088
FXUS62 KRAH 221450
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
950 AM EST Fri Nov 22 2024

.SYNOPSIS...
Low pressure will wobble over the Middle Atlantic today, then move
slowly northeastward toward Atlantic Canada through the weekend.
Meanwhile, initially chilly high pressure over the southern Plains
will modify while building across the Southeast.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM Friday...

Minimal changes were made with the morning update, primarily just
some minor tweaks to the temperature/dewpoint grids. Previous
discussion follows.


As of 400 AM Friday...

* Breezy, variably cloudy, and unseasonably cool today
* Mostly clear to fair, and seasonably chilly, tonight

A high latitude blocking anticyclone over Labrador Sea, and
associated negative phase of the NAO, will keep an anomalously
strong cyclone suppressed deep into the mid-latitudes and over the
Middle Atlantic, and surrounding cyclonic flow throughout the ern
US. A couple of shortwave perturbations evident in WV satellite data
this morning from swrn VA nwwd into the OH Valley will dig sewd into
the wrn Carolinas/srn Appalachians this morning, then pivot in
positive tilt fashion across and offshore the Carolinas through
early this afternoon. In the wake of that shortwave perturbation,
and as the center of the aforementioned cyclone wobbles away from
the Middle Atlantic coast, strong height rises and subsidence will
overspread the Carolinas later this afternoon through tonight.
Generally wnwly flow, including downslope in the low-levels, will
otherwise persist across cntl NC.

At the surface, low pressure over srn New England will continue to
fill/occlude while moving in a cyclonic loop across and offshore the
nrn Middle Atlantic, while high pressure will build from the Plains
and MS Valley sewd and across the Southeast.

As the shortwave perturbations dig into the wrn Carolinas this
morning, lift will increase and cause multi-layered cloudiness,
associated ceilings, and virga to blossom across the nwrn and srn NC
Piedmont. While measurable precipitation should hold in upslope flow
along and west of the Appalachians, a very light flurry may result
over the Triad, where ceilings may briefly lower to around 3500-4000
ft AGL in the few hours centered around 11-12Z. That cloud band and
virga will then pivot east and across and out of cntl NC with the
parent shortwave trough through early this afternoon, followed by a
scattering of mostly altocumulus near the VA border and mostly sunny
elsewhere. Otherwise, light, generally wly surface winds this
morning will increase and become gusty into the upr teens to 20s kts
again with daytime heating/mixing today, with unseasonably cool high
temperatures in the upr 40s to lwr 50s.

The GFS continued to be an outlier in its depiction of continued
mixed and breezy to windy conditions, and cloudy ones with a
saturated layer evident around 3000 ft AGL, overnight. The consensus
of other guidance suggests surface winds should diminish and
decouple from a strong, wnwly low-level jet above, with mostly clear
to fair skies. As such, temperatures tonight should cool into the
mid 30s and allow for the development of at least patchy frost over
the srn Piedmont and wrn Sandhills, where calm will become most
likely, ranging to upr 30s to around 40 with light surface stirring
elsewhere.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 415 AM Friday...

Saturday: A persistent and anomalously deep cyclone will move slowly
newd and along and just offshore the coast of the nern US. In its
wake, strongly rising heights and subsidence will continue over the
Middle Atlantic and Carolinas. Associated mostly sunny conditions
will be warmer ones, as unseasonably cool air now suppressed well
swd begins to retreat poleward with the parent cyclone, and as
surface high pressure modifies while building across the Southeast.
As such, high temperatures are expected to rebound to near average
and in the upr 50s to lwr 60s.

Winds will really drop off on Saturday night as high pressure over
the Deep South gets closer to central NC and the deep low moves
farther NE into Atlantic Canada. Model point soundings indicate
decoupling will take place with a strong inversion developing near
the surface. Thus we should radiate quite well as skies will be
clear. Despite rising low-level thicknesses (in the 1335-1345 m
range), temperatures are still expected to be drop into the mid-to-
upper-30s. Isolated lower-30s will even be possible in outlying
areas, most likely in the SW where the chances of winds going
completely calm are greatest. This will bring renewed frost and
possibly freeze concerns.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 420 AM Friday...

The surface high will begin to shift east and offshore on Sunday,
bringing a return to SW low-level flow and temperatures back above
normal. Sunday`s highs will be lower-to-mid-60s with lows in the
upper-30s to lower-40s. Monday and Tuesday will be even warmer with
highs in the mid-60s to lower-70s and lows in the lower-50s on
Monday night. Dry weather will prevail on Sunday and Monday as weak
mid-level ridging moves overhead.

Models have overall come into better agreement on the pattern
evolution next week, though exact details still need to be ironed
out. The next mid/upper trough will move across the Northern Plains
on Monday, then deepen (possibly into a closed low) over the Great
Lakes on Monday night and southern Quebec/Ontario on Tuesday. This
system will drag a strong cold front through central NC sometime
Tuesday, but with the best upper forcing well to our north it looks
like the front will be fairly moisture starved by the time it gets
here. However, the 00z ECMWF trended a bit wetter as it shows a
deeper mid-level trough and associated surface low over the
Northeast US that still brings moderate height falls to central NC.
Will need to see more consistency and support from other guidance
before raising POPs too much, but did bring them to slight across
the whole area.

Temperatures will drop significantly behind the cold front with lows
Tuesday night in the mid-30s to mid-40s, and highs Wednesday in the
mid-50s to lower-60s. This period should be dry as cool high
pressure briefly moves overhead. 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 mid-MS Valley on
Wednesday night and Thursday. Both the GFS and ECMWF also depict a
surface low riding along the front, which may lift back north as a
warm front. This looks to be the best chance for significant
precipitation in the entire forecast period, but capped POPs at
chance given it is Day 7.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
As of 125 AM Friday...

Periods of VFR, multi-layered clouds mostly between 5-15 thousand ft
AGL --and virga-- will continue through early this afternoon,
courtesy of the passage of a series of disturbances and lift in
cyclonic flow aloft.

Light, generally wly surface winds this morning will increase
and become gusty into the 20s kts with daytime heating/mixing.
Surface winds should mostly diminish after nightfall and
consequently present a good chance of low level wind beginning
around 02-03Z, as wnwly winds just above the surface strengthen to
between 35-45 kts around slow-moving low pressure across the Middle
Atlantic coast.

Outlook: Nwly surface winds will become gusty into the upr teens to
20s kts again Sat, as low pressure gradually tracks up the coast of
New England. A mostly moisture-starved cold front will move across
NC with a small chance of rain and flight restrictions on Tue.

&&

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

&&

$$
SYNOPSIS...MWS
NEAR TERM...Green/MWS
SHORT TERM...MWS/JD
LONG TERM...JD
AVIATION...MWS