Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC-- Remove Highlighting --
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FXUS62 KRAH 201822
Area Forecast Discussion
National Weather Service Raleigh NC
220 PM EDT THU OCT 20 2016
An amplifying upper level trough will dig southeast into the
Tennessee valley tonight, progress east of the mountains on Friday,
then track offshore Friday night. An associated cold front will
track east across the Carolinas on Friday. Seasonably cool high
pressure will build into the region in the wake of the front this
.NEAR TERM /TODAY AND TONIGHT/...
As of 1020 AM Thursday...
High pressure over the Carolinas is being squeezed today between an
area of low pressure north of the Bahamas and height falls
associated with an amplifying trough and cold front approaching the
Tenn Valley. The morning low-level thickness at GSO was 1403m, the
same as yesterday, which suggests near record warmth again this
afternoon under full sun. Guidance is a couple of degrees cooler
than yesterday, but then again, most all guidance missed on the
cooler side yesterday. Have nudged temps up a couple degrees to 83-
86, and records are listed below.
GSO - 86 in 1924
RDU - 87 in 1926
FAY - 89 in 1926
Little cloud cover and weak southerly flow will precede a cold front
approaching the mountains from the west tonight. As such, lows will
not be as warm as might otherwise be the case, in the lower 60s. -
.SHORT TERM /FRIDAY AND FRIDAY NIGHT/...
As of 300 AM Thursday...
Very little moisture/theta-e advection will occur in advance of the
approaching cold front in central NC late tonight/Friday morning
given a weak/baggy MSLP gradient in place, poor diurnal timing/
insufficient time prior to fropa. Strong height falls /DCVA/
associated with the amplifying upper level trough progressing east
across the Carolinas will generally lag the attendant cold front on
Friday, though it will do so with favorable diurnal timing. As a
result, model guidance continues to indicate light anafrontal
precipitation (showers along/behind the cold front) on Friday,
during the mid/late morning in the Western Piedmont, early/mid
afternoon along the Highway 1 corridor (Triangle/Fay) and mid/late
afternoon in the Coastal Plain (along/east of I-95). Highs on Friday
will occur relatively early in the day west of Hwy 1, and by
early/mid afternoon east of Hwy 1. In fact, rapid temperature falls
(~15F, falling from the 70s to upper 50s) and gusty NW winds
sustained at 15 knots with gusts as high as 30 knots may accompany
the cold frontal passage along/easy of Hwy 1 during the early/mid
afternoon where cold advection will be augmented/enhanced by
evaporative cooling assoc/w anafrontal precipitation. Expect highs
ranging from the mid/upper 60s in the Triad to mid/upper 70s in the
far SE Coastal Plain. Expect rapid clearing from west-east 3-6 hrs
after the cold frontal passage at any given location, with clear
skies and a NW breeze prevailing Friday night. Lows Saturday morning
will be driven by both cold advection and radiational cooling,
ranging from the low/mid 40s N/NW to mid/upper 40s S/SE. -Vincent
.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 230 AM Thursday...
A much cooler airmass will settle into the area over the weekend,
with highs on Saturday struggling into the lower 60s in northwest
flow despite sunny skies. Saturday night will provide ideal
radiation conditions as the pressure gradient relaxes and Sunday
morning mins will be mostly in the lower 40s with possibly some
upper 30s in outlying areas. Milder high pressure edges in from the
southwest Sunday, and highs will be a bit warmer, though still a
little below normal...mid to upper 60s.
The first half of next week looks mostly clear and dry, but a
reinforcing shot of cool air will move through on Monday, which will
maintain daily highs in the upper 60s to lower 70s after morning
mins in the mid and upper 40s.
.AVIATION /18Z THURSDAY THROUGH WEDNESDAY/...
-- Changed Discussion --As of 220 PM Thursday...
High confidence in VFR conditions this evening as high pressure
slowly weakens ahead of a cold front approaching the TN Valley. A
light southerly wind will continue through the night, and most model
forecast soundings indicate a good chance of IFR or LIFR stratus or
fog, with highest probability at FAY and RWI. A cold front and band
of showers should be just west of INT/GSO by 12Z, moving east to RDU
by 15Z. A brief shower and MVFR conditions is generally expected
with this band, with northwesterly gusts to 25 kt or so behind the
front. Each TAF site should see MVFR conditions during the
afternoon as the showers, and possibly a thunderstorm or two, move
Outlook: VFR conditions will return across all of central NC by
Friday evening, with a northwest wind that will remain at 5-10kt
Friday night and increase to 10-15kt, gusting to 20-25kt on
Saturday. Beyond Saturday, VFR conditions will continue, with a dry
backdoor cold front early next week.
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