000
FXUS62 KRAH 211834
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
235 PM EDT Sun Apr 21 2024

.SYNOPSIS...
A couple of mid and upper-level disturbances will approach and
interact with a frontal zone that will settle off the coast of the
Carolinas through this evening. High pressure will otherwise
build across the Middle-Atlantic states through Tuesday.

&&

.NEAR TERM /TONIGHT/...
As of 205 PM Sunday...

Surface low pressure is currently just east of Cape Hatteras with a
cold front extending to the southwest along the Atlantic coastline.
An upper low over Hudson Bay has a trough extending south to the
eastern Great Lakes which then curves southwest back into Missouri.
As the surface low moves east, rain will steadily decrease from west
to east. Most rain should be east of I-95 by sunset, with all
locations expected to be dry by sunset. An additional quarter to a
third of an inch is possible, with high values south and east of
Raleigh. Skies should partially clear across the Triad during the
late afternoon, although mid/high level clouds will fill back in
after midnight, keeping skies mostly cloudy everywhere through the
rest of the night. Low temperatures should range from the upper 30s
to the mid 40s.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 235 PM Sunday...

...Gradual moderation of Below-Normal Temperatures...

...Patchy Frost Possible Monday Night across the Piedmont...

Cool high pressure centered over the Lower MS Valley will build east
into the SE US through early Tuesday, and then off the SE coast late
Tuesday and Tuesday night. Aloft, a vigorous shortwave trough will
move through central NC during the day Monday, followed by strong
subsidence Monday night as Tuesday as shortwave ridging builds east
into the region.

Monday and Monday night: Considerable cloudiness and a passing
sprinkle Monday morning will give way to NW to SE clearing through
midday, leaving behind mostly sunny skies for the afternoon.
Otherwise dry with early day low-level CAA resulting in well-below
normal temperatures. Highs in the lower to mid 60s, which is 8-11
degrees below normal for late April. Clear skies and calm winds will
result in optimal radiational cooling Monday night. Expect lows in
the upper 30s to lower 40s, with some patchy frost possible over the
northern Piedmont, where temperatures could potentially cool to 34-
36 degrees. Will add a mention in the HWO.

Tuesday and Tuesday night: While still slightly below normal, the
onset of southerly return flow will yield moderating temperatures.
Under sunny skies, highs in the lower 70s. The approach of a clipper
style northern stream shortwave trough will lead to increase in
mid/high clouds over the northern/northwest Piedmont late Tuesday
nights. Lows 45-50.

&&

.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 305 AM Sunday...

Mostly dry forecast with only scattered sprinkles possible on Wed.
Forecast uncertainty for rain chances increases Fri night into Sat.

Shortwave ridging and elongated high pressure will spread across the
Carolinas on Tues and favor dry weather with only wisps of mid/upper
level moisture through the afternoon. An eager northern stream wave
on the southern periphery of a parent low will pivot across the
Great Lakes region and through the northern Mid-Atlantic Wed. The
better 700mb WAA and main shield of precipitation will be well
displaced north of central NC, but a trailing tail of mid-level
moisture and a progressive cold front may result in some light rain,
but mostly sprinkles, leaking across the mountains and into the
Piedmont of NC Wed morning into the early afternoon. Latest ensemble
and deterministic guidance is confident that the cold front should
progress completely through central NC by Thurs morning, but where
it becomes quasi-stationary largely remains in question with the 00z
GFS stalling this boundary noticeably farther north than 12z ECMWF.

The next minimal chance for precipitation will be associated with a
shortwave ejected from the Four Corners region Thurs morning and
riding up into the Northern Plains early Sat morning. The synoptic
forcing for ascent will stay west of the Appalachian mountains with
only weak isentropic ascent along the 290-295K surface a top the
quasi-stationary front. The 00z GFS and the 12z GEFS members are
much flatter with the building high amplitude ridging and largely
make up the precipitation chances during this time. Other model
guidance strengthens the surface high to the northeast and keeps the
lower level moisture return west of the mountains and thus minimal
precipitation chances. Below normal temperatures Fri will begin to
moderate towards above normal heading into the weekend.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
As of 140 PM Sunday...

TAF period: Restrictions will continue through the afternoon at all
terminals. FAY has been the trickiest site to forecast, with rain
and low ceilings both slower to arrive than expected. Think that it
is likely that INT/GSO will both have risen to VFR conditions by
sunset, as the northern edge of precipitation is currently near both
sites. RDU and RWI should have steady rain continue into the
evening, and conditions are likely to rise to VFR conditions as rain
ends. While some partial clearing is expected in the Triad during
the evening, it appears that mid/high level clouds will fill back in
around midnight, but have just kept a scattered deck in the INT/GSO
forecasts at this time. All sites should be VFR by 06Z, although
clouds will still be present. Think that significant clearing will
not occur until after sunrise Monday. The wind will also pick up mid
morning, but didn`t have enough confidence to put gusts in the
forecast yet.

Outlook: A dry cold front is expected to cross the region Wednesday.
However, VFR conditions are forecast through Friday.

&&

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

&&

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