SPC AC 061722
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1222 PM CDT FRI JUL 06 2007
VALID 071200Z - 081200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS NRN MN AND EXTREME NERN
ND...
...SYNOPSIS...
A SERIES OF STRONG SHORTWAVE TROUGHS MOVING EWD THROUGH SRN CANADA
WILL CONTINUE DE-AMPLIFICATION OF UPPER RIDGE IN THE WEST AND TROUGH
IN THE NORTHEAST. THIS WILL RESULT IN STRONGER STRENGTHENING
WLYS/ZONAL FLOW DEVELOPING ALONG THE NRN BORDER STATES. THE PRIMARY
FEATURE OF INTEREST FOR POTENTIAL STRONG/ SEVERE CONVECTION IS TIED
PRIMARILY TO A SHORTWAVE TROUGH...THAT THE MODELS ROTATE AROUND
UPPER RIDGE FROM ID TO MT BY EARLY SATURDAY MORNING AND EWD INTO NRN
MN BY LATE AFTERNOON. IN ASSOCIATION WITH THIS SYSTEM...A COLD FRONT
SWEEPS RAPIDLY EWD ACROSS THE DAKOTAS SATURDAY AND IS FORECAST TO
EXTEND FROM UPPER MI SWWD INTO NWRN NEB BY THE END OF THE PERIOD.
...FAR ERN ND EWD INTO THE UPPER GREAT LAKES...
AHEAD OF APPROACHING SHORTWAVE TROUGH AND COLD FRONT...VERY WARM
TEMPERATURES ABOVE THE BOUNDARY LAYER...850MB READINGS BETWEEN 20C
AND 26C AND 12C TO 14C AT 700 MB...WILL RESULT IN A STRONGLY CAPPED
ENVIRONMENT...INHIBITING CONVECTIVE DEVELOPMENT THROUGH MUCH OF THE
DAY. HOWEVER...LARGE SCALE LIFT/LOW LEVEL CONVERGENCE AND 60-90M
HEIGHT FALLS SHOULD AID IN WEAKENING THE CAP LATE IN THE DAY.
ALSO...THE ETA/GFS ARE CONSISTENT IN DEPICTING A LOW LEVEL JET
DEVELOPING FROM ERN NEB NEWD INTO MN SATURDAY AFTERNOON ...RESULTING
IN STRENGTHENING MASS CONVERGENCE ACROSS NRN MN.
GIVEN THAT THE NEAREST LOWER 70 DEWPOINTS ARE LOCATED ACROSS THE SRN
PLAINS...THE NAM APPEARS TO BE OVERDOING BOUNDARY LAYER MOISTURE AND
GFS FORECAST OF LOWER TO MID 60 DEWPOINTS APPEARS MORE REASONABLE.
WITH THE STEEP LAPSE RATES...THIS WOULD YIELD MLCAPES OF AT LEAST
2000 J/KG. EVEN THOUGH THE INSTABILITY MAY BE CONSIDERABLY LESS THAN
FORECAST BY NAM...THIS AMOUNT OF INSTABILITY COMBINED WITH DEEP
LAYER SHEAR AT 40-50 KT WOULD BE FAVORABLE FOR RAPIDLY DEVELOPING
SEVERE STORMS AND SUPERCELLS. THE STEEP LAPSE COMBINED WITH ROTATING
UPDRAFTS INDICATE THAT LARGE HAIL SHOULD BE THE MAIN THREAT. THE
RELATIVELY HIGH LCL/S AND DRY BOUNDARY LAYER ALSO INDICATE THAT A
DAMAGING WIND THREAT ALSO EXISTS.
...SRN MT SEWD INTO WRN SD...
THUNDERSTORMS ARE EXPECTED TO DEVELOP IN POST-FRONTAL UPSLOPE FLOW
AS SHORTWAVE TROUGH...CURRENTLY LOCATED ALONG THE CENTRAL CA COAST
...MOVES INTO THE REGION DURING THE MAX HEATING PERIOD. HOWEVER...
DESPITE STEEP MID LEVEL LAPSE RATES...A DRY BOUNDARY LAYER WILL ONLY
CONTRIBUTE TO MLCAPE VALUES BETWEEN 500 AND 1000 J/KG. ALTHOUGH THE
RELATIVELY DEEP MIXED BOUNDARY LAYER WOULD FAVOR STRONG/ISOLATED
SEVERE WIND GUSTS...ONLY LOW SEVERE PROBABILITIES ARE FORECAST ATTM
DUE TO THE EXPECTED WEAK INSTABILITY/UPDRAFTS.
...AZ AND WRN NM...
MID LEVEL MOISTURE WILL CONTINUE TO ROTATE SWWD ACROSS THE REGION
AROUND THE UPPER HIGH PRESSURE CENTER...FORECAST TO BE LOCATED OVER
SRN CA/NV. THIS SUGGESTS THAT CONVECTION SHOULD ONCE AGAIN FORM OVER
THE SRN ROCKIES/RIM AREA AND THEN MOVE SWWD INTO THE LOWER
ELEVATIONS. ALTHOUGH SURFACE DEWPOINTS ARE FORECAST TO SLOWLY
INCREASE...INVERTED-V PROFILES AND SUFFICIENT INSTABILITY WOULD BE
FAVORABLE FOR VERY ISOLATED STRONG/DAMAGING WINDS DURING THE
AFTERNOON.
..IMY.. 07/06/2007
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
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