Mesoscale Discussion 1768

Issued

Aug 15, 2012, 5:49 PM CDT (22:49 UTC)

Expired

Aug 15, 2012, 7:15 PM CDT

In force

86 min

Issued by

the Storm Prediction Center

480 
ACUS11 KWNS 152249
SWOMCD
SPC MCD 152249 
MNZ000-WIZ000-SDZ000-NDZ000-160015-

MESOSCALE DISCUSSION 1768
NWS STORM PREDICTION CENTER NORMAN OK
0549 PM CDT WED AUG 15 2012

AREAS AFFECTED...A LARGE PART OF MN...NWRN WI...FAR NERN SD...WRN
LAKE SUPERIOR

CONCERNING...SEVERE THUNDERSTORM WATCH 581...

VALID 152249Z - 160015Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 581
CONTINUES.

SUMMARY...SVR WIND GUSTS AND PERHAPS LOCALLY SVR HAIL WILL REMAIN OF
CONCERN ACROSS THE WW AREA THROUGH THE EVENING...AS A SQUALL LINE
CONTINUES TO EVOLVE.

DISCUSSION...A SQUALL LINE EXTENDING FROM N-CNTRL MN SSWWD INTO
W-CNTRL MN IS ADVANCING EWD AROUND 25-30 KT NEAR AND AHEAD OF A COLD
FRONT. AREA RADAR IMAGERY SUGGESTS THAT THE LINE ONLY EXHIBITS
MODEST ORGANIZATION ACROSS MN. WHILE AN EML PLUME FEATURING
MID-LEVEL LAPSE RATES OF 7-7.5 C/KM HAS BEEN DRAWN INTO THE REGION
IN ADVANCE OF THE FRONT...INHIBITION ASSOCIATED WITH THIS PLUME HAS
BEEN SLOW TO ERODE IN MANY AREAS OWING TO LIMITED LOW-LEVEL LAPSE
RATES IN CONJUNCTION WITH THE STRATOCUMULUS FIELD MAINTAINED THROUGH
THE DAY. AND...WITHOUT STRONGER FORCING FOR ASCENT AHEAD OF THE
SQUALL LINE...CONVECTION WILL LIKELY REMAIN SPATIALLY CONFINED TO
/1/ THE LEADING EDGE OF THE EVOLVING COLD POOL ATTENDANT TO THE
SQUALL LINE AND /2/ SEGMENTS OF THE FRONT WHERE OVERTURNING HAS BEEN
LIMITED. REGARDLESS...35 TO 45 KT OF EFFECTIVE BULK SHEAR WILL
LIKELY MAINTAIN A THREAT FOR SVR WIND GUSTS WITH THE SQUALL
LINE...AND PARTICULARLY WITH ANY EMBEDDED BOWING SEGMENTS.

ALSO OF NOTE...ACROSS S-CNTRL MN...GREATER COVERAGE OF INSOLATION
PER VISIBLE SATELLITE IMAGES IS BOOSTING INSTABILITY. AS SUCH...MORE
ROBUST EMBEDDED CONVECTIVE STRUCTURES...PERHAPS EXHIBITING
SEMI-DISCRETE CHARACTERISTICS IN INCIPIENT STAGES...WILL REMAIN
POSSIBLE INVOF THE SRN EXTENT OF THE LINE. BOTH SVR HAIL AND SVR
WIND GUSTS WILL BE OF CONCERN WITH THIS ACTIVITY. HOWEVER...IN THIS
AREA...THE LAGGING NATURE OF THE LOBE OF ASCENT ACCOMPANYING AN
APPROACHING SHORTWAVE TROUGH...AND LACK OF MORE SRN INFLUENCE TO THE
SQUALL-LINE-ACCOMPANYING COLD POOL...MAY LIMIT THE COVERAGE OF
CONVECTION ACROSS SRN AREAS OF THE WW.

THE SVR THREAT WILL RAPIDLY WANE FOLLOWING FRONTAL PASSAGE.

..COHEN.. 08/15/2012

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

ATTN...WFO...DLH...MPX...FGF...FSD...ABR...

LAT...LON   43539349 45199711 49179482 47579088 43539349

Mesoscale Discussions in Minnesota, 2012Mesoscale Discussions in Wisconsin, 2012Mesoscale Discussions in South Dakota, 2012Every mesoscale discussion in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive.