673
FXUS62 KRAH 170755
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
355 AM EDT Tue Sep 17 2024

.SYNOPSIS...
An area of low pressure centered across far northeast South Carolina
will drift west into upstate South Carolina tonight. The remnants of
this system will linger and gradually dissipate across the mid-
Atlantic through the end of the work week.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 350 AM Tuesday...

* Last large band/region of showers and storms spreading across the
  northern Coastal Plain and the northern Piedmont.
* Flooding threat has abated and Flood Watch will be cancelled.

The latest surface analysis shows the center of the surface low
located just south of Charlotte, near Lancaster SC. A surface trough
or occlusion extends east of the surface low with a narrow tongue of
instability extending east to west, from near KWEN to near KGSB,
just north of the boundary. In and north of this axis, the last band
of showers and a few embedded thunderstorms are streaming west
across the central and northern Coastal Plain and into the eastern
portions of the Triangle.

This band/region of showers and some thunderstorms will shift north
during the morning, perhaps beginning to exit much of the Triangle
area around the morning commute with generally dry weather to the
south. By midday and continuing into the afternoon hours, most of
the convection should be focused across the far northern Piedmont
and VA border counties. The narrow region of instability will also
transition north. With the wind field becoming less favorable into
the afternoon, any lingering severe weather and tornado threat
should transition north and fade away this morning. Will need to
keep an eye on cells in Wayne, Wilson and Edgecombe counties this
morning but the threat has decreased greatly.  Additional rainfall
amounts today will range around a half inch north of U.S. route 64,
perhaps a little more near 0.75 inches across the northern Coastal
Plain with rainfall amounts of a tenth or two south of U.S. 64. With
the widespread precipitation amounts decreasing we plan on canceling
the flood watch. Showers and a few storms across the north this
afternoon will gradually diminish into the evening hours. A much
less active radar is expected this evening and tonight although some
spotty rain associated with the remnant low level circulation may
spread a few showers across the far western Piedmont tonight.

Gust northeast to easterly winds early this morning will decrease
from south to north during the morning and especially this
afternoon. A few gusts through around daybreak in the northern
Piedmont and especially the Triad may range between 25 and 30 mph.
Highs today will range from the lower 70s in the western Piedmont
and VA border counties to the mid 70s to around 80 in the east. Lows
tonight will range in the mid to upper 60s. -Blaes

&&

.SHORT TERM /Wednesday/...
As of 355 AM Tuesday...

The surface and mid/upper low impacting the region over the past few
days will weaken into Wednesday as it shifts north and east.
Abundant moisture across the region will result in widespread low
clouds and perhaps some fog on Wednesday morning. A few showers and
perhaps a thunderstorm may develop during the afternoon with highs
ranging from the upper 70s in the Triad to the lower 80s in the
Coastal Plain.
&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
As of 345 AM Tuesday...

Mid/upper troughing will extend down the Eastern Seaboard including
into central NC from Wednesday night into Thursday. Meanwhile a
surface low will linger off the northern Mid-Atlantic coast. This
will bring one last day of upper forcing for ascent and above-normal
PW values, so POPs on Thursday are generally in the 30-40% range,
highest east and maximized during peak heating. There could be
enough instability for a few storms. QPF amounts in the models are
not impressive, so not concerned about an additional heavy rain
threat, and looks fairly low impact overall.

As a mid/upper ridge over the Plains begins to move east on Friday,
it will begin to push the trough east and offshore. This will result
in NW flow and much drier air moving into central NC, with PW values
trending below normal. At the surface, high pressure will gradually
nose down from SE Canada into the Mid-Atlantic from Friday into
Monday. Overall this pattern supports limited rain chances at best,
which is a significant change from last night when the models
depicted the mid/upper low moving back south across the area. Now,
they keep it and the associated surface low well to our east in the
western Atlantic. Instability looks minimal to non-existent as well
given the cool wedge of high pressure and NE flow near the surface.
The best chance for clouds and isolated showers looks to be in the
Coastal Plain closer to the low and where there will still be moist
onshore flow in the low levels, but even there POPs are only slight.
The GFS does try to bring a shortwave through the area on Sunday, so
POPs are slight that day areawide.

As for temperatures, highs should be within a few degrees of normal
from Thursday through Saturday, in the upper-70s to lower-80s. Lows
will gradually trend downward as the air mass turns drier, from mid-
to-upper-60s on Wednesday night to upper-50s to lower-60s by
Saturday night. On Sunday and Monday when the cool wedge of high
pressure really takes hold, forecast highs are only in the 70s with
lows in the mid-50s to lower-60s. If the raw GFS is to be believed,
some places won`t even get above the 60s on these days, but would
like to see more support from ensemble guidance before buying into
this too much.

&&

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

Widespread MVFR to IFR conditions primarily from low CIGS are noted
across central NC early this morning. CIGS are expected to lower
during the pre-dawn hours leading to IFR/LIFR conditions across much
of the area through the mid morning hours. A broad area of light
rain showers with a few embedded heavier showers extend from the
central and northern Coastal Plain west across the northern
Piedmont. This area of precipitation may also result in reduced
VSBYs at times as the overall rain axis shifts north through the
morning. An isolated thunderstorm is possible across the central
Coastal Plain, near but mainly south of the KRWI terminal. Low CIGS
are expected to persist for much of the day although cloud bases
will lift during the late morning and early afternoon with MVFR CIG
restrictions still commonplace during the afternoon. Some brief
improvement with VFR CIGS are expected late in the afternoon across
the Coastal Plain and Sandhills impacting the KRWI and KFAY
terminals. There is a limited risk of additional showers and perhaps
a storm this afternoon primarily near KINT/KGSO and KRDU. Another
round of MVFR to IFR CIGS are expected to return tonight and
continue into Wednesday morning.

A low pressure area is expected to track northwest across northern
SC through tonight. This will maintain a northeasterly surface wind
with gusts of 15 to 25kts at times overnight, perhaps a little
stronger in the Triad. Winds should begin to diminish from south to
north later this morning and especially this afternoon. A prolonged
period of LLWS should be relaxing early this morning. Recent data
from the WRAL tall tower southeast of Raleigh shows wind speeds
aloft at 2kft beginning to weaken. Will maintain a mention of LLWS
in the TAFs through around 09Z with the greatest risk of LLWS
condition in the Triad.

Outlook: After another period of IFR/LIFR CIGS early Wednesday
morning, an unsettled period will continue through Thursday with
area of late night and early morning stratus and a risk of some
afternoon showers and possibly a storm. Aviation conditions will
generally improve on Friday and Saturday. -Blaes

&&

.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 8 AM EDT Tuesday for NCZ007>011-021>028-
038>043-073>078-083>086-088-089.


&&

$$

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