SWODY1
SPC AC 191931
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0131 PM CST TUE JAN 19 2010
VALID 192000Z - 201200Z
...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTN ACROSS SOUTHERN
CALIFORNIA COASTAL AREAS...
...20Z UPDATE...
...SRN CA...
AS THE SOUTHERN PORTION OF ONE SPLITTING SHORT WAVE IMPULSE MIGRATES
INLAND THIS AFTERNOON...AND ANOTHER APPROACHES...LOW- LEVEL
CONVERGENCE/WARM ADVECTION ARE PROGGED TO REMAIN ENHANCED ACROSS THE
LOS ANGELES BASIN AND ADJACENT SOUTHERN CALIFORNIA COASTAL AREAS.
DESTABILIZATION IS ONGOING WITH PRECIPITABLE WATER INCREASING
THROUGH THE .75-1.00 INCH RANGE...AND AT LEAST WEAK MID-LEVEL
COOLING COULD STEEPEN MID-LEVEL LAPSE RATES BEFORE LOW-LEVEL
HODOGRAPHS BEGIN TO SHRINK TOWARD 20/00-02Z. THIS SUPPORTS
CONTINUING POTENTIAL FOR INTENSIFYING CONVECTIVE ELEMENTS AND
PERHAPS DISCRETE LOW TOPPED SUPERCELL DEVELOPMENT WITHIN FRONTAL
BAND...ACCOMPANIED BY THE RISK FOR DAMAGING SURFACE GUSTS ...AS WELL
AS AN ISOLATED TORNADO OR TWO.
..KERR.. 01/19/2010
.PREV DISCUSSION... /ISSUED 1010 AM CST TUE JAN 19 2010/
...SYNOPSIS...
SERIES OF FAST MOVING IMPULSES WILL MAINTAIN ACTIVE PATTERN ACROSS
THE WEST COAST TODAY...PARTICULARLY ALONG THE CA COAST. MORNING WV
IMAGERY IS SOMEWHAT NONDESCRIPT AS MID/UPPER LEVEL VORT MAXIMA NEAR
THE COAST...ALTHOUGH IT IS EVIDENT MULTIPLE ROUNDS OF DEEP ASCENT
WILL PROGRESS QUICKLY EWD ACROSS THE REGION. IN ADDITION...ENHANCED
JET STREAM WILL PERSIST ALONG THE SWRN U.S./MEXICAN BORDER EVIDENT
BY 120+ KT H25 JET OBSERVED ON MORNING UPPER AIR ANALYSIS. OVERALL
LARGE SCALE SETUP WILL REMAIN FAVORABLE FOR POSSIBLE SEVERE
THUNDERSTORMS INVOF SRN CA COAST...LARGELY DEPENDENT UPON
THERMODYNAMIC ENVIRONMENT TODAY.
FARTHER EAST...SURFACE WARM FRONT IS FORECAST TO BECOME BETTER
DEFINED EXTENDING EAST OF A LOW EXPECTED TO DEVELOP INTO SERN KS BY
THE END OF THE PERIOD INTO THE LOWER OH RIVER VALLEY. THIS WILL
OCCUR IN RESPONSE TO LEADING SRN STREAM SYSTEM AND ASSOCIATED
MID/UPPER LEVEL JET SHIFTING QUICKLY ENEWD ACROSS THE SRN
ROCKIES/HIGH PLAINS TODAY.
...SRN CA COAST...
LEADING FRONTAL RAIN BAND WAS MOVING ACROSS THE CENTRAL CA COAST
EARLY THIS MORNING BUT REMAINS OFF THE SRN CA COAST. THIS BAND WILL
CONTINUE MOVING EWD INTO SWRN CA DURING THE EARLY TO MID AFTERNOON.
VERY FAVORABLE LOW AND DEEP LAYER SHEAR SHOULD BE MAINTAINED AS
OROGRAPHIC INFLUENCES MAINTAIN ELY COMPONENT TO SURFACE WINDS SOUTH
OF POINT CONCEPTION. THIS SUGGESTS UPDRAFT ROTATION AND/OR
ORGANIZATION INTO SMALL LINES CAN BE EXPECTED SHOULD SUFFICIENT
INSTABILITY DEVELOP. ATTM...EXPECT AIR MASS WILL BECOME WEAKLY
UNSTABLE AS SFC TEMPERATURES AND DEW INCREASE TO AOA 50F. FURTHER
DESTABILIZATION SHOULD OCCUR IN POST-FRONTAL REGIME LATER TODAY IN
WAKE OF LEADING PRECIPITATION SHIELD...ALTHOUGH SHEAR WILL GRADUALLY
WEAKEN AS WLY LOW LEVEL WINDS BECOME MORE PREVALENT. AN EMBEDDED
DAMAGING WIND GUST OR TORNADO/WATERSPOUT MAY ACCOMPANY MORE
ORGANIZED ELEMENTS ALONG AND AHEAD OF LEADING MOIST
CONVECTION...WITH SOME SEVERE TSTM POTENTIAL CONTINUING INTO THE
EVENING AS MID LEVEL COLD POCKET MAINTAINS INSTABILITY AND OPEN-CELL
CUMULUS IN POST-FRONTAL ENVIRONMENT.
...CENTRAL CA INTO SWRN ORE COAST...
DEEP MOIST FETCH AND COOL POST-FRONTAL REGIME WILL CONTINUE OVER
THIS REGION TODAY AND TONIGHT. POCKETS OF WEAK INSTABILITY SHOULD
REMAIN SUFFICIENT FOR A FEW THUNDERSTORMS...INCLUDING LOW
PROBABILITIES OF HAIL AND/OR STRONG GUSTS WITH THE MORE ROBUST
UPDRAFTS.
...MID SOUTH AND VICINITY...
WILL MAINTAIN MARGINAL SEVERE THREAT LATE IN THE PERIOD ACROSS THIS
REGION AS 40+ KT SWLY LLJ INCREASES ASCENT FROM THE ARKLATEX INTO
THE MID SOUTH/LOWER OH RIVER VALLEYS BY WEDNESDAY MORNING. LOW
LEVEL MOISTURE WILL REMAIN SPARSE...ALTHOUGH FORECAST SOUNDINGS
SUGGEST STEEPENING MID LEVEL LAPSE RATES AND PERSISTENT ASCENT TO
THE BASE OF THE EML WILL BECOME SUFFICIENT FOR ELEVATED TSTMS LATE
THIS EVENING/OVERNIGHT. GIVEN THE RELATIVELY STEEP MID LEVEL LAPSE
RATES AND STRENGTHENING CLOUD LAYER SHEAR...MARGINALLY SEVERE HAIL
MAY ACCOMPANY MORE ROBUST UPDRAFTS TOWARDS DAYBREAK.
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