Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 180750
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
245 AM EST Sat Nov 18 2017

.SYNOPSIS...
Surface high pressure will move off the North Carolina coast early
this morning, resulting in a warm and gusty southwest flow today. A
cold front will sweep east across the area tonight. Chilly high
pressure will return for Sunday through Tuesday.

&&

.NEAR TERM /Today through tonight/...
As of 235 AM Saturday...

High pressure sitting over the eastern Carolinas early this morning
is poised to shift east and offshore in the next several hours
followed by warm front passage, initiating a strengthening low level
southwest flow that will dominate the day`s weather. Increasing and
deepening moisture advection will lead to thickening and lowering
high clouds, along with scattered stratocu (especially over the
western CWA). Based on latest high res model guidance and on
upstream conditions SE of the warm front, sustained winds will
increase this morning to 12-15 kts, with periodic gusts to 20-25
kts, strongest across the NW and N CWA this morning as a 35-40 kt
southwesterly 925 mb jetlet tracks from W NC into VA. Near normal
thicknesses to start the day coupled with the warm air advection
will push temps up to 63-71, coolest NW with thicker cloud cover.
Then tonight, a quickly-moving band of showers is expected ahead of
the cold front, which is expected to cross central NC 07z-12z.
Forcing for ascent will be on the upswing this evening/tonight with
a 130+ kt upper jet inducing improving upper divergence and weak
DPVA aloft accompanying broad mid level trough passage (although the
best DPVA heads to our north), but the overall lift will be modest,
and CAPE will be absent. High PW advects in ahead of the front, with
values well over 200% of normal in a narrow band which crosses the
area tonight, and this combined with the quick shot of lift should
bring about fairly high rain chances (mainly over the NW and N CWA)
but with low QPF (a tenth of an inch or less) given the fast
movement. SW flow will ramp back up after nightfall and remain
strong and gusty overnight, as 925 mb winds strengthen to 40-50 kts,
although not all of this will be realized at the surface, given the
low level buoyancy ahead of the front. It is worth noting, though,
that just behind the front, where we`ll still be well-mixed but with
low level subsidence taking place, and with 925 mb winds still
rather stout post-front at around 30 kts, we could see a period of
higher gusts from the NW just behind the front. The coolest air will
be delayed until after daybreak, and will stick with milder lows,
ranging from the mid 40s NW to the mid 50s SE. -GIH

&&

.SHORT TERM /Sunday through Sunday night/...
As of 245 AM Saturday...

Skies will be clearing early Sun morning, with the entire area
expected to be clear by 15z as surface high pressure builds in from
the west in conjunction with a trend to rising heights aloft behind
the exiting mid level trough axis. The tight MSLP gradient between
the departing cold front and incoming high will result in blustery
surface winds from the NW, although not as strong as today`s and
tonight`s SW winds. Expect sustained winds of 9-14 kts with gusts to
15-20 kts. Thicknesses should drop to around 20 m below normal, so
despite the plentiful sunshine, highs will be cool, 53-62. We may
see a brief resurgence in wind gusts Sun evening as one last mid
level vorticity lobe drops through the region (strongest across our
north and NE into VA), causing 925 mb winds to rebound to 25-35 kts
especially over the NE CWA. Otherwise, though, winds will be
diminishing Sun evening and night. Lows 27-32 with decent
radiational cooling under clear skies. -GIH

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 200 PM Friday...

Longer range forecast looking on track. A cold front will move east
of the area early Sunday morning. Gradient between the parent low
over Quebec and high pressure over lower Mississippi valley Sunday
will lead to northwesterly surface winds gusting to 15-20 kts.
Temperatures during this time frame should top out in the mid 50s
with low temperatures near or slightly below freezing. A warming
trend will begin on Tuesday as high pressure moves offshore and an
upper level trough sits to the west of the region.

On Wednesday the upper trough will pass mainly north of the area.
With very limited moisture in place do not believe there will be
much if any precip in the area.  A dry cold front will move through
Wednesday night bringing in a cooler airmass for the end of the work
week. For Friday, low pressure will move out of the Gulf of Mexico
and across the Florida peninsula spreading some rain northward into
eastern and southern sections of our area.

&&

.AVIATION /06Z Saturday through Wednesday/...
As of 130 AM Saturday...

VFR conditions will dominate at all central NC sites today, with the
exception of the potential for a few hours of MVFR cigs 14z-17z this
morning at INT/GSO. The bigger story will be the increasing winds
from the SW this morning, peaking this afternoon with periodic gusts
to 20-25 kts. There is a slight chance of low level wind shear this
morning as a 35-40 kt jet from the SW near 2000 ft AGL. LLWS chances
increase after 00z tonight as winds restrengthen from the SW around
2000 ft AGL to 40-50 kts. INT/GSO will see a trend to MVFR cigs and
perhaps MVFR vsbys in showers very late in the TAF valid period
(after 04z) ahead of a cold front approaching from the west.

Looking beyond 06z Sat: A few hours of MVFR to IFR conditions in
showers are expected late tonight as the cold front crosses the
forecast area. VFR conditions will return after 08z at INT/GSO,
after 10z at RDU, and after 11z at RWI/FAY, all with a drastic shift
in winds from SW to NW as the front moves through. VFR conditions
are likely Sunday through Tuesday as high pressure moves over the
area. A storm system will develop over the Gulf Coast and approach
our area Tue night/Wed, bringing possible sub-VFR conditions. -GIH

&&

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

&&

$$ SYNOPSIS...Hartfield
NEAR TERM...Hartfield
SHORT TERM...Hartfield
LONG TERM...Ellis/Franklin
AVIATION...Hartfield



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