Hail and Damaging Wind in Illinois, May 3, 2021

Area Forecast Discussion
National Weather Service Saint Louis MO
228 PM CDT Mon May 3 2021

.SHORT TERM...  (Through Late Tuesday Afternoon)
Issued at 227 PM CDT Mon May 3 2021

A cold front stretching from eastern Iowa southwest into Oklahoma
will continue moving to the southeast this evening.  The environment
ahead of the front is characterized by strong instability with
SBCAPE values in excess of 3000 J/Kg building by 00Z along and
southeast of I-44 in Missouri and I-70 in Illinois.  The 0-6km shear
is currently in the 35-45kt range, but the shear weakens by late
afternoon/early evening as the low level pressure gradient slackens
ahead of the front.  Regardless, there will be plenty of instability
and shear to fuel severe thunderstorms this afternoon and evening.
Indeed, even farther north in northeast Missouri where the
environment isn't as favorable, a strong storm has developed, and is
already being warned on.

In The big question is, will there be enough forcing to trigger
storms farther south in the most favorable environment? The cold
front is moving relatively slowly, and the wind ahead of the front
is from the southwest and west southwest. Therefore, convergence
along the front is not particularly strong, and there is a weak
capping inversion that updrafts must break through.  Most convection
allowing models (CAMs) show widely scattered thunderstorms late this
afternoon and this evening ahead of the front, but a few produce an
organized cluster or two. Rotating updrafts will be possible in any
storm that develops in the favorable instability/shear environment,
and therefore capable of producing golf ball size hail and damaging
wind in excess of 70 mph.

The threat for severe weather should end as the front passes, and
current indications are that the front will be through our
southeastern counties by 06-07Z.  However, that will not bring an
end to the showers...and possibly a few thunderstorms as well.
Another short wave trough ejects northeast from the Southern Plains
toward the Mid Mississippi Valley this evening.  The surface
reflection of this wave rides up along the front tonight which
strengthens the low level jet across Arkansas and southern Missouri.
 All deterministic guidance show strong moisture convergence along
the 850mb front on the nose of the low level jet, and they print out
QPF all the way back into east central Missouri and south central
Illinois behind the front late tonight and Tuesday.  I couldn't rule
out a few rumbles of thunder on Tuesday, but most of the instability
will be well south of the area.

Carney

.LONG TERM...  (Tuesday Night through Next Monday)
Issued at 227 PM CDT Mon May 3 2021

...pending...

&&

.PRELIMINARY POINT TEMPS/POPS...
Saint Louis     58  62  47  65 /  80  80  30   0
Quincy          52  57  44  63 /  30  20   0   0
Columbia        52  57  43  65 /  50  60   0   0
Jefferson City  54  58  43  66 /  60  80   0   0
Salem           61  65  48  65 /  80  80  60   0
Farmington      60  63  45  67 /  90  90  70   0

&&

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

WFO LSX

Hazardous Weather Outlook
National Weather Service Saint Louis MO
417 AM CDT Mon May 3 2021

ILZ058>060-064-065-069-070-074-079-095>102-MOZ018-019-026-027-
034>036-041-042-047>052-059>065-072>075-084-085-099-040930-
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-Saint Francois MO-Saint Louis City MO-Saint Louis MO-
Sainte Genevieve MO-Shelby MO-Warren MO-Washington IL-Washington MO-
417 AM CDT Mon May 3 2021

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

.DAY ONE...Today and tonight.

Thunderstorms are expected across the area this afternoon through
midnight tonight. Some storms could become strong to severe. Damaging
winds and large hail will be the primary threats, but tornadoes
cannot be ruled out.

.DAYS TWO THROUGH SEVEN...Tuesday through Sunday.

There is a chance of thunderstorms Tuesday, Thursday, and over the
weekend.

.SPOTTER INFORMATION STATEMENT...

Spotter activation will likely be needed this afternoon and tonight
across the area.

MRM

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
243 PM CDT MON MAY 3 2021

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

0241 PM     HAIL             3 SE EWING              39.97N 91.67W
05/03/2021  E1.75 INCH       LEWIS              MO   PUBLIC

            REPORT OF GOLF BALL SIZED HAIL IN DURHAM,
            MO.

&&

KD

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE ST LOUIS MO
250 PM CDT MON MAY 3 2021

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

0250 PM     HAIL             MAYWOOD                 39.95N 91.60W
05/03/2021  E1.25 INCH       LEWIS              MO   PUBLIC

            REPORTED IN MAYWOOD.

&&

KD