Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000
FXUS62 KRAH 230800
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
400 AM EDT Thu Mar 23 2017

.SYNOPSIS...
Continental polar high pressure will continue to modify over the srn
Middle Atlantic states through tonight. A warm front will retreat
north across the region on Fri, as the high drifts east toward
Bermuda.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 345 AM Thursday...

1034 mb high pressure now centered over ern PA and NJ will build
south to the srn Middle Atlantic coast by this evening, beneath
building heights aloft downstream of a progressive and increasingly
amplified longwave ridge axis approaching from the central U.S. The
presence of the surface ridge, one of cold and dry origin, will
result in cooler conditions than previous days. High temperatures,
unimpeded by occasional thin cirrus in NWly upper flow, will be in
the 50s. A generally light ENEly wind may briefly gust to near 20
mph between 9 AM and noon east of I-95, with otherwise
inconsequential gradually veering flow around the aforementioned
surface ridge.

The surface ridge will continue to extend across NC tonight.
Associated calm to light ESEly surface winds, combined with a mainly
clear sky aside from continued occasional thin cirrus, will favor
strong radiational cooling and a light freeze away from urban
centers; low temperatures in the upper 20s to middle 30s.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 355 AM Thursday...

Surface high pressure will drift to near and just north of Bermuda;
and associated return flow across the sern U.S. will allow a warm
front to retreat north through central NC during the day Fri. Both
temperatures and moisture will consequently be on the increase, with
highs in the mid-upper 60s N and NW, to lower 70s in the S, and
surface dewpoints in the 40s to near 50 degrees. The increasing low
level moisture values, and broad WAA regime, will favor a scattering
of flat/fair weather cumulus trapped beneath a subsidence inversion
hat will have become established courtesy of mid-upper level ridging
aloft.

Not as cool Fri night, though with decent radiational cooling
potential as the Bermuda surface ridge continues to extend west into
NC. Patchy radiation fog may result, with low temperatures in the
middle 40s to around 50 degrees.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 320 AM Thursday...

The extended will primarily feature a Bermuda high and warm
southerly flow, with highs in the 70s, at least 5-10 degrees
above normal.

Continued moistening Friday night may lead to some stratus near
and west of the Yadkin River Saturday morning, and a pronounced
cap will likely trap this moisture and yield partly to even
mostly cloudy by Saturday afternoon. Meanwhile, and upper low
over the Deep South will lift west of the mountains Saturday
night, providing a glancing blow of DECENT height falls that
should erode the cap and permit showers and storms, mainly west
on Sunday. Current timing suggest early day clouds and showers,
an extension of upstream convection on Saturday, may impede
warming and destablization enough in the west to limit any
severe with potential, though an axis of instability between the
morning convection and the stronger cap to the east could
support an isolated severe threat given 30-40kt bulk shear.

The cold front associated with Sunday`s lifting upper low looks
as though it will stay well west of the mountains and NC will
stay in the warm sector, with another, less amplified system
progged to cross the area on Tuesday. The latest ECMWF is much
less amplified with this wave that it`s previous run, as well as
the 00Z/23rd GFS runs. This system could be interesting given
the potential for decent destablization in the warm sector on
Tuesday and possibility of locally enhanced shear associated
with the shortwave. For now, chance POPs still look most
appropriate. After that, a backdoor cold front is forecast to
sink south into NC by mid to late week, though the presence of
the sub-tropical ridge makes frontal passage much less certain.

&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
As of 230 AM Thursday...

Continental polar high pressure will result in VFR conditions
through the TAF period. Surface winds around the high will
generally be light and gradually veer from NEly/ENEly this morning
to Ely/ESEly by this afternoon. The exception will be at FAY and RWI
for a few hours mid to late morning, when winds may briefly increase
to around 10-15 kts, with occasional gusts between 15-20 kts. Skies
will be clear, aside from periods of thin cirrus.

Outlook: There will be a chance of MVFR-IFR visibility restrictions
in radiation fog in SErn NC (FAY and possibly RWI) Fri morning, then
with patchy coverage throughout central NC Sat morning. A chance of
showers and storms and sub-VFR conditions mainly at Piedmont TAF
sites will follow for Sun.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...SMITH
AVIATION...MWS



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