143
FXUS62 KRAH 250241
AFDRAH

Area Forecast Discussion
National Weather Service Raleigh NC
940 PM EST Sun Nov 24 2024

.SYNOPSIS...
High pressure over the SE US will move offshore Monday, ahead of a
weak cold front that will track east across the area Tuesday. High
pressure will build briefly into the region on Wednesday. A
secondary, much stronger cold front will impact the region
Thanksgiving Day.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 839 PM Sunday...

Little changes to the forecast this evening.  Residual high clouds
will continue to stream across portions of central NC through the
overnight period.  While sfc flow has gone calm in most locations, a
few residual sswly light winds are showing at a few observational
sites.  Overall low-level thicknesses are expected to climb compared
to last night. As such, we should see a bit warmer overnight lows in
the upper 30s to around 40.  For counties where the growing season
is still active, temperatures should largely remain above frost
advisory criteria. However, can`t rule out localized frost primarily
in rural areas.

&&

.SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/...
As of 145 PM Sunday...

Aloft, ridging will shift offshore of the Mid-Atlantic Monday. In
its wake, a shortwave trough over the upper MS valley and Great
Lakes will progress into the lower Great Lakes Tuesday and then into
ME and Canada through 12z Wed. Height falls associated with the
trough will maximize Tue morning, before heights rise again in zonal
flow taking over Tue evening and Tue night.

At the surface, we`ll see high pressure over the SW Atlantic keeping
us in that warm SW flow Mon. A surface low tracking into the NE US
will drag a cold front through Tue morning and early Tue afternoon.
Behind it, cool high pressure over the MS valley will settle into
the southern Appalachians by Wed morning.

Mon will feature sunny skies and above average highs by about 8-10
degrees in the upper 60s N to the low 70s S. Clouds will increase
Mon night into Tue with the approach of the front. This along with
continued SW stirring will promote much warmer overnight lows in the
upper 40s NE to low 50s central and west/southern areas. The front
appears to have some weak lift into early Tue across our NW zones,
but any rain amounts appear to be light at best, despite PW`s rising
above average to around 1 inch. Have kept slight chance in the Triad.

Forcing for ascent largely stays to our north on Tue in VA, but
there does appear to be some saturation in the mixed-phase region
tied to some 850-500 mb saturation and weak isentropic lift. Many of
the LREF members show at least the potential for light QPF amounts
in spotty light rain tracking from NW to SE Tue morning. Amounts
range from just a trace to only a few hundredths. Thus, it will be
relatively minor and short-lived so have kept just slight chance
PoPs. Any pockets of rain will shift toward the coast by Tue aftn.
Although it will be cloudy, we`ll see sun breaking in with highs
still above normal in the mid 60s to near 70. Cool high pressure and
clear skies to light winds will promote a return to chilly overnight
lows in the low to mid/upper 30s by Wed morning.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
As of 145 PM Sunday...

* A period of active weather is expected on Thanksgiving, but
  forecast confidence on the details is lower than typical for a Day
  5 forecast.

After a period of dry weather Wed, unsettled weather is expected for
Thanksgiving but the details remain incredibly uncertain. Model
guidance is starting to separate into two plausible scenarios, that
are unfortunately very different from one another.

Most-likely scenario: Based on 00z cluster analysis, this scenario
features a more amplified mid/upper level pattern a quicker but more
dynamic system. This results in an area of low pressure that deepens
as it shifts from the Mid-MS Valley into the northern Mid-Atlantic
by Thurs evening. A low track of this nature would pull the front to
our south back north as a warm front and bring a majority of our
rain in 6 to 12 hrs from the pre-frontal convergence band and
potential risk for severe weather Thurs afternoon/evening. However,
even in this scenario, the severe threat is uncertain and will
depend on degree of instability that can lift into our area behind
the warm front.

Alternate scenario: This scenario features a less amplified system
and results in waves of moderate to heavy rain Thurs into early Fri
as multiple areas of low pressure ride along a wavy frontal zone.
Given the antecedent dry airmass in place with dew points in the 30s
to low 40s, a weak in-situ damming regime may develop as mid-level
WAA begins to spread light rain into the area by Thurs morning. This
scenario is also the wetter solution as multiple rounds of moderate
to heavy rain over 24 hours adds up to 0.75 to over 1.5 inches of
rain.

Forecast confidence increases behind this system and passage of the
first of several cold fronts expected through the weekend. The
coldest airmass of the season will likely be on our doorstep late
Sun as a strong 1045mb surface high over Saskatchewan continues to
slide southeast into the central CONUS.

&&

.AVIATION /00Z MONDAY THROUGH FRIDAY/...
As of 730 PM Sunday...

TAF period: There is high confidence of VFR conditions through the
TAF period. Scattered to occasionally broken cirrus will continue to
stream across the area. Winds will remain light and generally from
the SW.

Outlook: A band of light precip and sub-VFR restrictions are
expected late Monday night into Tuesday as a weak cold front moves
through the area. Following dry conditions Wednesday, a strong cold
front moving into the region will support another period of sub-VFR
restrictions and rain beginning late Wednesday night, and
potentially lingering through early Friday. A period of LLWS is also
possible Wednesday night/early Thursday as a 40-50 kt LLJ
traverses the region.

&&

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

&&

$$
SYNOPSIS...CBL
NEAR TERM...Luchetti
SHORT TERM...Kren
LONG TERM...Swiggett
AVIATION...CBL