-- Discussion containing changed information from previous version are highlighted. --
311
FXUS62 KRAH 210747
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
346 AM EDT Tue May 21 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 855 PM Monday...

Central NC will remain under the influence of weak high pressure
from the north and associated NELY low-level flow. An expansive
layer of marine stratus clouds that extends along much the mid-
Atlantic Seaboard is expected to advect inland into the coastal
plain/I-95 corridor overnight. Elsewhere, mostly clear skies will
prevail, with some areas of fog likely, potentially dense in some
locations, as overnight temperatures are expected to cool to near or
a few degrees lower than this afternoon`s crossover temperature.
Lows tonight in the lower/mid 50s north to mid/upper 50s elsewhere.

&&

.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/...
-- Changed Discussion --
As of 346 AM Tuesday...

Upper pattern through the extended: A low-amplitude upper trough
will lift through the Great Lakes Thursday.  A series of short waves
will then move through the TN Valley and wash out over the southern
Appalachians Friday through Monday.

Thursday:  On Thursday, a low-amplitude upper trough will lift
through the Great Lakes. Some mid-level energy associated with this
feature may trickle down into our central to northern locations and
promote showers/storms later in the day. While some deterministic
models suggest better coverage over central NC Thursday evening
(e.g. GFS, Canadian, EURO), ensemble guidance has higher
probabilities for precipitation staying north into central VA,
lowering with southeastward extend.  This makes sense conceptually
as the better forcing/low-level moisture still appears to stay to
our north. As such, decided to lean on ensemble guidance and
continue to hold just slight to low chance POPs Thursday
afternoon/evening.

Ensembles continue to simulate a potentially potent short wave
riding through the TN Valley Friday, followed by a secondary vort
signature passing over central NC on Saturday. Deterministic models
are still in a bit of disagreement wrt the evolution of these
features, but overall it still looks like periods of unsettled
weather should occur Friday through Monday. Severe weather
parameters are not popping off the charts at this point during this
period. However, ensembles continue to simulate periods of
relatively higher shear (~30 to 35 kts) and elongated hodographs on
Friday. Thus, a few isolated stronger storms may be possible Friday
afternoon/evening.

There is high probabilities amongst ensembles that temperatures will
exceed the mid 80s both Thursday and Friday.  The quartile spread
widens a bit more over the weekend, likely due to differing
solutions wrt to any sfc boundaries. Regardless, temps will likely
remain in the 80s this upcoming weekend and continue into early next
week.
-- End Changed Discussion --

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
As of 230 AM Tuesday...

The latest satellite trends suggest the area of LIFR-IFR stratus and
fog now over ern VA/NC will probably not bodily move wwd fast enough
to reach RWI prior to ~12Z, by which time diurnal heating will cause
the moist layer to erode and disperse to VFR. More likely will be
the development of patchier and more shallow radiation mist/fog at
RWI and more briefly around RDU and FAY through 12Z. High pressure
will favor VFR conditions otherwise and elsewhere through 06Z Wed,
along with calm to light and variable surface winds.

Outlook: A risk of fog/stratus will continue especially over ern and
e-cntl NC late tonight-Wed morning, followed by a chance of
afternoon-evening showers/storms mainly across the Piedmont Thu and
area-wide Fri-Sat.

&&

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

&&

$$
SYNOPSIS...Green
NEAR TERM...CBL
SHORT TERM...Danco
LONG TERM...Luchetti
AVIATION...MWS