Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 010141

Area Forecast Discussion
National Weather Service Raleigh NC
941 PM EDT Wed May 31 2023

A relatively cool northeast flow will persist over the region
through Thursday. This flow will weaken on Friday, allowing
temperatures to edge back closer to normal by Saturday. A backdoor
cold front will drop through the area Saturday evening and night,
bringing a few storms, followed by cooler weather behind the front
for Sunday.


As of 935 PM Wednesday...

A cool northeasterly flow will continue tonight, as surface high
pressure to the north of the area combines with a surface low
located to the east of Cape Hatteras to help to enhance the cool
northeast flow. This continued moist northeast flow will again lead
to cloudiness overnight across most of the area (less west),
especially across the eastern/northeastern half of the area, where
we could again see some areas of drizzle and light rain (after
midnight). Low temperatures are expected to range from the mid to
upper 50s across the rural Piedmont locations to the lower to mid
60s elsewhere.


.SHORT TERM /Thursday and Thursday night/...
As of 315 PM Wednesday...

The remnant cyclonic circulation off Cape Hatteras is forecast to
weaken/fill as moist high pressure continues to extend south into
the Carolina Piedmont. Daytime heating will lead to gradual lifting
of the morning stratus layer through the afternoon with isolated pop-
up showers possible CWA-wide.

If the stratus cloud layer is more eastern-central centric as a
majority of the forecast guidance suggests, afternoon highs could be
fairly uniform. Highs 75 to 80. Lows generally in the lower/mid 60s
with another night of a westward expanding stratus layer probable.


As of 355 PM Wednesday...

The overall upper pattern looks to be characterized by increasing
troughing over the East Coast during the extended period, resulting
in at least slight precipitation chances each day. However, details
on timing and intensity are still very uncertain, particularly next
week. The surface high centered off the northern Mid-Atlantic coast
will weaken, resulting in diminishing NE flow and warmer
temperatures close to normal (highs in the lower-to-mid-80s and lows
in the upper-50s to mid-60s) as low-level thicknesses increase by 10-
15 m compared to Thursday. CAPE values of 500-1000 J/kg may result
in more isolated pop-up showers and storms as the remnants of the
mid/upper low that has been affecting our region move back south
over NC. QPF amounts still look light given the weak upper forcing,
and shear also looks weak so not expecting a severe threat. Another
chance of showers and storms comes Saturday afternoon and especially
evening with a backdoor cold front. Guidance has trended toward more
instability ahead of the front on Saturday, with CAPE exceeding 1000
J/kg in some spots, as highs will be in the mid-to-upper-80s. The
GFS continues to show a line of fairly heavy showers and storms
moving south from VA and at least affecting the far NE Piedmont and
northern Coastal Plain in the evening. The ECMWF is drier but the
NAM looks more like the GFS at the end of its latest run. So
increased POPs to low chance in the NE.

Cooler and drier air should filter in behind the backdoor front on
Sunday, with highs in the 70s and dew points dropping into the 50s.
There is still some uncertainty with the evolution of a southern
stream trough/low that looks to move NE of FL into the western
Atlantic this weekend. But the environment should be unfavorable by
then for any tropical development, and models keep it well offshore.
However, both the GFS and ECMWF do show another closed mid/upper low
and associated cold front dropping south from Canada into the
Northeast US and Mid-Atlantic on Sunday and Monday. There is still a
lot of uncertainty with its evolution, and guidance has been very
inconsistent from run to run on timing and location. The GFS trended
east and faster with the low in its 12z run, but the 12z ECMWF
trended slower and farther west to look more similar to the GFS. So
POPs are slight chance each day from Monday through Wednesday, but
couldn`t go higher than that given the low confidence. There could
be enough instability for a few storms, but the temperature forecast
is also low confidence as it will depend on the evolution of the
upper low.


As of 710 PM Wednesday...

VFR conditions will dominate for the rest of the evening hours, and
while isolated light sprinkles or showers remain possible, mainly at
RDU/FAY, VFR vsbys will continue this evening. One exception is that
isolated locations may see vsbys drop to 5-6SM in haze/smoke, likely
due to light smoke from wildfires in E Canada being brought down
into NC within northeasterly low level flow. After midnight tonight,
eastern sections of central NC will begin to see a trend to MVFR
then IFR conditions, a result of the low level winds from the NE
bringing Atlantic moisture into the area. RWI is expected to trend
to MVFR by 06z, FAY by 07z, and RDU by 09z. RWI may have a period of
IFR cigs 10z-16z. RDU/FAY/RWI should trend back to VFR by around 17z-
19z Thu. At INT/GSO, the forecast confidence is lower, given that
drier low level air just off the ground is expected to work westward
into the NW Piedmont tonight, but there remains the chance for
shallow MVFR fog early Thu morning (09z-12z). VFR conditions should
dominate after 20z Thu, albeit with another round of isolated
sprinkles and showers Thu afternoon into evening. Surface flow will
be mainly from the NE, light tonight and 8-12 kts Thu.

Looking beyond 00z Fri, the cool surface ridge extending narrowly
through central NC will weaken further through Sat. A backdoor front
will drop toward the SSW through NC Sat evening, with cool high
pressure building back briefly from the NE Sun. This high will then
weaken and move offshore, with a warmer SW flow returning Mon. -GIH

Thu night/Fri: Sub-VFR conditions likely late Thu night through Fri
morning. Mostly VFR with a few showers Fri afternoon.
Sat: Mostly VFR during the day. Scattered showers/storms late Sat/Sat
night with sub-VFR possible Sat night.
Sun-Mon: Mostly dry and VFR.




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