Damaging Winds in Illinois, August 18, 2019

Area Forecast Discussion
National Weather Service Paducah KY
200 PM CDT Sun Aug 18 2019

.SHORT TERM...(Tonight through Tuesday night)
Issued at 200 PM CDT Sun Aug 18 2019

Several outflow boundaries seen on satellite today, along with a
weak front that was poised to our northwest. A weak upper level
disturbance will continue to move east into the area this afternoon
and allow for continued scattered convection. Exactly how widespread
and how far east to take PoPs is the main question right now.

Looking at the latest data, it appears the northern half of the area
has the best chances to see more widespread coverage the rest of
this afternoon through about mid evening. Deep moisture is
definitely lacking over western KY and this is evident in the upper
60s dewpoints, so chances there appear low at this time. SPC's day
one outlook confirms this. However, depending on how organized the
storms become, we could see activity cross over into west KY if the
thunderstorm outflows become strong enough. There is slight better
shear parameters up in the northern sections of the area, therefore
storm organization will be increased in S. IL/SW IN and parts of
SEMO, which is likely why the upgrade to slight risk was made to a
small part of the area and an expansion of the marginal risk, with
the late morning SPC day 1 update. In fact, a severe thunderstorm
watch for parts of SEMO/S. IL goes until 700pm, so a few strong to
possibly severe storms are likely. Will analyze latest
satellite/radar trends and make last minute decisions on how to
handle PoPs for the rest of this afternoon.

How much and exactly where convection will linger into this evening
will be most likely driven by outflow boundaries from this
afternoon's storms, as the upper level disturbance will be moving
off to the east by late evening. Will linger chances until about 03Z
and then taper off PoPs for the rest of the night. The fly in the
ointment will be the fact that various guidance is indicating the
possibility of additional activity in the unsettled northwest flow
aloft later tonight into Monday morning. This isolated to scattered
activity will be with us throughout the day on Monday as we continue
to deal with minor perturbations in the northwest flow aloft.
Meanwhile, the front that was mentioned earlier, will continue to
slowly sink southward and by Monday night, could be laying across
our northern counties. Coverage of any shower or thunderstorm
activity on Tuesday appears to be rather low, but chances will be
increasing late Tuesday night and especially as we head into
midweek, as another front sags south toward the area.

The heat will continue on Monday as a strong ridge of high pressure
develops in the south central Plains and noses into our area.
Expecting lower 90s for highs on Monday and Tuesday, with some mid
90s possible especially out west on Tuesday. These types of
temperatures combined with 70 to 75 degree dew points will likely
lead to 100 to 105 degree heat indices which for most us has been
the status quo lately. If we see indications that we will reach much
higher than that, an advisory will be needed.

.LONG TERM...(Wednesday through Sunday)
Issued at 200 PM CDT Sun Aug 18 2019

The models are really changing alot with how they handle the mid
week front and its entrance/passage. The ensemble/blend is now
hanging it up over the area, offering pretty good chances thru
Thursday, and then washing it out and while it does cool and dry a
little off the peaks, it is not really offering the plunge of
drier/cooler air to the degree that just one day ago, it was
suggesting. As a result, have some skepticism with the blend, esp
considering the 12Z GFS now oscillates back a little more toward
yesterday's output.

Nevertheless, am not comfortable with the outlier changes, so will
stick with the middle ground active/pops scenario thru Wed/Thu.,
then hope to fine tune it over the next 24-48 hours. That means
triple digit heat indices are possible Wed., with peak pops Wed-
Thu., waning to smaller mainly diurnal chance mentionable pops
finishing out the forecast. Highs in the 90s Wed will curb back to
the 80s thereafter, but dew points will remain in the upper 60s to
lower 70s as their fall off, with Lows mirroring that, except in the
north, where the drier/cooler air has a little better chance of
reaching down.

&&

.AVIATION...
Issued at 200 PM CDT Sun Aug 18 2019

Shower and thunderstorms will continue to develop to the
northwest of the terminals and move southeast this afternoon. KMVN
has the best chances of seeing more widespread convection so
added a tempo. Otherwise, KCGI/KEVV will have the next best
chance, so opted for a VCTS there, but will be watching closely
how the storms evolve, in case amendments are needed. Lesser
chances of activity farther east at KPAH and KOWB, but it will
depend on how much activity does develop and how strong the
outflow boundaries become. South to southwest winds have picked up
already and will be gusty from time to time. Expect any
convection to be waning by around 02Z, with only isolated chances
through the rest of the 24 hr period along with light winds. Fog
later tonight/Monday morning may be a concern in areas that do
receive rain later on today.

&&

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

SHORT TERM...CW
LONG TERM...DH
AVIATION...CW

Hazardous Weather Outlook
National Weather Service Paducah KY
115 PM CDT Sun Aug 18 2019

ILZ075>078-080>094-INZ081-082-085>088-KYZ001>022-MOZ076-086-087-
100-107>112-114-191000-
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-
115 PM CDT Sun Aug 18 2019

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

.DAY ONE...This Afternoon and Tonight

Thunderstorms will be likely this afternoon, mainly in portions
of southeast Missouri, southern Illinois and possibly southwest
IN. A severe thunderstorm watch has been issued for parts of
southeast MO and southern IL until 700pm. Strong to severe storm
are possible, with damaging winds and hail the main concerns.
Other storm related hazards include frequent lightning and locally
heavy downpours.

Highest heat index readings of 100 to 105 are also forecast this
afternoon.

.DAYS TWO THROUGH SEVEN...Monday through Saturday

Storm chances will occur almost daily, especially during the heat of
the day. The best chance for storms, including stronger storms,
will be Wednesday through Thursday, as a cold front makes its way
across the region. Primary storm hazards will be lightning, heavy
rain, and gusty winds.

Peak heat index readings of 100 to around 105 are forecast both
Monday and Tuesday afternoons.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will be needed in parts of southeast MO and
southern IL this afternoon.

Special Weather Statement
National Weather Service Paducah KY
139 PM CDT Sun Aug 18 2019

ILZ075-076-181930-
Jefferson IL-Wayne IL-
139 PM CDT Sun Aug 18 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTHWESTERN WAYNE AND JEFFERSON
COUNTIES UNTIL 230 PM CDT...

At 139 PM CDT, Doppler radar was tracking a strong thunderstorm 8
miles northeast of Mount Vernon, moving northeast at 25 mph.

Penny size hail and winds in excess of 40 mph will be possible with
this storm.

Locations impacted include...
Mount Vernon, Wayne City, Woodlawn, Bluford, Cisne, Dix, Waltonville,
Jeffersonville, Sims, Keenes and Johnsonville.

A Severe Thunderstorm Watch remains in effect until 700 PM CDT for
south central Illinois.

LAT...LON 3860 8834 3842 8833 3814 8915 3847 8914
      3847 8870 3861 8869
TIME...MOT...LOC 1839Z 241DEG 22KT 3842 8884

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