Severe Threat: Tornadoes sighted in southern Minnesota

As a major blizzard rages in the Red River Valley today, here's a quick update on a potential severe weather threat into early evening in southern Minnesota.

As I mentioned this morning, I am concerned there is enough shear and instability for low topped severe storms that may produce large hail, damaging winds and even tornadoes in southern Minnesota into this evening.

This has come to pass. There have already been multiple tornado sightings in southwest Minnesota.

MPX issues Tornado Warning for Yellow Medicine [MN] till 4:30 PM CDT * AT 408 PM CDT...A CONFIRMED TORNADO WAS LOCATED 8 MILES NORTHEAST OF TAUNTON...AND MOVING NORTH AT 40 MPH.

MPX issues Tornado Warning for Lac qui Parle [MN] till 4:45 PM CDT * AT 422 PM CDT...A CONFIRMED TORNADO WAS LOCATED 12 MILES NORTHEAST OF CANBY...AND MOVING NORTH AT 25 MPH.

This report of structural damage may have been caused by a tornado touchdown east of Canby, and another near Minneota.

3 SE ST LEO [Yellow Medicine Co, MN] LAW ENFORCEMENT reports TORNADO at 4:08 PM CDT -- STRUCTURAL DAMAGE REPORTED WITH PROBABLE TORNADO SOUTHEAST OF ST LEO. TIME ESTIMATED.

3 N Minneota [Lyon Co, MN] EMERGENCY MNGR reports TORNADO at 3:48 PM CDT -- STRUCTURAL DAMAGE

The National Oceanic and Atmospheric Administration's Storm Prediction Center has issued three separate "mesoscale discussions" on the threat for possible severe storms and for small tornadoes in southwest Minnesota.

Here are the details from NOAA.

MESOSCALE DISCUSSION 0238

NWS STORM PREDICTION CENTER NORMAN OK

0643 PM CDT MON MAR 31 2014

AREAS AFFECTED...CNTRL/SERN MN...ERN IA...FAR WRN WI...NERN MO

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 312343Z - 010215Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED SVR THUNDERSTORMS WILL BE POSSIBLE INTO THE EVENING. WHILE CONDITIONS WILL CONTINUE TO BE MONITORED...WW ISSUANCE IS CURRENTLY UNLIKELY.

DISCUSSION...AN ARC OF CONVECTION EXTENDS FROM CNTRL MN TO NRN MO WITHIN THE ERN SEMICIRCLE OF A DEEP CYCLONE WHOSE MID-LEVEL CENTER IS POSITIONED OVER SWRN MN PER RECENT MOISTURE-CHANNEL IMAGERY. THE PRESENCE OF 35-50-KT LOW/MID-LEVEL SLYS PER REGIONAL VWP DATA WILL

SUPPORT SOME ORGANIZED/PERSISTENT CONVECTION. THE GREATEST CONCENTRATION OF THIS ACTIVITY WILL REMAIN INVOF A COLD-FRONT-OVERTAKEN DRYLINE FROM SERN MN TO ERN IA AND NERN

MO...AND STORMS WITHIN THIS CORRIDOR COULD PRODUCE SPORADIC DMGG WIND GUSTS AND MARGINALLY SVR HAIL. FARTHER N...ASCENT ALONG A WARM FRONT EXTENDING FROM CNTRL MN TO W-CNTRL WI N OF MSP WILL ALSO REMAIN A POSSIBLE FOCUS FOR STRONG STORMS AND POSSIBLY A BRIEF

TORNADO OR TWO WHERE SFC WINDS ARE RELATIVELY MORE BACKED TO ENHANCE LOW-LEVEL SHEAR. THE PAUCITY OF LOW-LEVEL MOISTURE -- I.E. SFC DEWPOINTS IN THE LOWER/MIDDLE 40S -- SHOULD KEEP BUOYANCY

SUFFICIENTLY SMALL ACROSS THE DISCUSSION AREA TO PREVENT A GREATER SVR RISK FROM EVOLVING. NOCTURNAL COOLING WILL BE DETRIMENTAL FOR THE MAINTENANCE OF STRONGER UPDRAFTS AS STORMS APPROACH/CROSS THE MS

RIVER IN THE NEXT FEW HOURS.

MESOSCALE DISCUSSION 0234

NWS STORM PREDICTION CENTER NORMAN OK

0305 PM CDT MON MAR 31 2014

AREAS AFFECTED...SOUTHWEST MN

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 312005Z - 312200Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...LOW-TOPPED TSTMS MAY DEVELOP/INCREASE IN INTENSITY THROUGH MID/LATE AFTERNOON MAINLY ACROSS SOUTHWEST MN. A FUNNEL/BRIEF TORNADO RISK MAY BE POSSIBLE ASIDE FROM MARGINALLY SEVERE HAIL.

DISCUSSION...A NEARLY VERTICALLY STACKED CYCLONE IS CENTERED ACROSS THE MO RIVER VALLEY THIS AFTERNOON...WITH A 990 MB SURFACE LOW LOCATED NEAR/NORTHEAST OF SIOUX FALLS SD AS OF 20Z. SURFACE

DEWPOINTS HAVE RISEN INTO/PERSISTED IN THE MIDDLE/SOME UPPER 40S F ACROSS SOUTHWEST MN NEAR AND EAST-NORTHEAST OF A SURFACE TRIPLE POINT. OVER THE NEXT FEW HOURS...IT IS POSSIBLE THAT SUFFICIENT /ALBEIT MEAGER/ CAPE MAY BE ENOUGH TO CONTRIBUTE TO THE DEVELOPMENT/SUSTENANCE OF A FEW STRONGER LOW-TOPPED TSTMS.

WHILE DEEP LAYER SHEAR/LOW-LEVEL SRH ARE LIMITED IN THE PRESENCE OF WEAK LOW/MID-LEVEL WINDS...PLENTIFUL AMBIENT VERTICAL VORTICITY AND STEEP LAPSE RATES/MODEST LOW-LEVEL CAPE MAY BE SUFFICIENT FOR A FEW FUNNELS/POSSIBLY A BRIEF TORNADO AS WELL AS MAINLY SUB-SEVERE HAIL THROUGH AROUND SUNSET.

Here's the second discussion for the potential for severe storms in southern Minnesota and northern Iowa.

MESOSCALE DISCUSSION 0236

NWS STORM PREDICTION CENTER NORMAN OK

0352 PM CDT MON MAR 31 2014

AREAS AFFECTED...FAR SOUTH-CENTRAL MN/EAST-CENTRAL IA/NORTHERN MO

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 312052Z - 312245Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...ISOLATED/WIDELY SCATTERED TSTMS SHOULD DEVELOP/INCREASE THROUGH LATE AFTERNOON/EARLY EVENING WITHIN A GENERAL NORTH-SOUTH CORRIDOR ACROSS FAR SOUTH-CENTRAL MN/EAST-CENTRAL IA INTO NORTHERN MO. ISOLATED BOUTS OF DAMAGING WINDS/MARGINALLY SEVERE HAIL WOULD BE THE PRIMARY HAZARDS.

DISCUSSION...CUMULUS FIELD HAS INCREASED/DEEPENED IN VICINITY OF PRE-FRONTAL WEAK DRYLINE AND/OR MERGING COLD FRONT WITHIN A NORTH-SOUTH CORRIDOR ACROSS FAR SOUTH-CENTRAL MN/CENTRAL IA INTO

NORTHWEST MO. AIDED BY ADDITIONAL MIXING AND INFLUENCES OF THE MIDDLE MO VALLEY CYCLONE...TSTMS ARE EXPECTED TO DEVELOP/INCREASE THROUGH LATE AFTERNOON/EARLY EVENING ACROSS THE REGION. BUOYANCY WILL REMAIN LIMITED IN THE PRESENCE OF ONLY 40S F SURFACE DEWPOINTS...BUT STEEP LAPSE RATES AND STRONG/LARGELY UNIDIRECTIONAL DEEP LAYER WINDS WILL SUPPORT THE POTENTIAL FOR MAINLY LINE SEGMENTS CAPABLE OF MARGINALLY SEVERE HAIL/LOCALIZED WIND DAMAGE THROUGH

SUNSET.

A tornado warning was issued near Brookings, S.D., this afternoon based on radar rotation , but no tornado was sighted.

Expect scattered thunderstorms in southwest and south central Minnesota this evening. Thunderstorms may approach the metro after 6 p.m.

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