• Mesodiscussion 1433 for 2013

Mesodiscussion 1433




MESOSCALE DISCUSSION 1433
NWS STORM PREDICTION CENTER NORMAN OK
1053 AM CDT FRI JUL 19 2013

AREAS AFFECTED...LOWER MICHIGAN

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 191553Z - 191730Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...AT LEAST LOW PROBABILITIES FOR SEVERE WIND/HAIL MAY EXIST
WITH BROKEN BANDS OF CONVECTION OVERSPREADING LOWER MICHIGAN INTO
AND THROUGH THE AFTERNOON HOURS.  HOWEVER...THE NEED FOR A SEVERE
WEATHER WATCH IS NOT CURRENTLY ANTICIPATED...AT LEAST IN THE NEAR
TERM.

DISCUSSION...MID-LEVEL LAPSE RATES ARE NOT PARTICULARLY STEEP...BUT
SIZABLE MIXED LAYER CAPE STILL APPEARS LIKELY TO CONTINUE TO DEVELOP
ACROSS MUCH OF SOUTHERN AND EASTERN LOWER MICHIGAN DURING THE NEXT
FEW HOURS WITH FURTHER SURFACE HEATING OF A MOIST BOUNDARY LAYER
WITH DEW POINTS IN THE LOWER 70S.  ALTHOUGH THIS WOULD SEEM TO
BECOME INCREASINGLY SUPPORTIVE OF SEVERE STORM POTENTIAL IN THE
PRESENCE OF STRONG DEEP LAYER SHEAR BENEATH 30-50 KT CYCLONIC
WESTERLY 500 MB FLOW...THE EXTENT OF THIS THREAT REMAINS UNCERTAIN. 

BOUNDARY LAYER CONVERGENCE REMAINS WEAK ACROSS MUCH OF LOWER
MICHIGAN...AHEAD OF THE MAIN COLD FRONT...WHICH IS STILL LOCATED
ACROSS THE UPPER GREAT LAKES REGION...AND MAY NOT IMPACT THE MORE
UNSTABLE ENVIRONMENT ACROSS SOUTHEASTERN LOWER MICHIGAN UNTIL MUCH
LATER THIS AFTERNOON OR EVENING.  STRONGER MID/UPPER FORCING FOR
UPWARD VERTICAL MOTION IN THE BROAD WARM SECTOR OF THE SURFACE
CYCLONE MIGRATING ACROSS NORTHERN QUEBEC APPEARS LIKELY TO REMAIN
ACROSS THE CANADIAN PROVINCES THROUGH MUCH OF THE DAY AS WELL. 
WHILE ISOLATED STORMS COULD OCCASIONALLY FLARE UP IN ASSOCIATION
WITH A BAND OF WEAK TO MODEST MID-LEVEL LARGE SCALE ASCENT...NOW
OVERSPREADING NORTHERN LOWER MICHIGAN...AND POSSIBLY IMPACTING THE
MICHIGAN THUMB AND SOUTHEASTERN LOWER MICHIGAN THROUGH
18-21Z...SEVERE WEATHER POTENTIAL STILL SEEMS TOO LOW/SPARSE IN
NATURE TO REQUIRE A WW AT LEAST IN THE NEAR TERM.

..KERR/THOMPSON.. 07/19/2013

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

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

LAT...LON   41928344 41838471 42368576 43228553 44238451 45018223
            44418150 42948223 42338276 41928344