude trough
that moves in on Sunday into Monday. But today, the timing
between the models and strength of the cold front crossing the
area is different with the 12z GFS slower and weaker while the
12z ECMWF is slower, stronger and would provide more rain for
the region. The ECMWF right now has better run to run continuity
than the GFS as the 6z GFS was slower and wetter than the 12z
run. So for now have leaned a little more toward the slower
ECMWF for that part of the forecast.

On Thursday night through Friday, high pressure will be in
control of the regions weather with the high overhead expect to
see a very cool night with good radiational cooling, lows in the
m20s-l30s. Temperatures will begin to warm again on Friday as
warm advection begins with sw flow, expect highs in the u40s to
u50s. Mex guidance is a bit warmer and began to trend that
direction raising highs a few degrees above the other guidance.
The SW flow continues on Fri night with more dry weather and
maybe a few more clouds. Temperatures in the mid to upper 30s
are expected.

For Saturday through Sunday night, this is where the most
interesting portion of the extended lies as the quicker GFS has
the moisture and front approaching the area by late Sat
afternoon, which is about 6 to 12 hours faster than the 6z GFS
or ECMWF. At this range, did raise pops a touch, but kept the
forecast dry on Sat with temperatures getting back into the U50s
to l60s. But beginning Sat night did start to raise pops up to
high chance values. Some guidance suggest pops in the likely
range are possible now, but with timing issues and also the
questionable forcing have capped pops at 50% from Late Sat night
through Sunday with a slow clearing of the pops in Sunday
evening. Sunday looks like the most probably period for rain and
the ECMWF would indicate a beneficial rain, which would be good
for the drought areas, but at this range models have been
showing these types of events for the last few weeks, but the
plentiful rain has been materializing. Have kept temps mild on
Sat night and Sunday with lows in the 40s and highs still in the
60s.

The front should clear the area Sunday night with NW and high
pressure building in on Monday. The strength of the developing
upper trough will determine how strong the low over New England
gets Sunday night and this will impact temps on Monday. The
ECMWF would suggest temperatures cooler than the currently
forecast in the upper 40s to mid 50s on Monday. But for now will
not bit completely on the ECMWF.

&&

.AVIATION /12Z TUESDAY THROUGH SATURDAY/...
Lowering CIGS (to IFR/low end MVFR) continuing this morning. A
cold front is approaching from the W attm...and will push across
the FA late this morning/midday...then off the coast this
afternoon/eve. The front will be accompanied by SHRAs.
Instability with the front will also bring a lo prob for ISOLD
tstms through midday/early afternoon. Only mention of VCTS will
be at ECG. Clearing/improving conditions expected during the
afternoon/eve. Sfc hi pres builds into the local area from the
SW through Thu.

&&

.MARINE...
A tightening pres gradient ahead of an approaching cold front
will increase winds to 15 to 25 kt from the S-SW this morning.
These winds will persist thru midday/early aftn becoming rather
gusty by mid morning. Seas on the coastal waters building to
4-6 FT; waves 3-4 ft on the Bay rather quickly in response to
the SW winds. SCAs remain in effect for all waters today. With
the primary surface low so far displaced to the north it will be
hard to get Gales with warm S-SW winds over cold water this
time of year, but did keep mention of a few gusts to 35 kt for
our northern coastal waters.

Once the front clears the area late this afternoon/evening,
winds will shift to the west 15 kt tonight/Wed and then
northwest on Thursday. Waves/seas subside to 2-3 ft. There is
another surge of cold air Wed night into early Thu which will
maintain the NW winds of 15 kt with some higher gusts. Waves and
seas may increase by a foot to 2 to 4 ft with this surge Thu.
Conditions improve by Friday as high pressure builds into the
area.

&&

.CLIMATE...
Record high temperatures today.

     Tuesday
RIC  76/1974
ORF  76/1999
SBY  73/1999
ECG  76/1937

&&

.AKQ WATCHES/WARNINGS/ADVISORIES...
MD...None.
NC...None.
VA...None.
MARINE...Small Craft Advisory until 6 PM EST this evening for
     ANZ630>638.
     Small Craft Advisory until midnight EST tonight for ANZ650-652-
     654.
     Small Craft Advisory until 10 PM EST this evening for ANZ656-
     658.

&&

$$
SYNOPSIS...AJZ/LKB
NEAR TERM...ALB/LKB
SHORT TERM...ALB/LKB
LONG TERM...ESS
AVIATION...ALB
MARINE...MAS
CLIMATE...



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