SWODY1
SPC AC 260055
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0755 PM CDT FRI MAR 25 2011
VALID 260100Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS PORTIONS SERN PLAINS...ARKLATEX
TO LOWER MS VALLEY...
...SYNOPSIS...
SPLIT FLOW PREVAILS OVER NORTH AMERICA IN MID-UPPER LEVELS. THIS
PATTERN FEATURES STG RIDGING FROM DAKOTAS NWD TO CANADIAN
ARCTIC...CYCLONES OVER CANADIAN MARITIMES REGION AND OFFSHORE PAC
NW...AND BROAD FETCH OF QUASI-ZONAL FLOW FROM CA EWD OVER MUCH OF
ATLANTIC COAST. EMBEDDED SHORTWAVE TROUGH -- EVIDENT IN MOISTURE
CHANNEL IMAGERY OVER UT -- IS FCST TO CROSS CENTRAL ROCKIES
OVERNIGHT...REACHING CENTRAL HIGH PLAINS BY 12Z.
AS THIS OCCURS...SFC LOW ANALYZED AT 23Z NEAR LHX IS FCST TO
MOVE/REDEVELOP SEWD ALONG FRONTAL ZONE TO NEAR CDS...THEN EWD ALONG
FRONT AND ACROSS SWRN OK BY 12Z...PERHAPS MERGING WITH TRIPLE-POINT
LOW NOW ANALYZED INVOF ADM. WARM/STATIONARY FRONT WAS DRAWN FROM
SRN OK LOW ESEWD TO NEAR TXK...EWD ACROSS SRN TIER OF AR COUNTIES
AND OVER N-CENTRAL MS. SOME PORTIONS OF FRONT MAY CONTINUE TO DRIFT
NWD VERY SLOWLY...WITH OTHERS REMAINING/BECOMING QUASISTATIONARY IN
SEGMENTS...GIVEN LACK OF AMBIENT FORCING FOR FRONTAL MOTION.
...SERN PLAINS...ARKLATEX TO LOWER MS VALLEY...
INITIATION REMAINS POSSIBLE BEFORE 02Z...BUT THREAT REMAINS
CONDITIONAL/ISOLATED. REF SPC MESOSCALE DISCUSSION 272 FOR FULL
DETAILS ON NEAR-TERM RISK.
BULK OF CONVECTIVE COVERAGE STILL SHOULD BE AFTER 03Z...INCLUDING
THREAT FOR SUPERCELLS AMIDST FAVORABLE DEEP-LAYER SHEAR. IN ABSENCE
OF APPRECIABLE LARGE-SCALE SUPPORT...MESOSCALE/THERMODYNAMIC AND
FRONTAL FACTORS WILL BE PRIMARY SUPPORTERS OF CONVECTIVE POTENTIAL
OVERNIGHT...WHICH IS WHY PROBABILITIES REMAIN MAXIMIZED NEAR AND N
OF SFC FRONT. MOISTURE AND SHEAR IN LOW LEVELS EACH ARE FCST TO
STRENGTHEN THROUGH 06Z NEAR FRONTAL ZONE...AS BOUNDARY-LAYER MIXING
DIMINISHES AND WARM/MOIST ADVECTION CONTINUE. LLJ WILL STRENGTHEN
SLIGHTLY TO 25-35 KT RANGE...ENLARGING HODOGRAPHS...WHILE LOW-LEVEL
WINDS BECOME MORE CONFLUENT AND CONVERGENT JUST ABOVE SFC.
GREAT MAJORITY OF SREF MEMBERS AND HIGH-RES PROGS ACCORDINGLY
DEVELOP TSTMS NEAR RED RIVER BEFORE 06Z...EXPANDING/MOVING EWD
ACROSS ARKLATEX...WITH HRRR BEING NOTABLE/PERSISTENT EXCEPTION
DURING PAST FEW HOURS. ONLY A COUPLE OF SUPERCELLS NEED TO DEVELOP
TO YIELD CORRIDOR CONCENTRATED SVR THREAT OVER THIS REGION...WITH
POSSIBILITY STILL EXISTING FOR MORE THAN THAT...THEREFORE OUTLOOK
LARGELY IS MAINTAINED EXCEPT FOR SOME ADJUSTMENT ALONG PERIPHERY IN
DEFERENCE TO LATEST SATELLITE/OBSERVATIONAL TRENDS.
...SRN KS TO WRN OZARKS...
SECONDARY/ELEVATED AREA OF CONVECTIVE DEVELOPMENT STILL APPEARS
POSSIBLE ACROSS THIS REGION...PRIMARILY AFTER ABOUT 08Z. CONVECTION
SHOULD DEVELOP ALONG NWRN FRINGES OF SUPPORTIVE LOW-LEVEL
WAA/MOISTURE TRANSPORT. IN THAT REGIME...FCST SOUNDINGS INDICATE
SUBSTANTIAL INCREASE IN THETAE YIELDING LFC AROUND 850 MB...BENEATH
ROUGHLY 8.5 DEG C/KM 700-500 MB LAPSE RATE...YIELDING MUCAPE
1500-2000 J/KG OVER NERN OK THAT DIMINISHES BELOW 1000 J/KG NWWD
OVER S-CENTRAL KS WITH WEAKER LOW-LEVEL THETAE. STG MID-UPPER LEVEL
WINDS CONTRIBUTE TO 50-65 KT EFFECTIVE SHEAR IN SUPPORT OF POTENTIAL
FOR ISOLATED LARGE HAIL.
..EDWARDS.. 03/26/2011
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