-- Discussion containing changed information from previous version are highlighted. --
607
FXUS62 KRAH 041043
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
640 AM EDT Sat May 4 2024

.SYNOPSIS...
A series of upper level disturbances will move through the area
through Sunday. Meanwhile, a backdoor cold front will stall across
the area through tonight, before lifting north into Virginia early
Sunday.

&&

.NEAR TERM /THROUGH TONIGHT/...
-- Changed Discussion --
As of 320 AM Saturday...

A quasi-stationary surface front will meander across the northern
third of the forecast area through the evening, before lifting north
into VA tonight/early Sunday. While weak, subtle disturbances are
currently moving through the area, a more prominent shortwave
trough/vort cluster/MCV, currently over AL, will progress NEWD across
central NC during the late afternoon and into tonight. The
accompanying moisture feed will propel precipitable water values
towards daily maximum values of 1.5-1.7" inches, highest across the
NC Piedmont counties. As disturbances begin to interact with the the
stalled frontal zone, models indicate a weak sfc wave will develop
and will likely enhance lift and precip across the area.

A very moist and weakly unstable airmass will support
periods of showers with embedded thunderstorms throughout
the day and into the evening and overnight hours, with the greatest
coverage and frequency of rain expected along and west of US 1. It`s
entirely possible that that the eastern Sandhills and southern
coastal plain counties could remain largely dry until the shortwave
trough advances into eastern NC overnight/early Sunday.

Widespread clouds and rain will significantly temper insolation with
resultant weak buoyancy leading to some embedded thunder at times,
especially as the primary MCV tracks through the area during the
late afternoon and evening. Given equally weak shear, no severe
storms are expected. Rainfall amounts through tonight will range
from 0.75-1.0" in the NW Piedmont, to 0.25-0.50" across the
Triangle, to less than a tenth of an inch across the southern
coastal plain.

Highs will greatly depend on both the location of the front and the
spatial and temporal trends of rainfall through the afternoon. A
shallow wedge of cooler air/ hybrid CAD is likely along and north of
the front with a potential for low cloud ceilings/stratus to persist
across the far northern/northwestern zones. Highs ranging from lower
70s NW(potentially cooler) to lower/mid 80s SE. Lows tonight 60-65.
-- End Changed Discussion --


&&

.SHORT TERM /SUNDAY AND SUNDAY NIGHT/...
As of 320 AM Saturday...

The quasi-stationary front sagging across northern portions of the
forecast will retreat north early Sunday, leaving all of central NC
in the warm sector. The increasingly sheared shortwave trough will
exit east of the area during the early afternoon.

Ongoing scattered convection Sunday morning within the continued
anomalously moist PWATs should experience some re-newed vigor during
the afternoon as weak diurnal buoyancy flares up. Continued weak
shear will deter any severe potential.  Rainfall amounts will be
more equitable Sunday, with  0.2-0.3" expected area-wide.

Under mostly cloud skies, highs ranging from mid/upper 70s north to
lower 80s SE. Convection should largely dissipate as BL nocturnally
cools and stabilizes. Mild overnight temps in the 60s with stratus
likely to re-develop across the area as moisture remains high.

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
As of 250 AM Saturday...

The extended forecast will feature a continued chance of unsettled
weather to start the week Mon, followed by somewhat drier and hot
temperatures by the middle of the week. A potent late-week
system/trough looks to increase storm chances again by week`s end.

On Monday, models continue to show a shortwave over the TN valley
tracking east across the region in the afternoon/evening, before
exiting along the coast by Tue morning. A surface Piedmont trough
will be in place and combined with 200-percent of normal PW`s should
favor another day of scattered to perhaps numerous showers and
storms, maximizing during peak heating. Instability is between 500-
1000 J/kg but shear is weak, so severe chances are not expected,
though slow-moving storms could bring heavy rain. Activity should
wane overnight with loss of heating and as the trough slides toward
the coast. Highs should hover in the low/mid 80s with higher rain
chances and cloud cover.

As the trough moves to our east Tue, weak ridging starts to build
in, although the CMC/GFS show a weak perturbation riding along the
ridge. With a lack of large-scale forcing, confidence on coverage of
storms, if any, is low, such that storm activity should be
isolated/scattered in nature and focused along differential heating
boundaries and/or the sea-breeze. Highs should warm to the low to
upper 80s.

A drier pattern still appears to be favored midweek Wed and part of
Thu as ridging and southwest flow builds back into the region. This
will also be when the airmass will warm quite a bit with a lee
trough setting up east of the Appalachians and low-level thicknesses
well above average and highs some 12-15 degrees above normal in the
upper 80s to low 90s. The NBM still indicates a 60-80 percent chance
of 90 or greater maxT values across portions of the Sandhills,
Triangle region, and Coastal Plain during this period. Heat index
value could reach the mid 90s over these areas, making for an early
taste of summer. While this period looks drier, most guidance shows
a developing trough over the upper MS valley Thu, with solutions
indicating a decent plume of moisture tied to a perturbation
advecting ahead of a cold front draped over the OH valley. This
would favor better chances of isolated/scattered storms Thu aftn/eve
with higher instability coupled to higher shear.

Although model solutions diverge by late in the week with a frontal
system location, there is broad consensus that chances of storms
appear to remain elevated to close out the week as the trough slides
closer to the TN/OH valley and Great Lakes region with
instability/shear still favorable over the Carolinas.

&&

.AVIATION /11Z SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
As of 640 AM Saturday...

A back-door cold front, noted by a E-NELY wind shift, will stall
across the area today and this evening, before lifting north
into Virginia tonight and into early Sunday. Moisture pooling and
convergence will lead to the development of LIFR to MVFR ceilings
across the area this morning, impacting all TAF sites.

Flight restrictions at KFAY, KRDU, and KRWI should gradually lift to VFR from
south to north through 17-18z, with scattered showers and storms
possible during the afternoon and evening, mainly at KRDU.

At KGSO and KINT, ceilings could remain IFR to MVFR through the
afternoon and evening as intermittent showers and embedded
storms repeatedly re-develop and move through the area
through tonight.

LIFR to MVFR restrictions, primarily from ceilings, will re-develop
and spread south between 00 to 06z, lowest at KINt and KGSO
where the deepest moisture resides. -CBL

Outlook: IFR-MVFR ceilings are likely to redevelop each night-
morning through Monday, as are scattered to locally numerous
showers/storms each afternoon-evening. -MWS
-- End Changed Discussion --

&&

.CLIMATE...

Record High Minimum Temperatures:

May 4:
KGSO: 65/2022
KRDU: 68/1938
KFAY: 68/1942

&&

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

&&

$$
SYNOPSIS...CBL/Green
NEAR TERM...CBL
SHORT TERM...CBL
LONG TERM...Kren
AVIATION...CBL/MWS