Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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755
FXUS62 KRAH 232156
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
456 PM EST Fri Feb 23 2018

.SYNOPSIS...
A strong sub-tropical ridge aloft situated off the Southeast U.S.
coast will weaken while drifting south toward the Bahamas through
Saturday. Meanwhile, a quasi-stationary front will remain over
central NC through tonight, then retreat northward while dissipating
on Saturday.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 355 PM Friday...

Earlier low overcast has steadily eroded from the south this
afternoon, and lingers at 21Z only over the far nrn Piedmont and
Coastal Plain, north of a slowly nwd-retreating warm front that was
analyzed from near HKY to JNX to OCW. The associated scattering
out/clearing of the low overcast, and dissipation of diurnal cumulus
along and south of the warm front, will yield a mostly clear
evening. However, low clouds and fog are likely to redevelop both in
the residually-saturated remnant wedge airmass over the nrn
Piedmont, and like in previous mornings in the humid warm sector
(focused initially over the srn Coastal Plain and Sandhills), before
the two regimes likely merge and yield a solid blanket of low
overcast and areas of fog throughout cntl NC by Sat morning. Low
temperatures are expected to range from low-mid 50s in the remnant
wedge regime to around 60 degrees in the srn Coastal Plain.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 340 PM Friday...

Sub-tropical riding will remain centered in the vicinity or just
northeast of the Bahamas, with associated surface high pressure
extending from just south of Bermuda, wwd into the sern U.S. This
pattern will maintain unseasonably warm and relatively humid
conditions across cntl NC. Persistence high temperatures (relative
to the warm sector) are expected to be in the mid 70s to around 80
degrees once again, given projected low level thickness values in
the 1385-1390 meter range - very similar to Wed-Thu, and Fri in srn
NC. While the sub-tropical ridge will also maintain a generally warm
and capped environment to convection, small amplitude perturbations
in swly flow aloft will glance the wrn and nrn Piedmont; and these
may prove supportive of a few showers in a slightly less capped
environment there. It will remain mild in steady swly flow Sat
night, with low temperatures mainly in the lwr, to perhaps mid, 60s.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 240 PM Friday...

We remain in the warm sector for one final day Sunday with deep
southerly flow on the west side of stacked ridging offshore. Highs
Sunday will climb well into the 70s, with some very low 80s possible
in the southeast. Moisture will be on the increase in this flow
regime, and a cold front will be edging slowly east as the ridging
offshore is flattened/suppressed south by a strong short wave moving
across the midwest and into the Great Lakes region. The surface
front is expected to stall as it reaches the area on Sunday, with a
surface wave lifting northeast up the frontal zone on Monday.
Showers will thus be increasing from the west throughout the day on
Sunday, becoming likely across all of central NC Sunday night
through most of the day Monday. Widespread rainfall totals of one
half inch are expected, but we could see one inch amounts due to
training in some areas. Monday`s highs will be suppressed by rain in
addition to cool air advection, but the encroaching airmass will be
a bit warmer than seasonal, having originated in the lower midwest
and been allowed to further moderate due to slow eastward
progression.

High pressure will build into the mid Atlantic briefly Tuesday
through early Wednesday, with plenty of sun and drier conditions to
accompany seasonable temperatures in the low to mid 60s after
morning lows in the 40s. A warm front will lift north, accompanied
by increased cloud coverage and chances for showers by Wednesday
afternoon through Thursday, when our next cold front is expected to
sweep through and restart the cycle again. Highs Thursday will climb
back to the 65 to 70 range ahead of the front, with seasonable
temperatures near 60 to follow on Friday in the front`s wake.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 130 PM Friday...

The front that settled swwd through cntl NC last night-early this
morning has begun to retreat north as warm front in the past couple
of hours, with associated erosion and lifting of the srn edge of a
blanket of low overcast that had enveloped the region behind the
front. As such, current IFR-MVFR ceilings will continue to lift and
scatter from south to north and with time this afternoon, with an
associated return to VFR conditions probable by late this afternoon
and this evening. The VFR conditions will likely be short-lived,
however, as low overcast and fog are expected to redevelop tonight.
The low clouds and fog will then lift and disperse to VFR between 14-
18Z Sat.

Outlook: Increasing winds, particularly aloft, will limit fog
potential Sat night, except for at perhaps FAY and RWI where winds
will be relatively lighter, with overnight-early morning low stratus
anticipated otherwise and elsewhere. Those strengthening winds aloft
may also result in marginal low level wind shear conditions at
Piedmont sites Sat night, given the likely presence of a shallow,
~1000 ft inversion, which will tend to separate a steady and even
occasionally gusty ssw wind at the surface from an abrupt increase
in flow within and above the inversion. The approach and slow
passage of a frontal zone will result in a high probability of
showers, and some sub-VFR conditions, late Sun into early next week.

&&

.CLIMATE...

RDU Records:

Date     |  High  Year  |  High Min  Year
------------------------------------------
02/24       81    1982       58      1985

GSO Records:

Date     |  High  Year  |  High Min  Year
------------------------------------------
02/24       79    1982        55     1985

FAY Records:

Date     |  High  Year  |  High Min  Year
-------------------------------------------
02/23       80    1922        55     1922
02/24       83    1930        60     1975

&&

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

&&

$$

SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...mlm
AVIATION...MWS
CLIMATE...RAH



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