SPC AC 071937
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0237 PM CDT SUN SEP 07 2008
VALID 072000Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PARTS OF FAR ERN
CO...NRN KS AND SRN NEB...
...CNTRL PLAINS/CNTRL HIGH PLAINS...
A ZONAL FLOW PATTERN IS IN PLACE ACROSS THE CNTRL PLAINS WITH WATER
VAPOR IMAGERY SHOWING A PLUME OF MID-LEVEL MOISTURE EXTENDING FROM
CNTRL CO EWD ACROSS NRN KS. AT THE SFC...A 1010 MB LOW IS PRESENT
OVER NCNTRL CO WITH A BOUNDARY EXTENDING SEWD FROM THE LOW ACROSS NE
CO...WRN KS INTO NRN OK. THE AIRMASS ACROSS THE CNTRL AND SRN PLAINS
REMAINS CAPPED BUT ELEVATED INSTABILITY IS INCREASING ABOVE THE CAP
WITH THE RUC SUGGESTING MUCAPE VALUES ACROSS SW KS RANGE FROM 1000
TO 1500 J/KG. MODEL FORECASTS FAIL TO DEVELOP MUCH CONVECTION ACROSS
THE SRN AND CNTRL PLAINS LATE THIS AFTERNOON INTO THE EVENING DUE TO
THE CAP BUT DO AGREE INITIATING ELEVATED THUNDERSTORMS ALONG THE NRN
EDGE OF THE INSTABILITY IN ERN CO LATE THIS EVENING. THIS CONVECTION
SHOULD INITIATE NEAR THE BOUNDARY AND MOVE EWD ACROSS NRN KS DURING
THE OVERNIGHT PERIOD AS THE LOW-LEVEL JET STRENGTHENS.
FORECAST SOUNDINGS ACROSS NRN KS OVERNIGHT SHOW STRONG VERTICAL
SHEAR AND SOMEWHAT STEEPENED MID-LEVEL LAPSE RATES SUGGESTING A
THREAT FOR HAIL WILL EXIST WITH THE MORE ORGANIZED THUNDERSTORMS. IF
AN ELEVATED SUPERCELL CAN DEVELOP...THEN A CORRIDOR OF HAIL WOULD BE
POSSIBLE IN NRN KS LATE TONIGHT. ALTHOUGH LESS LIKELY...A MARGINAL
WIND DAMAGE THREAT MAY ALSO DEVELOP IF AN ORGANIZED MCS CAN DRIVE AN
INTENSE DOWNDRAFT THROUGH THE CAP.
...NM/FAR WEST TX...
THUNDERSTORMS ARE CURRENTLY DEVELOPING ACROSS CNTRL NM ASSOCIATED
WITH A SHORTWAVE TROUGH EVIDENT ON WATER VAPOR IMAGERY. RUC ANALYSIS
SUGGESTS SEVERAL POCKETS OF MODERATE INSTABILITY ARE LOCATED FROM SW
NM EXTENDING NEWD INTO THE ERN PLAINS OF NM WHERE MLCAPE VALUES
RANGE FROM 1500 TO 2500 J/KG. IN ADDITION...SFC WINDS ARE BACKED
ACROSS MUCH OF NM WHICH IS CREATING SUBSTANTIAL DIRECTIONAL SHEAR IN
THE LOW TO MID-LEVELS AS SHOWN BY REGIONAL WSR-88D VWPS. THIS
COMBINED WITH INSTABILITY AND STEEP MID-LEVEL LAPSE RATES EVIDENT ON
FORECAST SOUNDINGS MAY BE SUFFICIENT FOR AN ISOLATED HAIL THREAT
WITH THE STRONGER MULTICELLS.
...UPPER GREAT LAKES...
WATER VAPOR IMAGERY SHOWS A BROAD LOW-AMPLITUDE UPPER-LEVEL TROUGH
OVER THE UPPER MIDWEST. AT THE SFC...A COLD FRONT IS LOCATED ACROSS
NW WI SWWD INTO SE MN. SCATTERED THUNDERSTORMS ARE DEVELOPING NEAR
AND AHEAD OF THE BOUNDARY WHERE THE RUC SUGGESTS INSTABILITY IS WEAK
ATTM. HOWEVER...MODERATE TO STRONG VERTICAL SHEAR EXISTS ACROSS MUCH
OF THE REGION ACCORDING TO THE RUC WHICH COMBINED WITH COLD AIR
ALOFT /500 MB TEMPS OF -20 TO -22C/ MAY BE SUFFICIENT FOR A MARGINAL
HAIL THREAT THIS AFTERNOON.
..BROYLES.. 09/07/2008
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z
|
