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Mesoscale Discussion 1580
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   MESOSCALE DISCUSSION 1580
   NWS STORM PREDICTION CENTER NORMAN OK
   0421 AM CDT SUN AUG 02 2015

   AREAS AFFECTED...PORTIONS OF ERN MN...WI...UPPER PENINSULA OF MI

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 020921Z - 021145Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...A RISK FOR AT LEAST ISOLATED SVR TSTMS WILL INCREASE
   DURING THE EARLY-MORNING HOURS. WHILE CONVECTIVE TRENDS WILL
   CONTINUE TO BE MONITORED...THE ISSUANCE OF A WW IS PRESENTLY
   UNLIKELY.

   DISCUSSION...RECENT MOISTURE-CHANNEL IMAGERY IMPLIES A SUBTLE
   MID-LEVEL SPEED MAX ADVANCING ESEWD ACROSS PARTS OF THE UPPER MS
   VALLEY. THIS IS LIKELY AUGMENTING LOW-LEVEL WAA TO RESULT IN A
   COMPACT ZONE OF 2-HRLY SFC PRESSURE FALLS OF 1.5-2.5 MB ACROSS THE
   SRN HALF OF MN INTO W-CNTRL WI. RECENT MOSAIC RADAR AND IR IMAGERY
   INDICATE DEEPER CONVECTION BEGINNING TO EVOLVE FROM ACCAS/PATCHY
   SHOWERS ACROSS CNTRL/E-CNTRL MN...WITH CG LIGHTNING STRIKES NOW
   OCCURRING ESE OF BRD. AS THE SUBTLY ENHANCED DEEP ASCENT CONTINUES
   TO OVERSPREAD MODERATE TO STRONG ELEVATED BUOYANCY -- FED BY
   EWD-DIRECTED FLUXES OF RICH LOW-LEVEL THETA-E AIR PRECEDING THE
   SPEED MAX -- CONVECTION MAY CONTINUE TO INCREASE IN
   COVERAGE/INTENSITY DURING THE NEXT FEW HOURS. ALSO...REMNANT
   CONVECTION FROM NRN MN TO WRN LAKE SUPERIOR MAY DEVELOP ESEWD INTO
   WRN UPPER MI. ALL OF THIS ACTIVITY SHOULD SPREAD ESEWD/SEWD THROUGH
   THE EARLY-MORNING HOURS...AND BE CAPABLE OF ISOLATED SVR HAIL OWING
   TO 35-50 KT OF MID-LEVEL WLYS/NWLYS ENHANCING DEEP SHEAR TO
   ENCOURAGE CONVECTIVE ORGANIZATION.

   GIVEN THE MODEST NATURE OF THE LARGE-SCALE ASCENT...CONFIDENCE IN A
   STRONG NOCTURNAL UPSWING IN CONVECTIVE COVERAGE IS PRESENTLY
   LIMITED. REGARDLESS...THE MODERATELY STEEP NATURE OF MID-LEVEL LAPSE
   RATES -- AROUND 7.0-7.5 C/KM IN THE H7-H5 LAYER PER EARLIER ABR/MPX
   RAOBS -- COUPLED WITH THE PRESENCE OF A MID-LEVEL PERTURBATION OFFER
   CONCERN FOR AT LEAST ISOLATED SVR POTENTIAL. IF GREATER CONVECTIVE
   COVERAGE WERE TO ENSUE THAN PREVIOUSLY ANTICIPATED...AND IF
   CONFIDENCE WERE TO INCREASE IN AMALGAMATING COLD POOLS BREEDING
   UPSCALE GROWTH OF A LARGER CONVECTIVE SYSTEM AND GREATER SVR-WIND
   POTENTIAL...WW PROBABILITIES WOULD NEED TO BE RE-EVALUATED. ASIDE
   FROM THAT LOW-CONFIDENCE SCENARIO AT PRESENT...NOCTURNAL STATIC
   STABILITY MAY BE DETRIMENTAL FOR DOWNDRAFT PENETRATION TO THE
   SFC...MINIMIZING THE OVERALL SVR-WIND RISK.

   ..COHEN/EDWARDS.. 08/02/2015


   ATTN...WFO...MQT...GRB...MKX...DLH...ARX...MPX...

   LAT...LON   46119445 46729279 46868873 45458748 43718843 43819133
               44989412 46119445 

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Page last modified: August 02, 2015
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