SPC AC 121959
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0259 PM CDT SAT AUG 12 2006
VALID 122000Z - 131200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE
CNTRL/NRN PLAINS TO THE UPPER MS VLY...
...NRN/CNTRL PLAINS TO THE UPPER MS VLY...
TSTMS CONTINUE TO GRADUALLY INTENSIFY ALONG/AHEAD OF A PRE-FRONTAL
TROUGH COINCIDENT WITH A LOW-LEVEL THERMAL RIDGE FROM CNTRL SD SWD
INTO NERN CO THIS AFTN. 2-6KM SHEAR VECTORS HAVE HAD A BACKING
TENDENCY AHEAD OF THE DIGGING PAC NW TROUGH...NOW ALIGNED PARALLEL
TO THE INITIATING BOUNDARY. THIS SUGGESTS THAT STORMS WILL EVOLVE
PRIMARILY INTO LINE SEGMENTS. VERTICAL SHEAR WAS STRONGEST ACROSS
THE INTERNATIONAL BORDER AND ACROSS THE NRN HIGH PLAINS...BUT
MARGINALLY SUFFICIENT FOR PERHAPS A BRIEF SUPERCELL. PRESENT
INDICATIONS ARE THAT THE STORMS WILL SLOWLY INTENSIFY ACROSS
CNTRL/ERN SD SWD INTO CNTRL NEB THROUGH THE EVENING OWING TO STEEP
LOW-LEVEL LAPSE RATES. H7-H5 LAPSE RATES HAVE BEEN TEMPERED BY
INFLUX OF MONSOONAL MOISTURE ALOFT ON THE SUB-TROPICAL CONVEYOR AND
SHOULD LIMIT HAIL SIZE TO LESS THAN 2 INCHES. DAMAGING WINDS WILL
BE A THREAT AS STORMS DEVELOP INTO SMALL SCALE BOWS.
FURTHERMORE...THOUGH STORM EVOLUTION INTO A MORE LINEAR MODE WILL
TEND TO LIMIT THREAT FOR SUSTAINED LOW-LEVEL ROTATION...ISOLD
TORNADOES ARE PSBL ACROSS THE ERN DAKS/WRN MN WHERE THE BOUNDARY
LAYER FLOW REMAINS BACKED AHEAD OF A 1003 MB SFC-LOW OVER CNTRL SD.
HERE...LCLS ARE LOWER OWING TO SLIGHTLY COOLER TEMPERATURES AND
AMPLY MOIST BOUNDARY LAYER. ACTIVITY WILL GRADUALLY SPREAD ENEWD
INTO ERN SD...WRN MN AND NERN NEB OVERNIGHT WITH PERHAPS DAMAGING
WINDS.
FARTHER N...GLANCING INFLUENCE OF A LEAD MID-LEVEL SHORTWAVE TROUGH
MOVING INTO SRN MANITOBA HAS CONTRIBUTED TO A GRADUAL INCREASE IN
ELEVATED TSTMS ALONG/N OF THE PRIMARY COLD FRONT FROM NWRN
ONTARIO...SERN MANITOBA INTO CNTRL ND. THIS REGION IS SITUATED JUST
N OF THE SUB-TROPICAL MOIST PLUME AND MID-LEVEL TEMPERATURES ARE NOT
AS WARM AS FARTHER S. CLOUDS DOWNSTREAM FROM THE ACTIVITY WILL TEND
TO LIMIT SFC-BASED EVOLUTION...BUT ACTIVITY WILL LIKELY BUILD SWWD
ALONG THE FRONT TOWARD SWRN ND LATER THIS AFTN. LARGE HAIL WILL BE
THE PRIMARY THREAT WITH THIS ACTIVITY AS IT MOVES ENEWD INTO FAR
NWRN MN/LAKE OF THE WOODS LATER THIS EVENING/OVERNIGHT.
...NRN/CNTRL ROCKIES/HIGH PLAINS...
PRIMARY TROUGH AXIS NOW OVER ERN ORE AND ID WILL EJECT ENEWD INTO
THE NRN/CNTRL HIGH PLAINS TONIGHT. TSTMS WILL BE INCREASING THIS
EVENING ACROSS PORTIONS OF SRN MT AND WY IN ADVANCE OF THIS SYSTEM.
ACTIVITY WILL MOVE NEWD ONTO THE ADJACENT HIGH PLAINS OVERNIGHT.
LOW-LEVEL MOISTURE WILL BE SOMEWHAT LIMITED...BUT LARGE TEMP/DEW
POINT SPREADS AND COLDER AIR ALOFT FILTERING INTO THE REGION MAY
SUPPORT ISOLD GUSTY WINDS/HAIL.
..RACY.. 08/12/2006
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
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