Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 081122
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
522 AM CST Fri Dec 8 2017

.UPDATE...
Issued at 520 AM CST Fri Dec 8 2017

Updated for 12Z aviation forecast discussion.

&&

.SHORT TERM...(Today through Sunday night)
Issued at 215 AM CST Fri Dec 8 2017

At 06Z, an elongated surface ridge axis stretched from west TX into
the Ohio River Valley. We will watch this ridge axis slowly slide
south during the day today as another frontal system moves southeast
toward the area. We should see plenty of sunshine today except for
southern parts of west KY where high clouds will likely persist in
association with the weather system in the south. Temperatures will
stay in the upper 30s for the most part...maybe around 40 degrees in
southeast MO.

Low level clouds will start invading the area after midnight and
overspread the area during the overnight hours. As far as snow
showers or flurries are concerned, best chances will be up in the
Wasbash Valley and southwest IN between 06-12Z Saturday. Ended up
spreading the chance for flurries across a part of southern IL as
well.

On Saturday morning, the best chances to see some snowflakes will be
in our eastern half as the cold front moves through (i.e. southern
IL, southwest IN and west KY from the lakes into the Pennyrile). But
given the depth of the low level moisture and very steep low level
lapse rates, wouldn`t be surprised to see flurries or even light
snow showers just about anywhere Saturday morning. Kept it flurries
for now across much of the area in order to keep the collaborative
picture in check. No appreciable accumulations are expected at this
time but we will continue to watch as some minor accumulations are
not out of the question. Strong cold air advection during the
morning will keep us from reaching too far into the 30s for highs
Saturday, with readings near 40 degrees possible in parts of
southeast Missouri. Winds will be rather gusty out of the northwest
as well.

The low level moisture will move out of the region and push eastward
Saturday afternoon and evening, leading to a decrease in cloudiness.
Therefore, temperatures will drop back into the upper teens to lower
20s with no problem. After surface high pressure briefly builds into
the area Saturday night into early Sunday, another dry cold front
pushes through Sunday afternoon and evening. However, the bigger
story will be the warm air advection that will be setting in early
on Sunday. 850 mb temperatures will rise above zero throughout
the day. So highs on Sunday will soar into the 40s with the
warmest readings in southeast MO. The continuing warm air
advection will allow low temperatures to not drop nearly as low
Sunday night and drop to a bit below freezing.

.LONG TERM...(Monday through Thursday)
Issued at 215 AM CST Fri Dec 8 2017

The medium range models were in reasonable agreement depicting a
persistent mid level pattern that is conducive to below average to
average temps and dry conditions. An amplified mid level trof will
linger over more than half the country (the eastern half) through
the extended period, while a mid level ridge mostly west of the
Rockies will be undercut by a low over Baja California and old
Mexico. Embedded within the eastern longwave trof will be periodic
low-amplitude shortwave impulses diving out of western Canada.

One impulse of note is progged to arrive in the PAH forecast area
Mon, complete with a surface cold frontal passage. At this time, it
appears deeper moisture and dynamics will be to our northeast,
leaving us by Tue with at least a ten degree drop in high temps
compared to Mon, some cloudiness and brisk northwesterly winds, and
wind chill readings not getting out of the 30s, except for parts of
southeastern MO. The Evansville tri-state area`s wind chill index
may not get out of the 20s Tue.

Temps should stabilize to near seasonable levels by midweek, though
the latest GFS/ECMWF MOS and the predicted continuation of fast
northwesterly flow aloft, suggest our currently forecast high temps
may be a few degrees too high later in the week. For now, we did
alter the initialization blend solution down a tad, to better match
offices to our east.

A similar, moisture-starved impulse is forecast to sweep through our
region Thu. Models suggest that it may be less aggressive, with less
cold air behind it than the front earlier in the week. At this time,
the forecast is pcpn-free through the current Day 7.

&&

.AVIATION...
Issued at 520 AM CST Fri Dec 8 2017

VFR conditions the rule with surface high pressure axis moving
through. Only cloud cover are some high clouds streaming north
from the frontal boundary down along the gulf coast states. Light
W/NW winds will become southwest around 5-7 knots by
midday/afternoon. Toward the end of the period, low level moisture
will begin invading the area but likely will not become BKN until
after 12Z.

&&

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

$$


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