529
FXUS62 KRAH 121041
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
640 AM EDT Fri Jul 12 2024

.SYNOPSIS...
A frontal boundary over the region will pivot westward and stall out
over the western Piedmont tonight. The stalled front will weaken and
remain across the area Saturday, before diminishing Sunday. A lee
trough will then be in place across the western Piedmont into early
next week.

&&


.NEAR TERM /THROUGH TONIGHT/...
As of 345 AM Friday...

* Flood Watch remains in effect for all but the far western Piedmont
  counties until midnight tonight
* Potential exits for 4+ inches of rainfall over portions of the
  Piedmont and Coastal Plain

All remains on track with the forecast through tonight with little
change to the overall synoptic pattern and thermodynamics. Satellite
imagery and surface obs reveal a broad area of low pressure offshore
of GA/SC. At the same time, a surface frontal boundary was present
across the Piedmont of central NC and extending into VA. East of the
boundary, dewpoints have risen into the mid to upper 70s, with
current PWs upwards of 2.3-2.4 inches. With time, the majority of
the guidance shows this area of low pressure to move inland into
eastern portions of SC or just along the coast this afternoon, then
take a ENE track while weakening into central to eastern portions of
NC tonight into Sat morning. The circulation is most evident at 850
mb. With the cyclonic flow continuing to increase through the day,
the surface boundary will slowly progress into the far western
Piedmont and remain stationary or slowly move back east as the low
tracks ENE overnight.

There will be multiple waves of showers and storms through the
morning, afternoon, and evening with the moist onshore flow, strong
moisture transport, and frontogenetical forcing. The most widespread
coverage of storms should be focused in the aftn/eve with diurnal
heating, as MLCAPE ranges from 1200-1500 J/kg. The coverage of
showers and storms should diminish by late this evening as the low
pulls to the east and mid-level vorticity/energy shifts east with
southwest flow taking over aloft. The 00Z CAMs are indicating the
potential for some portions of the Piedmont and Coastal Plain to see
4-5+ inches of rainfall by tonight.

The HREF localized probability-matched mean (LPMM), which tries to
retain some of the high-res guidance of high rainfall rates,
indicates that an early morning (between now and a few hours after
sunrise) swath of showers/storms could develop roughly between the
Triad and Triangle, roughly from NE to SW from Person/Granville
Counties into Chatham to Moore Counties. Where this forms could vary
by 50 or so miles on either side due to model spread. But the signal
for this is likely due to frontogenetical forcing at the surface and
from low-mid levels combined with nearly stationary storm motion. A
second area to watch later this afternoon and evening will be along
and east of US-1, when peak heating and very low LCLs will generate
widespread showers/storms. Combined with slow storm motion, near all-
time high PWs of 2.2-2.5 in, and moisture transport maximizing
along/east of the Coastal Plain, will favor another swath of
potential high rainfall totals. Of course localized totals of 2-3+
inches are possible anywhere in the Flood Watch area, but the two
aforementioned locations were most evident in the guidance.

Highs should range in the upper 70s N to the mid 80s in the south.
Some patchy sun may shine in the Sandhills to southern Coastal
Plain, but most of the day will be cloudy overall. After showers
diminish in all but our far eastern zones overnight, low clouds are
likely to persist, with some fog also possible. Lows should be in
the low to mid 70s.

&&

.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 330 AM Friday...

Though weakening, the stalled front will continue to bisect the
area. Meanwhile, the axis of anomalously high moisture/PWATS will
gradually shift eastward throughout the day. Following a possible
early day lull, diurnal destablization should lead to scattered re-
development of showers and storms during the afternoon and evening,
mainly from the Triangle eastward. Highs ranging from upper 80s NE
to lower 90s elsewhere. The moist/humid dewpoint air in the lower to
mid 70s east of the front will result in heat indices in the lower
100s from the Triangle eastward. Balmy lows in the lower/mid 70s.



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

...Dangerous Heat Returns Sunday Through the Middle Part of Next
Week...

The main weather story will be the return of Dangerous Heat. Staying
under the influence of a ~591dm ridge and low-level W-SWLY flow,
1000-850 thicknesses and h8 temps are forecast to peak during the
Monday-Wednesday period, topping out ~1445m and 23-24C respectively.
Highs in the mid to upper 90s will be common place for Sunday
through Wednesday, with Monday or Tuesday currently forecast to be
the hottest day, with some lower 100s possible across central and
southern NC. There is a fairly strong and consistent model signal
for dewpoints to mix out into the lower 60s(and even quite possibly
into the upper 50s)across the western Piedmont each afternoon, which
should help to temper the heat risk over the western part of the
state. However, four consecutive days of heat indices in the 103 to
108 F degrees is likely from the Triangle eastward.

In terms of rain chances, a low-amplitude shortwave trough moving
slowly east through the mid-Atlantic region Sunday afternoon through
Monday will support isolated to scattered storm development Sunday
afternoon and evening, followed by mostly sea-breeze convection
Monday and isolated storms Tuesday, owing to the potential for weak
disturbances to move through the area. The approach of a front from
the NW and associated high rain chances late Wednesday and Thursday
will likely break the heat wave and could bring some widespread
significant rainfall to the area given the potential for the front
to slow down or stall out across the area to end the work week.

&&

.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
As of 640 AM Friday...

Largely MVFR to some brief IFR conditions are likely to start the
TAF period. Waves of showers and storms are expected through the day
and into the late evening hours, with activity waning after 03-06z.
While storm chances are possible nearly anytime today and tonight,
there are roughly two main time periods with the highest probability
of storms. The first main chance will be at the start of the 12z TAF
period between 12 and 14z. Based on current radar trends, the best
chance of VCTS or TSRA would be at RDU/FAY/RWI. The second and more
widespread storm potential will be this afternoon and evening,
between about 18-22z at GSO/INT/FAY, 19-23z at RDU, and 20-24z at
RWI. Outside of storms, conditions are likely to be MVFR, with even
some VFR this afternoon at the eastern sites (FAY/RWI). Some brief
IFR is also possible, largely confined with stronger storms. After
showers dissipate from west to east overnight tonight, ceilings are
expected to lower to between LIFR-IFR, lowest at GSO/INT/RDU. Some
patchy fog is possible, with the highest probability at GSO/INT.
Confidence, however, was too low to mention at this time.

Beyond 12Z Saturday: Morning LIFR/IFR stratus on Saturday will lift
to VFR with scattered storms in the aftn/eve, mainly at the eastern
terminals. Morning low stratus or fog is possible again Sun morning.
Storm chances Sun-Tue will trend to be more isolated in nature.

&&

.CLIMATE...
Record High Temperatures:

July 15:
KGSO: 97/1974
KRDU: 99/1997

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


Record High Minimum Temperatures:

July 11:
KGSO: 75/1992
KRDU: 77/1981
KFAY: 76/2019

July 12:
KGSO: 76/2011
KRDU: 78/2011
KFAY: 80/1935

July 13:
KGSO: 75/2017
KRDU: 78/2017
KFAY: 78/2017

July 14:
KGSO: 77/1981
KRDU: 77/2017
KFAY: 80/2017

July 15:
KGSO: 74/2019
KRDU: 76/1992
KFAY: 78/2015

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

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch from midnight EDT tonight through Friday evening for
NCZ007>011-022>028-039>043-074>078-083>086-088-089.

&&

$$
SYNOPSIS...Kren
NEAR TERM...Kren
SHORT TERM...CBL
LONG TERM...CBL
AVIATION...Kren
CLIMATE...RAH