524
FXUS62 KRAH 112007
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
407 PM EDT Thu Jul 11 2024

.SYNOPSIS...
A nearly stationary front over the Coastal Plain today will pivot
westward and stall over the Piedmont tonight through Friday night.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 348 PM Thursday...

A Flood Watch has been issued for most of central NC except those in
the far western Piedmont starting midnight tonight and extending
through midnight Friday night.

Convection thus far today has largely remained just east of our CWA
and near the coast as convergence tended to backbuild ese, as
opposed to retrograde west.  However, some convection is slowly
approaching the northern Coastal Plain currently.  The sfc boundary
remains east of our area, but should begin to ease westward through
later tonight. The associated instability axis will start to pivot
inland as well, and thus still expecting scattered showers and
storms to migrate into our Coastal Plain/Sandhills through this
evening.

As we enter the overnight period, onshore moisture flux, as noted in
IVT model fields, should increase for those east and southeast of
the Triad. Additionally, weak mid-level impulses will pivot across
these areas near sunrise Friday morning.  As such, scattered to
numerous showers and storms will likely increase in coverage early
Friday morning, and blossom across the Piedmont/Sandhills/Coastal
Plain through Friday afternoon. the 12Z HREF LPMM QPF guidance
continues to paint the highest QPF potential for those east of I-95,
and a secondary axis of higher amounts somewhere between the Triad
and the Triangle.  The latter of which, may mostly materialize early
Friday morning.

While instability will wane some overnight, PWAT will remain 120 to
150 % of normal (>2 inches) area wide. Given forecasted freezing
levels >15,000 feet, tall-skinny CAPE profiles, warm-cloud layer
depths > 12,000 feet, and very slow mean-cloud layer flow (~5 kts),
any convection that develops tonight could be capable of producing
highly efficient downpours. Despite quite dry soils, this type of
atmospheric environment could easily encourage efficient warm-cloud
processes and rain rates capable of producing flash flooding.
Biggest concerns would be over urban areas, but any efficient, slow-
moving storm could produce localized flooding even in rural areas.

Highs today will still push the upper 80s/lower 90s but with lower
humidity for much of the day.  Overnight lows will dip into the
lower to mid 70s.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 400 PM Thursday...

..Flash Flood Watch in effect through Friday evening.

On the wrn periphery of an expansive and anomalously strong 500 mb
high, with simulated heights up to 602-603 dam centered over the
cntl N. Atlantic, a convectively-amplified mid-level trough/banner
of vorticity will likely have developed across the e-cntl Carolinas
and cntl VA by Fri morning. That trough, associated MCVs, and
corridors of mesoscale forcing for ascent, should then drift newd
and reach the srn Middle Atlantic coast by 12Z Sat. Rising heights
aloft will otherwise result across the swrn N. Atlantic and South
Atlantic states, as the aforementioned mid-level high expands swwd,
with an area of ~5 sigma standardized height anomalies forecast to
become centered over the Bahamas through the same time.

At the surface, a quasi-stationary front, now extending along a line
from EDE-OAJ-ILM, will retreat wwd and reach the RAH Coastal Plain
and ern Sandhills (invof I-95) by 12Z Fri. The front should then
drift wwd and waver over the NC Piedmont through Fri night.

Anomalously high PWs that set a daily record in excess of 2.3" at
MHX this morning will spread wwd generally in tandem with the mid-
level trough and surface front and become centered over e-cntl NC
Fri, then edge ewd Fri night. While widespread clouds will limit
insolation and destabilization, deep, moist thermodynamic profiles
will become uninhibited with even weak heating into the upr 70s to
lwr 80s. As such, convection, probably ongoing over e-cntl NC at the
start of the period, will likely grow in both coverage and intensity
through early-mid afternoon, then linger particularly through early
Fri night. Slow storm motions (10-15 kt steering flow at 850-500 mb)
and very deep warm cloud layers of over 4 km will support efficient,
slow-moving convection capable of locally very heavy rain and flash
flooding. Convective coverage should gradually diminish from west to
east with the passage of the mid-level trough and waning instability
overnight-Sat morning. After high temperatures in the upr 70s to
middle 80s, muggy and mild lows in the lwr-mid 70s are forecast for
Fri night.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 330 PM Thursday...

Much needed shower/storm chances lower as wet system moves away
Saturday.

Another heat wave expected to develop Sunday and last into mid-week.

Showers and thunderstorms are expected to become widely scattered
through the day Saturday as the wet system over eastern NC pulls
away. It will continue warm and humid with highs returning into 90-
95 range. Heat indices should reach/return 100 to 104 in the eastern
Piedmont and Coastal Plain.

Heights continue to rise Monday and Tuesday. The low level flow is
also more westerly. Heat Advisory criteria looks likely to be met in
the southern and eastern areas where index values should reach and
exceed 105 Sunday and Monday even with some mixing out of the dew
points in the afternoon, then possibly Excessive Heat Warning
criteria of 110 on Tuesday and Wednesday as the heat wave peaks.
Actual highs should reach the mid 90s to lower 100s Tuesday and
Wednesday. Lows in the mid 70s to lower 80s. Both could challenge
daily records.

There is only a small chance of isolated storms Sunday and Monday.
The chance of mainly afternoon and evening thunderstorms returns
Tuesday especially in the west. All areas have a chance by Wednesday
afternoon and evening. The chance of showers and thunderstorms will
increase on Thursday as a cold front will approach from the NW. Highs
will "cool" into the lower to mid 90s.

A potential wet period with less heat late next week into the
weekend.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
As of 215 PM Thursday...

Convection has largely stayed east of central NC today. Some light
rain and MVFR stratus is starting to near the eastern TAF sites.
Expect some showers and a few storms to develop near KFAY/KRWI and
perhaps KRDU through 00Z tonight. Associated low-level moisture
could produce periods of MVFR conditions at these sites as well
during this period. Beyond 00Z tonight, ceilings will drop at all
terminals to MVFR/IFR and hold through the end of the 24 hr TAF
period. Additional scattered to numerous showers and storms will
blossom across the area early Friday morning through the end of the
TAF period. Atmospheric conditions will support the potential for
heavy downpours which could cause brief aviation restrictions at any
site (although best chances appear at KRDU/KFAY/KRWI).

Beyond 18Z Friday: Additional showers and storms are likely through
late Friday night as an area of low pressure lifts through eastern
NC. A strengthening low-level jet will pivot over eastern TAF sites
Friday, but the strongest LLWS will reside east over the Outer
Banks. Rain chances (and perhaps morning stratus/fog as well) will
largely remain across the east this weekend. Convection
Monday/Tuesday should be fairly 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...
None.

&&

$$
SYNOPSIS...MWS
NEAR TERM...Luchetti
SHORT TERM...MWS
LONG TERM...Badgett
AVIATION...Luchetti
CLIMATE...RAH