Sioux Falls, SD...Aberdeen, SD...Watertown, SD...Willmar, MN...Brookings, SD...
Probabilistic Tornado Graphic
Probability of a tornado within 25 miles of a point. Hatched Area: 10% or greater probability of EF2 - EF5 tornadoes within 25 miles of a point.
Day 1 Tornado Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Damaging Wind Graphic
Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
Day 1 Wind Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
No Risk Areas Forecast
Probabilistic Large Hail Graphic
Probability of hail 1" or larger within 25 miles of a point. Hatched Area: 10% or greater probability of hail 2" or larger within 25 miles of a point.
Day 1 Hail Risk
Area (sq. mi.)
Area Pop.
Some Larger Population Centers in Risk Area
5 %
50,208
826,593
Sioux Falls, SD...Aberdeen, SD...Watertown, SD...Willmar, MN...Brookings, SD...
SPC AC 221250
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0750 AM CDT TUE SEP 22 2015
VALID 221300Z - 231200Z
...THERE IS A MRGL RISK OF SVR TSTMS TONIGHT FOR ERN SD...SE
ND...AND SW MN...
...SUMMARY...
THUNDERSTORMS WILL DEVELOP TONIGHT ACROSS EASTERN SOUTH
DAKOTA...SOUTHWESTERN MINNESOTA...AND SOUTHEASTERN NORTH
DAKOTA...AND A FEW OF THE STORMS COULD PRODUCE MARGINALLY SEVERE
HAIL.
...SYNOPSIS...
IN THE WAKE OF A MIDLEVEL SHORTWAVE TROUGH OVER WRN ONTARIO...A
SURFACE COLD FRONT WILL DRIFT SEWD ACROSS MN/IA/NEB AND THEN STALL
NEAR THE NEB/KS BORDER THIS AFTERNOON. THE BOUNDARY WILL THEN BEGIN
TO MOVE NWD AS A WARM FRONT TONIGHT...IN RESPONSE TO WEAK LEE
CYCLOGENESIS ACROSS THE CENTRAL/NRN HIGH PLAINS. FARTHER S...A
SERIES OF VORTICITY MAXIMA WILL MOVE NEWD FROM THE FOUR CORNERS TO
THE CENTRAL HIGH PLAINS...ALONG WITH THE MIDLEVEL REMNANTS OF A
TROPICAL MOISTURE PLUME EMANATING FROM THE ERN PACIFIC.
SCATTERED THUNDERSTORMS ARE EXPECTED WITHIN THE MOISTURE PLUME
ACROSS AZ/NM INTO SE CO TODAY...AND THE STORMS WILL PERSIST WELL
INTO THE OVERNIGHT HOURS FROM ERN NM INTO ERN CO ALONG A WEAK LEE
TROUGH AND IN THE ZONE OF ASCENT IMMEDIATELY DOWNSTREAM FROM THE
SERIES OF VORTICITY MAXIMA. OTHER SCATTERED THUNDERSTORMS ARE ALSO
EXPECTED THIS AFTERNOON ACROSS S FL AND NEAR THE NE GULF COAST IN
ASSOCIATION WITH A WEAK MIDLEVEL TROUGH.
...ERN SD/SE ND/SW MN TONIGHT...
A SEPARATE AREA OF ELEVATED THUNDERSTORMS WILL FORM AS EARLY AS LATE
EVENING ACROSS NE NEB...WITH CONVECTION EXPECTED TO SPREAD NWD TO
ERN SD/SW MN LATE TONIGHT. THE CONVECTION WILL BE SUPPORTED BY WAA
WITH A 30-40 KT LLJ...ON THE NE EDGE OF A REMNANT EML PLUME. GIVEN
BOUNDARY LAYER DEWPOINTS IN THE MID 60S IN THE PLAINS WARM SECTOR
AND THE STEEP MIDLEVEL LAPSE RATES...MUCAPE WILL LIKELY REACH THE
1500-2000 J/KG RANGE. MEANWHILE...THE WAA REGIME AND WLY FLOW ALOFT
WILL CONTRIBUTE TO SUFFICIENT EFFECTIVE BULK SHEAR FOR AT LEAST SOME
RISK FOR ELEVATED SUPERCELLS. GIVEN THE ELEVATED NATURE OF THE
CONVECTION...ISOLATED LARGE HAIL WILL BE THE MAIN CONCERN TONIGHT.
..THOMPSON.. 09/22/2015
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z