627
FXUS62 KRAH 060617
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
216 AM EDT Sat Jul 6 2024

.SYNOPSIS...
A subtropical ridge will continue to extend across the South
Atlantic states ahead of a cold front that will move into the
southern Middle Atlantic and Carolinas this afternoon, then stall
and dissipate over the region through the weekend.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 852 PM Friday...

* Very warm and muggy tonight, with storms continuing to slowly
  wind down...

Scattered storms persist at this hour, albeit with gradually
decreasing coverage and intensity compared to this afternoon. The
latest surface analysis shows a weak trough extending down through
the heart of central NC. A steamy air mass remains in place this
evening with very light and erratic surface flow being largely
driven by the multitude of outflows (generated by earlier and
current convection) and sea breeze segments, all noted on radar
imagery. Weak to moderate elevated CAPE persists, highest in the
east, but decreasing surface temps from scattered storms and the
onset of nocturnal cooling have helped CINH to increase over the
area, amidst somewhat poor mid level lapse rates. So while PWs
remain high over the area 2.1-2.4"), the loss of heating and lack of
dynamic mechanisms to support ongoing convection should result in a
gradual steady decrease in showers and storms over the next few
hours. Storms should be last to dwindle over the N Piedmont, where
mid level flow remains the strongest (still modest, though, near 25
kts). Expect partly cloudy to fair skies overnight, more clouds NW
than SE. Current temps are still quite warm, in the upper 70s to
upper 80s, with dewpoints in the 70s, thus forecast lows in the mid
to upper 70s still appears reasonable. -GIH

Earlier discussion from 405 PM: The latest surface analysis shows a
broad surface troughs extending north to south across VA and the
Carolinas. A 1016mb surface high across the western Atlantic extends
southwest into the coastal Carolinas and FL. A cold front extends
southwest from a weak surface low over northeast PA into eastern OH
and KY. The airmass across central NC is hot and humid with surface
dew points in the lower 70s with some upper 60s noted in south
central NC and northern SC. It has been an extremely hot day with
temperatures at or in excess of 100 at numerous locations including
106 at KRDU; 101 at KFAY, KMEB, KGSB, KVUJ, KPOB, and KFBG; and 100
at KRWI.

Widely scattered showers and thunderstorms have developed across the
Piedmont and Coastal Plain near and east of the surface trough. With
weak shear, the convection has been very pulse-like and limited in
breadth. Slightly more organized and more widespread convection
developed in the Blue Ridge and across the NC mountains just east of
an advancing cold front. This convection will move into the Triad,
western Piedmont/Yadkin Valley area and the VA border counties late
this afternoon and evening. Storms today will still have the
potential to be efficient wind producers with an inverted-V sounding
noted and with DCAPE values in excess of 1000 across the western
Piedmont. SPC has a marginal risk of severe storms across the
northwest Piedmont area with this in mind. Convection will translate
east during the evening and gradually weaken during the mid to late
evening but unlike previous nights, it will tend to persist a bit
later into the overnight.

Outside of cooling from thunderstorms, temperatures will be slow to
cool this evening. Expect temperatures to persist in the lower and
mid 80s in most locations through midnight or later before
eventually dropping into the mid 70s to around 80 by Saturday
morning. -Blaes

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
As of 300 PM Friday...

* Hot and humid once again with Heat Advisories across the east
* Storm chances increase by early afternoon, periods of heavy rain
  could result in flash flooding

Upper low over the western Great Lakes will gradually weaken as it
moves into Ontario on Saturday. Longwave troughing and the
associated attendant surface cold front is likely to get hung up
west of the mountains and wash out before it ever arrives across
central NC. However, lingering boundaries from today`s (Friday`s)
convection will likely lay down a boundary somewhere across central
NC this evening, and that will serve as a focal point for shower and
thunderstorm development once again on Saturday.

Thermodynamic parameters aren`t overly impressive on Saturday with
MLCAPEs generally topping out around 1000-1500 J/KG. The combination
of modest instability, generally weak steering flow running parallel
to the stalled surface boundary, and 99th+ percentile PW`s across
the area (2.25 - 2.5 in) would suggest that anything that develops
tomorrow will be extremely efficient at producing rainfall. HREF
Local Probability Matched Mean QPF suggests the potential for upward
of 3-4 inches of rain (if not higher) where storms develop, with the
Sandhills suggested as the favored location for heaviest rainfall.
While the stalled boundary will likely help concentrate precip
across the eastern half of the CWA, it`s hard to pinpoint exactly
where the highest rainfall would be. Going to hold off on a Flood
Watch at this point given some of the geographic uncertainty of
where storms are most likely to occur. Also, the ground should be
able to accept at least some amount of rainfall given recent dryness
but high rainfall rates, especially across highly urbanized areas,
could necessitate a few short-fused flood advisories and/or flash
flood warnings tomorrow afternoon/evening.

Before any showers develop though, temps should easily rise into the
mid/upper 90s once again. Moisture pooling on the eastern side of
the stalled boundary and dewpoints once again in the mid to upper
70s will result in another dangerously hot day especially across the
Triangle and the Coastal Plain. While Heat Index values and ambient
air temperatures may fall a few degrees shy of today`s (Friday`s)
observed values, they will still be high enough to warrant a Heat
Advisory across eastern portions of our forecast area. Relief in the
form of clouds and rainfall will certainly help, although temps and
heat indices will likely reach dangerous values for several hours
before that relief arrives. Temps will be just a bit cooler in the
west (lower 90s) with heat indices hovering right around 100
degrees.  Lows tomorrow night will be tricky given lingering cloud
cover and rain cooled air but low to mid 70s is the general
consensus.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
As of 326 PM Friday...

A potentially unsettled pattern with daily pops aoa climo is shaping
up for much of the long term period, thanks to 1persistent lee
trough along with moist s to sw flow in the lower troposphere
resulting in abundant antecedent moisture as noted by forecast PWAT
values aoa 2 inches. Scattered shower/tstm activity will be
primarily diurnal in nature, as typical this time of year.
Meanwhile, we`re not expecting any notable change to the hot
airmass, so any prolonged dry episodes will result in above, or well-
above normal hot temperatures; however, since we`re likely to see an
abundance of clouds and scattered shower/tstm activity during this
time, high temps should mostly remain closers to climo (lower 90s)
each day.

&&

.AVIATION /06Z SATURDAY THROUGH WEDNESDAY/...
As of 215 AM Saturday...

A weakening convective cluster and now light stratiform rain and
mainly VFR visibilities will persist for another hour or two at
INT/GSO. It is unclear to what degree upstream redevelopment of
showers and storms toward CLT and DCM will hold together as they
follow an otherwise similar path toward the nw NC Piedmont, where
multiple rounds of convection may have sufficiently stabilized and
shielded that area from adverse conditions, through the rest of the
morning. To the east, an area of IFR-MVFR stratus now developing
over sern VA and nern NC may extend as far west as RWI between 09-
12Z. VFR conditions are forecast otherwise and elsewhere until
scattered to numerous, slow-moving showers/storms redevelop with
daytime heating along a surface trough/effective cold front this
afternoon, then continue into this evening.

Outlook: A good chance of fog/stratus will exist late tonight-Sun
morning, followed by a somewhat-typical summer time pattern of
afternoon-evening showers/storms and morning stratus and fog
through mid-week.

&&

.CLIMATE...
Record High Temperatures:

July 6:
KRDU: 102/2022
KFAY: 99/1990

Record High Minimum Temperatures:

July 5:
KGSO: 74/1999
KRDU: 78/1902
KFAY: 77/2005

July 6:
KGSO: 76/1999
KRDU: 79/1900
KFAY: 76/2017

July 7:
KGSO: 73/2019
KRDU: 77/1900
KFAY: 78/2017

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from 11 AM to 8 PM EDT Saturday for NCZ008>011-023>028-
040>043-075>078-084>086-088-089.

&&

$$
SYNOPSIS...MWS
NEAR TERM...Hartfield/Blaes
SHORT TERM...DL
LONG TERM...np
AVIATION...MWS
CLIMATE...RAH