362
FXUS62 KRAH 181653
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
1254 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 /UNTIL 6 AM FRIDAY MORNING/...
As of 1150 AM Thursday...

* Flood Watch expanded southwest to include the Triangle area
 and the Central Coastal Plain.

There was little change to the going forecast for this afternoon and
tonight. Based on 24-hour QPF amounts, areas from Person to Halifax
Counties received some 2-4 inches of rainfall last night. Based on
forecast QPF later today and tonight, 1-3 inches of additional
rainfall is possible. Current 3-hr FFG values in these counties
ranges from 1.5 to 2.5 inches. As a result, localized flash flooding
may occur and we went ahead and issued a Flood Watch until midnight
tonight, collaborating with neighboring offices. Storms appear to
still be relatively fast moving, even with the latest 12Z HRRR, but
given prior considerations from the prior discussion, some training
may be possible, especially over previously saturated ground.

Surface analysis shows the front is draped presently from eastern TN
into portions of WV and central PA. A pre-frontal trough was located
across western NC and into western VA. It still appears convection
will develop along the trough or just ahead of the cold front, with
storms initially being isolated to scattered. That activity is still
expected to become numerous to widespread as they track ESE into the
mid to late evening hours. The main action still looks to be between
about 2 to 8 PM, with most storm activity waning after midnight. The
front will slowly settle along the NC/VA border by sunrise Fri.

Highs this afternoon are expected to be in the upper 80s to lower
90s, as sunshine ahead of storms should allow us to warm up as most
guidance suggests.

If radar and observational trends become more apparent this
afternoon, the Flood Watch may be expanded to include portions of
the Triangle. But as it stands, there was limited confidence to
include these counties.

Lingering convection over the northern Coastal Plain early this
morning will continue to diminish over the next few hours.  Aloft,
water vapor imagery depicts broad swly flow over the southeast
associated with an upper trough currently lifting into the
northeast.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
As of 312 AM Thursday...

The front will become quasi-stationary over central NC on Friday
while the anomalously moist airmass lingers. Shear will weaken
Friday afternoon as the upper jet streak pulls off into eastern
Canada. As such, upper forcing during the daytime will be minimal as
weak ridging builds over the southeast. However, given the presence
of the front, and the anomalously moist airmass, scattered showers
and storms will likely develop during peak heating Friday afternoon.
Overall coverage will likely be less compared to Thursday, but given
slower expected storm motion, any training cells could lead to
instances of localized flash flooding.  The greatest threat for
flash flooding Friday will be south and east of Raleigh, areas that
will likely receive the highest rainfall on Thursday. Convection
should generally wane with loss of heating Friday evening.

Max temperatures Friday will reach the upper 80s. Overnight lows
will remain warm in the 70s.

&&

.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 /16Z THURSDAY THROUGH MONDAY/...
As of 642 AM Thursday...

Scattered to numerous showers and storms are expected to develop
this afternoon and evening, peaking near KRDU/KRWI/KFAY later today.
As such, expect temporary flight restrictions to develop at these
sites at times later today and tonight.  The bulk of the heavier
rain should move east of central NC late tonight, however MVFR to
IFR ceilings are expected to fill in over much of the eastern two
thirds of central NC starting near 03Z and persisting through the
end of the 24 hr TAF period.

Beyond 12Z Friday: A cold front will sag into and stall across the
region Friday through Sunday which will increase the chances for sub-
VFR conditions through this weekend.

&&

.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...Luchetti
LONG TERM...Leins
AVIATION...Luchetti
CLIMATE...RAH