787
FXUS62 KRAH 191837
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
237 PM EDT Thu Sep 19 2024

.SYNOPSIS...
An upper level low over the eastern Carolinas this afternoon will
lift northeast along the Mid Atlantic coast through Friday and then
persist as an upper level trough just off the East Coast through the
weekend. An upper level ridge of high pressure will move into the
northern Gulf States late in the weekend and then extend into the
Southeast states through early next week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 235 PM Thursday...

The latest surface analysis continues to show surface high
pressure centered over Quebec that extends southwest across the
eastern Great Lakes and into the southern Appalachians. A
frontal zone with weak areas of low pressure extends northeast
to southwest just off the East Coast. A light north to
northeasterly low level flow persists across the region in
rather moist air mass with PW values of 1.6 to 1.8 inches or
about 125% of normal. The airmass across the region is weakly to
moderately unstable with MLCAPE values of 500-1000 J/Kg,
greatest in the southeast. Further aloft, a persistent upper-
level low was centered across southeastern VA and northeast NC
with 500 mb temps of -10C and a cyclonic flow from the northwest
across central NC.

The forecast through tonight remains a little uncertain as a
moist and weakly to moderately unstable airmass across central
NC is triggered by various mid and upper level disturbances in
the cyclonic flow aloft. An area of showers and a few embedded
thunderstorms continues to shift south across the southern
Piedmont, Sandhills and southern Coastal Plain. This area
appears triggered by a disturbance in the mid levels as noted on
the 1.5 PVU surface. Another cluster or two of showers and
possibly storm`s will drop out of VA into northern and
northwestern NC late this afternoon and evening. The convection
has not been terribly deep but precipitation rates seem to over
perform modest radar reflectivity signatures. With a moist
airmass, the rain may be heavy at times and with saturated
soils, some localized flooding can`t be ruled out. Despite the
instability, the low and mid level flow is rather weak and the
CAPE is skinny so not too concerned about any severe storms.
CAMs suggest that the convective coverage will relax decrease
quickly during the evening hours with dry conditions overnight.
Another round of stratus and fog is expected late tonight with
perhaps a bit more fog than last night. Lows tonight should
range in the lower to mid 60s. -Blaes

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
As of 105 PM Thursday...

Aloft, the trough off the mid-Atlantic coast will continue to shift
ewd over the Atlantic, allowing high pressure to ridge enewd into
the area. A lobe of vorticity in the upper levels will swing sewd
through central NC Fri morn/aft, while a trailing mid-level
disturbance follows Fri aft/eve. At the surface, a low will continue
to meander off the northern mid-Atlantic/New England Coast Fri/Fri
night, while high pressure ridges swd through central NC. Some lower
dewpoint air should push into the far northeast portions of central
NC as the high ridges in. While widespread convection is not
anticipated, if showers do develop, the best chance would be over
the western Piedmont during the morn/aft with the passage of the
vort max aloft, and over the northeast Piedmont/northern Coastal
Plain during the aft/eve, generally along the dewpoint gradient as
the high ridges swd. The NAM does have some MUCAPE in the 500-1000
J/Kg range Fri morn through the eve, thus an isolated storm or two
is still possible if/where convection occurs. Highs should generally
range from around 80 degrees NE to mid 80s south, with lows in the
upper 50s to mid 60s expected.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
As of 325 PM Thursday...

Saturday morning, surface high pressure will be centered over
eastern Canada with a pressure ridge extending all the way to the
Gulf Coast. A weak front will move across the area Saturday night.
Am not terribly impressed by the depth of the moisture with the
front, but there are too many models, deterministic and ensembles,
to keep a dry forecast in that time period. Rainfall does not appear
to be substantial, but have gone ahead and added slight chance pops
across the northern half of the area. Sunday and Monday continue to
have a dry forecast as high pressure reestablishes itself, with just
the Triad being clipped on Tuesday with a slight chance of showers
in advance of the next front. Low pressure will move across the
Great Lakes during the middle of the week, and it currently appears
that the most likely timing for any showers or thunderstorms with
the upcoming cold front will be Wednesday night. Highs will be
slightly above normal for the weekend, then drop a few degrees below
normal for the weekdays. Lows will be near normal through the
extended period.
&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
As of 210 PM Thursday...

A mix of MVFR conditions from low CIGS and VFR conditions are noted
across central NC this afternoon. Low stratus CIGS and fog from this
morning have lifted a bit in most locations with some breaks in the
overcast noted. In addition, widely scattered showers are dropping
south across the area with brief MVFR VSBY restriction with the
greatest coverage across the southern Piedmont, Sandhills and
southern Coastal Plain. An isolated thunderstorm is possible,
primarily across the southern and easter locations, mainly the KFAY
terminal where a TEMPO group for a thunderstorm has been added.
While another batch of showers may drop across the Triad area
including the KINT and KGSO terminals through 02Z or so, shower and
thunderstorm activity will generally diminish quickly this evening
and shift of the area. Areas of IFR fog are apt to form after 06Z
with the fog favored across the Piedmont where some LIFR VSBY
restrictions in fog is possible toward daybreak.

Outlook: Areas of overnight and early morning fog and perhaps low
stratus are expected on Friday and Saturday morning. A transient
system may bring a few showers or storms to the area on Saturday
night otherwise a return to more tranquil weather is expected for
Sunday through Tuesday. -Blaes

&&

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

&&

$$

SYNOPSIS...Blaes
NEAR TERM...Blaes
SHORT TERM...KC
LONG TERM...Green
AVIATION...Blaes