Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 271926
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
325 PM EDT Wed Mar 27 2024

.SYNOPSIS...
An area of low pressure will lift northeast through the Southeast
states and eastern Carolinas today through Thursday. The cold front
will move eastward through central North Carolina Thursday night.
Dry and warming weather is expected Friday and Saturday.

&&

.NEAR TERM /THROUGH THURSDAY MORNING/...
As of 1145 AM Wednesday...

...Flood Watch for 8 PM today to 8 PM tomorrow extended to
include the NE Piedmont and Sandhills...

Deep moist southwesterly flow ahead of a broad mid/upper trough over
the Central and Eastern US, along with a slow-moving cold front
currently over the Appalachians and an area of low pressure moving
along the Southeast US coast, will result in multiple rounds of
moderate to heavy rainfall across central NC through tomorrow
morning.

The forecast generally looks on track this morning. The biggest
change for today was to lower high temperatures over the northern
and western Piedmont given they will be stuck in low overcast and
cool NE flow all day on the backside of the inverted surface trough
that extends into central NC. Forecast highs there are only in the
lower-to-mid-50s, coolest across the far north (including the
Triad). Furthermore, the surface warm front is analyzed over central
SC, south of which temperatures are already in the lower-70s and dew
points in the upper-60s. As an area of low pressure currently over
the central GOM moves NE and along the GA/SC/southern NC coast
tonight, it will push the warm front farther north and into
southeastern parts of central NC later today. So still expecting the
southern Sandhills and southern Coastal Plain to reach mid-60s to
lower-70s today. This is also where high-res models show as much as
500 J/kg of SBCAPE from about 18z-00z today. With decent low level
and deep layer shear, can`t rule out an isolated strong to severe
storm down there during this period. But it will be very conditional
and the best instability will remain to our south. Elsewhere,
thunder will continue to be possible through tonight, but convection
will remain elevated, so no severe threat is expected.

As for rainfall, still expecting a general 1-4 inches across
most of the area, highest over the Coastal Plain. The Triad may
be more in the half inch to an inch range, and there will be a
sharp cutoff on the western side, but exactly where that sets up
is still uncertain as guidance has been waffling back and
forth. The 12z HREF shifted the 2-4 inch axis farther west into
central NC to include the NE Piedmont and Sandhills. High-res
guidance depicts multiple rounds of showers today with a more
widespread area with heavier rates developing tonight across
much of the area as the low lifts NE. This will result in a risk
for flooding, including in urban areas like the Triangle and on
some mainstem rivers which are forecast to reach flood stage at
our eastern gauges. Given all of this, the Flood Watch from
this evening into tomorrow evening has been extended farther
west to include the NE Piedmont and Sandhills. Also increased
POPs to categorical over this entire area tonight. Still
expecting lows in the mid-40s to mid-50s. -JD

Thursday: Aloft, the s/w over the Deep South should continue
swinging through the Southeast Thu and offshore Thu night. At the
surface, the surface trough should finally move eastward and
offshore on Thu as the low deepens and tracks along the NC coast.
This low should shift eastward out over the Atlantic Thu eve/night,
with cool high pressure building into the area in its wake.

Precipitation: The moderate/heavy rain will likely continue through
Thu morning, finally shifting eastward and out of the area Thu
aft/eve as the surface low moves away.

Temperatures: Highs Thu will be lowest in the east where the
rain/clouds linger into the afternoon, with mid 50s expect, while in
the west where the weather may dry out and sun may try to peek out,
highs could rise into the low/mid 60s. -KCP


&&

.SHORT TERM /THURSDAY NIGHT THROUGH FRIDAY NIGHT/...
As of 325 PM Wednesday...

Thursday night: In the wake of the offshore surface low, the passage
of the trailing upper trough and a secondary cold front between 00
to 06z Fri will lead to clearing and modest low-level cold dry air
advection. There appears to be sufficient mixing in the BL to keep a
light breeze of 4-7 kts overnight, which should limit the threat for
frost as min temperatures bottom out in the mid to upper 30s.

Friday and Friday night: Heights aloft will steadily increase over
the region as a broad upper level ridge over the Central US builds
eastward. At the surface, a strong pressure gradient between the
rapidly deepening low pressure lifting up the New England coast and
high pressure building east over the Deep South will result in
breezy conditions. Expect frequent NWLY gusts of 20-30 mph, with
occasional gusts as high as 30 to 35 mph, highest across northern
portions of the piedmont and coastal plain counties. The brisk NW
flow will also result in favorable downslope drying/mixing out of
dewpoints  and low-level warming. Afternoon RH values are expected
to fall 25 to 35%, potentially as low as 20-25% across the NW
Piedmont. Fuels will likely be wet enough to avoid elevated fire
weather conditions.

Highs Friday ranging from mid 60s NE to lower 70s south. Lows 40-45.



&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
As of 300 PM Wednesday...

Sat through Sun night: A passing disturbance Sat afternoon will
bring a non-zero chance for some light rain near the VA/NC border,
but mostly expect an increase in cloud cover since the better DPVA
and mid-level WAA remains north of central NC. Otherwise, mid-level
height rises will persist through the weekend in response to a
closed low digging into the Four Corners Region resulting in mostly
dry conditions this weekend with highs rising into the mid/upper 70s
to low 80s.

Mon through Wed: Weak high pressure will build into the northern Mid-
Atlantic late Sun and push a shallow cold front south into VA by
early Mon morning. This boundary will likely represent the southern
extent of some light rain due to gradual moist isentropic upglide
Mon morning. However, the southern extent of the front remains in
question with latest model guidance suite keeping the front up in VA
with the 850mb front well displaced up into northern VA and MD. This
should keep central NC mostly dry through Mon.

By Tue, the now positively tilted trough axis will transport
increasing PWAT values ahead of the trough within the deep
southwesterly flow to around 1 to 1.25 inches over central NC. At
the surface, a deepening area of low pressure will migrate from the
Great Lakes Region into eastern Ontario with secondary cyclogenesis
expected to develop over the northern Mid-Atlantic and drift off the
Northeast coast early Wed morning. There is a high degree of timing
uncertain but this will result in a cold front marching through
central NC sometime between late Tues night and early Wed evening.
Ahead of the front, there will be a chance for showers/storms Tues
and Wed although the character/severity largely remains in question.
Wed will likely have a higher ceiling for severe storms, but will be
completely dependent on the timing of the cold frontal passage and
degree of instability that can develop out ahead of it. Temperatures
will remain unseasonably warm ahead of the cold front with a return
of near normal behind the front into midweek.

&&

.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
As of 230 PM Wednesday...

Widespread IFR to LIFR ceilings blanket across central NC as a
result of an area of showers and storms that has moved through. The
one exception is the far SE (including FAY) which is still VFR, but
they are also expected to drop to MVFR later this afternoon and
IFR/LIFR this evening. RWI may bounce between IFR and MVFR ceilings
(maybe even briefly VFR) this afternoon before also dropping to
IFR/LIFR this evening. Elsewhere across the Piedmont (including RDU,
GSO and INT), confidence is high that IFR to LIFR ceilings will
persist through tonight. While visibilities will improve some now
that the first round of showers is exiting to the NE, another area
of showers developing over SC will move across central NC later this
afternoon and this evening. It could be accompanied by some isolated
storms as well, particularly over the far SE (including FAY) where
they may have gusty winds. A more widespread and heavy area of
showers and isolated storms with IFR/LIFR visibilities will move
across central NC overnight tonight, particularly from around RDU to
the south and east. INT and GSO should largely miss out on the
heaviest rain, and it will exit to the east by early tomorrow
morning, allowing for ceilings there to gradually lift to MVFR and
maybe even VFR by the end of the TAF period. Farther east, the
showers will persist through tomorrow morning, and ceilings may only
slightly improve to IFR.

Outlook: Widespread showers will exit to the east by early afternoon
tomorrow, but isolated showers and storms remain possible through
the rest of the day especially east before we dry out in the
evening. VFR conditions will return from west to east Thursday
afternoon and evening and continue into Monday. Gusty winds of 20-30
kts are expected each day from Thu into Sat, from the N on Thu, from
the W/NW on Fri, and from the SW on Sat.

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 8 PM EDT this evening through Thursday
evening for NCZ007>011-024>028-040>043-075>078-084>086-088-089.

&&

$$

SYNOPSIS...Hartfield/KCP
NEAR TERM...Danco
SHORT TERM...CBL
LONG TERM...Swiggett
AVIATION...Danco


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