SPC MD 1645

MD 1645 CONCERNING SEVERE THUNDERSTORM WATCH 476… FOR PORTIONS IA…WRN IL…ERN NEB…NRN MO…EXTREME NERN KS.


MESOSCALE DISCUSSION 1645
NWS STORM PREDICTION CENTER NORMAN OK
0937 PM CDT TUE AUG 06 2013

AREAS AFFECTED...PORTIONS IA...WRN IL...ERN NEB...NRN MO...EXTREME
NERN KS.

CONCERNING...SEVERE THUNDERSTORM WATCH 476...

VALID 070237Z - 070430Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 476
CONTINUES.

SUMMARY...SVR HAIL/GUST THREAT CONTINUES OVER MAINLY SRN PORTIONS
WW. PER COORD W/AFFECTED WFOS...SOME NRN COUNTIES MAY BE CLEARED
SHORTLY...WHERE AIR MASS HAS BEEN AND WILL BE STABILIZED
SUBSTANTIALLY BY COMBINED EFFECTS OF CONVECTIVE OUTFLOW AND/OR
DIABATIC SFC COOLING.  ISOLATED SVR MAY OCCUR N OF WW FROM
CONVECTION OVER NRN IA...OR FROM TSTMS CURRENTLY OVER SERN NEB JUST
S OF WW...AND POTENTIALLY AFFECTING NEARBY PORTIONS MO/KS.
HOWEVER...OVERALL THREAT APPEARS TO BE GETTING MORE
ISOLATED/DISORGANIZED AREA-WIDE.  DEPENDING ON CONVECTIVE
TRENDS...MORE OF WW MAY BE CLEARED BEFORE SCHEDULED 05Z EXPIRATION.

DISCUSSION...MOST OF WW REMAINS AHEAD OF WEAK/SLOW-MOVING SFC COLD
FRONT ESTIMATED FROM S-CENTRAL MN SWWD ACROSS SUX/DVN/IML AREAS.
OUTFLOW BOUNDARY FROM EARLIER SVR TSTM APPEARS TO BE ENHANCING LIFT
FOR LATER TSTMS MOVING SEWD FROM PLATTE COUNTY NEB.  TSTM OUTFLOW
AND/OR DOWNSHEAR PRECIP HAS STABILIZED BOUNDARY LAYER OVER MUCH OF
I-80 CORRIDOR FROM DSM AREA EWD...AND OVER AREAS NW THROUGH E OF
OTM-AREA CONVECTION.  S AND W OF THAT ACTIVITY...PORTIONS SRN IA AND
SERN NEB REMAIN IN FAVORABLY UNSTABLE PRECONVECTIVE ENVIRONMENT.
RICH BOUNDARY-LAYER MOISTURE...WITH SFC DEW POINTS UPPER 60S TO LOW
70S F...WILL MAINTAIN ONLY SLOW RATE OF SFC COOLING AND CINH
INCREASE...KEEPING EFFECTIVE LIFTED PARCELS SFC-BASED FOR 2-3 MORE
HOURS AND MLCAPE AOA 2000 J/KG.  GIVEN 40-50 KT EFFECTIVE SHEAR
MAGNITUDES...ANY SUSTAINED CONVECTION STILL MAY ACQUIRE
SUPERCELLULAR CHARACTERISTICS...THOUGH WEAKNESS OF NEAR-SFC WINDS
WILL CONTINUE TO LIMIT HODOGRAPH SIZE.

..EDWARDS.. 08/07/2013

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

ATTN...WFO...ILX...LSX...DVN...ARX...DMX...EAX...FSD...OAX...
TOP...GID...

LAT...LON   39919572 40429672 41739767 42849468 43299280 42729134
            41649030 40189059 39909323 39919572

via SPC Forecast Products http://www.spc.noaa.gov/products/md/md1645.html