172
FXUS62 KRAH 212312
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
710 PM EDT Tue Jul 21 2026

.WHAT HAS CHANGED...

* Confidence continues to increase for a threat of heavy rainfall
  and flooding from late Wednesday into Saturday, as the latest
  models are slower the passage of a moisture-laden cold front.

&&

.KEY MESSAGES...
As of 425 PM Tuesday...

1) As a cold front approaches on Wednesday and Wednesday night,
showers and storms will become more widespread across the northern
Piedmont and northern Coastal Plain. Excessive rainfall and flash
flooding will be possible, and Flood Watches may need to be issued.
Locally damaging winds also can`t be ruled out.

2) Widespread showers and storms with a risk for flooding will
continue into at least Friday and possibly even this weekend,
particularly in our south and east, as a cold front stalls near the
NC/SC border.

&&

.DISCUSSION...
As of 425 PM Tuesday...

KEY MESSAGE 1... As a cold front approaches on Wednesday and
Wednesday night, showers and storms will become more widespread
across the northern Piedmont and northern Coastal Plain. Excessive
rainfall and flash flooding will be possible, and Flood Watches may
need to be issued. Locally damaging winds also can`t be ruled out.

Confidence is moderate-to-high for showers and storms to increase in
coverage across the northern Piedmont late this evening into early
Wednesday morning. A cold front pushing down slowly from Virginia
will stall near the North Carolina border overnight, bringing a risk
of continuous rainfall, which can be heavy at times, to the areas
along and south of the NC border around daybreak. While an isolated
severe storm with damaging wind gusts can`t be ruled out tonight,
the main concern will shift into Wednesday.

As mid/upper troughing with embedded shortwave impulses remains in
place across the Eastern US on Wednesday, a strong cold front will
approach and then slowly begin to cross the NW Piedmont on Wednesday
night. While widespread cloud cover through the day will limit
daytime heating across the north, models still show weak to moderate
instability (up to 1000-1500 J/kg of CAPE) there. Above-normal PW
values of 2-2.5 inches will also prevail ahead of the front, owing
in large part to highly anomalous moisture being drawn in from the
circulation of Tropical Storm Bertha over the northern Gulf.

CAMS generally show a band of showers and storms associated with a
prefrontal trough that is mainly concentrated near the NC/VA border
on Wednesday morning. This band will increase in coverage and
intensity as it sags SE into the northern/western Piedmont and
northern Coastal Plain in the afternoon and evening, continuing into
the overnight hours. However, timing of this band is still somewhat
uncertain, as it has slowed down in guidance like the GFS and NAM
compared to the last couple days. If the 12z NAM Nest is accurate it
won`t really get going across our north until the evening and
overnight hours, while the south stays mostly dry. So will have to
watch is this trend continues.

Regardless, once the band does set up, excessive rainfall is looking
increasingly likely given the very moist air mass and strong signal
for storm training, as the mean flow is from the WSW (roughly
parallel to the front). WPC QPF is in the 1-2.5 inch range across
our far northern counties, but HREF LPMM depicts potential for 3-5+
inches in localized spots. Some of these areas have already received
1-3 inches over the last 2 days. Thus after internal collaboration
with WPC, they are issuing a moderate (level 3 of 4) risk for
excessive rainfall in our far NE Piedmont and northern Coastal Plain
near the VA border for Wednesday and Wednesday night. Elsewhere, a
slight (level 2 of 4) risk is in effect. Flood Watches may
eventually be needed for parts of our area as well. Forecast
rainfall amounts through Wednesday night quickly decrease to the
south, with the 12z HREF mean depicting around a quarter inch or
less in our southernmost tier of counties.

Furthermore, deep-layer shear of 30-40 kts across our northern
counties could result in some organized storm cells/clusters that
become strong to severe in the afternoon and evening. Thus most of
central NC outside of the south is under a slight (level 2 of 5)
risk for severe weather. Damaging winds will again be the main
threat, and while 0-1 km SRH looks limited, an isolated tornado
can`t be totally ruled out.


KEY MESSAGE 2... Widespread showers and storms with a risk for
flooding will continue into at least Friday and possibly even this
weekend, particularly in our south and east, as a cold front stalls
near the NC/SC border.

The cold front will move only slightly south and east on Thursday,
and with rich Gulf moisture continuing to funnel NE along the front,
another day of heavy rainfall and possible flash flooding is
expected, this time across all of central NC. WPC QPF is 1-2 inches
on average across the region, but this time the heaviest rainfall
axis is shifted a bit SE. Once again, locally higher amounts will be
possible. Thus after internal collaboration, WPC is also issuing a
moderate (level 3 of 4) risk for excessive rainfall across eastern
NC that includes some of our Coastal Plain counties, with a slight
(level 2 of 4) risk for most of the rest of central NC.

This threat for heavy rainfall unfortunately looks to continue
across at least our SE zones on Friday and possibly even Saturday as
the cold front stalls or drifts very slowly south somewhere near the
NC/SC border. WPC QPF from Friday into Saturday depicts another 1-3
inches from Raleigh south and east. There is still disagreement
among the models on exact frontal placement, which will dictate
where the heavy rainfall threat will be. However, guidance has
generally been slowing down its southward progression and as a
result keeps showers and storms across central NC for longer.
Furthermore, a shortwave trough moving through the TN Valley and
southern Appalachians may actually enhance the moist air mass again
on Saturday as PW values increase to 2-2.5 inches, along with
providing additional forcing for ascent.

One silver lining is the severe threat at least looks to decrease on
Thursday and especially by Friday and Saturday. This is due to the
Eastern US troughing flattening, resulting in a weakening of the mid-
level flow, along with less instability to work with as the front
slowly sinks south. However, a few strong storms with water-loaded
downbursts still can`t be ruled out mainly in the SE.

There is higher confidence in drier conditions from Sunday through
Tuesday as the mid/upper troughing finally pushes to our east and
the flow aloft turns northwesterly. However, as temperatures heat
back up, isolated diurnally-driven convection still can`t be ruled
out each day.

&&

.AVIATION /23Z TUESDAY THROUGH SUNDAY/...
As of 710 PM Tuesday...

TAF period: High confidence in VFR conditions through most of the
next 24 hours, although precipitation that arrives Wednesday could
bring localized restrictions. Some very isolated showers will be
around over North Carolina this evening, while most of the rain
remains to the north across Virginia. With the loss of daytime
heating, just some mid and high level clouds will be around
overnight. While a low-level jet is expected to develop tonight,
have removed the LLWS mention from INT/GSO as the highest winds will
remain east of these terminals. Not terribly confident in whether
gusts will continue overnight at FAY, and have gone with both a gust
mention along with LLWS; RDU/RWI are not expected to have gusts and
have maintained LLWS there. LLWS should come to an end by sunrise,
with the bulk of precipitation slow to move into North Carolina on
Wednesday. There was enough confidence to add prevailing showers at
INT/GSO by late morning, with VCTS added to RDU/RWI during the
afternoon. Scattered convection is not expected to reach FAY until
after 00Z.

Outlook: Widespread precipitation is expected Wednesday night
through Saturday with showers and thunderstorms. Ceiling
restrictions are expected to also develop Wednesday night and
continue for several days.

&&

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

&&

$$

DISCUSSION...Danco/CA
AVIATION...Green