Thursday, June 17, 2010

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171627
SWODY1
SPC AC 171626

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1126 AM CDT THU JUN 17 2010

VALID 171630Z - 181200Z

...THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS OF EASTERN
SD...EASTERN NEB...CENTRAL/SOUTHERN MN...MUCH OF IA...AND WESTERN
WI...

...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE MIDWEST
STATES...

...THERE IS A SLGT RISK OF SVR TSTMS FROM SOUTHEAST MO/SOUTHERN IL
INTO MS/AL...

...UPPER MIDWEST...
A POWERFUL SHORTWAVE TROUGH IS ROTATING OUT OF THE NORTHERN HIGH
PLAINS AND INTO THE DAKOTAS TODAY...WITH AN ASSOCIATED 60-70 KNOT
MID LEVEL JET MAX NOSING INTO MN. LATEST SURFACE ANALYSIS SHOWS A
COLD FRONT SURGING EASTWARD ACROSS SD/NEB...WHICH IS LIKELY TO BE
THE PRIMARY FOCUS FOR INTENSE THUNDERSTORM ACTIVITY LATER TODAY.
STRONG SOUTHERLY LOW LEVEL WINDS AHEAD OF THE FRONT WILL MAINTAIN
NEAR 70F DEWPOINTS ACROSS EASTERN SD/NEB AND PORTIONS OF MN/IA WHERE
AFTERNOON MLCAPE VALUES OF 3000+ J/KG ARE EXPECTED. INCREASING
WINDS ALOFT WILL RESULT IN A VERY FAVORABLE ENVIRONMENT FOR SEVERE
STORMS BY MID-LATE AFTERNOON.

INITIAL THUNDERSTORM DEVELOPMENT IS EXPECTED BY EARLY AFTERNOON
ALONG THE FRONT OVER EASTERN SD AND NORTHEAST NEB. FORECAST
SOUNDINGS IN THIS REGION SHOW SUBSTANTIAL LOW LEVEL AND DEEP LAYER
VERTICAL SHEAR...WITH SHEAR VECTORS PERPENDICULAR TO THE FRONT
SUGGESTING DISCRETE SUPERCELLS ARE LIKELY. SUFFICIENTLY LOW LCL
HEIGHTS FURTHER INDICATE THAT A FEW TORNADOES /POSSIBLY STRONG/ MAY
OCCUR DURING THE FIRST FEW HOURS OF THE EVENT. VERY LARGE HAIL IS
ALSO A POSSIBILITY WITH SUPERCELL STRUCTURES ACROSS CENTRAL/
SOUTHERN MN AND WESTERN/CENTRAL IA THROUGH EARLY EVENING. WITH
TIME...LINEAR FORCING MECHANISMS WILL PROMOTE A MORE ORGANIZED
SQUALL LINE WITH WIDESPREAD DAMAGING WINDS BEING THE MOST LIKELY
THREAT ACROSS EASTERN MN INTO WESTERN WI.

...MID MS AND TN VALLEYS...
A COUPLE OF REMNANT MCSS ARE TRACKING SOUTHEASTWARD ALONG LOW LEVEL
INSTABILITY GRADIENT FROM SOUTHERN IL INTO MIDDLE TN. A VERY MOIST
AND UNSTABLE AIR MASS NEAR AND SOUTHWEST OF THIS AREA WILL HELP
STORMS INTENSIFY THROUGH THE AFTERNOON...DESPITE RATHER WEAK WIND
FIELDS. LOCALLY DAMAGING WINDS AND HAIL WILL BE POSSIBLE WITH THESE
STORMS.

...TX PANHANDLE...
MOST MODEL GUIDANCE INDICATES A CLUSTER OF THUNDERSTORMS WILL
DEVELOP OVER EASTERN NM/WEST TX LATER THIS AFTERNOON AND SPREAD INTO
THE WESTERN TX PANHANDLE. GIVEN THE HOT/MOIST ENVIRONMENT...
STRONGER STORMS MAY PRODUCE DAMAGING WINDS. AREAL COVERAGE AND
DURATION OF THREAT IS UNCERTAIN...SO WILL MAINTAIN ONLY LOW SEVERE
PROBABILITIES AT THIS TIME.

..HART/GRAMS.. 06/17/2010

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