Nc State University, North Carolina Weather Forecast Discussion

776
FXUS62 KRAH 201404
AFDRAH
Area Forecast Discussion
National Weather Service Raleigh NC
1000 AM EDT Sat Sep 20 2025
.SYNOPSIS...
A weak backdoor cold front will move south through NC later today
and tonight. High pressure will follow and extend across the Middle
Atlantic Sunday and Monday, then drift offshore.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 355 AM Saturday...
* Patchy fog still possible over the ne Piedmont and Coastal Plain
  this morning but with lesser probability of occurrence than
  previously forecast
* Continued unseasonably warm today, with isolated showers/storms
  primarily over both the far srn Piedmont and Sandhills and
  northeast Piedmont and nrn Coastal Plain
* Low stratus likely to develop overnight-Sunday morning over at
  least the nern half of NC
Shortwave perturbations spanning multiple branches of the mid-
latitude and sub-tropical westerlies have carved a mean, negatively-
tilted trough from the upr MS Valley to the Carolinas this morning.
A pocket of modestly cool mid-level temperatures, minus 9C to minus
14C and coolest over the MS and TN Valleys, were evident within the
trough axis in 00Z upr air charts. NWP guidance suggests the
upstream portion of the trough axis will dig slightly while pivoting
from the OH/TN Valleys early today to the Carolinas and srn Middle
Atlantic this afternoon through tonight. Associated, mid/upr-level Q-
vector convergence will become centered over cntl VA/NC between
approximately 18Z-00Z, coincident with the aforementioned cool
pocket aloft that will be characterized by minus 10-12C 500 mb
temperatures and 6-7 C/km 850-500 lapse rates.
At the surface, a backdoor cold front was evident in surface
observational and KDOX and KLWX radar data from the Lower Eastern
Shore nwwd across nrn VA, from near WAL to FRR at 0745Z and moving
sswd around 8-10 kts. The front has been accompanied by isolated,
nocturnal convection over nrn VA. Extrapolation of the current
movement of the front, it will likely settle into the far ne
Piedmont and nrn Coastal Plain around midday, then continue to drift
swwd across the remainder of cntl NC through this evening. NWP
guidance suggests the front will focus low-level moisture
convergence and pooling of generally lwr-mid 60s F surface dewpoints
along and immediately behind it, while the pre-frontal airmass over
srn and cntl NC will be characterized by deeper and stronger
boundary layer mixing and "mixing out"/vertical advection of drier
air, with associated mid 50s to lwr 60s F surface dewpoints this
afternoon. HREF instability fields indicate a narrow and relatively
uniform corridor of weak to moderate instability will result and
maximize across the Piedmont of VA and the Carolinas with diurnal
heating, with warmer surface temperature in the mid 80s to near
90 F likely to offset the aforementioned drier low-levels there.
Sharply drier air just above seasonably moist air at the surface,
evident on observed soundings last evening at MHX and WAL, will
probably favor more dew than fog this morning; and areas of
altocumulus bubbling along the I-95 corridor will also limit
radiational cooling and associated widespread radiation fog
formation. As such, fog, or lack thereof, in the Dense Fog Advisory
area may necessitate early cancellation. Observational trends will
be monitored for another few hours before making that decision,
however.
Thereafter, the aforementioned weak, large-scale forcing for ascent
accompanying the negatively-tilted shortwave perturbation, and
thermodynamics from the surface through the mid-levels, will
probably support the development of at least isolated convection
from cntl VA swwd through the cntl and wrn Carolinas. Despite
generally limited instability and updraft strength, a deeply-mixed
and dry boundary layer, with characteristic inverted-V shapes in
point forecast soundings from CLT to FAY, suggest there will be a
conditional risk of strong wind gusts to perhaps ~35-45 kts.
Areas of post-frontal stratus and fog will likely develop late
tonight-Sunday morning, especially over the nern half of cntl NC,
with low temperatures mostly upr 50s to lwr 60s.
&&
.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 410 AM Saturday...
In the wake of the shortwave trough that will pivot across the srn
Middle Atlantic later today-tonight, shortwave ridging will expand
from the swrn N. Atlantic to the Carolinas. Underlying surface high
pressure will ridge from the Middle Atlantic to the Carolinas, with
associated nely flow and slightly lower temperatures (ie. upr 70s to
mid 80s Sun and mid 50s to lwr 60s Sun night). It will otherwise be
dry, with areas of low overcast and fog both mornings.
&&
.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 308 AM Saturday...
There is good ensemble consensus that an upper low will form over
the central Plains on Tuesday before cutting off and lingering over
the mid-Mississippi to Ohio Valleys Wednesday into Friday. This will
initially focus the deeper moisture and precipitation over the
Mississippi Valley Monday through early Wednesday before shifting
over our area more-so late Wednesday into Saturday.
At the sfc, high pressure will shift away from New England on
Monday. The persistent nely flow we`ve seen the past week will turn
more esely by Monday afternoon. As mentioned above, anomalous
moisture and sfc/upper forcing will remain to our west on Monday and
as such expect a dry day with highs similar to Sunday in the upper
70s to mid 80s.
By Tuesday, sly flow will develop over central NC and as such expect
highs to peak a bit higher in the mid to upper 80s.  Some deeper
moisture may spill into our northern areas late in the day, but
overall forcing should focus precipitation again to our west and
north leaving us dry Tuesday.
As the upper cut off low slowly drifts north-northeast Wednesday
into the weekend ripples of mid-level perturbations will drift
across central NC. With anomalous moisture in place, we`ll see
periods of pre-frontal showers and storms during this stretch. Its a
bit too far out to get too into specifics. However, it`s worth
noting that ensembles do show periods of low Cape/high shear
environments Thursday and Friday. With the slow movement of the
cutoff upper low, hard to imagine we would be outlooked in anything
beyond Marginal at this point. Further, a few of the machine
learning severe outlook analogs are hinting at marginal-level
probabilities over our area during that time period (Pangu, FengWu,
CSU-mlp). Something to watch for sure as we progress through early
next week.
After a hot Wednesday (highs in the upper 80s to lower 90s), cloudy
skies and periods of rain may damped highs into the upper 70s/lower
80s a bit Thursday into the weekend.
&&
.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
As of 740 AM Saturday...
LIFR-IFR restrictions will linger at RWI and FAY through 13-14Z,
after which time VFR conditions and light nely surface winds are
expected. Otherwise, an isolated shower/storm will be possible (~15-
20% probability of occurrence) this afternoon from near AFP to MEB
and FAY, and also from near HNZ to IXA and RWI. Stratus and fog will
likely develop behind a backdoor cold front late tonight-Sunday
morning, most likely before 12Z at RWI and RDU and around or just
after 12Z at each of the other TAF sites.
Outlook: Areas of stratus and fog will be possible again late Sunday
night-Monday morning. Showers/storms and flight restrictions are
expected mid to late this upcoming week.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...MWS
NEAR TERM...MWS
SHORT TERM...MWS
LONG TERM...Luchetti
AVIATION...MWS

NWS RAH Office Area Forecast Discussion