Area Forecast Discussion
Issued by NWS Paducah, KY

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000
FXUS63 KPAH 301725
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
1225 PM CDT Thu Mar 30 2017

.UPDATE...
Issued at 1225 PM CDT Thu Mar 30 2017

The AVIATION section has been updated for the 18Z TAF issuance.

&&

.MESOSCALE DISCUSSION...
Issued at 1047 AM CDT Thu Mar 30 2017

From the standpoint of the timing of the main zone of convective
activity, the current gridded forecast still appears on track. Not
planning on any substantial changes through the noon hour.
Radar and Satellite trends appear to be in line with the 12z
Thursday 12km NAM-WRF and the 06z Thursday ESRL HRRR guidance.

Downward mixing and transport of winds within breaks of the
cloud over Southeast Missouri and southern Illinois is generating
surface wind gusts between 25 to 35 mph at times, which is in line
with the frictional reduction from the low level South-
Southwesterly 45 knot winds up through 6000 feet AGL. Anticipate
through at least noon this will be the primary range of wind
speeds until storm development and organization comes into play
this afternoon.

Wind Profiles from the KPAH WSR-88d showing relatively
unidirectional flow of 40-45 knot evident through 15z, with some
evidence of some evidence of slight veering/shearing in the
2-6kft, with 50-55kt slightly backed winds from 6-12kft.

Given the mixing out of the low level cloud deck, could see more
organized storm development moving into the WFO PAH forecast area
later this morning. The KPAH radar already showing weak linear
convective activity in place west of Ripley/Carter counties in
Southeast Missouri at 1530z.

The 12km NAM-WRF 0-2km AGL Lapse rates continue to remain in the
6C-8C/km range as you approach the Mississippi River by 18z today,
then advecting into Southwest Illinois and the Kentucky Pennyrile
by 21z. Given the entrainment of dry air and overturning of
parcels, along with the increase of SFC downdraft CAPE in the
NAM- WRF, am concerned that any thunderstorm downdrafts will be
enhanced in Southwest Illinois (going into Southeast IL) and near
the Land Between the Lakes counties in West Kentucky between
19z-20z (2-3 pm CDT). The NAM-WRF/RAP/HRRR/CMCnh also suggest a
descending 50kt wind max into the 6-7kft layer. If storms can tap
into and tranport these winds to the surface, could see more
widespread 40 mph winds, with isolated to scattered severe gusts
as the storms move into Southeast Illinois, Southwest Indiana, and
the Pennyrile region of West Kentucky between this afternoon,
mainly between 18z-23z (1 pm to 6 pm CDT).

A couple of complicating factors is that the rich surface plume of
moisture has been intercepted by the convective activity in
Louisiana overnight, so most of the rich moisture will be focused
east of the Mississippi River this afternoon. Therfore, the best
potential of enhancing uprdrafts with surface based moisture and
lift should remain over West Kentucky, parts of Southern Illinois,
and Southwest Indiana this afternoon. If we can achieve the
moisture potential, hail may become a greater concern, but it
still appears that strong to damaging winds would be the primary
hazard.

Any marginal to severe threat should exit the WFO PAH forecast
area by 6pm CDT.

&&


.SHORT TERM...(Today through Saturday night)
Issued at 327 AM CDT Thu Mar 30 2017

Upper low over the central Plains will move east and end up over
southern IL by 06z tonight, while surface low pressure tracks from
central Kansas to northern Indiana. High chance for convection
continues today. Severe weather potential still in play. Refer to
the SPC day 1 outlook for details.

The chance of convection will diminish tonight through Friday,
with dry weather Friday night through Saturday. After midnight
Saturday night, our next chance of convection enters into
southeast MO late. The rest of the area should be dry. Temps were
a blend of MOS and existing numbers. A NAM/GFS/HRRR blend was the
overall model preference.

.LONG TERM...(Sunday through Wednesday)
Issued at 327 AM CDT Thu Mar 30 2017

Forecast confidence in the extended remains average to below average
with continued variability among the forecast models.

Upper level energy currently entering the Pacific Northwest is
forecast to generate yet another closed low over the Southwest by
Friday. This low is forecast to track east across the Plains into
the Mississippi Valley early next week. Models continue to differ on
their handling of this low, but with the latest 00Z run, all are in
general agreement in taking it south of the immediate forecast area
or across our far southern reaches. The end result is the continued
potential for showers Sunday through Monday night, with chances
peaking Sunday night into Monday. Will keep a mention of thunder
Monday and Monday night with at least some elevated instability in
close proximity to the low.

A brief period of dry weather should return to the area on Tuesday
as a mid level ridge builds in. Our next chance of showers and
thunderstorms arrives mid week as yet another low pressure system
approaches from the Plains. Thunderstorm potential appears to be
somewhat higher with this system with the low`s track north of the
region and better mixed layer instability.

Forecast temperatures reflect a consensus model blend. Highs through
the period are forecast in the upper 60s to lower 70s. Lows should
average in the 50s.

&&

.AVIATION...
Issued at 1225 PM CDT Thu Mar 30 2017

A band of scattered thunderstorms will progress east northeast
through the area, potentially impacting all TAF sites by 00Z. As
the upper low moves over the region tonight, some lighter showers
will be possible, but they should have little impact. A large area
of MVFR ceilings should overspread the area late tonight into
Friday morning.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...None.
MO...None.
IN...None.
KY...None.
&&

$$

UPDATE...DRS
AVIATION...DRS


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