882
FXUS62 KRAH 300715
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
315 AM EDT Wed Sep 30 2026

.WHAT HAS CHANGED...

* There is increased confidence for cold air damming and below
  average temperatures during the latter half of the weekend, but
  the extent of sensible weather impacts will be influenced by the
  timing and likelihood of steadiest and heaviest rain that remains
  more uncertain.

&&

.KEY MESSAGES...
As of 300 AM Wednesday...

1) Patchy dense fog and low clouds will reduce visibility early this
morning across portions of central NC, with the lowest visibilities
and most persistent fog focused across the Sandhills and Coastal
Plain.

2) Temperatures will trend well above average through Friday, with
unseasonably hot, but not humid, afternoons.


3) Saturday will mark a transition to cloudy, much cooler, and
periods of wet conditions that will continue through the weekend.

&&

.DISCUSSION...
As of 300 AM Wednesday...

KEY MESSAGE 1...  Patchy dense fog and low clouds will reduce
visibility early this morning across portions of central NC, with
the lowest visibilities and most persistent fog focused across the
Sandhills and Coastal Plain.

Calm winds and high low level moisture early this morning will help
fog and low cloud development through daybreak. While patchy fog is
possible farther west in the Piedmont, the thickest fog and lowest
cloud cover will settle over eastern areas. Visibilities across the
Coastal Plain could drop to a mile or less at times during the
morning commute, creating localized travel delays. Morning sunlight
will quickly burn off the moisture, returning clear skies to the
entire region by mid morning.

KEY MESSAGE 2... Temperatures will trend well above average through
Friday, with unseasonably hot, but not humid, afternoons.

The models indicate a mid-level sub-tropical ridge over the srn
Appalachians will continue to strengthen while progressing across
and offshore the Carolinas during the next couple of days.

At the surface, a Canadian high and continental airmass now centered
over the Middle Atlantic will progress offshore today, then extend
from near Bermuda to the South Atlantic coast through Fri. Sly flow
around the Bermuda high, and subsidence beneath the ridging aloft,
will contribute to warming temperatures through the week and what
will likely be the last few days of summerlike temperatures of the
year. While hotter, and gradually more humid/muggy by night,
moisture return will be shallow and susceptible to vertical
advection/mixing of lingering dry/continental within the ridge axis
over NC, such that mixed/ afternoon dewpoints will probably only
increase from mid/upr 50s today to mostly mid 60s by Fri (with
afternoon RH in the 30s to 40s percent).

KEY MESSAGE 3... Saturday will mark a transition to cloudy, much
cooler, and periods of wet conditions that will continue through the
weekend.

A positively-tilted srn stream trough/shear axis will progress
slowly across the Southeast and Carolinas this weekend, just
downstream and equatorward of a series of prominent shortwaves that
will progress through a broad trough that will become centered over
ern Canada.

At the surface, high pressure extending from near Bermuda to the
South Atlantic coast will be displaced by a wavy frontal zone
forecast to settle swd and across cntl NC on Sat (~3-6 hours faster
than previous model cycles). Following, progressive but favorably
strong and located high pressure for cold air damming initially over
the Great Lakes at 1028 mb, will ridge swd across the Middle
Atlantic and Carolinas this weekend.

Given both earlier diurnal timing of the frontal passage on Sat
(prior to peak heating) and otherwise limited low-level moisture and
mid-level lapse rates, instability will be weak and unsupportive of
deep convection. A band of frontal showers and areas of light,
anafrontal rain will instead probably result Sat. A better chance of
steadier rain will result Sat night-Sun in cntl NC, when and where
sly and strengthening 850 mb flow will maximize isentropic lift atop
the CAD surface ridge. However, the lack of any substantial
perturbations forecast within the aforementioned srn stream trough
axis suggests frontal wave development will be limited, as will the
risk of any heavy rain. The isentropic upglide regime and saturated
CAD airmass will nonetheless favor periods of at least light rain
and drizzle late Sat through the weekend. As confidence in that
pattern (probably) increases in the coming days, forecast high
temperatures and diurnal ranges for the weekend will probably
require substantial adjustments downward from currently forecast
ones. In fact, if the previously noted pattern occurs, temperatures
on Sun will probably be similar to the 60s F that occurred in the
recent cold air damming episode on the 23rd.

A reinforcing cold front and following cP/Canadian surface high will
progress across the srn Middle Atlantic early next week.

&&

.AVIATION /06Z WEDNESDAY THROUGH SUNDAY/...
As of 215 AM Wednesday...

24 hour TAF period: VFR conditions currently prevail across central
NC, but light/calm winds and increasing low level moisture will lead
to patchy fog and low stratus development across the area mainly
between 09Z and 13Z. Sub VFR conditions are mainly expected at the
eastern terminals (KRDU, KINT, KFAY) during the early morning hours.
With a tad higher confidence in patchy fog/low status developing as
far west as KINT and KGSO, added a TEMPO to account for IFR/LIFR
visibilities and low cloud layers development. Rapid improvement to
VFR should occur by late morning, with light/variable winds
overnight turning light southerly to southwesterly winds this
afternoon.
Outlook: VFR conditions are likely to hold through at least Friday,
though areas of sub VFR fog and stratus remain possible each morning
(especially across the eastern terminals, with the highest potential
early Friday morning). The chance for showers and thunderstorms
producing sub VFR conditions will increase Saturday and remain
elevated through most of Monday as a cold front approaches and
sweeps across the area.

&&

.CLIMATE...

Record High Temperatures:

September 30:
KRDU: 89/1954

October 1:
KGSO: 90/1986
KRDU: 90/1986

&&

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

&&

$$

DISCUSSION...CA/MWS
AVIATION...CA