Area Forecast Discussion
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FXUS61 KAKQ 230813
Area Forecast Discussion
National Weather Service Wakefield VA
413 AM EDT FRI SEP 23 2016
Low pressure along with a weak frontal boundary will remain
stalled along or just off the Carolina coast today. High pressure
builds over the local area late today into Saturday morning. A
backdoor cold front drops across the region during Saturday. The
center of high pressure slides into southeast Canada during
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Sfc low pressure along a stationary frontal boundary remains
along/just off the Carolina coast today. Meanwhile, weak high
pressure remains in place across the local area with a cold front
crossing the Northeast. The coastal boundary will remain an
influence on SE portions of the FA today, and will therefore
maintain slight chc to low chc pops 20-35% for scattered showers.
Elsewhere, dry wx is expected today with morning stratus/patchy
fog giving way to sunshine. Could be some breaks in the clouds
across SE areas before dark. A bit warmer today with highs from
the upr 70s/low 80s SE to the mid 80s N/W.
.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
Weak sfc high pressure remains over the area tonight but a
backdoor cold front sags south overnight and reaches the northern
FA toward daybreak. Meanwhile, the coastal boundary dissipates and
slides farther offshore. Mainly clear and dry tonight with lows in
the 60s to near 70. Patchy fog possible toward morning. The
backdoor cold front will drop across the region during Sat with
the center of sfc high pressure building into SE Canada by Sun
morning. Will maintain dry wx Saturday, with generally a partly
sunny sky. Highs from the upr 70s Eastern Shore to the mid 80s
S/W. Models are keying on increased low level moisture and some
weak isentropic lift in the wake of the backdoor front for
Saturday night into Sunday. However, the depth of moisture is
rather shallow favoring only low end pcpn chances for pockets of
light rain/drizzle. For now will show slight chc pops across the
Piedmont Saturday night and in areas west of the Bay on Sunday.
Will have mostly cloudy/overcast skies for areas mainly west of
the Bay during this same time, and partly to mostly clear skies
for the Eastern Shore. Lows Saturday night from the mid 50s lower
MD Eastern Shore to the 60s elsewhere. Highs Sunday only in the
low to mid 70s.
.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
Medium range period characterized by continued large differences
amongst the deterministic models and even within their member
ensembles. Forecast period begins Sunday night with an amplified
upper level ridge/trough pattern, with the ridge axis being
centered from the OH/TN river valleys Into the central Gulf Coast.
At the surface, cool air wedge will continue to ridge down across
the local area from New England/QC. Have retained a slight chance
for some light rain Sunday night in association with some weak
overrunning moisture. Otherwise, remaining primarily dry albeit
with increasing clouds once again Sunday night and Monday.
Higher than average uncertainty remains for the remainder of the
forecast period, although it does appear as if the models are
trending toward a solution. The 00z/GFS and GEFS mean remain much
stronger than the ECMWF with strong upper ridging and a potent
(closed off) downstream trough over the upper midwest by later
Mon/Tue. By contrast, the 00z/ECMWF and the 12z/Thu EPS before it
confines blocking farther back (west) into the Canadian
Rockies...with the downstream, more progressive upper trough
quickly shoving through a strong cold front across the local area
by mid to late week (as soon as Later Wed/Thu). The CMC remains
the slowest solution wrt displacing the upper ridge off shore, and
therefore is the warmest/driest solution. Taken at face value, the
GFS solution would lead to more of a strong blocking pattern that
would slow the eastward progression of upper ridge axis
considerably, while the ECMWF would bring a quicker frontal
passage and resultant cooler temps for the late week period.
The good news is that the GFS has trended a bit toward the
operational EC with respect to shifting the Sfc high offshore
Tuesday into Wednesday...depicting a strong sfc cold frontal
passage for the mid to latter portion of next week. Have made
minimal changes to the going forecast for now until more
definitive model consensus can be reached and ideally retained
for a few cycles.
For temps, Highs will start off cool, averaging in the low-mid
70s with early morning lows in the upper 50s to mid 60s Mon. Sfc
high pressure becomes centered offshore by late Tue-Wed w/deeper
moisture and a strong front to approach the area from the W. Pops
remain a bit more broad-brushed in slight chc range 20% POP for
now during this period. Highs will avg 75-80 F Tue/Wed with lows
mainly in the 60-65 F range. Cooler by late in the week, with 00z
MOS guidance advertising highs trending back into the low to mid
70s post-frontal by next weekend. Again, will stay close to the
inherited forecast for now.
.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
Abundant low level moisture and onshore flow are promoting
widespread MVFR conditions this morning with some IFR cigs at
KSBY/KECG. These conditions will be slow to improve thru the late
morning. More favorable conditions are expected by midday today
with VFR conditions and mainly dry weather across the area.
OUTLOOK...A cold front sags south through the Mid Atlantic States
during the weekend. There are some indications that low clouds and
patchy light rain/drizzle could impact the TAF sites Sat night
Latest obs reflect diminishing NNE flow across the waters as
pressure gradient has relaxed over the past 3-6 hours w/weakening
low pressure lingering along the NC/SC coastline, even as high
pressure slowly builds south. Have dropped SCA across the waters
this morning, with seas finally subsiding a bit.
Winds remain sub-SCA out of the NNE today, winds 10kt or less. Seas
subside to 3-4 ft, 2-3 ft on the bay. Winds pick up a bit late
tonight as a weak Cold front drops across the waters late tonight
into Saturday, stalling just south of the waters Sat night and
Sunday before sliding south into the Carolinas on Monday. CAA surge
behind the front appears minimal. Wave energy kicks up on Saturday,
courtesy of distant tropical Cyclone Karl Invof Bermuda. Resultant
long period swell could well bring a period of SCA for hazardous
seas over the coastal waters Saturday/Sat night, averaging 4-5 ft
highest out by 20 nm marker. Wavewatch and NWPS both depict seas
subsiding once again for Sunday through Sunday night.
The Cashie River at Windsor is still within major flood stage,
which begins at 13 ft. The river is forecast to fall to around 12
ft by this evening (moderate flood stage) before steadily falling
over the next several days...possibly dropping back below flood
stage late Sunday.