Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 261133

Area Forecast Discussion
National Weather Service Wilmington NC
633 AM EST Sun Feb 26 2017

Much cooler temperatures expected today as high pressure builds
into the Carolinas. These cool temperatures will be short lived
as a warm front lifts north early Tuesday. Near record high
temperatures expected again by the middle of the week before a
cold front crosses the area on Thursday. A return to winter like
temperatures is expected for next weekend.


As of 630 AM Sunday...Last night`s cold front is now well
offshore, with breezy northwesterly winds blowing across the
eastern Carolinas. One interesting effect none of the models
were intense enough with was the sudden drop in dewpoints as the
front blew through. Dewpoints dropped 20-30 degrees in less
than an hour at most stations! Water vapor satellite imagery
showed bands of very warm brightness temperatures coincident
with the drop in dewpoints, perhaps implying strong downward
motion entraining dry mid-level air into the well-mixed boundary
layer in the post-frontal cold advection.

Surface high pressure over Tennessee this morning will work its way
to the Carolina coastal plain by late afternoon. The airmass is
quite a bit cooler than yesterday and even with full sunshine highs
are only expected to reach 60 degrees. With the high nearly overhead
and a dry airmass in place, temperatures should fall quickly after
sunset. Return flow behind the departing high will occur too late to
disturb a strong nocturnal inversion, and lows should fall into the
30s all the way down to the coast. I strongly favor the colder NAM
MOS number over the GFS tonight. Lows of 29-32 are expected across
the typically cold pocosins (peat soils) of southeastern North
Carolina and would trigger freeze warnings if this were a little
farther into spring and the growing season had begun.


As of 300 AM Sunday...High pressure will move farther away from
the U.S. east coast Monday and Tuesday, opening up the door for
subtropical warmth and humidity to return to the Carolinas. The
modification will begin Monday morning as the nocturnal
inversion breaks and southeasterly winds develop. Highs Monday
should reach the lower 70s inland with mid to upper 60s near the

The forecast has shifted somewhat for Monday night compared to 24
hours ago. While an approaching upper disturbance and low-level warm
advection should still work together to develop a large zone of weak
to moderate isentropic lift across the Carolinas, the quality of
moisture in the incoming southerly flow is not quite as good in the
current 00z model runs. In particular, large swaths of dry air at
5000-12000 ft AGL will act to reduce the areal coverage of rainfall.
The isentropic lift itself will proceed much as the models showed 24
hours ago, but without nearly as much moisture being lifted and
cooled to its dewpoint, the risk of rainfall has diminished. PoPs in
the 30-40 percent range are currently forecast for Monday night
(mainly after midnight) with lows in the mid to upper 50s.

By Tuesday the same airmass we had yesterday will be back, only with
higher dewpoints given its source region in the southern Bahamas.
Highs could approach 80 in a few inland spots with 70s expected for
all but the beaches. Surface-based instability should grow to 500-
1000 J/kg with bulk shear values increasing toward 40 kt by late
afternoon. Lapse rates aloft are not that bad, and given rather low
wet-bulb zero heights around 9500 feet I would not be surprised for
some sort of hail threat to develop in thunderstorms. Waning
instability during the evening should end the thunderstorm


As of 300 AM Sunday...Forecast area will be solidly in the warm
sector Wed with temperatures approaching 20 degrees above
normal. Convection will be possible Wed afternoon given low
level moisture and diurnal heating, but there will be several
limiting factors. Mid level subsidence and dry air above 850 mb
will be the biggest issue, but there is also a lack of forcing.
A modified sea breeze may lead to some storm development across
southeast NC but confidence is low. Better precip chances will
be late Wed night through early Thu as strong cold front moves
across the area. Frontal passage occurs Thu morning, coincident
with the surface based instability minimum. However, the front
and its 5h trough will provide strong lift and a healthy chance
of showers and isolated thunderstorms through the first part of
Thu morning.

Strong cold advection develops Thu with 850 temps dropping around
10C from Thu morning to Thu evening. Highs Thu will end up well
above climo, but will likely occur during the first few hours of the
morning with temps steadily trending down during the day. Incoming
air mass is very dry with potential for RH dipping below 30%. Temps
below climo Fri and Sat with a reinforcing shot of cold air expected
Fri night into Sat.


As of 12Z...High confidence for VFR conditions through the forecast
period. High pressure will continue to build in this morning, with
weak cold air advection. Northwest flow around 10 kts will diminish
by late afternoon. Do not currently have fog in the forecast, but
will reevaluate conditions with the next model run.

Extended Outlook...VFR. VSBY and ceilings lowered to MVFR/IFR with
pcp Mon night into Tues and again with SHWRs on Wed.


As of 630 AM Sunday...The cold front blasted offshore Saturday
evening with breezy northwest winds blowing all night. High
pressure over Tennessee will move eastward today, reaching the
coastal Carolinas this evening then moving offshore overnight.
Northwest winds will diminish in speed today, becoming light and
variable this evening, then turning easterly late tonight. The
Small Craft Advisory has been cancelled for North Carolina,
replaced with an Exercise Caution headline through 10 AM.

As of 300 AM Sunday...High pressure east of the Outer Banks
Monday morning will move farther offshore Monday night and
Tuesday. Southeasterly winds Monday should turn southerly by
Tuesday in the flow between the departing high and low pressure
advancing eastward across the Plains states.

As of 300 AM Sunday...Southwest flow will steadily increase
Wed, peaking at 20 to 25 kt in the afternoon and evening ahead
of cold front approaching from the west. Front moves east across
the waters Thu morning with offshore flow developing by midday.
Gradient and cold advection will keep offshore flow a solid 15
kt into Thu evening before northerly winds start to weaken. Seas
3 to 4 ft Wed morning will build to 4 to 7 ft Wed evening and
remain above SCA thresholds through much of Thu morning before
offshore flow drops seas to 3 to 5 ft Thu afternoon and 2 to 3
ft Thu night.





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