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556
FXUS63 KPAH 231135
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
635 AM CDT Mon Oct 23 2017

.UPDATE...
Issued at 635 AM CDT Mon Oct 23 2017

Updated for 12Z aviation forecast discussion.

&&

.SHORT TERM...(Today through Wednesday night)
Issued at 251 AM CDT Mon Oct 23 2017

Early this morning, an elongated surface low pressure was
situated over the Evansville Tri State region down into central
TN/AL. An upper level low pressure system was located over
southern MO/northern AR. This upper level low will shift slowly
eastward with time this morning. By 12Z Monday, the bulk of the
precipitation should be situated across our far eastern counties
and along the I-64 corridor, as the upper low sits over the
Mississippi River. Scattered showers will likely be present
elsewhere though. Between 12Z-18Z, the upper low pivots eastward
and acquires a bit of a negative tilt. As this occurs, the more
concentrated area of rain should move out of the CWA. However, we
will still be dealing with scattered showers during the morning
across a good portion of the area. We will definitely be seeing
most of southeast MO drying out between 12Z-18Z.

We will see a rapid departure of any remaining precipitation during
the afternoon today, as the upper system finally lifts out of the
region. Meanwhile, another upper trough will be diving south out
of the north central Plains states during the day today and reach
the Midwest by tonight. This upper trough will start impacting our
region tonight and bring a reinforcing cold front through the
area. Might see a few showers across parts of southern
IL/southwest IN and the Pennyrile region of west KY with the
passage of this front. This will mark a substantial change in air
mass for our area, as 850mb temperatures actually fall below zero
area wide by Tuesday morning. The heart of the upper level trough
will traverse the area on Tuesday and this will bring the brunt of
the colder air, along with some clouds and possible showers,
especially north. Highs will only be in the 50s on Tuesday. It
will be rather breezy behind that cold front and the gradient
stays tight during the day on Tuesday, so gusty conditions will be
forecast.

The upper level trough will shift eastward Tuesday night into
Wednesday. Not sure how much frost we will be able to develop
Tuesday night with the winds staying up, but temperatures will drop
into the 35-37 degree range. Best chance may be in western areas
where it will have a better chance to clear out.

With more sunshine and an increase in low level temperatures, we
will see high temperatures rise a few degrees by Wednesday.

.LONG TERM...(Thursday through Sunday)
Issued at 251 AM CDT Mon Oct 23 2017

High confidence in a cold front moving through Thursday night into
Friday morning. Low confidence in precip chances with the fropa.

The models have come into much better agreement on the synoptic
scale features late this week. However there is considerable
differences in when and where precipitation actually occurs.

A deep 500 mb longwave trough will stay over eastern North America
through the long term period. This will result in very cool
northwest flow most of the time. A strong cold front will bring a
chance of showers late in the workweek. The ECMWF has the rainfall
post frontal or Friday while the GFS keeps it a dry frontal passage.
Thus the blend has backed off pops considerably...obviously due to
this discontinuity. The ensembles GEFS etc are still placing precip
over the area but have cut back on amounts considerably. The blend
does reflect this trend so went with it. Also agree with previous
discussion that pops will likely be reduced in longevity as well.
Also will probably looking at a frost/freeze this weekend. MOS has
been trending that direction. Looking at a probable sct frost Friday
night with a freeze likely Saturday night and possibly a scattered
frost again Sunday night. Plan to monitor closely as we head through
the week.

&&

.AVIATION...
Issued at 635 AM CDT Mon Oct 23 2017

Main band of rain now just impacting KEVV/KOWB with scattered
showers or drizzle elsewhere. Cigs are mainly MVFR but pockets of
IFR or even LIFR do exist but are hard to pindown. Improving
conditions are in the offing however, with VFR cigs and an end to
the rain chances at KCGI within the next several hours, KPAH by
early afternoon and the eastern sites by late afternoon. Rain
chances appear to be mainly scattered and may not even be heavy
enough at times to restrict vsbys but any developing drizzle will
likely do so. Winds are variable near the sfc low at KEVV.
Otherwise a westerly component to the wind will be commonplace
with an occasional gust.

&&

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

$$