SPC drops severe T-Storm Watch; Hot breezy & humid today

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!

“Update:

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.

Stay tuned…

PH”

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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.

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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.

…MEAD

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.

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Keep an eye out for possible storm development today and especially this evening.

PH

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