894
FXUS62 KRAH 090743
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
342 AM EDT Wed Jul 9 2025

.SYNOPSIS...
Disturbances in unseasonably moist, southwesterly flow aloft will
interact with a surface trough over the Middle Atlantic and
Carolinas through Thursday.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 300 AM Wednesday...

* Scattered flash-flooding is expected this afternoon through late
  this evening, especially in urban areas of the Piedmont (including
  the Triad) as well as the hydrological sensitive areas of the
  eastern Piedmont from Chantal rainfall.

* Flood Watch in effect for a majority of the central NC Piedmont
  and western Sandhills from 2 PM today until 2 AM tonight.

Convectively amplified shortwaves are expected to ripple through the
base of the broad mid/upper level trough currently stretching from
the Great Lakes through the Ohio Valley and into the ArkLaTex
region. This will result in weak but gradual H5 heights falls to
leak into the Mid-Atlantic this afternoon through the overnight
period. Anomalous deep layer moisture will gradually increase to
around 2" areawide (exceeding the 90th percentile) and prime the
area for efficient heavy rainfall showers/storms during the
afternoon. Showers and storms are expected to develop along the
eastern slopes of the mountains and over western NC and gradually
shift eastward into central NC through mid-afternoon.

The likely greatest concern through tonight will be for scattered
instances of flash-flooding this afternoon through late this
evening. Anomalous deep-layer moisture, weak steering winds, a deep
warm-cloud layer >10,000 ft, and moderate to strong instability are
all very favorable ingredients for flash-flooding. Additionally, the
eastern Piedmont is still hydrological sensitive due to rainfall
from Chantal (soil moisture still 50-70% and FFG of around 2.5" in 6
hours). 00z HREF and the 18z REFS continue to indicate 40 to +60%
probabilities for >3" in 24 hours, but investigating the LPMM
fields, these areas of locally enhanced rainfall will likely be
scattered in nature in concentrated areas. The limited coverage of
these amounts in available guidance precludes higher probabilities
for flash-flooding at this time. Observational trends will be
assessed through this afternoon whether a moderate risk for excessive
rainfall (Level 3 out of 4) will be needed. Finally, even with
continued weak synoptic support for showers/storms to continue
overnight, available guidance still shows a noticeable weakening
trend to convective intensity from 03-06z. As such, will opt to not
extend the Flood Watch through the overnight hours at this time.

There is also a risk for wet-downbursts and convective clusters
along a common cold pool, which may result in isolated damaging wind
gusts. Downed trees and potential property damage may be locally
enhanced over the eastern Piedmont where still heavily saturated
soils would provide little resistance to even sub-severe wind gusts.
Temperatures in the low 90s and dew points in the mid 70s will
result in another hot and humid day with heat indices mostly ranging
from 100 to 104. Although brief periods of time when 105 will be
possible, short temporal duration and patchy areal coverage will
preclude the need for a heat advisory with the early-morning
forecast update.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
As of 330 AM Wednesday...

A mid/upper low will push east from SE Ontario into southern Quebec
on Thursday and Thursday night, with the associated longwave trough
extending south into the Appalachians. Southwesterly flow aloft will
prevail over central NC between this feature and a subtropical high
centered near Bermuda. This will bring in more anomalous deep-layer
moisture with PW values around 2 to 2.3 inches. At the surface, to
the south of a quasi-stationary front over the OH Valley and
northern Mid-Atlantic, dew points will again be in the 70s, along
with decent boundary layer heating. A series of upper impulses and a
Piedmont surface trough will combine with the ample moisture and
moderate destabilization to result in widespread showers and storms
in the afternoon and evening, potentially lingering into the early
overnight hours. CAMS show greatest coverage in the north and west
initially before later spreading south and east. Despite weak shear
(500 mb flow less than 20 kts) making any severe threat with a
particular cell short-lived, there is still a risk for isolated
damaging winds from wet microbursts. So SPC has a marginal (level 1
of 5) risk for severe storms on Thursday.

The more concerning threat looks to be another day of heavy rain and
flooding. The storms should be fairly slow moving with the weak mean
flow, and grounds will be saturated in areas of the Piedmont that
received heavy rainfall from Tropical Depression Chantal, along with
where additional showers and storms develop today (most likely
across northern and western parts of the area). In addition, with
the trough and axis of highest PW`s shifting a bit farther east, the
heavy rain threat looks to follow suit and encompass much of our
area. Thus the WPC has a slight (level 2 of 4) risk of excessive
rainfall over most of central NC outside of the far east where there
is a marginal (level 1 of 4). Flood Watches will likely be needed,
but held off for now given a lot will depend on how much rain falls
today and where. In addition, the most recent HREF guidance only
goes out to 00z Friday, and at least through that time, LPMM amounts
and neighborhood probabilities of exceeding 3 inches don`t look
overly impressive over our area. Will certainly continue to monitor.

High temperatures on Thursday will be back down to near normal (mid-
to-upper-80s) 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.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 330 AM Wednesday...

The longwave trough will push to our east from Friday into the
weekend, turning the mid-level flow more W/NW and bringing in some
drier air. Meanwhile a series of shortwaves will stay well to our
north across the Northern/Central Plains and Great Lakes. With
continued dew points in the 70s and good surface heating resulting
in moderate destabilization, along with a Piedmont surface trough
and possible sea breeze influence, showers and storms will be
possible each day. However, coverage will be on a downward trend
beginning Friday and should be mainly scattered in nature for the
weekend. Very weak mid-level flow and lack of any frontal passages
should preclude an organized severe threat. Will still need to watch
for a locally heavy rain threat, mainly Friday, given saturated
soils from previous days` rainfall.

Ridging aloft will then begin building into the Southeast US by
early next week. As the Bermuda high begins extending back westward
and moist southerly flow increases off the Atlantic, rising PW
values may yield higher shower/storm chances once again on Monday
and Tuesday, though overall QPF still isn`t as high as what we are
expecting today and tomorrow.

Temperatures will have little variation through the period, with
highs generally near to a few degrees above normal each day (upper-
80s to lower-90s). Some heat indices in the low-100s will be
possible in the south and east. Saturday and Sunday may be slightly
warmer than the rest of the period due to decreased cloud cover and
precipitation chances. Lows each night will be in the lower-to-mid-
70s.

&&

.AVIATION /05Z WEDNESDAY THROUGH SUNDAY/...
As of 105 AM Wednesday...

Minor tweaks were made to the 06z TAFs. VFR conditions begin the
forecast period with SCT MVFR beginning to develop in between the
FAY, RDU, and RWI terminals. This appears co-located where the
heaviest rain fell this past afternoon. How this expands is
uncertain, but a slow development of MVFR to IFR cigs is expected,
especially around sunrise. Slow improvement through the morning
hours with scattered to locally numerous showers/storms expected to
develop over western NC by early afternoon (16-18z) and slowly shift
eastward through midnight. Timing of TEMPOs at GSO, INT, and RDU for
storms was tweaked based on latest hi-res guidance timing.

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 Thurs. Early
morning fog and/or stratus will also be possible. Storm coverage
decreasing a bit this weekend as westerly flow aloft takes hold.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 2 PM EDT this afternoon through late tonight
for NCZ007>010-021>025-038>040-073>076-083>086.

&&

$$

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