209
FXUS62 KRAH 171740
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
142 PM 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 1048 AM Wednesday...

* One more day of hot temperatures
* Showers and storms possible this afternoon

Mid morning water vapor imagery and surface analysis depicts
longwave troughing across the lower Great Lakes, with a cold front
stretching from western NY through OH and into IL. Across NC, high
pressure remains off the coast with broad southwesterly flow aloft.
A series of weak perturbations are noted in WV imagery across GA and
SC, and there is some ongoing convection off the southeast NC coast,
but conditions remain mostly dry across central NC. Despite some
early morning cloud cover, temperatures have quickly risen into the
lower 80s in the Triad and in the mid/upper 80s in the east.

One more day of dangerously hot temperatures and high heat indices
are in store for the region as dewpoints remain in the low to mid
70s with air temps in the mid to upper 90s. Heat Advisories were
expanded overnight and look good based on obs as of 10am. As for
storm chances, 12Z HREF continues to depict an active afternoon not
only across the western Piedmont but also across the Coastal Plain.
Curiously enough, several consecutive runs of the NAM nest and HRRR
aren`t terribly enthused about storm chances in the east, and debris
cloud cover from morning convection off the coast could limit
heating and storm potential across the those areas. I`ll maintain at
least a 30-40 percent chance of storms across the southeast as it is
mostly clear across the Sandhills and the entire CWA should rapidly
destabilize by early afternoon. However the best forcing for ascent
and synoptic scale forcing will be closer to the longwave trough as
it migrates into New England this afternoon, and storm chances will
remain highest in the NW Piedmont, decreasing as one travels
eastward.

Forecast remains in good shape overall. Hot today, with overnight
lows in the mid to upper 70s.

&&

.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 WEDNESDAY/...
As of 142 PM Wednesday...

The extended will continue to feature high rain chances,
particularly in the beginning part of the period into the weekend.
Somewhat lower chances, but still above climo, will exist for the
early to middle part of next week.

On Friday, the cold front approaching from Thu is forecast in most
of the guidance to settle along the NC/SC border, then slowly lift
back north as a warm front Fri night to Saturday evening. During
this time, a trough/shortwave will be present over the TN valley,
fueling energy streaming in from the SSW and PWAT values roughly 120-
percent of normal. Storm chances will remain elevated at this time
with the boundary in place. WPC has retained a slight risk of
excessive rainfall across our SE zones Fri along the stalled front.
A marginal risk remains in place Sat as the front lifts back
northward in the moist southerly flow. Temperatures Fri/Sat look to
top out in the mid to upper 80s, warmest in the south to near 90.
This will be lower than the past several days with added rain
chances and cloud cover.

As we head from Sunday into the middle of next week, the front looks
to become more diffuse and washed out. A Bermuda high will exert
more influence, with continued warm and humid flow persisting.
Aloft, the trough over the TN valleys weakens and a ridge over the
western Atlantic will gradually shift west, resulting in a slight
rise in heights. This should favor a trend toward less rain chances
each day. However, PoPs will remain above climatological normals as
we remain in that moist and unstable environment, as well as with
slight troughing to our west over the Mid-Mississippi Valley
advecting in energy from mid-levels. WPC has another marginal risk
of excessive rainfall over the entire area Sunday. While there may
not be any main surface features, a Piedmont trough and sea-breeze
may enhance storm chances, focused mainly in the afternoon and
evening hours. Highs will largely hover in the mid/upper 80s to
lower 90s, trending warmer by midweek. Heat indices currently look
to stay below advisory criteria given the daily rain chances above
seasonal normals.

&&

.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...Leins
SHORT TERM...Danco
LONG TERM...Kren
AVIATION...Luchetti
CLIMATE...RAH