Durham, North Carolina 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

461
FXUS62 KRAH 231100
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
600 AM EST Sat Nov 23 2024

.SYNOPSIS...
High pressure will build across the Southeast through the weekend,
while low pressure will move slowly northeastward from the northern
Middle Atlantic and New England coast to Atlantic Canada.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 400 AM Saturday...

A persistent and anomalously deep cyclone will move slowly newd and
along and just offshore the coast of the nrn Middle Atlantic and New
England, then into Atlantic Canada. In its wake, strong height rises
(100-120 meter/12 hr at 500 mb) and deep subsidence will result over
cntl NC today, then gradually weaken tonight. However, strong nwly
directed orthogonal to the Appalachians and the presence of a
subsidence inversion will favor vertically propagating waves
favorable for orographically-enhanced cirrus, as upstream high-level
moisture from the OH to upr MS Valley streams sewd. Associated high-
level ceilings will likely develop and overspread the nrn NC
Piedmont from late morning through the afternoon, while mostly
sunny conditions are expected otherwise and elsewhere. Clear and
calm will develop tonight, as the center of surface high pressure
builds across the Southeast.

Temperatures are expected to be near average and in the upr 50s to
lwr 60s, except mid 50s over the nw Piedmont, where orographic
cirrus will likely be thickest and longest-lasting. Similarly-near
average low temperatures in the 30s, with excellent radiational
cooling, will support the development of frost. An Advisory may be
need where the growing season has not yet ended.

&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 340 AM Saturday...

In the mid/upper-levels, a low amplitude ridge will progress from
the mid MS Valley to the ern US. Continued rising heights, and
gradually weakening subsidence, will result over cntl NC.

At the surface, high pressure will build across and offshore the
South Atlantic states, while a lee trough will develop across the
wrn Piedmont/Foothills of the srn Middle Atlantic. Warming, swly
flow will result across both the srn Middle Atlantic and South
Atlantic states. Observed high temperatures often over-perform
relative to model guidance in these regimes, so forecast high
temperatures were weighted heavily toward the GEM (warmest
deterministic) and NBM 90th percentile. Forecast low temperatures in
the mid 30s to around 40, were weighted toward the cooler guidance
and NBM 10th-50th percentile, given favorably light to calm surface
winds and just passing high clouds Sun night.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 400 AM Saturday...

The extended period will start off dry with surface high pressure in
the western Atlantic centered just south of Bermuda, as low pressure
over the Great Lakes drags a cold front across the mid-MS and TN
Valleys. SW low-level flow out ahead of this front will bring above-
normal temperatures to central NC on Monday with highs in the mid-
60s to lower-70s. Clouds will be on the increase Monday night as the
mid-level trough becomes negatively tilted over the lower Great
Lakes and the cold front approaches from the west. Very mild lows
are expected (upper-40s to lower-50s).

Timing of the frontal passage looks to be on Tuesday morning, and
while the ECMWF is the only deterministic model really showing
widespread measurable precipitation, there continues to be enough
ensemble members showing some precipitation to include slight chance
POPs (and a chance of sprinkles) across the area from 06z to 18z
Tuesday. Regardless, amounts do not look high, only around a tenth
of an inch or less. Cloud cover and sprinkles combined with frontal
passage early in the day may keep temperatures down a bit, so leaned
forecast highs toward the cooler side of guidance, ranging from
lower-60s far NW to lower-70s far SE. Surface high pressure
approaching from the OH Valley should bring decent radiational
cooling conditions Tuesday night, so forecast lows are mostly mid-to-
upper-30s with lower-30s possible in outlying areas.

Models have continued to come into better agreement on the low
pressure system that looks to affect the region from mid to late
next week. Wednesday will be dry under the influence of high
pressure as the cold front drops well to our south, with high
temperatures dropping back down to near normal (mid-50s to lower-
60s). However, the dryness will be short-lived as the high quickly
moves offshore and a southern stream shortwave moves from the
Southern Plains into the TN Valley on Thursday and Thursday night,
then into the Mid-Atlantic on Friday. Both the GFS and ECMWF also
depict a surface low riding along the front, which may lift back
north as a warm front. This unfortunately likely means a wet and
chilly Thanksgiving is on tap for the area. It appears there may be
two rounds of precipitation, one more isentropic lift generated
during the day on Thursday as cool dry air gets wedged near the
surface, and a second potentially heavier round on Thursday night as
the low pressure system moves across the area. As for amounts,
latest ensemble guidance continues to indicate a quarter inch to an
inch as the most likely range. Given the consistency from run to run
and between guidance, opted to include low-end likely POPs across
nearly the entire region on Thursday night. With in-situ damming
possible on Thursday, the temperature forecast is highly uncertain,
but the raw GFS for what it`s worth depicts highs only in the 40s
across the north.

Rain will come to an end from west to east on Friday morning and
early afternoon. With strong CAA behind the departing deepening low,
forecast highs are only in the upper-40s to mid-50s.

&&

.AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
As of 600 AM Saturday...

A strong, wnwly low-level jet centered over VA and nrn NC, with
winds up to 40-50 kts around 2000 ft AGL and atop a lighter swly
surface wind, will favor a continued risk of low-level wind shear
until the nocturnal inversion breaks with daytime heating around
14Z. That heating, and mixing, will promote the redevelopment of
gusty wnwly surface winds through this afternoon, followed by calm
or nearly so tonight.

VFR conditions are otherwise forecast, with varying amounts of VFR-
based cloudiness and with greatest coverage in the form of ceilings
from orographically-generated cirrus at INT/GSO from approximately
15-20Z.

Outlook: VFR conditions are expected until a mostly dry cold front
moves across the region on Tue, during which time a fleeting MVFR
ceiling and light rain will be possible. Low-level wind shear will
also likely result ahead of that front Mon night.

&&

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

&&

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