030
FXUS62 KRAH 171033
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
631 AM EDT Wed Jul 17 2024

.SYNOPSIS...
A strong subtropical ridge will gradually weaken over the Southeast
though mid-week. A cold front will settle into the Carolinas on
Thursday, then become quasi-stationary while weakening into the
weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 250 AM Wednesday...

Water vapor imagery this morning depicts a low-amplitude trough over
the Great Lakes/northeast. More locally, a de-amplified mid-level
ridge remains off the southeast coast. At the sfc, a trough was
observed extending north from the southern Piedmont through the
northern Piedmont.

The upper trough will lift into the northeast this afternoon through
Thursday. While associated upper forcing and shear will maximize to
our north, some mid-level impulses embedded within the swly aloft
will trickle across central NC this afternoon. These features will
help to initiate scattered showers and storms along a pre-frontal
trough that will set up just west of the US-1 corridor. Storms will
generally flow from west to east through the afternoon before
diminishing with loss of heating tonight.  Bulk-layer shear will
peak around 20 kts, but spread relatively uniform across central NC.
A little better shear may develop across the NC/VA border late
afternoon, which may provide a bit better environment for a few
organized clusters to possibly develop.  If any stronger storms can
develop, isolated damaging wind gusts may be possible today.
Additionally, forecasted hodographs/supercell composite fields do
indicate a non-zero chance for perhaps a few supercells to develop
across the central/northern Piedmont into the northern Coastal
Plain.  Not overly concerned with tornado potential today given
relatively high LCLs. However, stronger gust potential may exist
with any isolated rotating updraft that could form later this
afternoon in the areas mentioned. Overall though, the severe threat
today should be relatively localized. A few residual showers/storms
may persist into the overnight period, but overall, rain chances
should wane overnight.

Max temperatures will soar into the mid 90s again today. Afternoon
dew points along and east of the sfc trough (roughly along and east
of US-1) will likely remain in the lower to mid 70s. West of the
boundary, dew points may mix out into the upper 60s. Given the
current position on the sfc trough mentioned above, as well as
latest high-res model trends, decided to expand the Heat Advisory
today a few counties westward.

Overnight lows in the mid to upper 70s are expected once again.

&&

.SHORT TERM /THURSDAY AND THURSDAY NIGHT/...
As of 345 AM Wednesday...

Broad mid-level troughing will dig from New England into the lower
MS Valley on Thursday, as a cold front approaches central NC from
the NW before moving through on Thursday night. The front will be
slow moving given the front-parallel (southwesterly) flow aloft,
which could result in training convection. There will be plenty of
moisture for this front to tap with PW values of 2 to 2.25 inches,
along with marginal to moderate instability of around 1000-2500
J/kg, highest SE. There will also be upper support as we will be in
the right entrance region of a jet streak over New England and the
northern Mid-Atlantic. Thus widespread showers and storms are
expected, and the vast majority (80-90%) of GEFS/EPS/CMC ensemble
members depict precipitation. Categorical POPs continue, maximized
with daytime heating in the afternoon/evening, though some chance
POPs still linger overnight. Total rainfall amounts on Thursday and
Thursday night are expected to range from 0.5 inches NW to as much
as 2 inches in the east, but locally higher amounts will be possible
especially where slow-moving storms occur. WPC continues a slight
(level 2 of 4) risk for excessive rain across roughly the eastern
half of central NC, with a marginal (level 1 of 4) risk elsewhere.
While the strongest mid-level flow will be north of the region, the
flow will still be perturbed enough that 20-30 kts of deep layer
shear is possible. So SPC has a marginal (level 1 of 5) risk for
severe storms, with damaging winds the main hazard. The dangerous
heat will finally come to an end on Thursday despite still being
ahead of the front, thanks to all the clouds and precipitation.
Forecast highs are in the upper-80s to lower-90s (near normal), with
lows Thursday night in the upper-60s to lower-70s.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 415 AM Wednesday...

The front will settle near the NC/SC border on Friday and then
slowly lift north through the day. More heavy rain will be possible
especially south where moisture and instability will be greatest.
Amounts do look to decrease a bit overall as upper support wanes
with the mid/upper trough lifting into Canada. Shear also looks even
weaker so severe weather may be even less of a concern. Forecast
amounts on Friday/Friday night range from around a quarter inch in
the north to around an inch in the south, but again locally higher
amounts will be possible, and WPC still has central NC in a marginal
(level 1 of 4) risk for excessive rain.

The front then looks to continue slowly lifting north through the
mid-Atlantic from Saturday through Tuesday, becoming more diffuse as
it does so. Overall rainfall amounts and shower/storm coverage
should continue to slowly decrease each day as Atlantic ridging
builds back westward and we actually get mild height rises, with the
front moving farther away. But rich moisture and marginal to
moderate instability will still be in place, so POPs stay above
climo. The upside is the drought relief all this rain will provide,
as well as keeping the heat at bay. Forecast highs from Friday
through Tuesday are mostly in the mid-to-upper-80s, gradually
moderating from slightly below normal to near normal. Lows will be
in the upper-60s to mid-70s.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
As of 631 AM Wednesday...

VFR conditions will prevail for much of the 24 hour TAF period.
However, scattered showers and storms will develop and spread west
to east this afternoon through tonight. Associated brief sub-VFR
restrictions could develop at any terminal during this period. Any
lingering showers/storms should diminish overnight.  Early morning
stratus looks possible across the I-95 corridor Thursday. However,
confidence was too low to include in the KRWI or kFAY TAFs with this
package.

Outlook:   A cold front will sag into and stall across the
region Thursday through Saturday which will increase the chances for
sub-VFR conditions through this weekend.

&&

.CLIMATE...
Record High Temperatures:

July 17:
KRDU: 100/1887
KFAY: 102/1932

Record High Minimum Temperatures:

July 17:
KGSO: 75/2013
KRDU: 80/1887
KFAY: 77/2019

July 18:
KGSO: 76/1986
KRDU: 79/1887
KFAY: 77/2019

July 19:
KGSO: 75/2016
KFAY: 77/2023

July 20:
KGSO: 75/2019
KRDU: 76/2020

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM this morning to 8 PM EDT this evening
for NCZ008>011-024>028-040>043-075>078-084>086-088-089.

&&

$$
SYNOPSIS...MWS
NEAR TERM...Luchetti
SHORT TERM...Danco
LONG TERM...Danco
AVIATION...Luchetti
CLIMATE...RAH