611
FXUS62 KRAH 160800
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
400 AM EDT Tue Jul 16 2024

.SYNOPSIS...
A strong subtropical ridge will gradually weaken over the Southeast
though mid-week. A cold front will settle into the Carolinas on
Thursday, then become quasi-stationary while weakening into the
weekend.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 330 AM Tuesday...

...Dangerous and Near Record Heat Continues...

...Heat Advisory Remains in Effect from Noon Today to 8 PM...

There is very little to no change in the synoptic pattern and
antecedent airmass in place as subtropical ridging and Bermuda high
pressure unite to sustain dangerous and near record heat across the
region. Highs will be very similar to yesterday, in 95-100 range,
with heat indices ranging from lower 100s in the NW Piedmont to as
high as 109-110 across interior and eastern/southern portions. As
such, Heat Advisory has been issued for generally the same
climatological divisions across central NC.

PWATs are progged to inch up slightly to around 2.2-2.3" and there
remains a signal in the hi-res models that convective coverage
should be higher than recent days as weak upper impulses emanating
through the ridge and atop lee troughing could potentially help to
drive a west to east moving cluster of showers and storms across
central NC between 18 to 03z. Given the moist environment, some
locally heavy rain rainfall and minor flooding is possible. Also,
given the high CAPE/steep lapse rate environment, cannot rule out an
isolated strong/severe downburst.

Bulk of convection should dissipate by midnight. Balmy overnight
lows in the mid to upper 70s, except for some lower 70s across the
far northern Piedmont counties.


&&

.SHORT TERM /WEDNESDAY AND WEDNESDAY NIGHT/...
As of 330 AM Tuesday...

...One Last Day of Dangerous Heat....

Moisture will continue to increase in advance of an upper trough and
attendant cold front that will progress SEwd into the Ohio and Tn
Valley late Wednesday-Wednesday night. The influx of ~2.5" PWATs
into the area will result in an uptick in showers and storms
Wednesday afternoon and Wednesday night as another parade of vort
impulses spread through the region during max heating/
destablization. While the increase in cloud cover and PoPs will
temper the dry-bulb temps more into the lower/mid 90 ranges, there
will be less mixing out of afternoon dewpoints. Thus, we`ll see one
last day of heat advisory criteria of heat indices in the 103-107
range across much of the same area.

Deep layer shear is forecast to increase to ~25kts, which is higher
than recent days. As such, SPC has introduced a level 1/marginal
severe threat across the northern half of the forecast area, with
wind the primary threat.

Given the moist airmass and weak height falls starting to spread
into the region , convection could linger well into the overnight
hours. Lows in the 70s.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
As of 400 AM Tuesday...

Widespread showers and some storms are expected on Thursday as a
cold front reaches central NC and slows down. Deep southwesterly
flow aloft ahead of broad mid-level troughing that digs from New
England into the lower MS Valley will continue to bring in above-
normal PW values of 2 to 2.5 inches. So there will be plenty of
moisture for this front to tap, along with moderate instability of
around 1000-2000 J/kg. There will also be upper support as we will
be in the right entrance region of a jet streak over New England and
the northern Mid-Atlantic. The vast majority (80-90%) of
GEFS/EPS/CMC ensemble members depict precipitation. Thus categorical
POPs are justified, maximized with daytime heating in the
afternoon/evening, though chance POPs still linger overnight. 1 to 2
inches are expected on average, highest SE, but locally higher
amounts will be possible especially where slow-moving storms occur.
WPC now has a slight (level 2 of 4) risk for excessive rain on
Thursday across nearly all of central NC. Fortunately widespread
severe weather is not a major concern given the weak shear, but
locally damaging winds can`t be totally ruled out. The front will
settle near the NC/SC border on Friday, and more heavy rain will be
possible especially south in closest proximity to the front. Amounts
may come down a bit overall as upper support wanes with the
mid/upper trough lifting into Canada. But WPC still has central NC
in a marginal (level 1 of 4) risk for excessive rain on Friday.

The front looks to retrograde back NW a bit to near the VA/NC border
from Saturday through Monday, wavering back and forth as it does so,
and likely POPs continue each day. Overall rainfall amounts may
continue to decrease slightly as Atlantic ridging builds back
westward, and we actually get mild height rises. But rich moisture
and moderate instability will still be in place. Ensemble mean QPF
through the whole extended period is generally 2 to 3 inches,
greatest south and east, and of course locally higher amounts will
always be possible where storms occur. While so much rain for
multiple days in a row will cause some flooding concerns, it will
provide more welcome drought relief. It will also help bring down
high temperatures to upper-80s to lower-90s on Thursday (near
normal) and only 80s from Friday through Monday, with the official
forecast tending toward the cooler end of guidance. Lows will be in
the upper-60s to mid-70s.

&&

.AVIATION /05Z MONDAY THROUGH SATURDAY/...
As of 127 AM Tuesday...

VFR conditions are mostly expected overnight. However, based on
persistent, cannot rule out isolated pockets of fog, mainly at KRWI.

Shower and storm coverage this afternoon and evening is expected to
be higher than the past couple of days, with a general consensus
that a cluster of storms will move west to east across the area
between 18 to 00z. Have added a prob30 for all TAF sites.
Convection should dissipate between 03 to 06z.

Outlook: Mainly VFR conditions are expected to continue away from
diurnally-driven convection, which will gradually increase in
coverage through Wed. A cold front will move into NC late Wed-Wed
night, then become quasi-stationary over the region Thu-Sat. Higher
chances of flight restrictions, both in and away from diurnally-
maximized convection, will consequently result Thu-Sat.

&&

.CLIMATE...
Record High Temperatures:

July 16:
KGSO: 99/1915
KRDU: 101/1887
KFAY: 103/1937

July 17:
KRDU: 100/1887
KFAY: 102/1932


Record High Minimum Temperatures:

July 16:
KGSO: 75/2010
KRDU: 77/2010
KFAY: 78/1992

July 17:
KGSO: 75/2013
KRDU: 80/1887
KFAY: 77/2019

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

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Heat Advisory from noon today to 8 PM EDT this evening for
NCZ007>011-023>028-039>043-073>078-083>086-088-089.

&&

$$

SYNOPSIS...MWS
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...Danco
AVIATION...CBL/Luchetti
CLIMATE...RAH