Severe Wx for CA on Thursday?!?!

[weatherlover427]

...SYNOPSIS...
CONTINUED NE MOTION OF SHORTWAVE TROUGH EXPECTED TO BE OVER THE MID ATLANTIC AT THE START OF THE PERIOD /THE SAME SYSTEM NOW ENTERING W TX/ WILL LEAVE A RATHER ZONAL FLOW PATTERN IN PLACE ACROSS THE LOWER 48 ON THURSDAY. AN EXCEPTION WILL BE OVER THE SWRN U.S...WHERE A COMPLEX EVOLUTION INVOLVING SEVERAL SYSTEMS NOW IN THE NE PACIFIC WILL YIELD A FAIRLY POTENT TROUGH OVER THE NRN BAJA AREA BY 12Z FRIDAY. CONFIDENCE IN THE DETAILS OF THIS EVOLUTION IS LOW GIVEN CONSIDERABLE SPREAD IN ENSEMBLE OUTPUT. BUT CONSIDERING BEHAVIOR OF SIMILAR LOWER LATITUDE SYSTEMS IN RECENT WEEKS...SLOWER/DEEPER SOLUTIONS OF THE ECMWF AND GFS APPEAR MORE REASONABLE THAN THAT OF THE ETA.

...SRN CA...
BOTH THE ECMWF AND GFS FORECAST THAT A FAIRLY STRONG SHORTWAVE IMPULSE WILL MOVE ACROSS SRN CA THURSDAY AFTERNOON AND EVENING. GIVEN FAVORABLE TIME OF DAY...OPEN NATURE OF UPPER TROUGH AND LIKELIHOOD FOR MODERATE/SUSTAINED ONSHORE/UPSLOPE FLOW...POTENTIAL WILL EXIST FOR THUNDERSTORMS. WITH SURFACE PRESSURE LIKELY TO REMAIN LOW OVER THE CNTRL AND NRN PARTS OF THE STATE...THERE WILL BE A TENDENCY TO MAINTAIN LOCALLY BACKED /SSELY/ FLOW ALONG THE COASTAL RANGES FROM LAX TO SAN. SUCH A SETUP COULD FOSTER UPDRAFT ROTATION IF STORMS DO INDEED FORM GIVEN PRESENCE OF 40+ KT DEEP WSWLY SHEAR ASSOCIATED WITH UPPER TROUGH.

[btangy]

Well, that probably means weak waterspouts and maybe a weak tornado at most. Instability looks nothing like what it did when that incredible hailstorm took shape over S,C LA. I think -2 at most, and models tend to exaggerate the LIs too. At least we'll get some decent rain.

[weatherlover427]

...SRN CA...
SE-MOVING PACIFIC IMPULSE WILL MOVE ACROSS SRN CA DURING THE DAY ON THURSDAY. GIVEN FAVORABLE TIME OF DAY AND MILD CONDITIONS IN PLACE AHEAD OF IT...POTENTIAL WILL EXIST FOR THUNDERSTORMS. HOWEVER...AS NOW FORECAST...UPPER SYSTEM WILL LIKELY FOLLOW AN INLAND TRACK ACROSS THE STATE. IN ADDITION...SURFACE PRESSURES OVER THE CNTRL AND NRN PART OF CA ARE NOW FORECAST TO BE SOMEWHAT HIGHER DURING THE PERIOD THAN THEY WERE FORECAST TO BE YESTERDAY AT THIS TIME. AS A RESULT...POTENTIAL FOR BACKED/UPSLOPE NEAR-SURFACE FLOW IN THE L.A. BASIN REGION APPEARS DIMINISHED RELATIVE TO YESTERDAY. WHILE DEEP SHEAR WILL BE MORE THAN SUFFICIENT FOR SUSTAINED/ROTATING STORMS ...DEGREE OF INSTABILITY/UPSLOPE FLOW AND CONVERGENCE APPEAR TOO LIMITED TO WARRANT AN OUTLOOK FOR SEVERE ALONG THE SRN CA CST. A FEW STORMS WITH HAIL MAY...NEVERTHELESS...AFFECT THE L.A. AREA...AS WELL AS ADJACENT PARTS OF THE SRN SAN JOAQUIN VLY AND DESERTS.