Special Weather Statement, NWS St. Louis, MO

Area Forecast Discussion
National Weather Service Saint Louis MO
341 PM CDT Wed Jun 26 2019

.SHORT TERM...  (Through Late Thursday Night)
Issued at 204 PM CDT Wed Jun 26 2019

An MCV over south-central MO was moving slowly eastward this
afternoon. This feature was supporting downstream SHRA/TSRA
development within a moist and very unstable air mass. Although
MLCAPE values were exceeding 3000 J/kg this afternoon, 0-6 km
shear values were quite low, and the lack of shear has been
hindering storm organization and may also limit how widespread
the severe weather threat becomes. Given the low shear, each
outflow boundary will become a new focus for potential SHRA/TSRA
development within such an unstable environment.

Storms should continue progressing eastward in tandem with the
slow-moving MCV, but precipitation coverage should diminish across
the northern half of the LSX CWA this evening with the loss of
diurnal heating. Farther south, the slow-moving MCV may continue
to support isolated to scattered SHRA/TSRA into the evening and
overnight hours over parts of southern and southeastern MO into
southern IL.

Flash flooding will be possible if multiple thunderstorm cores
repeatedly move over the same locations, but this does not appear
to be a widespread threat at this time.

SHRA/TSRA will probably continue to percolate across southeastern
MO and southern IL on Thu until the MCV has either dissipated or
shifted far enough eastward to limit its influence.

A pattern change begins taking place on Thu in which an upper
ridge axis simultaneously shifts eastward and amplifies
downstream of a large closed low over the Pacific Northwest. This
pattern will bring warmer weather to the LSX CWA along with lower
rain chances.

Highs on Thu should be similar to or perhaps a few degrees warmer
than they were on Wed (upper 80s to low 90s). Overnight lows on
Wed night and Thu night should be similar (upper 60s to around
70).

Kanofsky

.LONG TERM...  (Friday through Next Wednesday)
Issued at 204 PM CDT Wed Jun 26 2019

By Fri, the upper ridge axis will be located slightly west of the
LSX CWA, and the ridge itself will extend well into central
Canada. Several PV anomalies are noted moving around the
periphery of the ridge, but the ridge's high amplitude means that
these systems will likely remain in Canada or perhaps the extreme
northern CONUS. The ridge remains firmly entrenched through the
weekend before models suggest that it begins to flatten or perhaps
start to break down early next week. At the surface, southerly to
southwesterly flow around a surface high pressure center located
over the southeastern CONUS will funnel warm and moist air into
the region. The combination of heat (highs in the low to mid 90s)
and humidity will likely yield heat index values in the mid to
upper 90s. Heat index values could be higher depending on the dew
points.

The next chance for widespread rain appears to be early next week
when a weak disturbance moves through the central CONUS after the
ridge has flattened.

Kanofsky

&&

.AVIATION...  (For the 18z TAFs through 18z Thursday Afternoon)
Issued at 1151 AM CDT Wed Jun 26 2019

SPECIFICS FOR KCOU, KUIN: A remnant thunderstorm complex over
southwestern MO was moving very slowly eastward at TAF issuance.
This feature will support scattered SHRA/TSRA from around 26/21z
through around 27/02z, but it is unclear whether SHRA/TSRA will
extend far enough northward to affect KCOU. Similar concerns exist
for KUIN due to a separate remnant thunderstorm complex which was
located over extreme northwestern MO at TAF issuance. Otherwise,
expect diurnal cumulus and light southerly to southwesterly winds.

SPECIFICS FOR KSTL, KSUS, KCPS: VFR conditions are expected for
the first 0-3 hours of the valid TAF period, but uncertainty
increases after 21z. A remnant thunderstorm complex over
southwestern MO was moving very slowly eastward at TAF issuance,
and while it is expected to generate additional thunderstorms
this afternoon, it is unclear how far north the convection might
spread. VCTS from 26/21z - 27/02z seems appropriate at this time
until the northern extent of the convection has been established.
Otherwise, light southerly to southwesterly winds will persist
through the period.

Kanofsky

&&

.LSX WATCHES/WARNINGS/ADVISORIES...
MO...None.
IL...None.
&&

WFO LSX

Hazardous Weather Outlook
National Weather Service Saint Louis MO
357 PM CDT Wed Jun 26 2019

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-271200-
Adams IL-Audrain MO-Bond IL-Boone MO-Brown IL-Calhoun IL-Callaway MO-
Clinton IL-Cole MO-Crawford MO-Fayette IL-Franklin MO-Gasconade MO-
Greene IL-Iron MO-Jefferson MO-Jersey IL-Knox MO-Lewis MO-Lincoln MO-
Macoupin IL-Madison IL-Madison MO-Marion IL-Marion MO-Moniteau MO-
Monroe IL-Monroe MO-Montgomery IL-Montgomery MO-Osage MO-Pike IL-
Pike MO-Ralls MO-Randolph IL-Reynolds MO-Saint Charles MO-
Saint Clair IL-Saint Francois MO-Saint Louis City MO-Saint Louis MO-
Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO-
357 PM CDT Wed Jun 26 2019

This Hazardous Weather Outlook is for portions of eastern and
central Missouri as well as west central and southwest Illinois.

.DAY ONE...Tonight.

Scattered thunderstorms will continue into the evening hours. A few
of the storms may be strong to severe and capable of producing hail
and gusty winds.

.DAYS TWO THROUGH SEVEN...Thursday through Tuesday.

There is a chance of thunderstorms across southeast Missouri and
southwest Illinois on Thursday. There is also a chance of
thunderstorms across parts of the region on Monday and Tuesday.

.SPOTTER INFORMATION STATEMENT...

Spotters are encouraged to report any severe weather, if observed,
to the National Weather Service..

Kanofsky

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
425 PM CDT WED JUN 26 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0419 PM     HAIL             1 W TROY                38.73N 89.91W
06/26/2019  E0.25 INCH       MADISON            IL   AMATEUR RADIO

            PEA SIZE HAIL REPORTED AT THE TROY IL EXIT
            FROM I-55.

&&

KANOFSKY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
426 PM CDT WED JUN 26 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0350 PM     HAIL             2 E SHREWSBURY          38.59N 90.29W
06/26/2019  E0.70 INCH       ST. LOUIS CITY     MO   PUBLIC

&&

KANOFSKY

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
443 PM CDT WED JUN 26 2019

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0442 PM     HAIL             AVISTON                 38.61N 89.61W
06/26/2019  E0.25 INCH       CLINTON            IL   TRAINED SPOTTER

&&

MAB

Special Weather Statement
National Weather Service St Louis MO
449 PM CDT Wed Jun 26 2019

ILZ064-069-262230-
Bond IL-Clinton IL-
449 PM CDT Wed Jun 26 2019

...SIGNIFICANT WEATHER ADVISORY FOR NORTH CENTRAL CLINTON AND BOND
COUNTIES UNTIL 530 PM CDT...

At 449 PM CDT, Doppler radar was tracking a strong thunderstorm near
Pocahontas, moving east at 10 mph.

Nickel size hail and wind gusts of 50 to 55 mph will be possible with
this storm.

Locations impacted include...
Greenville, Pocahontas, Tamalco, Beaver Creek, Jamestown, Woburn,
Pleasant Mound, Pierron, Keyesport, Smithboro, Old Ripley and
Dudleyville.

This includes Interstate 70 in Illinois between exits 36 and 45.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Torrential rainfall is also occurring with this storm, and may lead
to localized flooding. Do not drive your vehicle through flooded
roadways.

Frequent cloud to ground lightning is occurring with this storm.
Lightning can strike 10 miles away from a thunderstorm. Seek a safe
shelter inside a building or vehicle.

This storm may intensify, so be certain to monitor local radio
stations and available television stations for additional information
and possible warnings from the National Weather Service.

&&

LAT...LON 3872 8925 3870 8959 3880 8960 3887 8960
      3888 8961 3889 8961 3898 8931
TIME...MOT...LOC 2149Z 250DEG 8KT 3878 8956

Britt