Special Weather Statement, NWS Raleigh, NC

AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
1045 AM EDT Mon May 3 2021

.SYNOPSIS...
A passing disturbance will bring a chance for showers and strong
storms today. An approaching cold front and upper level trough from
the west will produce another chance of showers and storms late
Tuesday into Wednesday. The cold front will move through the area
and settle to our southeast Wednesday night, as cooler high pressure
starts to build in from the northwest, however developing low
pressure centers tracking along the front will keep our weather
unsettled into Friday.

&&

.NEAR TERM /TODAY AND TONIGHT/...
As of 1045 AM Monday...

...Threat for some strong to severe thunderstorms persists for this
afternoon into early evening...

Latest surface analysis shows a warm front lifting north across the
Carolinas with a moist and unstable airmass spreading across central
NC this morning. Surface dew points have climbed into the mid and
upper 60s across the northern areas, north of U.S. 64 to the upper
60s to around 70 to the south. This airmass is presently weakly to
moderately unstable with MLCAPE values ranging around 500 J/Kg near
the VA border to over 1500 across the Sandhills and Southern
Piedmont. A mid level trough across the OH and TN Valleys this
morning is spreading a belt of 50+ kts of flow across the western
Carolinas this morning with 0-6km bulk shear values ranging between
30 and 45 kts across central NC, strongest to the west.

One cluster of showers and storms moved across the Triad earlier this
morning with another band of showers and storms poised to move into
the western Piedmont and Triad over the next hour or two. Convection
allowing models note that a larger broken band of clusters of
showers and storms is likely to spread east and southeast across
central NC during the mid afternoon to early evening hours. This
particular band will be the primary severe weather threat. While the
SPC trimmed back the slight risk area toward SC in the 13Z update,
the greatest severe weather threat will extend in an arc from the
Southern Piedmont, across the Sandhills, into the Southern and
Central Coastal Plain from about 18 to 01 UTC. As SPC noted, messy
clusters of storms are expected with a few supercells possible.
Given the profile, straight hodographs and time of year, expect a
decent number of hailers today with a left mover possible along with
a damaging wind threat. Showers and storms should push east and
diminish pretty quickly this evening. Highs today will range in the
mid to upper 70s in the Western Piedmont and Triad where showers and
clouds will keep temperatures suppressed. Further east, highs will climb
into the 80s across eastern Piedmont, Sandhills and Coastal Plain
with a few mid 80s possible in locations to the southeast where the
rain holds off the longest. Lows tonight will range in the mid to
upper 60s. -Blaes

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 410 AM Monday...

After a relative lull in shower chances extending through the first
half of Tue, the approach of our next mid level trough, currently
over UT moving into the Four Corners, will bring what may be a
decent shot at more strong to possibly severe storms over our W
sections starting late Tue, although the moisture and instability
may not quite line up temporally with the best dynamic forcing for
ascent. Low clouds should start the day, but the column just aloft
will be fairly dry, noted by a region of mid level dry air spreading
into the region from the W late tonight through Tue morning in
alignment with the mid level shortwave ridging. Expect a dry morning
into early afternoon with the low clouds lifting and dispersing, and
increasing insolation by midday leading to a fairly deep mixed layer
by early afternoon. This heating and mixing with clouds largely
limited to flat daytime cu (resulting from the lifting stratus) and
thicknesses over 30 m above normal support highs in the upper 80s to
lower 90s. The mid level trough is expected to shift through the
Miss Valley into the OH Valley and Mid South Tue evening, so the
falling heights, DPVA, and strengthening cyclonic flow through the
mid levels will likely not arrive until just after peak heating. And
while the hot temps and dewpoints in the 60s will push late-day
SBCAPE up to around 2000 J/kg once again, the moisture through the
column is more limited than today, and the deep layer bulk shear
will be rather weak (under 20 kts) for much of the day, only
increasing from W to E in the evening and overnight. So we should
see convection developing and strengthening in the mid to late
afternoon over W NC shifting into our W and SW sections into the
evening, with activity spreading E into Tue night but likely
decreasing in coverage and intensity as it does so due to gradual
nocturnal stabilization. Expect late-day good chance to likely pops
over the W and SW, with lower pops E and NE, with all pops
decreasing after sunset. Lows in the mid 60s to lower 70s. -GIH

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 255 AM Monday...

Continue to not be terribly impressed with the cold front bisecting
the area Wednesday morning. The GFS is definitely a fast outlier
with the system and has not been used in this part of the forecast.
Meanwhile, the NAM does show modest instability along the front, but
the Carolinas are well removed from the best dynamics and there is
no deep moisture locally. Will maintain high chance pops. Showers
could linger into Wednesday evening, then conditions will dry out
until Thursday evening. Models just cannot remain consistent with
their scenarios for Thursday evening and Friday. Forecast has been
consistent showing a large upper low over eastern Canada, but what
manifests locally continues to differ. The 00Z GFS shows a coastal
low developing Thursday night that moves up the coast Friday (which
has been the forecast scenario for the last day or two), while the
02/12Z and 03/00Z Euro show no coastal system and instead focus more
on a shortwave rotating through the Ohio Valley and Mid-Atlantic
states. This is the part of the extended forecast with the lowest
confidence, and have stuck with slight chance/chance pops, with the
highest pops to the northeast. Behind that system, high pressure
will build across the southeastern United States for the weekend.
The next system appears as if it will remain far enough west that
Sunday afternoon should remain dry.

There is still a lot of variability with differing model solutions
for Wednesday's highs depending on the speed of the cold front, but
highs will definitely be cooler Wednesday than they are on Tuesday.
Temperatures will then fall below normal on Thursday, bottoming out
Friday before returning to near normal values on Saturday and above
normal values on Sunday.

&&

.AVIATION /12Z MONDAY THROUGH FRIDAY/...
As of 620 AM Monday...

Aviation conditions across central NC will continue to worsen this
morning. MVFR cigs in the W (INT/GSO) are expected to drop to IFR by
13z, while further E, cigs at RDU/FAY/RWI should be mostly MVFR
between 13z and 16z. Spotty showers will track toward the NE through
the area through mid morning, but vsbys should stay VFR. We'll have
a briefly lull in precip chances from 15z until 18z, during which
time cigs should rise to MVFR then VFR, with highest confidence over
SE sections (including FAY and perhaps RDU/RWI). But during this
time we'll then see development of showers and strong storms near
and SW of CLT spreading E and NE during the afternoon. Storms are
possible everywhere, but FAY/RDU/RWI will see the best chance of a
strong to severe storm, between 19z and 00z. Gusty and shifting SW
winds will also be possible during this time areawide. Shower/storm
chances will decrease after 00z with brief prevailing VFR
conditions, but there will be a trend to MVFR to IFR cigs after 06z
at INT/GSO/RDU as low stratus develops across the area. Low clouds
are less likely at RWI/FAY late tonight. LLWS conditions are
possible after 04z tonight with the arrival of 35-40 kt SW winds at
1500-2000 ft AGL, however considering that SW winds will stay
elevated down to the surface overnight, will not include LLWS in the
terminal forecasts just yet.

Looking beyond 12z Tue, cigs are expected to stay sub-VFR through
Tue morning, mainly IFR/LIFR until 13z then trending to MVFR through
late morning and to VFR by 17z. Scattered showers/storms are
possible Tue afternoon (mainly across the S) followed by a lower
chance Wed ahead of a passing cold front. VFR conditions will
dominate Thu/Fri as high pressure noses in from the NW, although a
passing strong disturbance aloft may bring a period of showers and
sub-VFR conditions Thu evening into early Fri. -GIH

&&

.CLIMATE...
Record low min temperatures for 5/4 and 5/5:

GSO: 65 (2019) on 5/4 and 65 (2019) on 5/5
RDU: 68 (1938) on 5/4 and 67 (1950) on 5/5
FAY: 68 (1942) on 5/4 and 68 (2012) on 5/5

&&

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

&&

SYNOPSIS...Hartfield
NEAR TERM...Blaes
SHORT TERM...Hartfield
LONG TERM...Green
AVIATION...Hartfield

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Special Weather Statement
National Weather Service Raleigh NC
848 AM EDT Mon May 3 2021

NCZ021-022-031345-
Guilford NC-Forsyth NC-
848 AM EDT Mon May 3 2021

...A STRONG THUNDERSTORM WILL AFFECT FORSYTH AND NORTHWESTERN
GUILFORD COUNTIES UNTIL 945 AM EDT...

At 847 AM EDT, Doppler radar was tracking a strong thunderstorm near
Clemmons, or near Winston-Salem, moving northeast at 45 mph.

Wind gusts up to 40 mph will be possible with this storm.

Locations impacted include...
Greensboro, Winston-Salem, Kernersville, Clemmons, Bermuda Run,
Lewisville, Summerfield, Stokesdale, Walkertown and Rural Hall.

LAT...LON 3611 8051 3612 8046 3614 8044 3617 8044
      3626 8031 3624 7957 3602 8016 3603 8021
      3600 8022 3599 8024 3600 8032 3597 8040
      3599 8042 3601 8042 3606 8046 3604 8049
      3606 8051
TIME...MOT...LOC 1247Z 237DEG 38KT 3607 8036

JJT

Special Weather Statement
National Weather Service Raleigh NC
1152 AM EDT Mon May 3 2021

NCZ022>024-039-031645-
Guilford NC-Alamance NC-Randolph NC-Orange NC-
1152 AM EDT Mon May 3 2021

...A STRONG THUNDERSTORM WILL AFFECT ALAMANCE...NORTHWESTERN
ORANGE...NORTHEASTERN RANDOLPH AND SOUTHERN GUILFORD COUNTIES UNTIL
1245 PM EDT...

At 1152 AM EDT, Doppler radar was tracking a strong thunderstorm 8
miles north of Randleman, moving northeast at 40 mph.

Wind gusts up to 40 mph will be possible with this storm.

Locations impacted include...
Greensboro, High Point, Burlington, Graham, Hillsborough, Randleman,
Mebane, Elon, McLeansville and Archdale.

LAT...LON 3625 7940 3624 7922 3605 7908 3575 7987
      3594 7999 3625 7941
TIME...MOT...LOC 1552Z 243DEG 36KT 3594 7976

JJT