Saturday, September 29, 2007

DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 300043
SWODY1
SPC AC 300040

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0740 PM CDT SAT SEP 29 2007

VALID 300100Z - 301200Z

..THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE CNTRL
AND NRN PLAINS...

..CNTRL/NRN PLAINS...
ON THE LARGE SCALE...WATER VAPOR IMAGERY SUGGESTS THAT A LEAD WAVE
WAS EJECTING ACROSS THE NRN HIGH PLAINS WITH THE STRONGER PRIMARY
WAVE BEGINNING TO TURN EWD ACROSS UT/WRN CO. AT THE SFC...23Z SFC
ANALYSIS PLACED A 995 MB LOW OVER SWRN MANITOBA WITH A COLD FRONT
SURGING SEWD ACROSS CNTRL ND AND NWRN SD...TRAILING INTO CNTRL WY.
WEAK CYCLOGENESIS CONTINUES ALONG THE NEB/CO BORDER WITH A
LEE-TROUGH/DRYLINE EXTENDING SWWD INTO ERN NM.

AS THE LEAD WAVE EJECTS NEWD...THE COLD FRONT WILL DECELERATE ACROSS
ERN ND AND CNTRL SD. MEANWHILE...THE SECONDARY LOW WILL DEVELOP
INTO WRN NEB WITH INCREASING FRONTOGENESIS EXPECTED ACROSS THE CNTRL
HIGH PLAINS BY 12Z IN ADVANCE OF THE APPROACHING UT WAVE.

HIGH-BASED TSTMS THAT DEVELOPED IN THE DEEPLY MIXED ENVIRONMENT
LATE THIS AFTN SHOULD GRADUALLY ROOT INTO THE WRN EDGE OF MORE
SUBSTANTIAL MOISTURE/INSTABILITY ACROSS CNTRL NEB AND WRN KS THIS
EVENING. 00Z LBF SOUNDING SUGGESTS THAT CINH HAS WEAKENED IN A
NARROW ZONE IMMEDIATELY AHEAD OF THE DRYLINE SINCE 18Z OWING TO
HEATING AND MOISTENING. BUT...00Z ABR SOUNDING...AND IN PARTICULAR
THE DDC SONDE...SAMPLED MORE SUBSTANTIAL CINH. THIS SUGGESTS THAT
EVENING SVR THREATS WILL LIKELY BE CONFINED TO A NARROW AXIS FROM
EXTREME WRN KS NEWD INTO CNTRL SD.

SWLY MID-LEVEL FLOW AOA 50 KTS ATOP STRONG SLY FLOW HAS BOOSTED BULK
SHEAR SUFFICIENT FOR SUPERCELLS...THOUGH NUMBER OF STORMS AND MODEST
CINH WILL FAVOR EVOLUTION INTO SHORT LINE SEGMENTS BY MID-EVENING.
LARGE HAIL AND DMGG WINDS WILL BE THE PRIMARY THREATS. LOW-LEVEL
SHEAR...PARTICULARLY VCNTY THE LOW OVER NWRN KS AND WRN NEB...WAS
RATHER STRONG...BUT LCLS WERE HIGH AND CONVECTIVE MODE WILL LIKELY
NOT STRONGLY FAVOR TORNADOES.

ACTIVITY SHOULD SLOWLY PROGRESS EWD ACROSS THE PLAINS OVERNIGHT...
WHILE DEVELOPING AND/OR MOVING NEWD INTO THE ERN DAKS AND WRN MN
MORE QUICKLY. STEEP LAPSE RATES AND EVOLUTION OF A 50 KT SSWLY LLJ
INTO THE ERN DAKS AND WRN MN WILL INCREASE THE PROSPECTS FOR LARGE
HAIL WITH THE MORE ELEVATED ACTIVITY LATER TONIGHT.

.RACY.. 09/30/2007

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