MESO: Mesoscale Discussion 1872

ACUS11 KWNS 212017
SWOMCD
SPC MCD 212016
MIZ000-212145-

MESOSCALE DISCUSSION 1872
NWS STORM PREDICTION CENTER NORMAN OK
0316 PM CDT TUE SEP 21 2010

AREAS AFFECTED...LOWER MI

CONCERNING...SEVERE THUNDERSTORM WATCH 676...

VALID 212016Z - 212145Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 676
CONTINUES.

SEVERE TSTM WATCH 676 CONTINUES UNTIL 01Z...WITH DAMAGING WINDS AS
THE PRIMARY CONCERN IN ADDITION TO HAIL.

AHEAD OF A PARENT SHORTWAVE TROUGH RACING NORTHEASTWARD OVER
NORTHERN ONTARIO...A COUPLE OF FAST MOVING BANDS OF TSTMS HAVE
EVOLVED...WITH ADDITIONAL TOWERING CU NOTED BENEATH A CIRRUS
CANOPY...ACROSS NORTHERN LOWER MI THIS AFTERNOON. A MOIST/MODERATELY
UNSTABLE...AND WEAKLY CAPPED...BOUNDARY LAYER IS IN PLACE ACROSS THE
MAJORITY OF NORTHERN/CENTRAL LOWER MI. A SPECIAL 18Z OBSERVED APX
RAOB REFLECTED STEEP LOW/MID LEVEL LAPSE RATES WITH AROUND 1900 J/KG
OF MLCAPE...WITH ROBUST SPEED SHEAR /60+ KT EFFECTIVE LAYER/ AMID A
LARGELY UNIDIRECTIONAL WIND PROFILE. IN SPITE OF A HIGHLY FAVORABLE
THERMODYNAMIC/KINEMATIC ENVIRONMENT FOR SEVERE STORMS CAPABLE OF
PRIMARILY DAMAGING WINDS/SOME HAIL...A FEW UNCERTAINTIES/PERHAPS
LIMITATIONS EXIST. LOW LEVEL WINDS CONTINUE TO VEER WITH MODEST MASS
CONVERGENCE ACROSS THE MAJORITY OF NORTHERN LOWER MI...OWING TO
PRE-COLD FRONTAL CONFLUENCE ACROSS FAR EASTERN LOWER
MI...ATTRIBUTABLE TO THE PARENT UPPER SYSTEM QUICKLY SHIFTING
NORTHEASTWARD ACROSS NORTHERN ONTARIO. THUS...WHILE THE
EXTENT/COVERAGE OF ADDITIONAL DEEP CONVECTIVE DEVELOPMENT IN THE
SHORT TERM IS SOMEWHAT QUESTIONABLE...AN OTHERWISE FAVORABLE
ENVIRONMENT WILL PROMOTE A SEVERE RISK WITH ANY SURFACE BASED TSTMS
THIS AFTERNOON.

..GUYER.. 09/21/2010

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...DTX...APX...GRR...

LAT...LON 45408474 45458266 43358372 43468615 45408474

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