050
FXUS62 KRAH 182345
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
745 PM EDT Thu Jul 18 2024

.SYNOPSIS...
A cold front will approach the region today, bringing showers and
storms to the area. The front will remain stationary through the end
of the week resulting in unsettled weather and cooler
temperatures.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 310 PM Thursday...

* Flood Watch remains in effect until late tonight for the Triangle,
  northeast Piedmont, and northern Coastal Plain.
* Severe Thunderstorm Watch remains in effect until late tonight for
  all but Forsyth and Guilford Counties.

Latest satellite and radar indicate that the surface cold front
likely extends from eastern TN into south-central VA. A surface
trough/boundary extends from just SE of the Triad into the northern
Triangle region and the far NE Piedmont into the northern Coastal
Plain. Over the next several hours into the late afternoon, a line
of showers and storms presently over the Triangle and northeast
Piedmont should continue to progress south and east into the central
Coastal Plain into early evening hours. Damaging winds will remain
the primary threat with these storm cells. Mesoanalysis also reveals
a weak surface low over the Triangle. In addition to the severe
risk, the Flood Watch remains in effect and isolated flash flooding
could develop over the next few hours along and east-northeast of
the Triangle as training of storm cells becomes increasingly favored
along the low pressure system. The flood threat should wane by mid
to late evening.

A second batch of storms also exists across far western NC out ahead
of the cold front. The ARW, which has depicted the current placement
of storms reasonably well, shows this activity reach the southern
sections of the Triad into the southern Piedmont and Sandills later
this afternoon and into the mid to late evening. This seems
reasonable given upstream development just west of Charlotte. This
batch will also have the threat of damaging winds. Isolated flash
flooding cannot be ruled out with these line of storms as well but
fast-moving cells should prohibit any flood watch in these areas at
the moment.

Most storm activity should wane by late evening, exiting the Coastal
Plain and Sandhills around midnight or shortly thereafter. Guidance
again favors the development of low clouds and possible fog as the
cold front settles into the NC/SC border by Fri morning. The best
chance of fog would appear to be along/south of the boundary, where
moisture-rich air remains. This would be in the Sandhills to Coastal
Plain region, but perhaps also the Triangle. Overnight lows will dip
into the upper 60s to lower 70s.


&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 230 PM Thursday...

The weak frontal zone (more of a sturdy outflow than a true synoptic
cold front) will be pushed to along the E and S edges of the
forecast area by Fri morning, propelled in part by large scale mid
level troughing from New England and the N Mid Atlantic coast SE
across the Ohio Valley and central Miss Valley. The front is likely
to stall there and weaken further through Fri night as a wavy mid
level southern stream southwesterly flow persists, parallel to the
surface frontal zone and on the E side of a mid level trough
extending from SW MI through the Miss Valley to NE TX. The deepest
moisture, in the form of a stream of 2.2-2.4" PW, will be pushed to
across our SE half. While there will not be quite as much upper
divergence as today, the upper jetlet snaking from central TN
through N PA and off Cape Cod and the Canadian Maritimes in
conjunction with passage of a series of minor mid level
perturbations may provide added forcing for ascent, on top of the
favorable thermodynamics (projected SBCAPE of 1500-2000 J/kg),
although deep layer bulk shear will remain rather modest at just
around 20 kts. Given the fairly slow storm motion, the potential for
multicell clusters, and the deep warm layer nearing 4 km, the threat
for locally heavy flood-producing downpours across the SE remains
valid, and this threat will be enhanced in areas that get
considerable rainfall through tonight. Will have highest pops across
the S and SE, but expect above-climo pops areawide. Showers/storms
should have plenty of juice in terms of low level moisture and
warmth to keep moderate CAPE going well into the night, so expect
storms to be maintained through the evening and slow to wind down
overnight. After highs in the 80s to around 90 under variably cloudy
skies, expect lows of around 70 to 75 Fri night. -GIH

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 1254 PM Thursday...

The forecast from Saturday onward will feature broad southwesterly
flow aloft as a 594dm H5 ridge remains in place off the southeast
coast. Longwave troughing will stretch from eastern Canada back
through the Ohio valley into eastern Texas next week, with a series
of weak embedded shortwave troughs moving through the flow. This
will allow for daily shower and thunderstorm chances, primarily
during the afternoon and evening hours with a fairly typical
climatological distribution of PoPs (highest values across the NW
Piedmont, Sandhills/southern Coastal Plain). While grand ensemble
model agreement is good for this time period, timing the exact
arrival of any of these shortwaves is a challenge although it looks
like Saturday and Sunday may be particularly wet, with decreasing
chances Monday and/or Tuesday as mid level dry air works in from the
east. A further confinement of the highest PoPs to the NW Piedmont
looks warranted Wednesday and Thursday as the center of the offshore
ridge migrates closer to the coast, but I`ll maintain at least 30-40
PoPs area-wide given the inherent uncertainty in forecasting
convection within low shear environments such as this. The primary
threats with any storms this week should be locally heavy rainfall
as shear and other thermodynamic parameters are largely unsupportive
of widespread severe weather.

Temperatures this weekend into early next week should be within a
few degrees of normal with highs in the upper 80s to lower 90s.
Overnight lows will once again remain on the mild side with readings
generally in the low to mid 70s. With these types of temperatures,
heat indices should generally remain at or just below triple digits
this weekend into next week.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
As of 745 PM Thursday...

Widespread convection across central NC this afternoon and evening
continues to shift east and southeast and has cleared well to the
southeast of the Triad terminals of KINT/KGSO and a little south of
KRDU/KRWI. The threat for showers and storms will continue at the
KFAY terminal through around 02 or 3Z with a few showers persisting
to around 04 or 05Z.

A cold front that triggered the thunderstorms will settle through
the area overnight and guidance continues to show a strong signal
for IFR/MVFR stratus developing overnight, with perhaps LIFR early
Fri morning. There is a lesser threat of fog but have included some
visibility restrictions overnight. The worst conditions are expected
in the eastern areas including KRDU/KFAY/KRWI. Ceilings should
gradually lift on Friday morning and should become VFR by late
morning. There is a limited chance of late afternoon convection on
Friday.

Outlook: A period of unsettled weather with scattered showers and
storms will continue through the weekend into Tuesday with periods
of late night and early morning fog and stratus during the period. -
Blaes
&&

.CLIMATE...
Record High Minimum Temperatures:

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

July 21: KGSO: 76/2011 KRDU: 78/1932 KFAY: 80/2017

July 22: KRDU: 78/2011

July 23: KRDU: 78/2011

July 24: KRDU: 79/2011 KFAY: 79/1945

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch until midnight EDT tonight for NCZ007>011-024>028-
041>043-078.

&&

$$

SYNOPSIS...DL
NEAR TERM...Kren
SHORT TERM...Hartfield
LONG TERM...Leins
AVIATION...Blaes
CLIMATE...RAH