Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 220308
AFDPAH

Area Forecast Discussion
National Weather Service Paducah KY
908 PM CST Sun Jan 21 2018

.UPDATE...
Issued at 908 PM CST Sun Jan 21 2018

Still monitoring severe weather potential after midnight over our
far western counties in southeast Missouri. The 00Z NAM sounding
from around Van Buren, MO shows a stable layer near the surface
just above 900mb at 09Z as the column becomes saturated. This
effectively wastes much of the immense shear. The low-level jet
will be near 70kts, so it would not be far-fetched for some of
that momentum to come to ground within a precipitation core.

Farther east toward the Mississippi River, the stable layer
deepens and the LLJ is weaker. In addition, the mid and upper-
level winds back with time as the system moves eastward, further
decreasing the severe weather potential with eastward extent
overnight.

We will continue to monitor the convective line as it approaches
the area just after midnight, but the prospects for any organized
severe weather are low and appear to be limited to Carter and
Ripley counties in Missouri as depicted by SPC`s final Day 1
Outlook.

&&

.SHORT TERM...(Tonight through Monday)
Issued at 302 PM CST Sun Jan 21 2018

Upper low will move from the central Plains this evening, to over
western IL by Monday evening. Mostly quiet conditions can be
expected through the early p.m. hours, with shower and isolated
storm chances entering SEMO toward the midnight hour. Until then,
from SEMO, into SW IL, just a slight chance of showers.
Essentially dry weather this evening west KY, as drier air works
north. Even notable clearing late today moving up from west TN. We
do expect some clouds to move back in through the evening. From
midnight on through Monday morning, showers and a few storms will
progress east reaching southern IL and west KY by 12z. Through the
morning the band of convection will continue east across SW IN
and the rest of west KY. Limited TSRA chance across the west 2/3
of the CWFA. It`s basically outta here by 18z. First, ground
conditions some areas are super saturated, especially west KY into
parts of southern IL. It will not take much rain at all to
possibly create some standing water issues. Having said that, our
latest QPF forecast is not as high. The models have backed down.
We think any problems would be isolated.

Not too concerned with the marginal SPC risk over our west 4
counties in SEMO. Mainly elevated instability forecast. Will
monitor for gusty wind potential. The low level jet is quite
impressive into SEMO by 06-09z, 50 to 65+ kts at 850mb. But low
level lapse rates are not impressive at all. So we may not realize
the potential. Monday afternoon will be rather breezy in the dry
slot, with some decrease in clouds, and mild temperatures,
especially from SEMO into west KY. We used a model blend overall,
incorporating GFS and NAM 1 hr data with some HRRR guidance timing
the PoPs overnight. Temperatures will not go down much overnight.

.LONG TERM...(Monday night through Sunday)
Issued at 302 PM CST Sun Jan 21 2018

The upper low will reach the Great Lakes region by 12z Tuesday,
and head on east and away from the area. Will monitor the I-64
corridor Monday night for a small rain chance. Then high pressure
builds in, and keeps our weather dry from Tuesday through Thursday
night. It will be a little cooler once again Tuesday and
Wednesday due to the influence of surface high pressure. Then it
will turn milder Thursday through Saturday ahead of the next
system forecast to affect the area as it moves in from the west.
That system is forecast to be an evolving mid level trof that will
end up over the central U.S. by 12z Saturday. Return southerly
flow will develop ahead of it from Thursday on. Rain shower
chances are expected to increase late Friday into Friday night,
peak Saturday, then diminish from west to east Saturday night.
There is somewhat limited confidence with respect to timing. More
solutions than not were showing slower solutions, and suggesting
the precip could last longer into the weekend. However the 12z GFS
is radically faster. The 12z ECMWF is a tad quicker than several
previous runs. All of this includes taking into account ensemble
mean solutions from both models. We are somewhere in the middle
of these timing differences for now. There is a chance that the
precip could end with a rain/snow mix. That`s way out there in
time, so just something we noticed for now.

&&

.AVIATION...
Issued at 302 PM CST Sun Jan 21 2018

Difficult aviation forecast as some areas are still experiencing
IFR cigs, while conditions have significantly improved into west
KY as drier air works north. We do expect improving cig conditions
through this evening. Not sure how far north and west the
improvements will carry. Best chances of showers, and possibly
thunder will be after 06z, continuing from west to east through
tomorrow morning, and ending from west to east. Gusty SSW winds
will persist tonight. Some gusts 20 to 30 kts possible mainly
after 06z. MVFR/IFR vsbys possible with the main band of showers
and embedded storms later tonight into early tomorrow morning.


&&

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

$$

UPDATE...DRS



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