104
FXUS62 KRAH 041820
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
220 PM EDT Fri Sep 4 2026

.WHAT HAS CHANGED...

* Heat Advisory has been expanded to cover all of central NC
  until 8 PM this evening.

* A new Heat Advisory has been issued for Saturday where
  forecast confidence was greatest. This Advisory will be in
  effect from 11 AM until 8 PM.

&&

.KEY MESSAGES...
As of 215 PM Friday...

1) A new Heat Advisory has been issued for Saturday from 11 AM
until 8 PM.

2) Scattered to locally numerous showers/storms will be
possible through this afternoon into the evening hours.

3) A conditional severe risk persists on Saturday ahead of a
cold front.

4) A cold frontal passage Sunday will bring cooler and drier
air early next week, but not before some isolated to scattered
showers remain possible late this weekend.


&&

.DISCUSSION...
As of 215 PM Friday...

KEY MESSAGE 1... A new Heat Advisory has been issued for
Saturday from 11 AM until 8 PM.

The Heat Advisory was expanded to all of central NC for today
until 8 PM. Surface observations across the northern Piedmont up
into Virginia have shown heat indices rising into 102 to around
105 and this will likely continue until convective outflow from
developing showers/storms cool the area or until 8 PM as
nocturnal cooling begins.

A cold front is expected to remain well to our north through
the daylight hours on Sat. However, the hot and humid air mass
that has plagued the southern Mid-Atlantic and Carolinas this
week will likely be convectively contaminated by cloud debris,
lingering outflows, and pockets of rain cooled/moistened soils
from convection this afternoon. Additionally, A canopy of mid-
level convective debris cloudiness from the (probably weakening)
remnants of an overnight convective cluster from OH to the
Virginias may limit insolation and curb the heat over especially
the nrn half of cntl NC on Sat. And if that convective cluster
were to maintain intensity more than currently forecast, which
they oftentimes do east of the Appalachians, then a more-
prominent cold pool/outflow and possible ongoing convection
would further limit early day heating there. The airmass will
nonetheless have the potential to be as hot (or nearly so) as
previous days in the absence of those lower predictability
influences from convection/clouds. A Heat Advisory has been
issued for Saturday across the southern half of central NC where
confidence is greatest that at least two hours of +105 is
probable before convection/cloud cover move into the area. This
area may need to be adjusted with the overnight forecast update.


KEY MESSAGE 2... Scattered to locally numerous showers/storms
will be possible through this afternoon into the evening hours.

The leading edge of a cold front is beginning to work down into
northern VA this afternoon, but is expected to stay well north
of the forecast area. The primary triggering mechanism for
convection is expected to be along a leading pre-frontal trough
acting as a low-lvl convergence boundary and is draped near or
just south of the VA/NC border. The air mass in place remains
hot and humid with temperatures regularly in the upper 90s to
around 100 degrees and surface dew points in the upper 60s to
low 70s. When combined with slightly cooler 500-700mb
temperatures on the northeast side of the lower/mid level
subtropical ridge over the southern Appalachians and extending
into SC, moderate to high instability is expected (1500- 3500
MLCAPE) around the initiating boundary and locations to its
south in central NC. Storm coverage and intensity remains
uncertain given the lack of a strong forcing mechanism and
minimal mid/upper lvl support from any upstream MCV`s given our
location relative to the strong ridge.

If deep convection is able to develop, mean cloud-layer winds
of 10- 25 kts over the southern Mid-Atlantic oriented about 30
degrees off the initiating boundary should allow for convection
to shift off the boundary and track generally east-
southeastward. Deep layer shear of 25-35 kts should support
storm organization along a common cold pool within small scale
bowing clusters, although splitting cells and transient mid-lvl
rotation will be possible with short, straight hodographs if
storm collisions can remain at a minimum (00z HREF highlights
10-30% of short segments of either right or left moving storms
in the 6-11 PM timeframe).

Steep low-lvl lapse rates, high LCLs, and strong DCAPE, will
favor strong diabatic cooling within collapsing deep-convection
and result in the primary risk coming from damaging straight-
line winds, especially within any storm clusters oriented along
a common cold pool. Isolated large hail can`t be ruled out, but
given the hot temperatures, it will likely require an incredibly
deep storm and/or some mid-lvl storm rotation to have the hail
survive its journey to the surface.


KEY MESSAGE 3... A conditional severe risk persists on Saturday
ahead of a cold front.

A decaying, convectively-induced mid-level disturbance over the
lower Ohio Valley will interact with a backdoor cold front
sliding south through the Mid-Atlantic on Saturday. Deep-layer
shear will increase compared to Friday, with mid-level flow
strengthening as the East Coast trough digs further west,
supporting multicell storms capable of producing damaging wind
gusts and large hail. A Slight Risk remains in place for the
majority of central North Carolina. This severe threat, however,
remains conditional. Upstream decaying convection out of
western VA could focus debris cloudiness across our northern
tier of counties. Realistically, a gradual thinning of these
clouds will take shape through the late morning and early
afternoon. A southward moving effective front/outflow may then
trigger afternoon and evening convection. Where that convection
initiates will depend on conditional factors mentioned, but
could be most focused from along and south of US-64 per the
latest 12z HREF. WPC has much of the area in an excessive
rainfall risk, but this is also conditional. Nevertheless, brief
heavy rainfall in some slow- moving storms could favor isolated
flash flooding given the anomalous moisture in place.


KEY MESSAGE 4... A cold frontal passage Sunday will bring
cooler and drier air early next week, but not before some
isolated to scattered showers remain possible late this weekend.

The cold front is expected to push through by Sunday morning.
However, the trend since Monday has been for a slow erosion of
the low-level moisture, coupled to the fact that a moist
northeasterly flow behind the front could favor upslope stratus
in the morning and early afternoon. The guidance is now honing
in on a weak mid-level impulse diving down out of WV/VA during
the day Sunday. Coupled to the still high dewpoints in the upper
60s for most areas, weak instability could support low-topped
isolated to scattered showers, especially along and west of the
Triangle into the western/southern Piedmont.

Drier air and more seasonal temperatures will arrive in time
for Labor Day and persist into Wednesday. Monday and Tuesday
should feature much lower humidity, with dewpoints expected to
range from the upper 50s to lower 60s, and highs largely in the
80s. Unfortunately, this reprieve from the heat will be brief,
with high temperatures expected to rebound into the low-to-
mid/upper 90s by Wednesday and Thursday. The ridge is expected
to extend from the central US this time late next week as
opposed to over the southern Appalachians, which may limit our
overall heat risk. And ensembles continue to suggest a late-week
front sometime Thu-Fri. There is a large degree of spread,
however, in the trough/ridge pattern at this time range, so
confidence on storm chances are low, though highest late Thu-
Fri.


&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
As of 215 PM Friday...

Convection remains the primary driver in aviation restrictions
through the 24 hour TAF period. Today features a noticeable
increase in potential showers/storms at the northern 4 terminals
(less chance for TSRA to reach FAY) and PROB30s have been
maintained. Any terminals that receive heavy rainfall may bring
a risk for morning stratus/mist or even fog.

Outlook: Convective coverage and intensity is expected to
increase on Sat relative to the past several days ahead of a
cold front slow shifting south into the Carolinas from VA.
Northeast flow behind a backdoor cold front may support areas of
IFR-MVFR ceilings Sun morning and Mon morning.


&&

.CLIMATE...
Records within reach this forecast period:

Record High Temperatures:

September 4: KRDU: 100/1925 KFAY: 100/1944
September 5: KGSO:  97/1954 KRDU:  98/2023 KFAY: 99/1932


Record High Minimum Temperatures:

September 4: KGSO: 72/2018 KRDU: 74/1921 KFAY: 75/2020
September 5: KGSO: 73/2018 KRDU: 74/2012 KFAY: 74/1935

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for NCZ007>011-
021>028-038>043-073>078-083>086-088-089.
Air Quality Alert until 8 PM EDT this evening for NCZ021>023-
038-039.
Heat Advisory from 11 AM to 8 PM EDT Saturday for NCZ042-
073>078-083>086-088-089.

&&

$$

DISCUSSION...AS/MWS/Kren
AVIATION...AS/MWS