DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 020558
SWODY1
SPC AC 020556

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1256 AM CDT SUN JUN 02 2013

VALID 021200Z - 031200Z

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NERN CONUS...

...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS NM AND FAR W TX...

...SYNOPSIS...
UPPER-AIR PATTERN FCST TO BE RATHER PROGRESSIVE THROUGH PERIOD. STG
SHORTWAVE TROUGH -- NOW EVIDENT IN MOISTURE CHANNEL IMAGERY OVER
INLAND PAC NW AND BC -- IS FCST TO MOVE EWD ACROSS NWRN CONUS AND
SWRN CANADA THROUGH PERIOD. WEAK/EMBEDDED 500-MB LOW MAY EVOLVE
OVER CENTRAL MT BY 3/12Z. DOWNSTREAM...RIDGING WILL SHIFT EWD OVER
NRN PLAINS...WHILE MID-UPPER LEVEL LOW NOW OVER EXTREME NWRN ONT
PIVOTS ACROSS NRN ONT TO SRN JAMES BAY REGION. SYNOPTIC-SCALE
TROUGHING THAT EXTENDS SSWWD FROM THAT LOW WILL SHIFT EWD OVER UPPER
GREAT LAKES AND MS VALLEY. EMBEDDED SHORTWAVE TROUGH -- NOW LOCATED
OVER IL/WRN INDIANA -- WILL EJECT NEWD AND GRADUALLY
DEAMPLIFY...CROSSING WRN PORTIONS PA/NY AROUND 02/18Z...THEN
WEAKENING FURTHER WHILE MOVING NEWD DOWN ST LAWRENCE RIVER AREA.

AT SFC...COLD FRONT NOW EXTENDING FROM LM AREA ACROSS SRN IL...AR
AND CENTRAL/SW TX SHOULD REACH NRN NY...WRN PA...CENTRAL/ERN
KY...WRN/MID TN...SRN LA...AND S-CENTRAL TX. FRONT SHOULD PROCEED
EWD TO NEW ENGLAND...INLAND MID-ATLC AND AL BY END OF PERIOD.

...PORTIONS NERN CONUS TO DIXIE...
SCATTERED TO NUMEROUS TSTMS ARE FCST TO DEVELOP MOSTLY AHEAD OF SFC
COLD FRONT...INVOF NEARLY PARALLEL PREFRONTAL SFC TROUGH AND ANY
OTHER MESOSCALE BOUNDARIES THAT MAY DEVELOP. DAMAGING WIND WILL BE
MAIN THREAT..WITH BOW/LEWP FORMATIONS...WITH ISOLATED HAIL POSSIBLE.
TORNADO POTENTIAL IS VERY CONDITIONAL GIVEN LIKELY CONVECTIVE MODE.
FLOW ALOFT WILL BEAR STRONGEST FLOW COMPONENT PARALLEL TO THESE
BOUNDARIES...AND SHOULD BE CLOSE TO UNIDIRECTIONAL THROUGH DEEP
LAYER. THIS WILL LIMIT DEEP SHEAR...THOUGH CINH WILL BE WEAK ENOUGH
THAT EVEN WEAK-MDT CONVERGENCE SHOULD PERMIT CONSIDERABLE CONVECTIVE
COVERAGE. AS SUCH...DOMINANT STORM MODE SHOULD BE
QUASI-LINEAR...THOUGH AT LEAST BRIEF SUPERCELL STRUCTURES MAY OCCUR
FROM ERN NY AND MA NEWD WHERE LOW-LEVEL SRH WILL BE RELATIVELY
MAXIMIZED.

ALTHOUGH APCHG SHORTWAVE TROUGH WILL BE DEAMPLIFYING...RELATED
DCVA/ASCENT MAY CONTRIBUTE SOME ENHANCEMENT OF MIDLEVEL LAPSE RATES
OVER PORTIONS NY/NEW ENGLAND. THIS WILL BE CONCURRENT WITH MORE
THERMODYNAMICALLY IMPORTANT PROCESS OF DESTABILIZATION OF BOUNDARY
LAYER DUE TO BOTH THETAE ADVECTION AND SFC DIABATIC HEATING.
THOSE...COMBINED WITH SFC DEW POINTS MID-UPPER 60S F...SHOULD YIELD
MLCAPE 1000-2000 J/KG.

LOW-LEVEL SHEAR AND CONVERGENCE EACH SHOULD DECREASE WITH SWWD
EXTENT DOWN CENTRAL/SRN APPALACHIANS/PIEDMONT INTO PORTIONS
MS/AL...WHERE CONVECTIVE STRUCTURES SHOULD BE MORE DISORGANIZED.
NONETHELESS...STG SFC HEATING AND AT LEAST SUBTLE LIFT ALONG
FRONTAL/OUTFLOW BOUNDARIES SHOULD OFFER POTENTIAL FOR DOWNBURSTS AND
ISOLATED LARGE HAIL OVER SERN CONUS CONVECTIVE CORRIDOR.

...PORTIONS NM AND FAR W TX...
WIDELY SCATTERED TSTMS SHOULD FORM MID-LATE AFTN...ESPECIALLY INVOF
ELEVATED TERRAIN NEAR AND BEHIND WRN LIMB OF LOW-LEVEL BAROCLINIC
ZONE. BACKED LOW-LEVEL FLOW AND RELATED MOIST ADVECTION/TRANSPORT
WILL COMBINE WITH UPSLOPE FLOW COMPONENT TO CONTRIBUTE TO CONVECTIVE
DEVELOPMENT AND MAINTENANCE. STEEP DEEP-LAYER LAPSE RATES WILL
CONTRIBUTE FURTHER TO MLCAPE IN 1500-2500 J/KG RANGE...OVER
WELL-MIXED BOUNDARY LAYER SUITABLE FOR MAINTAINING HAIL/GUSTS TO
SFC. STG DIRECTIONAL SHEAR WILL COUNTERBALANCE WEAK RELATIVELY WEAK
MIDLEVEL WINDS TO YIELD 30-40 KT EFFECTIVE SHEAR MAGNITUDES IN
SUPPORT OF TSTM ORGANIZATION. THREAT SHOULD LAST INTO EARLY-MID
EVENING ON AT LEAST ISOLATED BASIS UNTIL COMBINATION OF OUTFLOW
SPREADING AND DIABATIC COOLING REDUCE BOUNDARY-LAYER INSTABILITY.

...PORTIONS MT...
ISOLATED TO WIDELY SCATTERED TSTMS ARE EXPECTED TO DEVELOP AND MOVE
NEWD ACROSS THIS REGION DURING AFTERNOON...IN REGIME OF
STRENGTHENING DEEP-LAYER SHEAR AND FAVORABLE SFC HEATING. MAIN
LIMITING FACTOR WILL BE MRGL MOISTURE...WITH DEW POINTS GENERALLY
30S AND 40S F. HIGH-BASED ACTIVITY MAY PRODUCE ISOLATED SVR HAIL
AND DAMAGING GUSTS.

..EDWARDS/BUNTING.. 06/02/2013

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