Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 122320
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
620 PM CDT Tue Sep 12 2017

.UPDATE...
Issued at 620 PM CDT Tue Sep 12 2017

Updated for 00Z aviation forecast discussion.

&&

.SHORT TERM...(Tonight through Thursday night)
Issued at 205 PM CDT Tue Sep 12 2017

The center of the remnant low of Irma was located over the
northwest corner of Alabama at 18z. Slightly drier air wrapped
westward into our region today, allowing for a few peeks of
sunshine in western KY. Northeast winds were generally around 10
kt at the surface, with a few gusts around 20 kt.

As the low pressure center pushes northward, periods of rain will
develop once again. The short-range models such as the
nam/ruc/hrrr indicate rain will move back into western Kentucky
late this afternoon, then overspread the lower Ohio Valley and se
Missouri this evening. The rain could be rather persistent under
the deformation zone on the northwest side of the mid-level
closed low. Another area of rain is forecast to move north into
western Kentucky late tonight, closely tied to the low-level
circulation center. Pops will be in the categorical range in parts
of west Kentucky, tapering to 50 percent in the kmvn/kmdh areas
of srn Illinois. Winds will continue to decrease, allowing for fog
and stratus to develop overnight. See aviation section for
details.

On Wednesday, the weak remnant low pressure center will drift
northeast across west KY and southern IL. Light rain and drizzle
will be fairly widespread in the morning, then a decreasing trend
should occur in the afternoon as the low moves into the Wabash
Valley. Pockets of moderate rain are possible. For tonight through
Wednesday, most qpf guidance is in the one-quarter to one-half
inch range in west Kentucky, and a little less to the west. Under
the thickest cloudcover and most persistent rain, highs will be
only in the mid 60s. Lower 70s are forecast across se Missouri,
where some afternoon peeks of sun are possible.

Wednesday night and Thursday, drier air will filter in from the
west and southwest as the low moves away. Any additional rainfall
will be very light, confined mainly to sw Indiana and the
Pennyrile region of west KY. Due to lingering moist ground, light
winds, and 60-degree dew points, there could be some concerns with
early morning fog where skies clear out Wed night. Increasing sun
is expected Thursday, with light southwest winds. Highs should be
mainly in the lower 80s.

.LONG TERM...(Friday through Tuesday)
Issued at 322 PM CDT Tue Sep 12 2017

Through the weekend, as a large trof digs into the the southwestern
CONUS, the PAH forecast area will be under weak anti-cyclonic flow
aloft and general southerly low level flow (after it recovers from
the presence of tropical remnants). The medium range models appear
to agree that this will result in warm, dry, mostly clear
conditions, with an increase in cloud cover toward the end of the
weekend. Overall model agreement is quite good through Day 7.

There has been some uncertainty about whether a surface cold front
would make it into our region by the end of the weekend, driven by
the ejecting western trof as it traverses the upper Midwest. The
models now are showing a fairly strong signal for possible pcpn
associated with the front, with some timing differences, despite the
continued presence of weak ridging aloft. The front should slow and
become diffuse by Mon night, diminishing whatever available focus
for lift that there was. Thus, PoPs (for showers and some tstms)
will go from 20-30 percent Sun night/Mon to almost nil for Mon
night/Tue in the forecast. This will be subject to some change in
future forecasts.

&&

.AVIATION...
Issued at 620 PM CDT Tue Sep 12 2017

Periods of rain and/or drizzle will continue through this taf
period as the low pressure center slowly lifts northward from
Alabama to western Kentucky. There should be a gradual decrease in
cigs and vsbys tonight as winds become lighter. The combination
of light winds and very moist air will result in widespread ifr
conditions by morning, with local lifr conditions. Conditions will
be slow to improve on Wed morning, and many places could remain
ifr through the morning.

&&

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

$$



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