SPC has dropped the watch for Minnesota and the metro. Severe weather is unlikely this afternoon, but we may see a few storms develop along a cold front to the northwest (between Fargo and Alex) this evening.
Here’s my internal email to MPR staffers after SPC issued the watch today. Enjoy the hot, breezy humid summer day!
My own read of this situation is that SPC may have jumped the gun a bit on throwing out this watch. The weak disturbance that caused the Wisconsin storms is moving away from us, and the cold front that may fire storms later is still up to the northwest between Fargo and Alex.
Bottom line my read is that storms are more likely to develop later this evening…but the folks at SPC are the best trained severe weather minds in the world, so stay alert for possible development near the metro today.
I’ll let you know if I see anything pop. I’m thinking we may see storms develop along I-94 between Fargo and Alex in the next two hours, and the best chance for metro storms may be this evening…even as late as 9 or 10pm.
Original post 2:05pm
Our hot humid summery air mass has prompted a severe T-Storm Watch until 9pm that includes much of central MN and the metro.
Initial storms fired along a weak boundary east and west of the Twin Cities, but activity has died down a bit since then. It is possible the initial storms were caused by a weak passing “short wave” in northern Wisconsin, and that additional development may hold off until this evening.
Still, the watch is in effect until 9pm and we should stay alert for possible development and warnings.
URGENT – IMMEDIATE BROADCAST REQUESTED
SEVERE THUNDERSTORM WATCH NUMBER 704
NWS STORM PREDICTION CENTER NORMAN OK
130 PM CDT SAT JUL 30 2011
THE NWS STORM PREDICTION CENTER HAS ISSUED A
SEVERE THUNDERSTORM WATCH FOR PORTIONS OF
CENTRAL AND SOUTHERN MINNESOTA
EASTERN SOUTH DAKOTA
EFFECTIVE THIS SATURDAY AFTERNOON AND EVENING FROM 130 PM UNTIL
900 PM CDT.
HAIL TO 2.5 INCHES IN DIAMETER…THUNDERSTORM WIND GUSTS TO 70
MPH…AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.
THE SEVERE THUNDERSTORM WATCH AREA IS APPROXIMATELY ALONG AND 55
STATUTE MILES NORTH AND SOUTH OF A LINE FROM 40 MILES WEST
SOUTHWEST OF WATERTOWN SOUTH DAKOTA TO 20 MILES SOUTHEAST OF
MINNEAPOLIS MINNESOTA. FOR A COMPLETE DEPICTION OF THE WATCH SEE
THE ASSOCIATED WATCH OUTLINE UPDATE (WOUS64 KWNS WOU4).
REMEMBER…A SEVERE THUNDERSTORM WATCH MEANS CONDITIONS ARE
FAVORABLE FOR SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH
AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR
THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS
AND POSSIBLE WARNINGS. SEVERE THUNDERSTORMS CAN AND OCCASIONALLY
DO PRODUCE TORNADOES.
OTHER WATCH INFORMATION…CONTINUE…WW 703…
(Here’s the SPC technical “weather geek” discussion)
DISCUSSION…AN INCIPIENT SUPERCELL APPEARS TO BE EVOLVING NEAR VVV
WITH ADDITIONAL STORM DEVELOPMENT ANTICIPATED THIS AFTERNOON ALONG
OUTFLOW BOUNDARY EXTENDING FROM N OF ABR-N OF MSP. MODIFICATION OF 12Z ABR/MPX SOUNDINGS FOR CURRENT SURFACE CONDITIONS INDICATES THAT CAP IS NOW QUITE WEAK WITH MLCAPE UPWARDS OF 3000-4000 J/KG. AREA
VADS AND WOOD LAKE MN PROFILER SHOW THAT LOW-LEVEL WIND FIELD IS
RATHER WEAK…BUT SUFFICIENT DEEP-LAYER SHEAR DOES EXIST TO SUPPORT
SUPERCELL STRUCTURES. WHILE A TORNADO IS POSSIBLE…IT DOES APPEAR
THAT VERY LARGE HAIL AND DAMAGING WINDS WILL BE THE PRIMARY HAZARDS.
STORMS MAY TEND TO MERGE AND EVOLVE INTO AN MCS LATE THIS AFTERNOON INTO EVENING WITH A CONTINUE THREAT FOR DAMAGING WINDS AND HAIL.
AVIATION…A FEW SEVERE THUNDERSTORMS WITH HAIL SURFACE AND ALOFT
TO 2.5 INCHES. EXTREME TURBULENCE AND SURFACE WIND GUSTS TO 60
KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO 600. MEAN STORM
MOTION VECTOR 30015.
Looking at the GOES 1km visible satellite image below (FREE from College of Du Page Leather Lab) you can see a psuedo line where storms may fire near the metro. The secod yellw line is the approaching cold front, and this could be the area where storms are more likely to form later today and this evening.
Keep an eye out for possible storm development today and especially this evening.