Severe Thunderstorm Warning 239, NWS Paducah, KY

Area Forecast Discussion
National Weather Service Paducah KY
314 PM CDT Fri Jun 30 2023

.SHORT TERM...(Tonight through Sunday night)
Issued at 313 PM CDT Fri Jun 30 2023

The heat finally arrived with a vengeance today. Heat indices as
of 19z were 110 to 120 at the asos and awos sites in the Excessive
Heat Warning area, with 102 to 114 in the advisory area.

The heat and humidity have combined to bring extreme instability
across our region. SPC mesoanalysis as of 19z showed mixed-layer
capes were around 5000 joules across the region. An outflow
boundary from a convective complex earlier today is moving south
to the Interstate 64 corridor. This boundary is marked by a broad
area of towering cumulus clouds, from kfam (Farmington, MO) east
across southern Illinois. A mesoscale discussion from the SPC has
detailed the severe weather potential. Although wind fields aloft
are relatively weak, the tremendous buoyancy and water-loading in
the storms will result in high potential for microbursts and
hail. Very high rainfall rates will accompany the storms, but they
should keep moving at 20 knots or so.

The storms may be slow to diminish tonight. Outflow boundaries
in this very moist and unstable air mass will tend to remain
active well into the evening. Some of the cam models suggest that
residual showers and convective cloudiness will last into Saturday
morning, possibly impacting thunderstorm timing on Saturday.

Whatever the case with early morning clouds and lingering
convection, there is a strong likelihood that heating will be
sufficient Saturday for another round of storms. Wind fields will
be stronger Saturday as a 500 mb shortwave slowly ejects east
across the Plains. A mainly westerly uni-directional shear profile
could support a linear mcs in the afternoon. The SPC enhanced risk
discussion details this scenario. Pops will be in the likely
category Saturday afternoon and evening, with mention of damaging
winds in the afternoon.

The timing of the storms may be slow enough that heat indices
reach 105 degrees in the midday hours. A Heat Advisory may be
needed if the storm timing remains mid to late afternoon.

Saturday night will gradually quiet down as instability decreases
from nocturnal cooling and stabilization behind the storms.
However, storms will likely refire again Sunday as the 500 mb
shortwave trough crosses the mid Mississippi Valley. The storms
will develop further east, potentially bringing some severe
potential to areas mainly east of the Mississippi River Sunday
afternoon. Instability is forecast to be somewhat lower as
previous thunderstorm complexes will have overturned the
atmosphere. Heat indices will be in the 90s ahead of the storms.

Sunday night will quiet down as the shortwave trough passes to our
east and slightly cooler and drier air arrives.

.LONG TERM...(Monday through Friday)
Issued at 313 PM CDT Fri Jun 30 2023

A general lull in our daily thunderstorm chances will occur
Monday in the wake of the 500 mb shortwave. A few isolated storms
are possible in the lingering heat and humidity.

A weak westerly flow aloft Tuesday through Wednesday may contain a
few 500 mb impulses that generate isolated to scattered
convection. The convection would be mainly diurnal. Highs will be
in the lower 90s with continued high humidity.

A potentially more active convective period could occur Thursday
or Friday. The ecmwf ensemble means still deepen a 500 mb trough
as it moves east into the Great Lakes region. The trailing end of
this trough would be more than sufficient to trigger convection
across our area, given the heat and humidity.

&&

.AVIATION...
Issued at 313 PM CDT Fri Jun 30 2023

A surface boundary across southern IL at 20z was already
generating considerable amounts of cumulus clouds. This will
likely be where the first thunderstorms initiate this afternoon.
Elsewhere, random development of thunderstorms could occur after
21z. The tafs contain vcts for now, and this would be changed to
a tempo or prevailing group if and when the threat increases. Any
storms will contain gusty winds and torrential rain, reducing vsby
sharply.

Storms may linger well into the evening, but at this time there is
not enough potential to continue them in the tafs past 01z. Skies
should again clear out once the storms end.

On Saturday, vfr conditions will begin the day. Thunderstorms are
likely later in the day, mainly after the taf period ends at 18z.

&&

.PAH WATCHES/WARNINGS/ADVISORIES...
IL...Heat Advisory until 8 PM CDT this evening for ILZ075>078-080>083-
     086-087-090-091.

     Excessive Heat Warning until 8 PM CDT this evening for ILZ084-
     085-088-089-092>094.

MO...Excessive Heat Warning until 8 PM CDT this evening for MOZ076-
     086-087-100-107>112-114.

IN...Heat Advisory until 8 PM CDT /9 PM EDT/ this evening for INZ081-
     082-085>088.

KY...Heat Advisory until 8 PM CDT this evening for KYZ007-010>022.

     Excessive Heat Warning until 8 PM CDT this evening for
     KYZ001>006-008-009.

&&

SHORT TERM...MY
LONG TERM...MY
AVIATION...MY

Hazardous Weather Outlook
National Weather Service Paducah KY
426 PM CDT Fri Jun 30 2023

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-012130-
Jefferson-Wayne IL-Edwards-Wabash-Perry IL-Franklin-Hamilton-
White-Jackson-Williamson-Saline-Gallatin-Union-Johnson-Pope-
Hardin-Alexander-Pulaski-Massac-Gibson-Pike-Posey-Vanderburgh-
Warrick-Spencer-Fulton-Hickman-Carlisle-Ballard-McCracken-Graves-
Livingston-Marshall-Calloway-Crittenden-Lyon-Trigg-Caldwell-
Union KY-Webster-Hopkins-Christian-Henderson-Daviess-McLean-
Muhlenberg-Todd-Perry MO-Bollinger-Cape Girardeau-Wayne MO-Carter-
Ripley-Butler-Stoddard-Scott-Mississippi-New Madrid-
426 PM CDT Fri Jun 30 2023 /526 PM EDT Fri Jun 30 2023/

This Hazardous Weather Outlook is for portions of southern
Illinois, southwest Indiana, western Kentucky, and southeast
Missouri.

.DAY ONE...Tonight

Scattered thunderstorms will continue through this evening.
Isolated large hail and damaging winds are likely with the
strongest storms. A Severe Thunderstorm Watch is in effect for
much of the region this evening. The storms will also produce
torrential rainfall capable of isolated flash flooding.

Dangerously high heat indices will continue through sunset or
until thunderstorms occur. An Excessive Heat Warning covers
southeast Missouri, southwest Illinois, and far west Kentucky this
evening. A Heat Advisory remains in effect this evening for
southwest Indiana, southeast Illinois, and the Pennyrile region of
west Kentucky.

.DAYS TWO THROUGH SEVEN...Saturday through Thursday

Thunderstorm chances will increase on Saturday. There is the
potential for scattered to numerous damaging wind events during
the afternoon and evening. Isolated large hail and isolated flash
flooding is also possible.

Heat indices on Saturday could exceed 100 degrees before
storms arrive.

Another round of thunderstorms is likely on Sunday, especially in
the afternoon. Isolated severe storms with damaging winds are
possible.

There is a daily chance of thunderstorms Monday through Thursday.
The activity is expected to be isolated Monday through Wednesday
before becoming more numerous Thursday.

.SPOTTER INFORMATION STATEMENT...

Spotter activation has been requested in the Severe Thunderstorm
Watch area this evening. Spotter activation may be requested
Saturday and Sunday.

MY

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