209
FXUS62 KRAH 051505
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
1100 AM 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 /THROUGH TONIGHT/...
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 /SATURDAY AND SATURDAY NIGHT/...
As of 330 AM Friday...

* Hot and humid conditions continue Saturday with heat indices
  climbing to 100 to 105 degrees
* Isolated to scattered flash flooding possible as storms will be
  slow moving and efficient rainfall producers.

A compact, but flattening, shortwave embedded within the broad
troughing will lift through the Lower Great Lakes into southern
Quebec by Sun morning. The related surface pattern will shift a
surface low into the Northeast with a trailing cold front extending
into the Ohio and Tennessee Valley. Weakening dynamics at the
surface will likely prevent the surface cold front from traversing
the Appalachian mountains. Ahead of the front and east of the
mountains, a continued hot and humid airmass will be in place as
early afternoon temperatures quickly rise into the 90s to around 100
degrees with surface dew points in the upper 60s to mid 70s,
resulting in heat indices of 100 to 105 degrees. Heat indices over
the western Piedmont may be closer to the mid 90s as
increasing/thickening cloud cover spreads in from the west and
proximity to greater chances for showers/storms and convective
outflow slowing rise in afternoon temps. Although details will be
dependent on convective activity Fri/Fri night, another heat
advisory will likely be needed for at least the Coastal Plain and
eastern Sandhills for Sat.

Showers and thunderstorms are expected to initiate along a lee
trough that develops with diurnal heating over the western Piedmont
with the a hot and humid airmass in place along and east of the
trough. Moderate instability is expected to develop by early
afternoon as MLCAPE values rise to 1500-2500 J/kg and MLCIN erodes.
Flooding will likely be the primary hazard with these storms with
anomalous deep layer moisture (PWAT >2.25), warm cloud layer between
10,000 to 15,000 and weak cloud layer flow and Corfidi vectors.
Additionally, deterministic Hi-Res guidance depicts initial storm
outflow to congeal creating basically an effective front draped SW
to NE across central NC that slowly progresses eastward with time.
This orientation would align cloud-layer flow parallel to the front
which would bring a risk for training storms. 00z HREF aligns with
theses thoughts depicting of 1" to 2"/hr rain rates and the
strongest storms capable of over 3"/hr. Current forecast has
widespread rain of 0.5 to 1.5 inches, but as finer details become
clear expect the range between min/mix to increase with isolated
locations capable of seeing over 3 inches.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 330 AM Friday...

A rather persistent pattern is expected through the remainder of
the extended as central NC will be tucked between broad reinforcing
troughing through the central CONUS with the stationary sub-tropical
high broadly draped across the western Atlantic in the eastern GOM.
NWP guidance has been consistent with a closed low drifting across
the western Atlantic and retrograding towards the Carolina coast,
but is expected to remain over the Atlantic. At the surface a
diffuse pressure gradient will feature a lee-trough redeveloping
over the region each afternoon with continued anomalous deep layer
moisture in place as PWAT values remain at-or-above 2 inches.

This pattern will favor continued above normal temperatures with
highs in the mid 90s in the urban areas and overnight lows only
reaching into the mid 70s. With continued heat related stresses heat
related illnesses will be possible especially among individuals
sensitive to heat and do not have access to effective cooling and/or
adequate hydration. Diurnally favored showers/storms and storms will
also be possible each afternoon into the evening, likely focused
along the lee-trough and any subsequent outflow boundaries
thereafter. Organized convection appears to be at a minimum with
deep layer shear remains weak around 10 to 20 kts, strongest across
the NW Piedmont, and result in mostly pulse summer-time
showers/storms. Greatest coverage could be Tues into Tues night with
proximity of mid/upper troughing swings through the Great Lakes
region.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
As of 745 AM Thursday...

Patchy MVFR visibility restrictions around GSO will become VFR by
~12Z. VFR conditions are otherwise expected away from scattered
showers/storms that are expected to redevelop with afternoon
heating. Some clustering and more-prolonged risk of showers/storms
will be possible at INT/GSO this evening-early tonight, where lift
will be maximized in the vicinity of a lee surface trough, outflow
from upstream convection, and glancing influence of a mid-level
trough. A slightly better chance (than recent mornings) of stratus
and fog will exist late tonight-Sat morning, especially at INT/GSO,
as low-level moisture and humidity values gradually increase.

Outlook: A good chance of morning stratus and fog and mainly
afternoon-evening showers/storms will exist through early-mid next
week, as a surface trough/front settle into the region and interact
with an unseasonably moist air mass in place.

&&

.CLIMATE...
Record High Temperatures:

July 5:
KGSO: 98/2012
KRDU: 102/1999
KFAY: 101/2002

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 this morning to 8 PM EDT this evening
for NCZ007-021>023-038-039-073>075-078-083>086-088-089.
Excessive Heat Warning from 11 AM this morning to 8 PM EDT
this evening for NCZ008>011-024>028-040>043-076-077.

&&

$$
SYNOPSIS...Blaes
NEAR TERM...Blaes
SHORT TERM...Swiggett
LONG TERM...Swiggett
AVIATION...MWS
CLIMATE...RAH