Area Forecast Discussion
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FXUS62 KRAH 221127
Area Forecast Discussion
National Weather Service Raleigh NC
627 AM EST Sun Jan 22 2017
A potent low pressure system will track northeast from the Deep
South into the Carolinas this afternoon into tonight, linger over
the area on Monday, then track offshore the Mid-Atlantic coast on
.NEAR TERM /TODAY AND TONIGHT/...
As of 630 AM Sunday...
...Severe Weather Possible this Evening...
Update: Widespread dense fog has lifted into a layer of stratus with
ceilings ranging from 200-400 ft AGL over the past few hours. As a
result, the Dense fog advisory has been cancelled.
Unseasonably rich moisture continues surging N/NE from the GOMEX
into the Carolinas this morning as low-level flow backs/strengthens
in response to height falls in advance of a potent upper level low
progressing east from the lower MS river valley into the Deep South.
Significant moistening has occurred over the past 24 hrs, as
evidenced by PWAT values near 1.25" on the 00Z GSO RAOB (roughly
double the PWAT observed on the 12Z Saturday GSO RAOB). An MCS
upstream over AL/GA at 06Z is expected to progress rapidly E/NE into
the Carolinas this morning, the northern portion of which should
cross central NC between 12-17Z (roughly from sunrise to noon). In
the wake of the departing MCS, expect a lull in precipitation during
the early/mid afternoon as a dry mid-level airmass /modified
elevated mixed layer/ advects northeast into central NC.
Chances for convection will increase from SW-NE by late afternoon as
small amplitude waves rounding the base of the upper low eject NE
from the Deep South into the Carolinas amidst diffluent flow aloft
and increasingly favorable thermodynamics as rich low-level moisture
advects poleward underneath a modified elevated mixed layer
characterized by H7-H5 lapse rates on the order of 7-8 C/km. A slow
moving warm front is expected to bi-sect central NC from SW-NE or
WSW-ENE (i.e. along or south of CLT-RDU-RWI) this afternoon. If
sufficient forcing is available to break the cap at the base of the
EML in the warm sector along/south of the front this afternoon, the
thermodynamic/kinematic env would favor supercells capable of
producing all severe weather hazards. Thus, a conditional potential
for severe weather will exist during the mid to late afternoon.
Temperatures may range from the low/mid 70s south of the warm front
to the mid/upper 50s north of the warm front.
A squall line is expected to develop in AL/GA this afternoon, along
a cold front assoc/w a rapidly deepening sfc cyclone tracking NE
from the Deep South into the western Carolinas, in advance of a
potent upper level low tracking ENE through the Deep South. The
aforementioned squall line is expected to propagate E/NE through
portions of the Carolinas this evening (00-06Z Mon). Thus, the
primary severe weather threat is expected to unfold this evening (00-
06Z Mon) as the aforementioned squall line propagates across the
Carolinas. While damaging straight line winds will be the primary
threat with the squall line, a few tornadoes will be possible in the
warm sector along the coast and in vicinity of the warm/occluded
front further inland over portions of central NC. Expect lows
tonight ranging from the upper 40s in the NW Piedmont to the lower
50s elsewhere. -Vincent
.SHORT TERM /MONDAY AND MONDAY NIGHT/...
As of 317 AM Sunday...
Models have trended slower and farther south with the deepening
upper low and attendant upper trough moving through the area Monday.
Cold core aloft featuring H5 temps of -22 to -24C and mid-level
lapse rates of 7 to 7.25 C/km will support instability showers in a
southwest to northeast fashion throughout the day with rain expected
to finally shift northeast of the area between 06 to 09z Tuesday.
Highs Monday ranging from mid 50s NW to lower 60s east.
Drier air filtering into the area with the departure of the system
should lead to SW to NE clearing late Monday night into Tuesday
morning. Lows Monday night in the lower 40s NW to mid 40s
.LONG TERM /TUESDAY THROUGH SATURDAY/...
As of 317 AM Sunday...
Tuesday through Thursday: The return of sunshine will be a welcomed
change during the mid-week period as shortwave ridging shifts over
the region Tuesday and Wednesday. Meanwhile, northward extension of
a surface high over the Deep South/GOM region will result in above
normal temps, peaking Wednesday afternoon with highs 65 to 70.
Shortwave energy moving through an amplifying long wave positively-
tilted trough setting over the central and eastern conus could lead
to scattered showers across the area late Wednesday night and
Thursday as the attendant cold front moves through the area.
Friday through the weekend: Below normal temperatures are expected
Friday and through the weekend with the development of a deep trough
east of the Rockies. Dry with no prospects for precip at this time.
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
As of 615 AM Sunday...
24-HR TAF Period: Conditions ranging from IFR to VLIFR were present
across central NC at 11Z this morning. The worst conditions were
located at the INT/GSO/RDU/RWI terminals across the Northern
Piedmont and NE Coastal Plain, north of a warm front extending SW-NE
across portions of the Sandhills and SE Coastal Plain. As the warm
front pushed north of the FAY terminal early this morning,
conditions improved to MVFR, however, ceilings have since
deteriorated to IFR. Expect conditions to remain relatively steady
state this morning. Ceilings are likely to remain in the IFR/LIFR
category at the INT/GSO/RDU/RWI terminals through this afternoon as
morning precip helps to reinforce an in-situ CAD wedge along and
north of the Hwy 64 corridor. The FAY terminal will be situated
south of the warm front and should see IFR/MVFR ceilings prevail
today. A Squall line is expected to develop upstream this afternoon,
then track E/NE across central NC terminals late this evening,
between 00-06Z. Isolated severe thunderstorms will be possible
during this time frame, particularly at the FAY terminal, though the
RDU/RWI terminals may also be affected. Some improvement will be
possible by the end of the TAF period (06-12Z Monday) as low-level
flow veers to the SW in the wake of the squall line.
Looking Ahead: Any improvement late tonight and early Monday will be
short-lived, however, with showers increasing in coverage and
IFR/MVFR ceilings returning after sunrise Monday morning as a potent
vertically stacked low rotates slowly eastward across the Carolinas.
Gusty NW winds will be possible on the back side of the system
Monday evening/night. Conditions are expected to improve /return to
VFR/ sometime late Monday night or early Tuesday as the
aforementioned system tracks offshore the Carolina/Mid-Atlantic