Brown Summit, North Carolina Weather Forecast Discussion

039
FXUS62 KRAH 151758
AFDRAH
Area Forecast Discussion
National Weather Service Raleigh NC
200 PM EDT Mon Sep 15 2025
.SYNOPSIS...
Low pressure will drift into, and meander over, eastern NC through
mid-week, while Canadian high pressure will otherwise extend across
the eastern US.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 145 PM Monday...
* Flood Watch hoisted for the far NE Piedmont and northern Coastal
  Plain starting tonight
* Heavy rainfall threat develops overnight tonight into early Tue
Latest satellite imagery reveals the offshore low churning southeast
of the NC coast. Model agreement has come into better alignment with
the 12z guidance, specifically with the track of the low. The HRRR
was somewhat of an eastern outlier with the track, but has come in
better agreement. The consensus takes the low to the WNW into far
eastern or northeastern sections of NC by Tue morning. The upper-
low, presently off the NC/SC coast, will track northwest into
central NC by tomorrow morning. The upper-low will strengthen
overnight, aided by strong upper-level divergence over east and
northeastern NC, tied to a RRQ of a jet streak near New England.
Height falls will reach or exceed 20 dm. In addition to that, the
low-level flow, specifically at 850mb, shows anomalous moist onshore
flow driving intense moisture confluence into the northeast Piedmont
and northern Coastal Plain.
The combination of the upper and lower-level forcing appear to
maximize between late tonight and early Tue morning over the Flood
Watch area of the northeast Piedmont and northern Coastal Plain. The
heaviest rainfall is likely to fall along an axis of strong
frontogenetical forcing to the northwest of the low, in an area
closely aligned with the 12z HREF footprint. That footprint shows a
half to 1 inch over the Triangle, to 2 to 4 inches over the northern
Coastal Plain by Tue morning. However, given some elevated
instability upwards of 500 J/kg supporting storm potential,
localized amounts of 4 to 6 inches are not out of the realm of
possibility in the far NE sections of central NC, per HREF/HRRR
solutions. Little if any rainfall will be felt by tomorrow morning
over the western/southern Piedmont and Sandhills. Lows tonight to
range from the upper 50s to low 60s.
&&
.SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/...
As of 145 PM Monday...
* Flood Watch in effect through late Tue night for NE Piedmont and
  northern Coastal Plain
* Heaviest rainfall centered on Tue morning into late Tuesday
  afternoon to early evening
* Well below normal temperatures with some gusty winds up to 30 mph
The Flood Watch will remain in effect through late Tue evening for
the far northeast Piedmont to northern Coastal Plain, though later
shifts may opt to extend the watch west to include the Triangle,
especially if model solutions show a western extension of the higher
QPF amounts of 3 or more inches.
The surface low will be over far eastern to northeastern sections of
the state in the morning. The low is forecast to move little into
Wed morning, circulating over the far northeast part of the state.
Deep onshore moist flow will continue, especially to the west and
northwest of the surface low where frontogenetical forcing and
instability will combine with the mid/upper-level dynamics. These
forcing mechanisms appear to maximize largely from early Tue morning
into late Tue afternoon to early evening. After that, the system
appears to occlude, which should favor a gradual weakening and thus
lead to lower rainfall rates by Tue night. The heaviest QPF amounts
are favored over the east and northeast Piedmont to northern Coastal
Plain of central NC, with the highest totals in the Flood Watch area
of the far northeast Piedmont and northern Coastal Plain.
The 12z HREF shows a narrow swath of possibly 5 to 10 inches over
portions of Edgecombe and Halifax Counties by Tue night. Otherwise,
anywhere from 3 to 5 inches is possible in this area. Further west,
anywhere from 2 to 5 inches is possible, higher as you go north and
east of the Triangle (north of US-64 and east of US-1). The Flood
Watch may need to be expanded west to include portions of the
Triangle but after coordination with other local forecast offices,
decided to just include our far NE counties, where confidence is
higher. This system shows some similarities to Chantal in regards to
its QPF footprint and dynamics. Even though the region has been dry
with higher flash flood guidance values, the overall dynamics and
thermodynamics and moisture can still favor higher rainfall rates
for flash flooding over the watch area.
Highs will be rather chilly, perhaps 10 to 20 degrees below normal,
in the low to mid 60s east to near 70 in the west and southwest.
Lows will be in the upper 50s to low 60s. As for winds, gusts,
especially over the northeast, will reach between 20 and 30 mph
during the afternoon to early evening hours.
&&
.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 145 PM Monday...
The low will begin to lift out to the NE and while doing so the rain
will also gradually end from SW to NE during the daytime Wednesday.
While low clouds and fog may linger Wednesday night, the weather
should be rain-free.
A weak upper trough may linger over the Carolinas on Thursday and
provide a fair amount of cloudiness but dry weather as the large
scale synoptic scale lift will be well to our east. By Friday a
ridge to our north will help push some drier air into our region, so
perhaps a bit more sunshine along with temps several deg above
normal.
Right now we have mainly dry weather with seasonable temps over the
weekend thanks to high pressure to our north which will extend down
into the Carolinas during that time.  This is subject to change
however, given that there will be active weather systems not too far
away to both our east and west during that time.
&&
.AVIATION /18Z MONDAY THROUGH SATURDAY/...
As of 200 PM Monday...
A coastal low east of ILM today will begin to drift toward the coast
tonight and inland on Tuesday. Aviation conditions, while still VFR
this afternoon, will begin to deteriorate from east to west tonight.
There is highest confidence at RWI of MVFR transitioning to IFR
tonight with rain beginning late this evening and continuing through
Tuesday.  RDU do you will be on the edge of the low clouds tonight
and there is lower confidence in the timing of onset sub-VFR, but
sub-VFR is expected by 12 Tuesday. Confidence is then even lower at
GSO, INT and FAY, where the track of the low into northeastern North
Carolina may have lesser impacts on those sites. That said the
increase in moisture should eventually ta145ke all sites to at least
MFR by midday Tuesday.
Winds will also increase late tonight and Tuesday has the low
approaches, with sustained winds of 1015 KT gusting into the
2025kt range Tuesday afternoon.
Outlook: High probability of sub-VFR conditions through Wednesday.
Improving conditions are possible on Thursday and especially Friday.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 11 PM EDT this evening through late Tuesday night
for NCZ009>011-026>028-043.
&&
$$
SYNOPSIS...MWS
NEAR TERM...Kren
SHORT TERM...Kren
LONG TERM...np
AVIATION...BLS

NWS RAH Office Area Forecast Discussion