-- Discussion containing changed information from previous version are highlighted. --
990
FXUS62 KRAH 202327
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
727 PM EDT Mon May 20 2024

.SYNOPSIS...
High pressure will remain along the East Coast through Wednesday
before a cold front approaches the region Thursday and brings
unsettled weather into the weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 145 PM Monday...

Weak high pressure is currently centered along the coast of New
Jersey. This has allowed the wind to continue out of the northeast,
providing slightly below normal temperatures. A wide area of low
stratus from early this morning has transitioned to diurnal cumulus,
with slightly greater coverage across the eastern half of the
forecast area. These clouds should quickly dissipate around sunset,
leaving clear skies during the evening and into the overnight hours.
Considering there has been minimal change in the air mass, expect
that some cloud cover should regenerate overnight as temperatures
cool off. However, think that the coverage of clouds will be a bit
less than last night, primarily affecting areas along and east of I-
95. There could be some some patchy fog around, but there is not
enough confidence to include this in the forecast. Tonight`s low
should be similar to last night`s values and the coolest out of the
next seven days, in the 50s.

&&

.SHORT TERM /TUESDAY AND TUESDAY NIGHT/...
As of 220 PM Monday...

Mid-level ridging will extend NE from the western Gulf of Mexico
into the Mid-Atlantic on Tuesday, in between a weak shortwave over
the Appalachians and stronger, broader troughing off the Southeast
US coast. At the surface, high pressure nosing down from the Mid-
Atlantic coast will slowly push east, helping turn the flow more
southeasterly during the day which will warm temperatures into the
lower-to-mid-80s (near to 5 degrees above normal). The weak
shortwave will move across central NC on Tuesday night, but with dry
air in place no impacts on sensible weather are expected. High-res
guidance including the RAP and HRRR is showing potential for enough
low-level moisture from the SE flow to result in some fog across
eastern NC, which may reach into our far eastern counties early
Wednesday morning. Otherwise it will be mostly clear with lows in
the mid-50s to lower-60s.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
As of 152 PM Monday...

The extended continues to favor increasing chances of showers and
storms as we end the week and go into the weekend. Temperatures will
be on the rise, as will humidity levels Thu-Sat.

Ridging aloft over the region Wed will transition to a WSW flow Thu
into Sat as a trough over the upper Midwest slowly tracks into
eastern Canada by the start of the weekend. Southwesterly surface
flow will return Wed and persist through at least Fri as high
pressure slides offshore. Temperatures Wed into Fri will range from
the upper 80s to low 90s, some 5-10 degrees above normal.

As the aforementioned trough moves east, shortwave energy will start
to spread south from the TN/OH valleys and skirt across NC/VA as
early as Thu evening. We retained the chance of showers/storms
during this period, with highest chances across the north, in closer
proximity to a slowly moving boundary. Instability does not appear
that high but could see a strong storm or two with increasing shear
aloft.

Deterministic and probabilistic data appear in at least moderate
agreement for a late-week convective complex initially forming over
the southern Plains reaching our area late Fri and lingering into
Sat. The GFS/ECMWF/CMC all show this MCS/shortwave moving through
during peak heating Fri. This would potentially be the better chance
of strong to severe storms given 30-40 kts of 0-6 km shear and
upwards of 1500 J/kg of CAPE. The storm chance should linger into
Sat as the system remains overhead. Thus, our highest rain chances
are Fri-Sat. There could be a heavy rain threat as well given PW`s
near the 90th percentile at 1.5 inches.

It would appear models and their ensembles show some degree of drier
westerly flow building back in Sun as the shortwave moves offshore,
but lingering instability should warrant at least a chance of
diurnally driven storms Sun. Another system could approach early
next week, but there is more spread in the guidance at this time
frame such that we kept storm chances mainly during peak heating.
Temperatures should remain in the 80s through the remainder of the
period.

&&

.AVIATION /00Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --
As of 725 PM Monday...

Lingering fair weather cumulus will continue to disperse through the
evening hours with winds going light to calm overnight. Marine layer
stratus around 400-800 feet is beginning to advect onshore over
eastern NC and will continue to spread through the Coastal Plain
affecting RWI around 10z. Ahead of this stratus layer, optimal
radiational cooling will result in patchy fog, potentially dense in
spots, to develop late tonight into Tues morning. IFR/LIFR fog will
be most probable where temperatures begin to dip below the afternoon
crossover temperature (RDU/RWI) with MVFR fog most likely elsewhere.
Shallow morning fog/stratus will disperse/lift to VFR by mid-morning
with surface winds light and variable underneath surface high
pressure during the afternoon.

Outlook: Wednesday morning could have yet another round of
restrictions, although most guidance is showing it should be
contained to the eastern third of the state, locally only impacting
RWI. Otherwise, the forecast will be dry through Thursday afternoon,
then diurnally driven showers/thunderstorms are expected into the
weekend.
-- End Changed Discussion --

&&

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

&&

$$
SYNOPSIS...Green
NEAR TERM...Green
SHORT TERM...Danco
LONG TERM...Kren
AVIATION...Swiggett/Green