Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 020921
SWOMCD
SPC MCD 020921
MIZ000-WIZ000-MNZ000-021145-

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

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

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

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




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