-- Discussion containing changed information from previous version are highlighted. --
745
FXUS62 KRAH 090745
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
345 AM EDT Thu May 9 2024

.SYNOPSIS...
Multiple upper level disturbances will allow for unsettled weather
to continue through Friday. A cold front moving through the region
on Friday will bring below normal temperatures for the weekend.

&&

.NEAR TERM /TODAY THROUGH TONIGHT/...
As of 225 AM Thursday...

An upper level shortwave is supporting a MCS that is just about to
enter the forecast area. While the nocturnal timing will help to
limit overall instability, the line of thunderstorms is expected to
hold together through most of the forecast area. High-resolution
models are not in total agreement as to the evolution, but with
greater instability to the south, the odds of the line holding
together across the forecast area will be higher across the south.
The bulk of the rain appears to be near the I-95 corridor around
sunrise and pushing east of the area by mid-morning. Unfortunately,
models diverge as to the evolution of precipitation for the rest of
the day. Will go with scattered thunderstorms through the afternoon,
but models might have a better handle on the environment across the
area once the current line of showers/thunderstorms moves through.
The entire forecast area is under a slight (level 2 of 5) risk for
severe thunderstorms, with the primary threat coming from damaging
wind gusts. The greatest threat is likely to come in the morning
with the overnight line of thunderstorms departing the region, but
the scattered thunderstorms in the afternoon could also generate
strong winds. Model guidance has come in a few degrees cooler than
the previous forecast, which removes the 90s from the forecast, but
still has highs in the 80s everywhere.

Scattered thunderstorms could continue east of US-1 into the
evening, but conditions should dry out overnight. Lows will range
from the upper 50s to the upper 60s.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
-- Changed Discussion --
As of 300 AM Thursday...

A positively-tilted shortwave trough will approach from the TN
Valley on Friday, becoming more neutrally-tilted as it crosses
central NC on Friday evening. An MCS will also be moving east across
GA and SC early in the day, and while the exact location it will be
is still unclear, most high-res guidance keeps it to our south as it
exits into the Atlantic. At the surface, a cold front will begin to
cross through central NC as a wave of low pressure rides along it,
but exactly how far south and east it gets is a bit uncertain. The
aforementioned shortwave will provide some upper forcing for ascent,
so scattered showers will be possible anywhere on Friday afternoon
and evening, but the main threat of storms will be along and ahead
of where the front sets up. The 00z HREF has CAPE values around 500-
1000 J/kg across our southernmost tier of counties, which is where
the SPC expanded a marginal (level 1 of 5) risk of severe storms.
Damaging straight-line winds and hail are the main threats.
Instability and moisture will not be as high as today or yesterday
even down there, so convective coverage doesn`t appear great enough
to justify likely POPs anywhere, but they are still around 50% in
the far south. Forecast highs range from mid-70s far north to lower-
80s far south. Any precipitation will come to an end Friday night as
the cold front sweeps off the coast and lows turn slightly below
normal (upper-40s to mid-50s).
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
-- Changed Discussion --
As of 345 AM Thursday...

NW flow will dominate this weekend between broad troughing over the
Northeast US and mid-level ridging over the southern Plains and
lower MS Valley. A shortwave will move across the OH Valley and
northern Mid-Atlantic on Saturday, which could bring weak height
falls and forcing for ascent across northern portions of central NC
in the afternoon and evening. This will help increase moisture
around 700 mb, but model soundings indicate dry air in the low
levels from the NW flow and PW values only around 0.5-0.75 inches
(50-75% of normal). So any precipitation would be very light and
likely just some sprinkles across the far north if anything.
Otherwise it will be a very pleasant weekend with temperatures
remaining slightly below normal. Forecast highs are lower-to-mid-70s
on Saturday and mid-to-upper-70s on Sunday, with lows remaining in
the upper-40s to mid-50s. Dew points will only be in the 40s.

The surface high will move offshore on Monday and turn the flow
southerly, which will help increase high temperatures back to near
normal (upper-70s to lower-80s). Meanwhile a closed mid/upper low
will move into the southern Plains on Monday, becoming more of an
open wave as it traverses east into the mid-MS and TN valleys. SW
flow ahead of this system will increase moisture across our region
once more. However, models continue to differ significantly on how
quickly it will move east, with the GFS still much faster and the
ECMWF and Canadian holding it back. This affects when we would begin
to see any precipitation from this system. The earliest we see
anything should be Monday night, with POPs increasing to high chance
to likely through Tuesday and Wednesday, maximized during time of
peak diurnal heating (afternoon and evening) both days. The
deterministic GFS depicts a quick exit of the system with a mostly
dry Wednesday, but this appears to be an outlier as even most of its
ensembles are wet. The widespread clouds and precipitation may keep
temperatures down on Tuesday, as the raw GFS, ECMWF and CMC are only
indicating highs in the 60s to lower-70s. Models indicate a warmer
and more unstable air mass in place on Wednesday with highs in the
mid-70s to lower-80s.
-- End Changed Discussion --

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
As of 135 AM Thursday...

TAF period: A line of showers and thunderstorms is expected to move
across the forecast area overnight into Thursday morning. There is
some uncertainty with high-resolution models as to how well the
thunderstorms will hold up considering the overnight timing. Was
confident enough to keep prevailing thunderstorms for some time at
all sites except RWI, as some models indicate the northern portion
of the line may significantly weaken before reaching RWI. Also have
gone with higher wind gusts in tempo groups for thunderstorms at all
sites before RWI. Do not think that ceilings will be as low as
previously forecast; think that INT/GSO could briefly have IFR cigs,
but otherwise INT/GSO/RDU should drop to MVFR with lesser potential
of restrictions at FAY/RWI. Think that the bulk of the rain should
move through by 15Z, then confidence in rain coverage is very low
through the afternoon. That potential will likely be dependent on
just how much convection holds together overnight, so have generally
gone with VCSH. The bulk of the rain should be over by sunset, and
have removed showers and dropped wind gusts that will occur during
the afternoon.

Outlook: Scattered showers/thunderstorms are possible everywhere
Friday with more isolated coverage on Saturday. Otherwise VFR
conditions are generally expected.

&&

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

&&

$$

SYNOPSIS...Green
NEAR TERM...Green
SHORT TERM...Danco
LONG TERM...Danco
AVIATION...Green