AREAS AFFECTED...PARTS OF ERN SD...SRN MN...PARTS OF NE IA...SWRN
WI...NRN IL
CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE
VALID 240413Z - 240545Z
PROBABILITY OF WATCH ISSUANCE...40 PERCENT
SUMMARY...THE SEVERE WEATHER THREAT MAY NOT BE COMPLETELY NEGLIGIBLE
IN THE NEAR TERM ...AND IT APPEARS POSSIBLE THAT IT COULD INCREASE
AFTER 06Z ACROSS PARTS OF SOUTHERN MINNESOTA...PERHAPS EASTWARD INTO
SOUTHERN WISCONSIN/NORTHERN ILLINOIS. TRENDS ARE BEING MONITORED
FOR AN INCREASING THREAT THAT COULD REQUIRE A WATCH.
DISCUSSION...A GRADUAL INCREASE IN CONVECTIVE DEVELOPMENT IS
UNDERWAY WITHIN A PERSISTENT ZONE OF STRONGER LOWER/MID TROPOSPHERIC
WARM ADVECTION ...ON THE NORTHERN EDGE OF MORE STRONGLY CAPPING
ELEVATED MIXED LAYER AIR ADVECTING AROUND THE CENTRAL U.S.
SUBTROPICAL HIGH CENTER. THROUGH THE 06-09Z TIME FRAME...ACTIVITY
IS EXPECTED TO DEVELOP EAST SOUTHEASTWARD INTO SOUTHERN
WISCONSIN...WHILE CONTINUING TO REDEVELOP ACROSS SOUTHERN
MINNESOTA...NEAR THE NOSE OF A 40+ KT SOUTHWESTERLY 850 MB JET.
HIGH PRECIPITABLE WATER ON THE ORDER OF 1.75 TO 2 INCHES IS
CONTRIBUTING TO LARGE CAPE ALONG THIS CORRIDOR...WHICH APPEARS TO
COINCIDE WITH A BELT OF 40-50 KT WEST NORTHWESTERLY 500 MB FLOW.
VERTICAL SHEAR IS SUFFICIENT FOR ORGANIZED CONVECTIVE
DEVELOPMENT...INCLUDING SUPERCELL STRUCTURES WHICH MAY ENHANCE THE
POTENTIAL FOR LARGE HAIL. CELL TRAINING MAY LEAD TO LOCALLY HEAVY
RAINFALL...AND THE UPSCALE GROWTH OF ONE OR TWO LARGER STORM
CLUSTERS MAY NOT BE OUT OF THE QUESTION. HIGHEST POTENTIAL FOR THIS
SEEMS TO BE ACROSS SOUTHWESTERN MINNESOTA AFTER 06Z...AS FORCING FOR
UPWARD VERTICAL MOTION IS ENHANCED BY AN IMPULSE PROGRESSING
EASTWARD ACROSS SOUTH DAKOTA. IF THIS OCCURS...HEAVY PRECIPITATION
LOADING MAY LEAD TO ONE OR TWO DOWNBURSTS WITH STRONG SURFACE
GUSTS...AND EVENTUALLY THE DEVELOPMENT OF A SIGNIFICANT EAST
SOUTHEASTWARD PROPAGATING COLD POOL.
..KERR/CARBIN.. 07/24/2012
...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...
ATTN...WFO...LOT...MKX...DVN...ARX...MPX...DMX...FSD...ABR...
LAT...LON 44969544 44599212 43278901 42268940 43409369 43719601
44469689 44969544
