Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 120856
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
256 AM CST Tue Dec 12 2017

.SHORT TERM...(Today through Thursday night)
Issued at 256 AM CST Tue Dec 12 2017

High amplitude pattern will persist through the short term. A
series of waves will move southeast within the NW flow across the
nation`s mid section. The temperature roller coaster will
continue. We generally used a NAM/GFS blend for the forecast. To
start, some very light/trace precipitation mainly in the form of
sprinkles was moving southeast across the east 1/2 of the CWFA.
This will quickly depart through daybreak and shortly afternoon.
Abundant cloud cover to start will be followed by some clearing.
It will be considerably cooler today as CAA continues upon
northwest low level flow. There will be a limited fire danger over
southeast Missouri. The risk will be a bit earlier in the day, as
winds are forecast to diminish some by afternoon when humidity
levels are at their lowest.

The surface flow will back tonight, ahead of a mid level wave and
low pressure ending up over the Upper Midwest by 12z Wednesday.
As the features move southeast, expect gusty southwest winds and
warmer temps Wednesday. It will remain dry. Next cold front will
move through Wednesday evening, with a colder day on tap for
Thursday. The next in the series of mid level waves will move from
over the northern Plains 12z Thursday, ending up over MO/KS by
06z Friday. The models depict more moisture associated with this
system. Would not rule out some light precipitation. However
confidence is low. Will keep it dry for now. But some small PoPs
may have to be introduced with time, for very light snow or
flurries.

.LONG TERM...(Friday through Monday)
Issued at 256 AM CST Tue Dec 12 2017

Confidence in the long term portion of the forecast is average to
below average with inconsistencies in some of the model data,
particularly with respect to the chance of precipitation over the
weekend.

At the start of the period, 00Z models indicate the passage of a
progressive upper level trough on Friday. Surface low pressure
should be positioned over northern Lake Michigan with a cold front
draped south from the low Friday morning. Models differ on whether
there will be enough moisture through the column to generate light
precipitation. The GFS suggests the potential for a few flurries
during the morning hours, the CMC holds the chance for sprinkles off
until afternoon, while the ECMWF keeps conditions mainly dry. Am
inclined to keep the forecast dry for now until models become better
aligned.

While cooler than normal temperatures are expected on Friday, a
warming trend appears likely over the weekend as a weak upper level
ridge develops over the eastern U.S. while low level winds become
southerly. Low pressure is forecast to develop over the southern
Plains Saturday into Saturday night as progressive southern stream
energy crosses the Rockies. The approach of this low and its frontal
system should lead to our next chance of rain beginning late
Saturday night and continuing through Sunday into Sunday evening.
The 00Z ECMWF closes off the upper low over the Ozarks by Monday,
which would keep the chance of rain around longer. However, the
consensus of available guidance is more progressive with the system,
which suggests an end to the precipitation sometime Sunday night.

With less amplification to the upper level flow pattern compared to
the last several days, temperatures late in the period are forecast
to be relatively mild. Consensus guidance has highs in the upper 40s
to mid 50s Sunday and Monday with lows generally in the 30s.

&&

.AVIATION...
Issued at 338 PM CST Mon Dec 11 2017

A quick look at frontal position at 21Z shows it is on
track/poised to make passage across the terminals during the next
3 to 6 hours. We`ll see VFR conditions deteriorate shortly after
passage, with MVFR bases appearing, possibly going with CIGS for a
short duration as winds shift to gusty northwest. The chance of
pcpn reaching the ground is minimal, with very dry air above and
below the roughly 2-3K FT cloud thickness. While winds
continue/gusty northwest tmrw, skies should abruptly clear by late
morning/into the planning period.

&&

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

$$



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