Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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FXUS62 KRAH 211157

National Weather Service Raleigh NC
757 AM EDT Mon Oct 21 2019

Weak high pressure across the area will move offshore this evening.
A strong cold front will cross the region Tuesday afternoon,
followed by high pressure building in from the west on Wednesday.


As of 400 AM Monday...

Overview: An upper level low over the Central US Plains will deepen
and occlude as it moves NE through the Upper MS Valley today and
will reach the Great Lakes by daybreak Tuesday. Attendant cold front
will advance east through the Tn Valley and into the southern
Appalachians late tonight/predawn hours Tuesday. Downstream of this
strong system, high pressure will start out in control today, before
shifting east and offshore during the late afternoon and evening.

Today: An area of fog developing across the western Piedmont and
lingering low ceilings associated with the remnants of Nestor across
the NC coastal plain will largely lift and scatter out during the
mid to late morning hours, with the potential for a slower demise
across the NW Piedmont where a weak upslope component underneath an
inversion centered between 850-700 mb could allow a low ceiling to
persist well into the afternoon. Highs today ranging from upper 60s
NW to mid 70s SE, potentially cooler in the mid 60s over the NW
Piedmont if the low ceilings hang on through the afternoon.

Tonight: Rooted within the WCB on the cyclonic side of the upper
trough, strong low to mid-level moist warm air advection streaming
into the area from the SW will fuel increasing rain chances between
06 to 12z, with the bulk of the precip remaining west of US 1
through daybreak. Lows in the mid/upper 50s NE to lower 60s SW.


As of 500 AM Monday...

...Slight risk of Severe Storms on Tuesday...

The upper trough associated with the occluded low pressure system
lifting north into Ontario will become negatively-tilt as it moves
into the region through Tuesday night. Pre-frontal morning
convection, mostly in the form of showers, will result in extensive
cloudiness across the area. However, models show an influx of upper
60s to lower 70s dewpoints across the Sandhills and southern/central
coastal plain, ahead of the cold front and a triple point low
feature that will lead to weak to moderate destabilization(500 to
1000 J/Kg MLCAPE) during the late morning/afternoon hours.
Given strong deep layer shear of 50-60 kts across the region along
with an area of enhanced 0-1 km helicity of 400 to 500 ms-2 INVOF of
the triple point low, there is the potential for an organized severe
wind threat, as well as an isolated tornado threat Tuesday
afternoon. This severe threat along with rain chances should be east
and out of the area by 00z Wednesday. With clearing overnight in the
wake of the front.

Highs Tuesday ranging from lower 70s NW to near 80 SE. Much cooler
behind the cold front Tuesday night with lows in the mid 40s to
lower 50s.


As of 240 AM Monday...

Wednesday and Thursday: The upper level trough will swing through
the area early Wednesday, resulting in southwest flow aloft setting
up through Thursday night. At the surface, cool high pressure will
build eastward into and over the area in the wake of the front.
Generally expect cool, dry weather to persist through Thursday, with
highs in the mid 60s to low 70s Wednesday and Thursday and lows in
the low to mid 40s Wednesday night. Some moderation in lows is
possible for Thursday night ahead of the next frontal system, so for
now expect lows in the upper 40s NW to low 50s SE Thursday night.

Friday through Sunday: Still significant forecast uncertainty due to
very different medium range model solutions with the next system.
Generally, some moderation in temperatures and an increase in
precipitation chances are expected. Synoptically, medium-range
models suggest an upper level trough will dig southward through the
Plains on Thursday. In the ECMWF solution the low becomes cutoff
over TX/OK on Friday, thus slowing the eastward progression of the
front. Conversely, the GFS holds an open trough progressing eastward
through the Midwest toward the mid-Atlantic Friday and Saturday.
Meanwhile over central NC, as the trough digs over the Midwest and
the cold front pushes eastward, a warm front tries to lift northward
into the region as a low develops along the front. While the low
developing along the front should increase rain chances, timing and
location differences between the models make pin-pointing the best
rainfall chances, amounts and timing difficult. Do expect another
round of wet weather between Friday and Sunday, with a good chance
of some significant precipitation for central NC.


As of 757 AM Monday...

Back-edge of IFR to MVFR ceilings associated with the remnants of
Nestor has cleared all TAF sites but RWI, with the potential for
these sub-VFR ceilings to linger through 15z this morning.
Meanwhile, areas of fog with some pockets of LIFR dense fog and
ceilings has developed across the western Piedmont, INVOF KGSO and
KINT. This fog could potentially lift to an MVFR stratus cloud deck
through the late morning and then VFR during the mid afternoon.
Widespread IFR to MVFR ceilings and rain showers are expected to
return late tonight and Tuesday morning, in response to strong
moisture transport in advance of a cold front approaching from the

Looking beyond 12Z Tuesday: Sub-VFR conditions in showers will
continue through the day on Tuesday with a chance for some scattered
strong thunderstorms Tuesday afternoon as the cold front crosses the
area. VFR conditions will return Tuesday night and should remain VFR
through Thursday.





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