137
FXUS62 KRAH 080752
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
352 AM EDT Tue Jul 8 2025

.SYNOPSIS...
A weak surface trough will linger over the Middle Atlantic and
Carolinas through mid-week.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 350 AM Tuesday...

* A Heat Advisory is in place for the eastern Piedmont, Sandhills,
  and Coastal Plain for heat indices of 105 to 109.

* Although most locations should remain dry today, scattered slow
  moving wet-downbursts may result in isolated strong to severe
  wind gusts as well as isolated flash flooding in urban and
  within the areas of heavily saturated soils from Chantal
  rainfall.

A broad trough draped across the northern Plains through the Great
Lakes into the Northeast will gradually sharpen through early Wed
morning, but change very little over the Southeast. At the surface,
Bermuda high pressure will extend westward into the Carolinas with
the sharpening of the Piedmont trough through the afternoon hours.

Diurnal heating of the humid airmass over the Mid-Atlantic through
this afternoon will result in temperatures rising into the 90s by
early afternoon and combine with surface dew points in the low/mid
70s to produce heat indices of 105 to 109 degrees. A Heat Advisory
is in place to account for this risk for dangerous heat. Reminder
that the heat index represents the feels-like temperature in the
shade and doesn`t account for additional stress from direct sunlight
when heat stress would develop more rapidly. Drink plenty of fluids
and take breaks in the shade or air-conditioned areas if you must be
outside during peak heating.

The airmass should quickly become weakly capped as moderate to high
surface based instability develops with low/mid 70s dewpoints and
temps in the 90s. Weak to negligible synoptic forcing will have to
rely surface forcing from seabreeze and the sharpening of the
Piedmont trough, although convective temperatures may also be
breached as well. Isolated deeper convection may still develop in
the vicinity of the surface forcing and be capable of primarily
strong to severe wet-downburst. Anomalous deep-layer moisture, a
deep warm cloud layer of >12k ft, and slow steering winds will also
add the risk for torrential rainfall to produce isolated instances
of flash flooding. Urban areas and poor drainage locations will be
at greatest risk, but also within the footprint of rainfall from
Chantal where flash-flood guidance is significantly lower and MRMS
Flash Crest-Soil Moisture is still very saturated showing 40 to 80%
(only taking 2.5" in 6 hrs to fill basins in the eastern Piedmont).
The biggest question mark will be magnitude of background synoptic
descent associated the Bermuda ridge in the western Atlantic. This
may prevent much more than scattered convection and isolated deep
convection due to poor mid-lapse rates and warm temperatures at
850mb.

&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 350 AM Tuesday...

* Increasing concerns for scattered flash flooding for the NC
  Piedmont Wednesday afternoon/evening.

Convectively amplified shortwaves are expected to ripple through the
base of the broad mid/upper level trough Wed and result in weak but
gradual H5 heights falls to leak into the Mid-Atlantic Wed afternoon
through the overnight period. Anomalous deep layer moisture will
gradually increase to around 2" areawide (exceeding the 90th
percentile areawide and prime the area for efficient heavy rainfall
showers/storms during the afternoon. Although an isolated strong to
severe wet-downburst is possible, the greater concerns may be the
threat for scattered instances of flash-flooding.

HREF guidance suggest weak H5 height falls will trigger numerous to
widespread showers and storms with a moderate to strongly
unstable airmass, especially over the Piedmont between 18z Wed
and 00z Thurs. As mentioned in the near term section, a large
portion of the eastern Piedmont remains especially sensitive to
flash flooding due to high soil moisture resulting in
significantly lower flash-flood guidance where Chantal brought
3-8 inches to locally as much as 11 inches. Latest guidance
suggest it would only take 2.5 inches in 6 hours to fill local
basins in these areas and the 00z HREF is beginning to highlight
30-50% probabilities of >3" in just 3 hrs from these storms.
Additionally, 00z HREF LPMM is highlighting concentrated areas
of 2 to 5 inches possible in 6 hours.

Now it is important to note that this setup is very different from a
tropical system moving through the region. Primarily convective
events are difficult to predict where these consecrated areas of
higher rainfall will occur and may fall outside of the more
sensitive areas altogether. Additionally, these setups more likely
result in localized areas of enhanced rainfall rather than large
swaths of flash flooding from tropical events. There are still a lot
of details to be worked out, but the pattern is there for at least
increased awareness heading into mid-week.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 340 AM Tuesday...

A mid/upper trough will push east from SE Ontario into southern
Quebec on Thursday and Friday, as a pair of shortwaves moves across
the Northern and Central Plains. Meanwhile the broad longwave trough
will extend south into the TN Valley. Southwesterly flow aloft will
prevail over central NC between this feature and a subtropical high
centered near Bermuda. This will bring in plenty of moisture with PW
values near or exceeding 2 inches. A series of upper impulses and a
Piedmont surface trough will combine with the ample moisture and
moderate destabilization south of a quasi-stationary front over the
OH Valley and northern Mid-Atlantic to result in widespread shower
and storm development on Thursday and Friday, maximized in the
afternoon and evening. The greatest coverage looks to be on Thursday
when POPs are categorical everywhere. Similar to previous days,
despite weak shear, there still could be a threat for isolated
damaging winds from wet downbursts, and SPC introduced a marginal
(level 1 of 5) risk for severe storms on Thursday.

The more concerning threat, however, looks to be heavy rain and
flooding. The storms should be fairly slow moving with the weak mean
flow, and grounds will be saturated due to recent heavy rainfall
from Tropical Depression Chantal along with additional expected
showers and storms today and tomorrow. Thus the WPC has a marginal
(level 1 of 4) risk for excessive rainfall on both Thursday and
Friday, with even a slight (level 2 of 4) area over the NC Piedmont
where locally very heavy rain just fell from Chantal. Flood Watches
may be needed, and additional river flooding will be possible as
some points along the Haw, Little, and Cape Fear Rivers are already
above or near flood stage.

High temperatures on Thursday and Friday will be back down to near
normal (mid-80s to 90) with the widespread clouds and precipitation
chances, but it will still be uncomfortably humid with widespread
dew points in the 70s. The cloud cover will also keep lows on the
mild side, in the upper-60s to mid-70s.

The longwave trough will push to our east this weekend, turning the
mid-level flow more W/NW and bringing in some drier air. The
shortwaves over the North-Central US will lift into Canada, and
ridging will begin building into the Southeast US especially by
Monday. Thus convective coverage should decrease somewhat, but with
moderate destabilization and the boundary remaining to our north,
along with a continued Piedmont surface trough, scattered showers
and storms will still be possible each day. This pattern will result
in a slight increase in temperatures but still within a few degrees
of normal, with highs in the upper-80s to lower-90s. Lows will be in
the lower-to-mid-70s. Heat indices in the low-100s will be possible
in the south and east by Sunday and Monday.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
As of 125 AM Tuesday...

No major changes with the 06z TAF package as prevailing VFR is
expected at all TAF sites with PROB30s for late afternoon storms and
associated restrictions. We are watching an area of IFR/MVFR cigs
pinned along the NC coast as some guidance suggest a period of SCT
to perhaps BKN cigs may lift northward and affect FAY and RWI in the
10-14z window. Mixing after sunrise may additionally result in a
short window of MVFR cigs at FAY before scattering/lifting to VFR by
mid-morning.

Outlook: Scattered storms are expected each afternoon and evening
through Fri, as a weak upper trough slowly approaches from the west;
greatest coverage through the outlook period may be Wed and Thurs.
Early morning fog and/or stratus will also be possible. Storm
coverage decreasing a bit this weekend as westerly flow aloft takes
hold.

&&

.HYDROLOGY...
As of 350 AM Tuesday...

River Flood Warnings remain in effect for a few locations across
central NC. As of this morning, this includes the following:

Haw River at Bynum (although is falling quickly)
Little River at Manchester
Cape Fear at Fayetteville

After coordination with local emergency management, the flood
warning was allowed to expire late last night due to slowly
improving conditions and receding waters. There still remain a
significant amount of road closures as well as several roadways
that have been completely washed away. Continue to heed road
closures and find alternate routes. Rivers and streams still
remain relatively elevated, fast moving, and dangerous for the
next couple days.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 10 AM this morning to 8 PM EDT this evening
for NCZ007>011-023>028-040>043-075>078-084>086-088-089.

&&

$$

SYNOPSIS...Leins
NEAR TERM...Swiggett
SHORT TERM...Swiggett
LONG TERM...Danco
AVIATION...Swiggett/MWS
HYDROLOGY...Swiggett