Area Forecast Discussion
Issued by NWS Paducah, KY

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FXUS63 KPAH 251742

Area Forecast Discussion
National Weather Service Paducah KY
1242 PM CDT Tue Apr 25 2017

Issued at 1242 PM CDT Tue Apr 25 2017

The AVIATION section has been updated for the 18Z TAF issuance.


.SHORT TERM...(Today through Thursday night)
Issued at 320 AM CDT Tue Apr 25 2017

Main near term forecast concern is the potential for thunderstorms,
some possibly strong to severe, late Wednesday afternoon and
Wednesday night. Forecast confidence is relatively high through
Thursday night with generally good overall model agreement.

Dry and unseasonably warm weather will continue today as southerly
flow picks up between high pressure departing to the east and low
pressure developing over the Great Plains. With abundant sunshine
and southerly winds, temperatures should have no trouble reaching
the 80 degree mark across much of the area this afternoon. South
winds over the western 2/3 of the area will be quite strong by
late morning and afternoon--sustained around 15 mph with occasional
gusts of 25 to 30 mph.

Shortwave energy currently entering the Pacific Northwest is
forecast to drop southeast into the southern Plains by Wednesday
before taking on a negative tilt and pivoting northeast across the
Mid and Upper Mississippi Valley Wednesday night. The approach and
passage of this trough and its associated cold frontal boundary
will provide the focus for shower and thunderstorm development
Wednesday and Wednesday night. With forecast model soundings
indicating the presence of a strong mid level capping inversion
through much of the daytime hours Wednesday, any convective
development during the day would likely be elevated and related to
low level convergence across southeast Missouri and far southwest
Illinois. The main event will be focused from late Wednesday
afternoon into Wednesday night as the cold front makes passage.

With dew points in the lower 60s, decent instability and 0-6km
bulk shear of 50 to 60 knots, strong to severe thunderstorms
remain possible, especially across the western half of the area
where the better instability is forecast. The storms may have
trouble maintaining their strength as instability begins to wane
by late evening and after midnight Wednesday night. While some
discrete cells are possible early on over southeast Missouri,
deep-layered shear vectors oriented nearly parallel to the line of
forcing suggests the activity should quickly become linear early
in the evening. Damaging winds appear to be the primary concern,
while large hail and an isolated tornado cannot be ruled out with
any discrete cells early on--especially west of the Mississippi

Any lingering showers should taper off early Thursday morning as the
storm system departs to the east. Much of Thursday should actually
be dry, albeit cooler in the wake of the front. After highs in the
mid 70s to lower 80s on Wednesday, highs on Thursday are forecast in
the mid to upper 60s. The next chance of showers should hold off
until late Thursday night at the earliest as the front begins to
return north as a warm front.

.LONG TERM...(Friday through Monday)
Issued at 320 AM CDT Tue Apr 25 2017

Well, much of the extended looks to be summed up as very wet and
unsettled as deep swly flow becomes established to the west of a mid
level blocking high pressure system off the Southeast U.S. coast. A
surface front will likely become stationary somewhere close to the
Ohio River early in the period, parallel to the mid level flow. The
front will likely be a focus for the highest shower/thunderstorm
chances Friday/Friday night.

The front is then expected to lift back to the north as a warm front
over the weekend as a surface low lifts northeast from the southern
Plains. This will probably offer the highest chances for strong to
severe thunderstorms as a cold front is eventually drug east across
the region sometime on Sunday. In the meantime, the potential exists
for several rounds of thunderstorms with heavy rainfall Friday into
Saturday as PW values soar to very high levels for this time of
year, possibly 1.75 to 2" over about the western third of the
forecast area. Multiple short waves may eject northeast out of the
base of the deep H50 trof. The timing of any impulses will be
difficult at best, so will not get too specific in that regard.
Right now, it appears the highest rainfall totals may be focused
over southeast MO into southwest IL, but again, this could be
subject to change with time. Some places across the region may be
subject to several inches of rainfall by the time all is said and
done Sunday night. Regarding the severe storm potential, SPC has
already included a good portion of the forecast area in a 15% risk
for Sunday.

The region should finally get a break by early next week as high
pressure build in behind the frontal passage. Temperatures will
likely stay on the mild side as the high actually builds in from the
Southern Plains states.


Issued at 1242 PM CDT Tue Apr 25 2017

A nice cu field has developed over KEVV and KOWB, but any brief
ceilings should be comfortably into VFR territory. Otherwise,
south winds will increase across the region this afternoon, with
some gusts possible over southeast Missouri and southern Illinois.
As gusts subside this evening and winds aloft increase, LLWS will
be a concern overnight at KPAH and KCGI. Finally low-level cloud
cover will increase from the southwest toward daybreak and into
Wednesday morning. Brought MVFR ceilings into KCGI and KPAH, but
held them above 3kft farther east. IFR ceilings are not out of the
question in the west.




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