DAY1SVR: Day 1 Convective Outlook

ACUS01 KWNS 121627
SWODY1
SPC AC 121625

DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1125 AM CDT TUE JUN 12 2012

VALID 121630Z - 131200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE HIGH PLAINS TO
CNTRL GULF COAST...

...SYNOPSIS...

LARGE-SCALE PATTERN WILL UNDERGO SLIGHT DE-AMPLIFICATION DURING THE
D1 PERIOD AS PRIMARY UPPER TROUGH MOVES FROM ONTARIO INTO QUEBEC.
12Z UPPER-AIR ANALYSIS DEPICTS A COUPLE OF HIGHER MOMENTUM FLOW
CHANNELS IN THE MID TO UPPER-TROPOSPHERE...ONE FROM THE PACIFIC NW
THROUGH CNTRL PLAINS INTO GREAT LAKES...AND THE OTHER FROM SRN CA
INTO SRN HIGH PLAINS AND S TX. WITHIN THIS BROADER-SCALE
PATTERN...WATER VAPOR IMAGERY SHOWS A NUMBER OF WEAK
PERTURBATIONS...TWO OF WHICH MAY BE INSTRUMENTAL IN SEVERE TSTM
DEVELOPMENT LATER TODAY INTO TONIGHT. THE FIRST IS EMBEDDED WITHIN
POLAR BRANCH OF WESTERLIES OVER N-CNTRL WY WHICH WILL TRANSLATE EWD
INTO WRN SD BY AFTERNOON. THE OTHER IS A BIT WEAKER AND LOCATED IN
SUB-TROPICAL AIR STREAM NEAR THE FOUR CORNERS...WITH THIS FEATURE
MOVING INTO THE SRN HIGH PLAINS BY LATE AFTERNOON INTO EVENING.

AT THE SURFACE...SEGMENT OF COLD FRONT FROM CENTRAL OH TO MS-OH
RIVER CONFLUENCE WILL ADVANCE THROUGH THE LOWER GREAT LAKES AND INTO
THE CNTRL APPALACHIANS AND TN VALLEY. THE WRN EXTENSION OF SYNOPTIC
FRONT HAS BEEN MASKED BY A NUMBER OF CONVECTIVE OUTFLOW BOUNDARIES
RESIDING ACROSS THE SRN PLAINS WITH A BROAD CONFLUENCE AXIS
STRETCHING FROM THE RED RIVER INTO PERMIAN BASIN OF TX.
ELSEWHERE...A LEE CYCLONE DEVELOPING ALONG THE CHEYENNE RIDGE WILL
MOVE SLOWLY EWD TODAY WITH A LEE TROUGH BECOMING BETTER-DEFINED WITH
TIME ACROSS THE CO FRONT RANGE.

...SRN PLAINS...

TSTMS WHICH INITIATED LATE MONDAY NIGHT OVER NERN NM ARE ONGOING
OVER NWRN TX...FORCED BY A WEAK MIDLEVEL IMPULSE AND LOW-LEVEL
WAA/ISENTROPIC ASCENT ABOVE SHALLOW OUTFLOW BOUNDARY/FRONT. AIR
MASS AHEAD OF THESE STORMS ACROSS N-CNTRL/CNTRL TX SHOULD UNDERGO
RAPID DESTABILIZATION TODAY OWING TO THE PRESENCE OF STEEP MIDLEVEL
LAPSE RATES AND AN INCREASINGLY MOIST BOUNDARY LAYER WITH SWD EXTENT
INTO CNTRL TX WHERE AFTERNOON MLCAPE WILL APPROACH 2500-3500 J/KG.
IN FACT...THERE IS SOME INDICATION IN CONVECTION-ALLOWING AND
DETERMINISTIC MESOSCALE MODEL GUIDANCE THAT THESE STORMS COULD GROW
UPSCALE INTO A FORWARD-PROPAGATING MCS WITH A DAMAGING WIND AND HAIL
THREAT SPREADING SEWD TOWARD THE SABINE RIVER VALLEY AND UPPER TX
COAST.

OVER THE HIGH PLAINS...OUTFLOW IN THE WAKE OF NWRN TX TSTMS WILL
ENHANCE LOW-LEVEL UPSLOPE FLOW COMPONENT...WHICH WHEN COUPLED WITH
THE POTENTIAL INFLUENCE OF WEAK FOUR CORNERS IMPULSE...WILL FOSTER
WIDELY SCATTERED TSTMS ACROSS PORTIONS OF NERN/E-CNTRL NM INTO WRN
TX BY MID-LATE AFTERNOON. AMBIENT ENVIRONMENT WILL BE CHARACTERIZED
BY MLCAPE OF 1500-2500 J/KG AND 40-50 KT OF DEEP WLY SHEAR WHICH
WILL FAVOR SUPERCELLS AS THE INITIAL STORM MODE WITH AN ASSOCIATED
RISK FOR A FEW TORNADOES...DAMAGING WINDS AND VERY LARGE HAIL.
THEREAFTER...THERE IS REASONABLY GOOD AGREEMENT IN THE
CONVECTION-ALLOWING AND MESOSCALE MODELS THAT STORMS WILL MERGE INTO
ONE OR MULTIPLE MCSS WHICH WOULD PROGRESS SEWD INTO LOWER ELEVATIONS
OF THE SRN PLAINS WITH THE POTENTIAL FOR SWATHS OF DAMAGING WINDS
AND LARGE HAIL ALONG SYSTEM TRACK/S/.

...NRN/CNTRL HIGH PLAINS...

FORCING ASSOCIATED WITH WY IMPULSE WILL AUGMENT LOW-LEVEL
CONVERGENCE ASCENT INVOF LEE CYCLONE AND TROUGH TO GIVE RISE TO
WIDELY SCATTERED TSTMS BY MID AFTERNOON FROM WRN SD INTO ERN CO.
WHILE THE BOUNDARY LAYER WILL BE LESS MOIST THAN POINTS TO THE
SOUTH...STEEP LOW TO MIDLEVEL LAPSE RATES WILL YIELD MLCAPE VALUES
OF 1000-1500 J/KG IN THE PRESENCE OF 40-50 KT DEEP WNWLY SHEAR.
HERE TOO...SUPERCELLS APPEAR LIKELY WITH THE POTENTIAL FOR LARGE
HAIL...DAMAGING WINDS...AND PERHAPS A TORNADO.

...SRN LA...

THE INFLUX OF A MODERATELY UNSTABLE AND VERY MOIST AIR MASS INTO
SWD-PROPAGATING MCS WILL MAINTAIN ROBUST UPDRAFT DEVELOPMENT ALONG
LEADING EDGE OF SYSTEM COLD POOL. WHILE SOME LARGE HAIL IS
POSSIBLE...DAMAGING WINDS WILL BE THE PRIMARY HAZARD.

...UPPER OH VALLEY/LOWER GREAT LAKES SWD INTO THE CNTRL
APPALACHIANS...

UPLIFT ALONG COLD FRONT AND DEEPER-LAYER FORCING ASSOCIATED WITH A
VORTICITY MAXIMUM MOVING ACROSS THE REGION WILL SUPPORT AN INCREASE
IN TSTM ACTIVITY THIS AFTERNOON INTO EVENING. WHILE VERTICAL SHEAR
WILL REMAIN SUB-OPTIMAL FOR STORM ORGANIZATION/SUSTENANCE...THE
PRESENCE OF A MOIST...MODERATELY UNSTABLE AIR MASS /I.E. MLCAPE
VALUES OF 1000-2000 J PER KG/ WILL SUPPORT A FEW VIGOROUS STORMS
CAPABLE OF MARGINALLY SEVERE HAIL AND LOCALLY STRONG WIND GUSTS INTO
THIS EVENING.

...MID ATLANTIC AND SERN STATES...

12Z SOUNDINGS AND SATELLITE-DERIVED PW IMAGERY INDICATE THE PRESENCE
OF A VERY MOIST AIR MASS /I.E. PW VALUES OF 1.75-2.00 INCHES/ WHICH
WILL CONTRIBUTE TO POCKETS OF MODERATE INSTABILITY BY AFTERNOON.
THIS IS ESPECIALLY THE CASE ACROSS PORTIONS OF GA/NRN FL INTO SC
WHERE VISIBLE SATELLITE SUGGESTS THE POTENTIAL FOR STRONGER DAYTIME
HEATING. A DEVELOPING LEE TROUGH WILL COMBINE WITH EXISTING
CONVECTIVE OUTFLOW BOUNDARIES AND AN MCV OVER THE SAVANNAH RIVER
VALLEY TO PROMOTE SCATTERED TSTMS THIS AFTERNOON. VERTICAL SHEAR
WILL REMAIN WEAK...BUT THE HIGH MOISTURE CONTENT WILL BE FAVORABLE
FOR WET MICROBURST FORMATION OWING TO WATER LOADING EFFECTS.

..MEAD/ROGERS.. 06/12/2012

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