Special Weather Statement, NWS Raleigh, NC

AREA FORECAST DISCUSSION
National Weather Service Raleigh NC
945 PM EDT Tue Aug 17 2021

.SYNOPSIS...
The remains of Tropical Storm Fred will track slowly north
through the southern Appalachians through early Wednesday.
After this system moves north and away from the area, typical warm
and humid summertime weather will return to the region later in the
week, with a daily risk of scattered storms.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 945 PM Tuesday...

TD Fred's center is located over far E central TN, near the NC
border, at this hour, and it will continue to track northward over
the S Appalachians overnight, reaching W WV toward daybreak. The
anticipated relative lull in precip over central NC continues this
evening, with only isolated to scattered disorganized showers in the
last several hours. While this low-pop period should persist for
another hour or two, attention then turns to the line of strong and
potentially tornadic storms E of Fred, over the NC Foothills into W
and central SC. The latest HRRR runs take this line into our W
shortly after midnight and drift it slowly eastward (although
individual convective elements will be moving nearly due N)
overnight, reaching the Triangle region toward sunrise. While
nocturnal stabilization with loss of heating would seem to be in our
favor here, the current RAP-estimated MLCAPE remains 1000-1500 J/kg,
with the better effective deep layer shear and 200+ m2/s2 SRH both
expected to continue to ease slowly from W NC northeastward across
the NW Piedmont overnight. So, we are not yet out of the woods in
terms of both a severe threat (mainly in the NW Piedmont overnight)
and a heavy rain threat (with training cells and still-anomalously-
high PW likely to lead to higher totals). Have made some pop
adjustments to account for this timing and threat heading through
tonight and into early Wed morning. Still expect lows mostly in the
low to mid 70s. -GIH

Earlier discussion from 325 PM: Fred has weakened to a tropical
depression, with its circulation center approaching the southern NC
mtns. The weakening remnants of Fred will continue to track north-
northeast through the NC mtns during the late afternoon and evening
hours. With the 2.0-2.3" tropical moisture centered over central NC,
intermittent shower activity will continue through tonight, with
some daytime enhancement of some thunderstorms through the
afternoon.

In the wake of the broken convective band that's currently moving
north through the northern Piedmont and northern coastal plain
counties, latest radar trends suggest central NC will experience a
late afternoon/early evening lull. Rain chances are then expected to
increase after midnight as the primary rain tropical rain
band(currently over central SC and eastern Ga moves through the
area. Additional rainfall amounts through daybreak are expected to
range from a half inch across the NW Piedmont to around a tenth of
an inch across the NE coastal plain.

Despite the recent increase in rain that central NC has seen over
the past several days, rainfall amounts have been hit and miss.
Antecedent hydrological conditions are still rather dry, with 1 to 3
hr FFG still in the 2.5-3.5" range. Thus, do not think a Flash Flood
watch is warranted, with only isolated instances of minor flooding
possible, mainly in poor drainage and/or urban areas.

Additionally, close proximity to Fred's stronger low-level wind
field will provide some favorable low-level kinematics to support
some rotation within any strong updrafts that develop, mainly during
peak heating and across western NC.

Lows tonight in the 70s.

&&

.SHORT TERM /WEDNESDAY THROUGH THURSDAY NIGHT/...
As of 325 PM Tuesday...

The remnants of Fred will race newd away from the area, moving
through the central Appalachians through the afternoon, and reaching
the NE US by the evening. The tropical moisture plume of 2-2.25"
will shift eastward over eastern NC by late morning/early afternoon,
with slightly drier filtering into western piedmont counties.
Scattered showers and thunderstorms will continuously re-develop
within this axis of anomalously high PWATs, with diurnal
destabilization allowing for some isolated/widely scattered re-
development back over the western Piedmont. Could still see some
locally heavy rain that could result in some minor flooding.
Otherwise, weak shear and lapse rates should preclude a severe
threat. Highs ranging from mid 80s west to upper 80s east.

Cannot rule out some isolated showers Wednesday evening, but
otherwise it should be mostly dry Wednesday night with areas of fog
possible. Lows 70 to 75. -CBL

A negatively-tilted mid-level trough will approach the region on
Thursday, resulting in decent height falls and forcing for
precipitation. Thus, have high chance POPs on Thursday. A
subtropical ridge will also extend across the western Atlantic on
Thursday, which will pump warm and very humid air into our region,
with highs in the upper-80s to lower-90s and dew points in the mid-
to-upper-70s. This could bring heat indices up to 105F in portions
of the eastern Piedmont, Sandhills, and southern Coastal Plain, and
a Heat Advisory may be needed for this area on Thursday. -JD

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...
As of 945 PM Tuesday...

Fri/Fri night: A surface frontal zone to our NW, on the SE side of
the baggy closed low over OH/WV/PA, will slowly drift southeastward
into central NC. This weak low level mass convergence plus incoming
DPVA aloft, increasing upper divergence in the LFQ of a 60+ kt
northwesterly jetlet over the Ohio Valley, and 2-2.25" PWs streaming
over much of our area (esp E) all support high pops, peaking in the
afternoon/evening. Thicknesses will still be a bit above normal but
temps should be modulated by considerable cloudiness. Highs around
90 to the lower 90s. The combination of incoming surface high
pressure drifting over WV, the surface circulation around Henri as
it moves northward well off the NC coast, and SE-moving convection
outflow Fri evening and night should help push the surface front to
our E and S sections overnight. Lows 70-76 with decreasing pops and
partial clearing W late.

Sat through Sun night: The surface front should hold over our SE CWA
Sat, prompting better convection coverage there in the afternoon in
contrast to the slightly drier NW sections. Then, as so often
happens with summertime fronts over NC, the front should quickly
lift north and effectively wash out by Sunday, as mid level ridging
builds anew from TX/OK across the lower Miss Valley and Mid South to
the interior Southeast states. But Henri may still affect our
weather as it is expected to drift N or NNW over the NW Atlantic
toward the New England coast over the weekend: Depending on its
exact location and the degree to which it merges with the mid level
low, there is a chance that the surface front could hold up across
our far NE, if the Henri circulation prompts frontogenesis in that
area. Will retain mostly diurnally-favored pops Sun, highest in our
E half (SE and along the front in the NE), where low level moisture
should be most abundant. Expect highs both days close to normal, in
the upper 80s to around 90, with lows in the upper 60s/lower 70s.

Mon through Tue: Tough forecast as NC will be the battleground
between the Southern Plains / Lower Miss Valley mid level ridge and
the baggy trough / shear axis extending along the East Coast, with
any surface features very weak. The ECMWF keeps pops high, esp E
(assuming warmer mid levels and lower CAPE further W). The latest
few GFS runs are drier but have trended toward less ridging
extending into the Carolinas and a greater number of ridge-riding
MCSs or MCVs tracking from the Midwest and Ohio Valley through VA
and NE NC. Without a clear signal favoring one way or the other,
will stay the course with temps near to slightly above normal, esp
W, and pops close to climatology, chances of mainly afternoon
storms, higher SE. -GIH

&&

.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
As of 815 PM Tuesday...

The remnants of TS Fred will continue to move north through the NC
mountains tonight and early Wednesday.  While there is a lull in
showers across central NC this evening, a line of showers and
isolated storms in upstate SC will move gradually north-northeast
overnight, impacting GSO/INT between roughly 04-08Z, with scattered
showers possible further east toward RDU/RWI/FAY overnight. Very
heavy rain and low vsbys will occur within the showers and storms.
The line of showers will continue to move east during the morning
hours and may increase again during the day on Wednesday. Ceilings
will lower to MVFR/IFR overnight and only gradually lift to VFR
through Wednesday afternoon as winds shift from SErly tonight to
SSWrly on Wednesday.

Outlook: Afternoon showers and storms will return Thursday and
continue each day through the weekend. Sub-VFR conditions from
fog/low stratus will be possible each morning.

&&

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

&&

SYNOPSIS...Hartfield
NEAR TERM...CBL
SHORT TERM...CBL/Danco
LONG TERM...Hartfield
AVIATION...Smith

Hazardous Weather Outlook...UPDATED
National Weather Service Raleigh NC
1147 PM EDT Tue Aug 17 2021

NCZ007-021>025-038>040-073>076-083-084-181000-
Person-Forsyth-Guilford-Alamance-Orange-Durham-Davidson-Randolph-
Chatham-Stanly-Montgomery-Moore-Lee-Anson-Richmond-
1147 PM EDT Tue Aug 17 2021

This Hazardous Weather Outlook is for central North Carolina.

.DAY ONE...Tonight.

Locally heavy downpours and minor flooding will be possible within
scattered to locally numerous thunderstorms overnight. Additionally,
an isolated strong to severe storm capable of producing a weak
tornado is possible through the rest of tonight.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

Hazardous weather is not expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

NCZ008>011-026>028-041>043-077-078-085-086-088-089-181000-
Granville-Vance-Warren-Halifax-Franklin-Nash-Edgecombe-Wake-Johnston-
Wilson-Harnett-Wayne-Scotland-Hoke-Cumberland-Sampson-
1147 PM EDT Tue Aug 17 2021

This Hazardous Weather Outlook is for central North Carolina.

.DAY ONE...Tonight.

No hazardous weather is expected at this time.

.DAYS TWO THROUGH SEVEN...Wednesday through Monday.

No hazardous weather is expected at this time.

.SPOTTER INFORMATION STATEMENT...

Spotter activation is not expected at this time.

Special Weather Statement
National Weather Service Raleigh NC
1231 AM EDT Wed Aug 18 2021

NCZ021-022-038-039-073-074-083-180530-
Guilford NC-Stanly NC-Anson NC-Forsyth NC-Randolph NC-Davidson NC-
Montgomery NC-
1231 AM EDT Wed Aug 18 2021

...A line of strong thunderstorms will impact portions of Forsyth,
Davidson, western Anson, western Montgomery, western Randolph,
Stanly and western Guilford Counties through 130 AM EDT...

At 1227 AM EDT, Doppler radar was tracking strong thunderstorms
along a line extending from Nebo to 6 miles northeast of Midland to
7 miles southeast of Buford. Movement was northeast at 40 mph.

HAZARD...Winds in excess of 40 mph. Weak tornadoes are also
         possible.

SOURCE...Radar indicated.

IMPACT...Gusty winds could knock down tree limbs and blow around
         unsecured objects.

Locations impacted include...
Winston-Salem, High Point, Lexington, Albemarle, Badin Lake,
Thomasville, Kernersville, Clemmons, Bermuda Run and Ansonville.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Doppler radar has indicated weak rotation with these storms. If they
intensify and rotation strengthens, a warning may need to be issued.
If outdoors, consider seeking shelter inside a building.

Persons in campgrounds should consider seeking sturdy shelter until
these storms pass.

Torrential rainfall is also occurring with these storms and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

&&

LAT...LON 3550 8030 3551 8018 3572 8033 3574 8046
      3584 8048 3584 8039 3588 8042 3589 8037
      3601 8042 3608 8052 3614 8044 3626 8045
      3626 8003 3590 7994 3514 8002 3514 8008
      3481 8012 3482 8032 3519 8028 3519 8051
TIME...MOT...LOC 0427Z 216DEG 36KT 3623 8068 3528 8040 3466 8055

MAX HAIL SIZE...0.00 IN
MAX WIND GUST...40 MPH

10