DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 031631
SWODY1
SPC AC 031629

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1129 AM CDT SUN JUN 03 2012

VALID 031630Z - 041200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM THE TX
PANHANDLE...OK/AR...ACROSS THE MS VALLEY TO THE TN VALLEY...

...SYNOPSIS...
A DEEP UPPER CYCLONE OVER SRN ONTARIO WILL BEGIN TO TRANSITION INTO
MORE OF AN OPEN WAVE TROUGH WHILE SPREADING SEWD ACROSS THE ERN
GREAT LAKES. A BROAD BELT OF MODERATE TO STRONG NWLY MID LEVEL FLOW
EXISTS ON THE SWRN FLANK OF THIS LARGE SCALE TROUGH WITH 40-70KT
500MB WINDS EXTENDING FROM UPPER MS VALLEY TO THE SOUTHEAST. WHILE A
LARGE SCALE RIDGE AXIS EXISTS ACROSS MUCH OF THE CNTRL U.S. EAST OF
THE ROCKIES...MINOR PERTURBATIONS...SOME CONVECTIVELY INDUCED AND
MAINTAINED...ARE EMBEDDED WITHIN THE ARC OF ANTICYCLONIC LARGE SCALE
FLOW OVER THIS REGION OF THE COUNTRY. A COMPLEX OF THESE SMALLER
SCALE IMPULSES...ACCOMPANIED BY SLIGHTLY STRONGER MID LEVEL FLOW
ACROSS THE PLAINS THIS MORNING...WILL CONTINUE TO PLAY SOME ROLE IN
TSTM DEVELOPMENT AND COVERAGE LATER TODAY FROM THE SRN PLAINS ACROSS
THE MS VALLEY TO THE SOUTHEAST.

UPPER RIDGING IS FORECAST TO STRENGTHEN OVER THE FOUR CORNERS AREA
THROUGH THE PERIOD AS A STRONG TROUGH MOVES TOWARD THE WEST COAST BY
EARLY MONDAY.

...MO/AR TO MS/AL...
OVERALL FORECAST UNCERTAINTY REMAINS RATHER HIGH OVER THE ENTIRE
COUNTRY THIS PERIOD AS SHOWN IN THE WIDE RANGE OF CHANGES TO THE
OUTLOOK OVER THE PAST 72 HOURS. THIS IS DUE IN PART TO STORM SCALE
AND MESOSCALE INFLUENCES ON BOTH THE BOUNDARY LAYER AND UPPER LEVELS
THAT ARE NOT ALWAYS WELL DEPICTED OR HANDLED BY TRADITIONAL
NUMERICAL MODELS.

LATEST UA AND SURFACE ANALYSIS REVEAL A SHORT WAVE TROUGH/MCV
DRIVING A SMALL CLUSTER OF CONVECTION ACROSS NERN AR. AIRMASS
UPSTREAM FROM THESE WEAK TSTMS WILL CONTINUE TO DESTABILIZE BENEATH
CAPPING INVERSION THAT WEAKENS WITH EWD EXTENT. VERY WARM BOUNDARY
LAYER AND WEAK BUT PERSISTENT ISENTROPIC ASCENT FROM THE MS RIVER
EAST ACROSS MS AND AL MAY CONTRIBUTE TO AN INCREASING CHANCE FOR
SURFACE-BASED TSTM DEVELOPMENT LATER THIS AFTERNOON. THESE AREAS
RESIDE ON THE SWRN FLANK OF STRONGER WNWLY FLOW ALOFT AND BENEATH
THE RIGHT ENTRANCE REGION OF MID LEVEL JET SITUATED ACROSS THE CNTRL
APPALACHIANS AND EAST COAST. ANY DEEP CONVECTION DEVELOPING IN THIS
REGIME WILL EXIST AMIDST SUFFICIENT SHEAR AND FLOW TO SUPPORT AN
INCREASING CHANCE FOR MULTICELLS AND PERHAPS EVEN SUPERCELLS WITH
ATTENDANT THREATS OF HAIL/WIND INTO THE EVENING.

IN ADDITION TO THE POSSIBILITY OF THE ABOVE SCENARIO...LATEST NAM
SUGGESTS ANOTHER UPSTREAM MCS DEVELOPING FROM THE MO BOOTHEEL ACROSS
THE MS RIVER LATE TONIGHT. THIS COMPLEX IS FORECAST TO SPREAD SEWD
ACROSS PARTS OF THE TN VALLEY THROUGH EARLY MONDAY AND COULD ALSO
BRING WITH IT ANOTHER ROUND OF STRONG WINDS AND PERHAPS SOME HAIL
EVENTS.

GIVEN THESE PROSPECTS FOR STRONG TO SEVERE STORMS THROUGHOUT THE
REST OF THIS FORECAST PERIOD...THE SLGT RISK AREA HAS BEEN EXPANDED
EAST ACROSS THE MS RIVER AND INTO THE TN VALLEY.

...SRN PLAINS...
REMNANTS OF OVERNIGHT MCS WAS DISSIPATING WHILE SPREADING INTO MO/AR
LATE THIS MORNING. IN THE WAKE OF THIS DECAYING CONVECTIVE SYSTEM
THERE IS A WEAK SHORT-WAVE TROUGH OBSERVED ACROSS THE HIGH PLAINS OF
ERN CO/NERN NM THAT IS EXPECTED TO PROGRESS ESEWD TOWARD WRN OK BY
04/00Z. CONSIDERABLE LEFT-OVER MID LEVEL CONVECTIVE DEBRIS IS NOTED
LATE THIS MORNING ACROSS MUCH OF KS AND EVEN ACROSS PARTS OF NRN OK.
HOWEVER...STRONG BOUNDARY LAYER HEATING IS UNDERWAY ACROSS THE HIGH
PLAINS FROM SERN CO INTO THE TX PANHANDLE. ALTHOUGH A SUBSTANTIAL
EML HAS OVERSPREAD THE SRN HIGH PLAINS...IT APPEARS BOUNDARY LAYER
HEATING WILL BE INTENSE ENOUGH THAT CONVECTIVE TEMPERATURES WILL BE
BREACHED ALONG THE DRY LINE ACROSS THE ERN OK/TX PANHANDLE INTO
PORTIONS OF NWRN TX LATER THIS AFTERNOON.

THERE IS INCREASING CONFIDENCE THAT A CLUSTER OF STRONG TO SEVERE
THUNDERSTORMS WILL EVOLVE ALONG THE SRN INFLUENCE OF THE
AFOREMENTIONED CLOUDINESS ACROSS KS SUCH THAT AN MCS MAY EVOLVE OVER
NWRN OK THIS EVENING. LATEST MODEL GUIDANCE SUGGESTS THIS ACTIVITY
WILL DEVELOP WITHIN AN INCREASINGLY UNSTABLE AIR MASS CHARACTERIZED
BY SBCAPE IN EXCESS OF 3000 J/KG AND DEEP LAYER SHEAR MORE THAN
ADEQUATE TO SUPPORT AN UPSCALE EVOLVING MCS AFTER DARK. FOR THIS
REASON HAVE INCREASED THE PROBABILITY FOR SEVERE HAIL/WIND...AND
INCLUDE THE RISK OF SIG HAIL /2 INCHES OR GREATER/ ACROSS NWRN/CNRTL
OK WITH BOTH INITIAL SUPERCELL STRUCTURES AND STORM MERGERS. HAVE
ALSO SHIFTED 5 PCT TOR PROBS SWD TO BETTER REFLECT THE MOST LIKELY
POSITION OF WEAK SFC BOUNDARY THAT COULD AID IN THE DEVELOPMENT OF A
COUPLE OF TORNADOES. LATEST THINKING IS SEVERE MCS MAY SPREAD ESEWD
ACROSS MUCH OF NRN OK THIS EVENING...POSSIBLY EXTENDING INTO
PORTIONS OF CNTRL OK AS LLJ INCREASES INTO THIS PART OF THE STATE
AFTER DARK.

...CNTRL/NRN ROCKIES AND THE ADJACENT HIGH PLAINS...
MID/UPPER FLOW WILL CONTINUE TO BUCKLE AS A RIDGE AMPLIFIES OVER THE
NRN ROCKIES/HIGH PLAINS IN RESPONSE TO A DIGGING ERN PACIFIC TROUGH.
WHILE THIS LARGE-SCALE PATTERN WILL NOT BE AS FAVORABLE FOR SVR
STORMS TODAY AS IT WAS YESTERDAY...SUFFICIENTLY COOL MID-LEVEL
TEMPERATURES WILL SUPPORT A BROAD AREA OF STEEP LAPSE RATES ATOP THE
WRN FRINGES OF THE GULF OF MEXICO LOW-LEVEL MOISTURE PLUME. THIS
WILL YIELD MARGINAL DESTABILIZATION FROM SWRN/S-CNTRL MT SWD ACROSS
THE CNTRL ROCKIES/HIGH PLAINS.

WITH OROGRAPHIC ASCENT INCREASING THIS AFTERNOON DUE TO DIABATIC
HEATING...ISOLATED TO SCATTERED STORMS SHOULD DEVELOP OVER THE
ROCKIES AND BE STEERED EWD/SEWD OVER THE ADJACENT HIGH PLAINS.
ISOLATED INSTANCES OF SVR HAIL WILL BE THE GREATEST CONCERN WITH
THESE STORMS...PARTICULARLY ACROSS PARTS OF SWRN/S-CNTRL MT WHICH
WILL BE IN CLOSER PROXIMITY TO THE ZONE OF STRONGER DEEP SHEAR
ATTENDANT TO THE POLAR STREAM OVER THE NRN FRINGES OF THE AMPLIFYING
UPPER RIDGE. ONE OR TWO STORM CLUSTERS COULD EVOLVE FROM THE MT
ACTIVITY AND SHIFT EWD INTO THE EARLY EVENING. THE OVERALL SVR
THREAT IS EXPECTED TO DIMINISH ACROSS THE ENTIRE AREA THROUGH THE
EVENING GIVEN BOUNDARY LAYER STABILIZATION AND THE LACK OF STRONGER
DEEP FORCING FOR ASCENT.

...NORTHEAST/MID ATLANTIC...
COLD POOL ALOFT ASSOCIATED WITH THE DEEP LOW/TROUGH OVER ERN GREAT
LAKES WILL CONTRIBUTE TO AN INCREASE IN LOW TOPPED SHOWER AND TSTM
DEVELOPMENT FROM SERN NY ACROSS PA/NJ AND PARTS OF THE MID ATLANTIC
THROUGH THE AFTERNOON. WHILE BOUNDARY LAYER WARMING SHOULD
CONTRIBUTE TO WEAK DESTABILIZATION...MEAGER LOW LEVEL MOISTURE AND
LACK OF STRONGER LOW LEVEL CONVERGENCE ARE EXPECTED TO LIMIT OVERALL
CONVECTIVE VIGOR. NONETHELESS...SHOWERS/STORMS COULD PRODUCE LOCALLY
GUSTY WINDS AND A ISOLATED STRONGER CELLS COULD GENERATE COPIOUS
AMOUNTS OF SMALL HAIL.

..CARBIN/DARROW/COHEN.. 06/03/2012

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