Area Forecast Discussion
Issued by NWS Wakefield, VA-- Remove Highlighting --
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FXUS61 KAKQ 251747
Area Forecast Discussion
National Weather Service Wakefield VA
147 PM EDT SUN SEP 25 2016
A backdoor cold front settles across the Carolinas today. High
pressure will build across New England...ridging south into the
area through early Monday. A second and stronger cold front will
cross the region Tuesday.
.NEAR TERM /THROUGH TONIGHT/...
Late morning MSAS shwoing the cold front across southern NC with
sfc high pressure north of Lake Ontario. Drier air nosing down the
coast has resulted in mainly clr skies across the Delmarva, a
buffer zone ivof Ches Bay sct-bkn SC with bkn-ovc SC across the
piedmont. 12Z soundings / high res data continue to show weak
shallow isentropic lift and onshore flow keeps the bkn-ovc sky
coverage across the piedmont...variably cloudy ivof the bay and
pt to mstly sunny ern shore areas this afternoon. Feeling more
like fall than recent days with highs in the low to mid 70s.
After some short-lived clearing early tonight, clouds re-develop
by midnight and through the overnight as the cool air wedge is
reinforced by renewed isentropic lift, underneath upper ridge axis
nudging in from the west. Sky cover ranges from overcast with
areas of light rain or drizzle well inland across the piedmont to
partly cloudy along the VA coast over to the MD Eastern Shore.
Look for chilly early morning lows from around 50 MD Eastern
Shore...to mid 50s to around 60 central and south (mid to upper
60s along the SE coast.
.SHORT TERM /MONDAY THROUGH TUESDAY/...
High pressure moves offshore of the New England coast on Monday
as the next front approaches from the west Monday afternoon.
Flattening of upper ridge will slow the advance of the front, and
serve to break down the cool air wedge slowly from NW to SE
Monday afternoon as the sfc high slides offshore. However, clouds
should hold firm across the piedmont through much of the day,
resulting in another mostly cloudy to overcast day Monday,
variably cloudy along the coast. Highs in the mid to upr 70s.
A strong cold front still on track to cross into the region late
Monday night ahead of a potent northern stream trough. Moisture
increases along the front with PW`s climbing above 1.75 inches
along with marginal instability per Showalter values trending
around 0 after 00z/Tue. Pcpn enters the region from the NW with
highest pops Monday evening, spreading east as best forcing nudges
from sw to ne Tuesday morning. Lows Mon night in the mid 60s.
Models show possible weak s/w energy riding east along the
boundary Tuesday. This will likely enhance pcpn and allow it to
linger a bit longer especially along coastal sections. Likely pops
linger across the Se zones through Tue. Kept thunder chcs in as
well, again with modest instability lingering. Highs Tuesday in
the low to mid 70s. QPF generally between 1/2 to 3/4 inch.
.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
Medium range guidance continues to indicate anomalous heights over
Canada through the period, as well as over the western Atlantic. A
deep/anomalous upper low drops over the eastern Great Lakes region
Wednesday, under the upper ridge. Ensemble and deterministic
guidance continues to struggle with a more progressive versus
blocked flow over the eastern CONUS. The result is a relatively low
confidence forecast, but have trended more toward GFS/GEFS
Tuesdays cold front progged to stall along the coast in deep layer
southwesterly flow across the Mid-Atlantic. POPs taper off inland
Tuesday night, with chance POPs remaining across the southeast
forecast area. A series of upper level disturbances will lift along
the frontal boundary Wednesday. The combination of waves lifting
along the front and strong upward vertical motion will bring solid
chance POPs back to the southeast local area and slight chance to
low end chance inland. The upper low locates in the vicinity of the
Mid Atlantic region Thursday. While the best moisture pushes
offshore, will keep mention of slight chance to chance POPs Thursday
and Thursday night to account for uncertainty and potential light
rain. Thereafter, the upper low likely begins to slowly lift
northeastward as the upper ridge over the western Atlantic begins to
break down. With the upper low lifting away from the region Friday
and Saturday, large scale subsidence over the region will result in
a drying trend. Will keep chance POPs northeast Friday and retain
silent POPs on Saturday.
Slightly below normal temperatures forecast through the period, with
highs generally in the low to mid 70`s. Lows range from the low to
mid 50`s inland to mid 60`s along the coast.
.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
-- Changed Discussion --Drier air from the north continues to filter south along the coast
this afternoon. This is resulting in VFR conditions with only SCT
SC along the Delmarva, SCT-BKN SC between 4-5K ft ivof the Ches
Bay, BKN-OVC SC between 3-5K ft across the piedmont. Nearest MVFR
cigs are across the mts. Models now showing only SCT clouds along
the coast tonight with differing solutions for RIC. Given the lgt
onshore flow and position of the high, decided to keep a BKN SC
deck around 4K ft at RIC through the night with SCT SC elsewhere.
Fog not expected to be a big issue tonight but can`t rule out some
ptchy MVFR VSBYS toward sunrise in areas where it does CLR. Any
pcpn is expected to be confined to the mts.
OUTLOOK...The next chance for widespread precipitation arrives
Monday night into Tuesday ahead of a strong cold front. Showers
will linger through the mid week period as an upper level low
tracks across the region.
-- End Changed Discussion --
Cold front has located south of the waters early this morning, as
high pressure builds in from the north. North to northeast winds of
10 to 15 knots observed over the waters, with occasional gusts of 20
knots over the southern coastal waters. Have dropped SCA headlines
for the lower Chesapeake Bay. Seas remain elevated thanks to distant
tropical cyclone Karl and onshore flow, ranging from 3 to 5 feet.
SCA headlines remain in effect for the coastal waters. Based on the
latest guidance, have extended headlines through 1 pm this
afternoon. Thereafter, seas subside to 3 to 4 feet. This mornings
cold front lifts back to the north Monday as a cold front approaches
from the northwest. Flow becomes south to southeast with marginal
SCA conditions possible late Monday into Monday night. The front
pushes across the region Tuesday, likely stalling along the coast
Tuesday night and Wednesday. A weak pressure gradient progged over
the region, but a cooler and drier air mass may result in at least
marginal SCA conditions late Tuesday night. An upper level low is
progged to drop into the region Wednesday and Thursday, resulting in
unsettled weather conditions through the end of the week. Flow
generally out of the north.
The Cashie River at Windsor remains in minor flood stage. The
river is forecast to slowly fall below flood stage by late this
afternoon. See FLSAKQ for details.
-- Changed Discussion --MD...None.
MARINE...Small Craft Advisory until 4 PM EDT this afternoon for ANZ656-
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