SWODY2
SPC AC 091729
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1229 PM CDT MON APR 09 2012
VALID 101200Z - 111200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SRN HIGH PLAINS...
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS MS DELTA REGION...
...SYNOPSIS...
UPPER-AIR PATTERN FCST TO REMAIN DOMINATED BY HIGH-AMPLITUDE RIDGING
OVER ROCKIES...BRACKETED BY DEEP TROUGHING OVER SERN CANADA AND U.S.
ATLC COAST...AND MEAN TROUGHING OVER NERN PAC. LARGE MID-UPPER
LEVEL CYCLONE -- NOW CENTERED OVER LOWER ST. LAWRENCE RIVER AREA --
IS EXPECTED TO RETROGRADE SLOWLY WWD AND SWWD ACROSS QUE WHILE
GRADUALLY FILLING. STG HEIGHT GRADIENT AND FLOW ALOFT WILL BE
MAINTAINED S AND SW OF THIS FEATURE...FROM DAKOTAS TO MID-ATLC
REGION. PARTS OF VORTICITY FIELD ASSOCIATED WITH SECONDARY
MID-UPPER CYCLONE -- NOW OVER MB/ONT BORDER REGION -- SHOULD BECOME
ENTRAINED IN THAT ENHANCED NWLY FLOW DAY-2. THIS PERTURBATION
SHOULD MOVE SEWD ACROSS OH VALLEY AND SRN/CENTRAL APPALACHIANS
DURING MIDDLE-LATTER PART OF PERIOD...AS PART OF LOW-AMPLITUDE
SHORTWAVE TROUGH.
AT SWRN FRINGES OF THIS BELT OF NW FLOW ALOFT...POTENTIAL EXISTS FOR
MCV TO EVOLVE FROM DAY-1/OVERNIGHT CONVECTION AND MOVE SEWD ACROSS
PORTIONS N AND E TX AND LA. MEANWHILE...SYNOPTIC-SCALE RIDGE OVER
ROCKIES IS EXPECTED TO MOVE SLOWLY EWD ACROSS TO HIGH PLAINS LATE IN
PERIOD...AS SERIES OF SHORTWAVE TROUGHS EJECT NEWD FROM PAC MEAN
TROUGH.
AT SFC...FRONTOGENESIS IS FCST ACROSS PORTIONS AR...SRN OK...N
TX...AND TX PANHANDLE. THIS WILL OCCUR AS POLAR RIDGING IS
REINFORCED ACROSS CENTRAL/NRN PLAINS BEHIND AFOREMENTIONED GREAT
LAKES/APPALACHIANS PERTURBATION. FURTHER MESOSCALE ENHANCEMENTS TO
THAT SYNOPTICALLY REINFORCED LOW-LEVEL BAROCLINICITY ALSO ARE LIKELY
FROM PRIOR/OVERNIGHT MCS THAT IS EXPECTED OVER PORTIONS OK AND
PERHAPS N TX. ERN PORTION OF FRONT SHOULD MOVE SWD ACROSS AR AND
ERN OK THROUGH ABOUT 11/00Z BEFORE STALLING...WHILE WRN PORTION
STALLS OVER TX PANHANDLE AND NERN NM. LATE-AFTERNOON DRYLINE IS
EXPECTED FROM N-CENTRAL/NERN TX PANHANDLE SWD ACROSS W-CENTRAL TX TO
NRN COAHUILA...RETREATING WWD ACROSS PANHANDLE/S-PLAINS REGION
DURING EVENING.
...SRN HIGH PLAINS...
WIDELY SCATTERED TO SCATTERED TSTMS MAY FORM ALONG DRYLINE AND INVOF
FRONTAL/OUTFLOW BOUNDARY DURING AFTERNOON...WITH ADDITIONAL
DEVELOPMENT POSSIBLE DURING EVENING AS DRYLINE RETREATS. DEEP-LAYER
SHEAR WILL BE FAVORABLE FOR SUPERCELL STRUCTURES...ESPECIALLY OVER
PANHANDLE/WRN OK REGION. AREA OF RELATIVELY BACKED/SELY FLOW IS
EXPECTED TO DEVELOP DURING AFTERNOON ALONG AND EVEN S OF FRONT OVER
PORTIONS OK AND NRN TX PANHANDLE...ENHANCING LOW-LEVEL SHEAR AND
STORM-RELATIVE INFLOW FOR ANY SUSTAINED CONVECTION THAT CAN OCCUR.
WEAKER VERTICAL MIXING IN THAT REGIME...COMPARED TO FARTHER S ACROSS
W-CENTRAL TX...ALSO WILL HELP TO MAINTAIN GREATER BOUNDARY-LAYER
MOISTURE CONTENT. ALTHOUGH DIRECTIONAL SHEAR WILL REMAIN PRONOUNCED
FARTHER S ACROSS W-CENTRAL/SW TX...WEAKER FLOW WILL YIELD SMALLER
HODOGRAPHS AND MORE CONDITIONAL/MRGL SUPERCELL RISK.
WITHIN BROAD 15% AREA...RELATIVELY CONCENTRATED SWATH OF SVR IS
LIKELY TO OCCUR. HOWEVER...TWO MAIN CONCERNS PRECLUDE 30% AND/OR
SIGNIFICANT-SVR SWATH FOR SUPERCELLULAR HAIL...
1. LACK OF ANY SUBSTANTIAL UPPER PERTURBATIONS...AND EVEN MORE
IMPORTANTLY
2. CONSIDERABLE UNCERTAINTIES REGARDING MORE SPECIFIC LOCATION OF
FRONTAL/OUTFLOW BOUNDARY THAT WILL MOST TIGHTLY FOCUS LOW LEVEL
MOISTURE/LIFT/VORTICITY E OF DRYLINE.
...SRN LOW PLAINS TO MS DELTA REGION...
SOME POTENTIAL STILL EXISTS FOR MCS TO PERSIST THROUGH EARLY MORNING
INTO AFTERNOON...THEN REJUVENATE ACROSS CENTRAL/NRN TX OR ARKLATEX
REGION INTO LOWER MS VALLEY. THIS MAY EVOLVE EITHER FROM DAY-1
DRYLINE OR FRONTAL CONVECTION...LATTER BEING ON FARTHER E POTENTIAL
TRACK ACROSS CENTRAL/ERN OK INTO ARKLATEX. AHEAD OF ANY
PROSPECTIVE/PERSISTENT MCS...FAVORABLE LOW-LEVEL MOISTURE WITH SFC
DEW POINTS 60S F WILL JUXTAPOSE WITH STG SFC HEATING TO YIELD
FAVORABLE BUOYANCY...ALTHOUGH LOW-LEVEL FLOW AND SHEAR WILL BE WEAK.
WILL CONTINUE 15% TOTAL-SVR OUTLOOK OVER THIS REGION WITH MINOR
MODIFICATIONS...THOUGH CONFIDENCE IN TIMING/LOCATION OF AFTERNOON
CONVECTION AND RESULTANT RELATIVE SVR MAX IS RATHER LOW.
..EDWARDS.. 04/09/2012
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