SPC AC 211251
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0751 AM CDT SUN MAY 21 2006
VALID 211300Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM SE KS INTO THE TN VLY...
...THERE IS A SLGT RISK OF SVR TSTMS OVER THE CNTRL HI PLNS...
...THERE IS A SLGT RISK OF SVR TSTMS OVER INTERIOR PARTS OF THE PAC
NW/MT...
...SYNOPSIS...
RCKYS RIDGE EXPECTED TO AMPLIFY SLIGHTLY AS IT SHIFTS E INTO THE HI
PLNS BETWEEN NOW AND MONDAY...LARGELY IN RESPONSE TO DEEPENING OF
UPR LOW W OF BC. DEEPENING OF BC LOW SHOULD DRIVE UPR SYSTEM NOW
OFF THE CNTRL CA CST SE TOWARD SAN DIEGO BY EARLY MONDAY...AND
MAINTAIN DEEP SSWLY FLOW OVER THE FAR WEST. AT THE SAME TIME...
SYSTEM THAT CROSSED THE UPR GRT LKS YESTERDAY WILL REINFORCE
EXISTING TROUGH OVER THE NORTHEAST. ASSOCIATED COLD FRONT SHOULD
CONTINUE SW INTO THE LWR MO/MID MS VLYS...AND S/SE ACROSS THE OH VLY
AND MID ATLANTIC STATES. THE FRONT SHOULD EVENTUALLY MERGE WITH
WEAKER ONE NOW EXTENDING FROM CNTRL KS ESE INTO THE TN VLY.
...KS/MO E/SE INTO TN VLY...
WHILE UPR RIDGE WILL AMPLIFY SOMEWHAT OVER THE HI PLNS...GLANCING
INFLUENCE OF GRT LKS SPEED MAX WILL MAINTAIN 25-30 KT MID LEVEL
WNWLY FLOW ABOVE WEAK FRONT STALLED FROM KS/SRN MO ESE INTO THE TN
VLY. MODERATE SURFACE HEATING...RELATIVELY STEEP MID LEVEL LAPSE
RATES /7.5-8.5 DEG C PER KM/...FAIRLY MOIST AIR /WARM SECTOR
DEWPOINTS IN THE LOW 60S/ AND FRONTAL CONVERGENCE TOGETHER SHOULD
SUPPORT RENEWED STORM DEVELOPMENT ALONG THE BOUNDARY BY MID TO LATE
AFTERNOON. THIS POTENTIAL APPEARS MOST LIKELY FROM SE KS INTO SW
MO...WHERE A RELATIVE MAXIMUM IN LOW LEVEL INFLOW SHOULD EXIST INVOF
OUTFLOW BOUNDARIES LEFT BY OVERNIGHT STORMS. MORE WIDELY SCATTERED/
LESS SUSTAINED ACTIVITY SHOULD PREVAIL FARTHER E/SE ALONG FRONT...
FROM THE TN VLY TO THE SC CST.
30-35 KT DEEP NWLY SHEAR SHOULD BE SUFFICIENT FOR ORGANIZED/
SUSTAINED STORMS AND POSSIBLE SUPERCELLS WITH HAIL/HIGH WIND...
ESPECIALLY GIVEN ENHANCED DIRECTIONAL COMPONENT INVOF FRONT.
ADDITIONAL STORMS MAY FORM N OF BOUNDARY IN MO TONIGHT/EARLY MONDAY
AS NOCTURNAL STRENGTHENING/VEERING OF LLJ...AND AFOREMENTIONED
MERGING OF FRONTS...ENHANCE WAA ACROSS THE REGION.
...CNTRL HI PLNS...
WIDELY SCATTERED TSTMS THAT EVOLVE INTO LOOSELY ORGANIZED CLUSTERS
WITH A THREAT FOR HIGH WIND MAY FORM LATE THIS AFTERNOON/EARLY
TONIGHT FROM NE CO INTO ERN WY/THE NEB PANHANDLE. INITIATION WILL
BE SUPPORTED BY ELY/UPSLOPE SFC FLOW...DUE LARGELY TO STRONG HEATING
OF ELEVATED TERRAIN. SLOWLY RISING HEIGHTS ALOFT AND WEAK LOW LEVEL
WINDS SHOULD LIMIT OVERALL STORM STRENGTH. BUT 25+ KT MID LEVEL WNW
FLOW AND VERY DEEPLY MIXED BOUNDARY LAYER ENVIRONMENT WILL SUPPORT
STRONG STORM OUTFLOW AND UPSCALE GROWTH INTO CLUSTERS.
...INTERIOR PAC NW INTO MT...
WATER VAPOR IMAGERY AND RUC 500 MB VORT ANALYSIS SHOW A WEAK IMPULSE
OVER NE NV THAT SHOULD CONTINUE NNE ACROSS SRN/ERN ID THROUGH
MIDDAY...AND INTO N CNTRL MT BY THIS LATE AFTERNOON. THIS
FEATURE...COUPLED WITH SURFACE HEATING...OROGRAPHIC ASCENT AND
WEAKLY CONVERGENT LOW LEVEL FLOW...MAY SUPPORT ANOTHER ROUND OF
STRONG TO SEVERE STORMS IN CNTRL MT. LARGE TEMP-DEWPOINT SPREADS
AND MODERATE UNIDIRECTIONAL CLOUD LAYER FLOW SUGGEST MAIN SEVERE
THREATS WILL BE WIND AND MARGINALLY SEVERE HAIL.
FARTHER W...A CONDITIONAL RISK FOR STRONG/POSSIBLY SEVERE DIURNAL
STORMS WILL EXIST IN MORE STRONGLY SHEARED UNIDIRECTIONAL WIND
ENVIRONMENT OVER ERN/NRN ORE AND SE WA/WRN ID. MODIFIED ETA/WRF
SOUNDINGS WITH SFC TEMPS IN THE LOW 70S AND DEWPOINTS IN THE LOW 50S
F YIELD WELL-MIXED BOUNDARY LAYERS WITH LITTLE OR NO
CINH...INVERTED-VEE SUBCLOUD LAYER THERMODYNAMIC PROFILES...AND
ABOUT 1000 J/KG MLCAPE. COUPLED WITH 40+ KT DEEP SLY FLOW ON ERN
FRINGE OF OFFSHORE TROUGH...SUCH A SETUP WOULD SUPPORT SUSTAINED
STORMS AND POSSIBLE SUPERCELLS. ASSOCIATED EMBEDDED BOWS WOULD HAVE
THE POTENTIAL FOR BOTH HIGH WIND AND HAIL. A MAJOR UNCERTAINTY
REMAINS...HOWEVER...REGARDING CONVECTIVE COVERAGE AS LARGE SCALE
FORCING FOR ASCENT SHOULD REMAIN WEAK...AND MID/HIGH LEVEL CLOUDS
WILL LIMIT LOW LEVEL HEATING. SEEMS PRUDENT ATTM TO MAINTAIN A LOW
PROBABILITY RISK FOR SEVERE IN THIS AREA UNTIL IT IS CLEAR THAT
STORMS WILL INDEED NOT FORM.
..CORFIDI/GRAMS.. 05/21/2006
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NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z
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