-- Discussion containing changed information from previous version are highlighted. --
852
FXUS62 KRAH 060649
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
250 AM EDT Mon May 6 2024

.SYNOPSIS...
An upper-level disturbance will approach the mid-Atlantic on Monday
and exit the region on Tuesday. High pressure will extend into the
region during the mid week before a cold front approaches late in
the work week.

&&

.NEAR TERM /TONIGHT/...
As of 905 PM Sunday...

The remnants of an MCV has moved over the eastern portion of the
forecast area, with scattered showers and an isolated thunderstorm.
Otherwise, the region is dry right now. Much of the western half of
the area is clear, and with calm/light wind, have already seen
visibilities go below a mile at Sanford and Roxboro. With the wind
not expected to remain calm overnight, some stirring should allow
the fog to mix out. However, plenty of low level moisture remains
and low stratus is expected to develop near the Virginia/North
Carolina border by midnight and expand to the south, eventually
covering all locations. The scattered showers will likely persist
around Rocky Mount through midnight, then just an isolated shower is
possible along the eastern and western edges of the region with
little in the way of forcing mechanisms to generate precipitation.
It will be a muggy night with overnight temperatures in the low to
mid 60s.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
As of 210 PM Sunday...

Aloft, the sub-tropical ridge will try to briefly build over the
Southeast US on Mon, but will then be pushed eastward again as the
s/w to the west moves eastward across the Appalachians and into the
mid-Atlantic late Mon/Mon night. This s/w trough may become slightly
negatively tilted as it swings through the region. At the surface,
high pressure will sit over Bermuda, ridging swwd into the Southeast
US through Mon night. A quasi-stationary frontal zone will extend
from the Northeast US, wswwd through the OH Valley and mid-MS
Valley, remaining north of the area through Mon night. Expect sly to
swly flow over central NC Mon/Mon night, resulting in continued
advection of warm, moist air into the area.

Precipitation/Convection: With the continued feed of warm, moist air
into the area, MUCAPE of 800-1500 J/Kg is forecast by both the NAM
and GFS across the area during the day, while effective shear is
forecast to be about 15-20 kts. After a brief drop in PWATs tonight,
they should climb back into the 1.5-1.75 inch range on Mon. All of
the ingredients will be present for storms to develop, contingent on
forcing. The best forcing for ascent will be with the s/w aloft,
however the models vary with the timing of that feature. The hi-res
model guidance from 12Z suggests showers and storms may develop over
the Piedmont during the afternoon, then move eastward through the
evening. A secondary round of showers and storms moving across the
mountains Mon eve could continue eastward through the area Mon
night. For now, central NC remains in general thunder from the SPC
and the hi-res guidance varies on the coverage and intensity of
convection. Given all of the above, cannot rule out an isolated
strong/severe storm should all the ingredients come together at the
right time Mon aft/eve, before loss of heating and nocturnal
stabilization commences.

Temperatures: Expect largely broken/overcast skies through Mon
night. Highs should range from the upper 70s NW to mid 80s SE, with
lows mainly in the low to mid 60s Mon night.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
As of 250 AM Monday...

The extended continues to focus on the potential for heat Wed/Thu,
but more importantly the threat of severe weather Wed/Thu. Drier
weather looks favored for the weekend, along with temperatures near
to below normal.

Wed will feature weak ridging aloft transitioning to WSW flow. A
trough over the Plains and Upper MS valley will aid perturbations
tracking across the TN valley and Carolinas in the late afternoon
and evening/overnight. A broad SW flow will exist at the surface,
with a lee trough during the day. With rising thicknesses,
temperatures should rise into the upper 80s to lower 90s. Dewpoints
in the upper 60s to low 70s will result in heat indices in the
mid/upper 90s in the Triangle/Sandhills. While there is no clear
discernible boundary on Wed, broad 850-700 mb WAA coupled with a
surface low moving into the OH valley as a cold front reaches
western TN will aid impulses of energy tracking through in the SW
flow. The Carolinas look to be on the nose of the left-exit region
of a jet streak over SC. This pattern should favor the chance of
disorganized showers/storms both Wed aftn across the south and Wed
night along/north of US-64. Coverage and location is difficult to
determine thus far in the WAA flow, but some storms could be severe
with models showing 1500-2000 J/kg of MLCAPE, DCAPE over 1000 J/kg,
and 25-30 kt of shear, supportive of a hail/wind threat.

Thu/Fri: Thu still looks warm in the mid 80s to low 90s, warmest in
the Sandhills to Coastal Plain, but the main concern is the severe
risk. Deterministic and ensemble data, including the CSU/CIPS severe
analogs, continue to highlight a consistent severe potential Thu
aftn/eve. The low pressure from Wed (over OH valley Thu) is forecast
to bring a strong cold front through the area as early as Fri
morning. Ahead of the front, increasing SW flow aloft will combine
with moisture-rich air with low 70s dewpoints to promote another
round of showers/storms. Models appear to depict a line of storms
tracking east from eastern TN/western NC in the aftn/eve, though
early morning convection from Wed night could complicate things. The
environment ahead of the storms shows upwards of 2000 J/kg of MLCAPE
and 2500 J/kg of SBCAPE, along with low/deep layer shear favorable
for all hazards. We will continue to monitor this as we get closer,
but it appears models are honing in on the best severe potential on
Thu/Thu night. Some recent model/ensemble trends has been for the
cold front to move through early Fri, shunting the severe/storm risk
south/east of the area. However, a few ensemble members from the
GEFS/EPS/GEPS still show the front held up over the Carolinas, so we
kept low chance PoPs for Fri aftn.

Sat/Sun: A drier pattern is still looking favored for the weekend as
a WNW flow takes over at mid-levels with troughing over the Mid-
Atlantic. However, some ensemble solutions show energy building back
in for Sun with troughing over the Midwest/OH valley. For now, have
leaned on a drier forecast until there is better model agreement.
Temperatures will be more seasonal to slightly below normal with mid
to upper 70s and humidity much more bearable with dewpoints in the
40s to low 50s.
-- End Changed Discussion --

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
As of 130 AM Monday...

24-hour TAF period: Convection has dissipated across the area.
Widespread LIFR to IFR ceilings will continue to spread south
across all TAF sites through the remainder of the overnight
and into early morning hours. Additionally, an area of dense fog
has developed across the northern Piedmont. Model guidance suggests
the dense fog could impact KGSO and KINT terminals over the next few
hours.

Conditions will improve to MVFR in most places by mid to late
morning and should improve to VFR by early afternoon, slowest to
improve in the Triad. Thereafter, scattered to numerous showers and
storms are expected to develop, with some TAF sites potentially
experiencing multiple rounds of storms and restrictions through the
late evening.

Outlook: Rain chances decrease for Tuesday and Wednesday with
showers and storms more isolated/widely scattered in nature.
However, storm coverage coverage should increase on Thursday. With a
moist airmass in place, areas of fog and stratus are possible on
Tuesday morning with reduced chances during mid week.

&&

.CLIMATE...

Record High Minimum Temperatures:

May 8: KGSO: 66/1938 KRDU: 68/1930 KFAY: 70/2003

May 9: KGSO: 68/2002 KRDU: 70/1936 KFAY: 71/2009

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

SYNOPSIS...Blaes
NEAR TERM...Green
SHORT TERM...KCP
LONG TERM...Kren
AVIATION...CBL
CLIMATE...RAH