SWODY2
SPC AC 201722
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1222 PM CDT SAT JUN 20 2009
VALID 211200Z - 221200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NRN GRT
BASIN/INTERMOUNTAIN W...
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE MID-MS
VLY/CORN BELT...
...SYNOPSIS...
UPR FLOW REGIME WILL GAIN HIGHER AMPLITUDE THROUGH THE WEEKEND AS
EXPANSIVE RIDGE BUILDS NWD THROUGH THE CNTRL PORTIONS OF THE COUNTRY
AND TROUGHS REMAIN STRONG ALONG BOTH CSTS. E CST TROUGH WILL CLOSE
OFF INTO A LOW WITH INDIVIDUAL DISTURBANCES DIGGING INTO THE SERN
STATES. MEANWHILE...SEVERAL VORTICITY MAXIMA WILL LIFT NEWD FROM
THE BASE OF THE WRN STATES TROUGH...AFFECTING THE GRT BASIN AND THE
CNTRL/NRN ROCKIES.
...NRN SECTIONS OF THE GRT BASIN/INTERMOUNTAIN W...
CONVECTION/TSTMS...TIED TO A LEAD MID-LVL SHORTWAVE TROUGH NOW
MOVING ACROSS NV...WILL BE ONGOING OVER PARTS OF THE NRN
ROCKIES/INTERMOUNTAIN W EARLY IN THE PD. THIS ACTIVITY SHOULD MOVE
NWD THROUGH MT AND INTO SK/AB DURING THE AFTN. IN ITS WAKE...
THINNING CLOUD COVER WILL ALLOW AIR MASS TO RECOVER AHEAD OF A
SECONDARY IMPULSE PROGGED TO MOVE INTO THE GRT BASIN BY SUNDAY AFTN.
THIS FEATURE WILL BE ACCOMPANIED BY A 50 KT SWLY H5 JET AND
RELATIVELY COOL MID-TROPOSPHERIC TEMPERATURES /AOB MINUS 15 DEG C/.
GIVEN PWATS OF AROUND 3/4 OF AN INCH AND APPROACH OF MODEST LARGE
SCALE FORCING...SCTD TSTMS ARE EXPECTED TO FORM ACROSS NERN NV/NRN
UT BY MID/LATE AFTN...GENERALLY ALONG/E OF A MID-LVL BAROCLINIC
ZONE. ROUGHLY 40-45 KTS OF BULK SHEAR COULD LEAD TO BRIEF SUPERCELL
STRUCTURES WITH EVOLUTION INTO LINE SEGMENTS AS THE STORMS TRANSLATE
NEWD INTO ERN ID/WRN WY AND SWRN MT. LARGE HAIL AND DMGG WINDS WILL
BE POSSIBLE.
...MID-MS VLY/CORN BELT...
DEEP LAYER MOISTURE SURGE/WARM ADVECTION...ENHANCED BY SUB-TROPICAL
PERTURBATIONS...WILL YIELD CONSIDERABLE CONVECTION ACROSS THE CNTRL
PLAINS TODAY. ACTIVITY WILL CONTINUE NEWD INTO THE MID-MS VLY/CORN
BELT TONIGHT AND EARLY ON SUNDAY...THEN INTO THE UPR MS VLY REGION
BY AFTN. IN ITS WAKE...WARM SECTOR WILL BE CHARACTERIZED BY
DEEP...NEARLY MOIST-ADIABATIC PROFILES/VERY WARM MID-LVL
TEMPERATURES. A HOT BOUNDARY LAYER AND SUSTAINED LLVL CONVERGENCE
INVOF THE WRMFNT MAY CONTRIBUTE TO RISK FOR SFC-BASED STORM
DEVELOPMENT ALONG BACK FRINGE OF EARLY DAY CONVECTION ACROSS PARTS
OF IA...NERN MO AND WRN IL. WILL MAINTAIN SLGT RISK GIVEN POTENTIAL
FOR ISOLD TORNADOES/WET MICROBURSTS INVOF THE WRMFNT WHERE RESIDUAL
LLVL HELICITY WILL REMAIN MODEST. HOWEVER...THREAT WILL BE HIGHLY
CONDITIONAL ON DEVELOPMENT OF STORMS AMIDST THE WEAKENING BULK SHEAR
AND AFOREMENTIONED NEARLY MOIST-ADIABATIC ENVIRONMENT.
...KY SEWD TO THE SE ATLANTIC CST...
NW-SE ORIENTED BAROCLINIC ZONE MAY SERVE AS A FOCUS FOR ISOLD TSTMS
THROUGH THE DAY 2 PD. AIR MASS INVOF THE FRONT WILL REMAIN
MOIST/UNSTABLE...BUT MID-LVLS WILL ALSO BE QUITE WARM. ANY STRONGER
STORMS MAY TAP THE 35-45 KT NWLY H5 FLOW AND BECOME ORGANIZED. MAIN
THREATS WILL BE FOR DMGG WIND GUSTS.
..RACY.. 06/20/2009
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