DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 171222
SWODY1
SPC AC 171220

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0720 AM CDT MON SEP 17 2007

VALID 171300Z - 181200Z

..THERE IS A SLGT RISK OF SVR TSTMS FROM THE CENTRAL PLAINS INTO
THE UPPER MS RIVER VALLEY...

..CENTRAL/NRN PLAINS...
PRONOUNCED MID LEVEL TROUGH NOW OVER THE GREAT BASIN WILL CONTINUE
TO EJECT NEWD ACROSS THE CENTRAL ROCKIES. AHEAD OF THIS
SYSTEM...MODELS CONTINUE TO DEPICT A SERIES OF LOWER AMPLITUDE
TROUGHS EMBEDDED WITHIN BROAD MID LEVEL MOISTURE PLUME AND RESIDUAL
MOIST CONVECTION SPREADING NEWD OVER THE CENTRAL ROCKIES THIS
MORNING. THESE IMPULSES WILL LIKEWISE EJECT NEWD ACROSS THE NRN
PLAINS TODAY...WHILE A SURFACE TROUGH/WEAK COLD FRONT BECOMES BETTER
DEFINED FROM THE NRN RED RIVER VALLEY INTO THE CENTRAL HIGH PLAINS.
A SURFACE WARM FRONT WAS ALREADY BEGINNING TO TAKE SHAPE FROM
CENTRAL IA INTO CENTRAL SD...WHICH WILL ALSO LIFT QUICKLY NWD
THROUGH THE DAY ALLOWING MID/UPPER 60F SURFACE DEW POINTS TO ADVECT
ACROSS MUCH OF MN AND THE ERN DAKOTAS. CLOUDS AND EARLY-DAY
CONVECTION WILL LIKELY CONTINUE TO OVERSPREAD THE REGION AHEAD OF
PRIMARY MID/UPPER LEVEL TROUGH. THIS WILL LIMIT HEATING AND
AVAILABLE INSTABILITY FOR MUCH OF THE DAY. DESPITE THIS...INCREASED
CONVERGENCE INVOF SURFACE TROUGH AND DEEP ASCENT SHOULD BREAK CAP
AND INITIATE STRONG THUNDERSTORMS WITHIN AXIS OF MODERATE
INSTABILITY LATER TODAY. ADDITIONAL DEVELOPMENT MAY OCCUR OVER PART
OF THE CENTRAL HIGH PLAINS LATE THIS AFTERNOON/EARLY THIS EVENING IN
PROXIMITY TO STRONG VORT MAX/SHORTWAVE TROUGH EJECTING ACROSS THE
CENTRAL ROCKIES.

STORMS WILL DEVELOP WITHIN A STRONGLY SHEARED ENVIRONMENT...
ESPECIALLY FROM NEB INTO THE UPPER MS RIVER VALLEY INVOF 50+ KT SWLY
MID LEVEL JET MAX. THUS...STORMS SHOULD ORGANIZE INTO SUPERCELLS
AND LINES THROUGH THE EVENING WITH PRIMARY SEVERE THREATS BEING
LARGE HAIL AND DAMAGING WINDS. ISOLATED TORNADOES MAY ALSO
OCCUR...ESPECIALLY INTO MN WHERE STORMS SHOULD DEVELOP WITHIN 40+ KT
SSWLY H85 JET WHICH WILL ENHANCE LOW LEVEL HODOGRAPHS.

..FOUR CORNERS ACROSS THE CENTRAL ROCKIES...
TERRAIN FORCING AND INCREASED LARGE-SCALE FORCING FOR ASCENT THIS
AFTERNOON AND EVENING ARE EXPECTED TO CONTRIBUTE TO FAIRLY
WIDESPREAD TSTM DEVELOPMENT. STEEP LOW TO MID-LEVEL LAPSE RATES AND
STRENGTHENING VERTICAL SHEAR THROUGH THE PERIOD SUGGESTS SOME
POTENTIAL WILL EXIST FOR A FEW ORGANIZED STORMS WITH A THREAT OF
LOCALLY STRONG WIND GUSTS AND SOME MARGINALLY SEVERE HAIL.

.EVANS/CROSBIE.. 09/17/2007

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