340
FXUS62 KRAH 051926
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
326 PM EDT Fri Jul 5 2024

.SYNOPSIS...
Surface high pressure across the western Atlantic and Deep South
will shift east through tonight as a surface trough extends south
across the Piedmont of Virginia and North Carolina. A cold front
will approach the region from the northwest this evening and then
move into and stall across Virginia and Carolinas this weekend.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
As of 1100 AM Friday...

* Dangerously hot today with record high temperatures
* Scattered afternoon and evening thunderstorms, especially across
  the west and north which may produce strong gusty winds

The latest surface analysis shows a couple of surface troughs
extending north to south across VA and the Carolinas with the
eastern trough likely enhanced by convection on Thursday evening. A
1017mb 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 northern PA into eastern OH and central
KY and central TN. The airmass across central NC is already very
warm and humid with surface dew points in the lower 70s with a few
mid 70s across the Coastal Plain. Temperatures as of 10am were
already in the lower to mid 80s. The morning sounding from KGSO
depicted a moist profile with a PW of 1.83 and a generally light
westerly flow. The morning low level thickness was observed at
1428m, 10m warmer than Thursday and the KMHX RAOB was 15m warmer as
well. These soundings suggest highs will range from 3 to 5 degrees
warmer today, than yesterday in many locations.

Highs should range in the upper 90s to low 100s in most locations
and will threaten daily high records in many locations. The mid
shift upgraded the Heat Advisory to an Excessive Heat Warning for
the ne Piedmont, nrn Coastal Plain, and the nrn Sandhills, where
heat index values around 110 F will be likely this afternoon. The
Heat Advisory remains otherwise unchanged in time and location, for
peak heat index values generally in the 105 to 109 F range.

Visible satellite imagery depicts mainly clear skies across central
NC this morning with some patchy stratus across parts of the
southern Piedmont and Sandhills. The sunshine will will quickly
erode morning convective inhibition and the atmosphere will become
moderately unstable with MLCAPE values of 1200 to 2400 J/Kg this
afternoon, notably more than on Thursday. Expect cumulus clouds to
pop after 11am and they should be more widespread that previous
days. Isolated to widely scattered convection may develop in the
Piedmont and Sandhills in the vicinity of the lee trough with more
numerous thunderstorms apt to develop across western NC and near the
VA border area north of the Triad and then push east. 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 introduced 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 /19Z FRIDAY THROUGH WEDNESDAY/...
As of 315 PM Thursday...

Scattered showers and thunderstorms will continue to develop across
central NC this afternoon and evening. Convection will be most
favored a little later this evening perhaps 21 to 01Z in the Triad
terminals at KINT and KGSO where a line of convection moving east
from the NC mountains approaches. Convection will become widely
scattered or isolated late this evening before dissipating after
midnight. Some localized patches of stratus and perhaps fog will
develop tonight, favored in locations where rainfall occurs and
across the Coastal Plain and Sandhills where moisture is greatest.
Generally fair weather is expected for Saturday morning before
scattered convection begins to develop during the afternoon. Light
mainly south to southwest at less than 10 kts are expected during
the period. In addition, a brief period of marginal LLWS may occur
overnight, most favored near and to the northeast of the KRDU
terminal.

Outlook: A more typical summer time weather pattern will setup late
in the weekend through mid week featuring scattered afternoon and
evening showers/storms and a good chance of late night and early
morning stratus and fog. -Blaes

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 8 PM EDT this evening for NCZ007-021>023-
038-039-073>075-078-083>086-088-089.
Excessive Heat Warning until 8 PM EDT this evening for
NCZ008>011-024>028-040>043-076-077.
Heat Advisory from 11 AM to 8 PM EDT Saturday for NCZ008>011-
023>028-040>043-075>078-084>086-088-089.

&&

$$

SYNOPSIS...Blaes
NEAR TERM...Blaes
SHORT TERM...DL
LONG TERM...np
AVIATION...Blaes