SPC AC 310553
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1253 AM CDT SUN MAY 31 2009
VALID 311200Z - 011200Z
...THERE IS A SLGT RISK OF SVR TSTMS ACROSS PORTIONS OF THE CNTRL
PLAINS...
...SYNOPSIS...
WLYS ARE EXPECTED TO BECOME MORE ZONAL ON SUNDAY IN WAKE OF THE
DEPARTING POLAR VORTEX THAT IS PROGGED TO MOVE ACROSS NEW ENGLAND BY
EVENING. NEXT IMPULSE IS EXPECTED TO MOVE FROM MT/SRN ALBERTA INTO
THE UPR MS VLY BY SUNDAY EVENING. IN THE LWR LVLS...A CDFNT WILL
MOVE EWD THROUGH NEW ENGLAND SUNDAY AFTN WITH THE SRN EXTENSION
SAGGING SWD THROUGH THE CAROLINAS AND SRN APLCNS. FAR WRN SECTIONS
OF THE FRONT WILL REDEVELOP NWD AS A WRMFNT FROM THE LWR/MID MO VLY
TO THE CORN BELT/NRN PLNS BY LATE SUNDAY AFTN. THIS FRONT WILL
LIKELY INTERSECT WITH A NEW CDFNT/SFC LOW OVER CNTRL SD.
...CNTRL PLNS TO THE UPR MS VLY...
BOUNDARY LAYER MOISTURE WILL REMAIN MEAGER ACROSS THE REGION ON
SUNDAY...BUT STRONG HEATING...MID-LVL LAPSE RATES IN EXCESS OF 7 DEG
C/KM AND SFC DEW POINTS IN THE 50S WILL RESULT IN MLCAPES OF
1000-2000 J/KG. PERSISTENT CONVERGENCE NEAR THE CNTRL SD TRIPLE
POINT/WRMFNT IN COMBINATION WITH WEAK PVA SPREADING ACROSS THE
REGION DURING THE AFTN WILL WEAKEN CINH AND RESULT IN ISOLD
HIGH-BASED TSTM DEVELOPMENT ACROSS CNTRL/ERN SD AND PERHAPS NRN NEB.
OTHER STORMS MAY DEVELOP SEPARATELY FARTHER TO THE SW ALONG A
PRE-FRONTAL TROUGH ACROSS CNTRL NEB AND NERN CO.
STRONGEST DEEP LAYER SHEAR WILL REMAIN REMOVED FROM THE WARM SECTOR
TO THE NE...BUT SELY LLVL FLOW NEAR THE WRMFNT BENEATH WNW FLOW OF
25+ KTS SHOULD YIELD SUFFICIENT SHEAR TO SUPPORT SUPERCELLS WITH
PRIMARILY LARGE HAIL.
OVERNIGHT...WSWLY LLJ WILL BEGIN TO FOCUS MODEST WARM/MOIST
ADVECTION FARTHER TO THE NE ACROSS PARTS OF MN AND IA. THUS...THE
PLAINS STORMS MAY WEAKEN GRADUALLY DURING THE EVENING WITH
ADDITIONAL ACTIVITY FORMING DOWNSTREAM. THE NEW STORMS WILL LIKELY
BE SLIGHTLY ELEVATED WITH ONLY MODEST BUOYANCY AND MEAGER
CLOUD-BEARING SHEAR. THUS...WHILE OVERNIGHT STORMS MAY PRODUCE
GUSTY WINDS AND MARGINALLY SVR HAIL...A WIDESPREAD SVR MCS IS NOT
LIKELY.
...NRN/CNTRL NEW ENGLAND...
FAIRLY STRONG LARGE SCALE FORCING ASSOCD WITH THE POLAR VORTEX WILL
BOOST UVV INVOF THE CDFNT DURING PEAK HEATING SUNDAY. H5
TEMPERATURES AOB MINUS 20 DEG C ATOP UPR 40S/LWR 50S SFC DEW POINTS
AND PRESENCE OF STRONG CYCLONIC FLOW SHOULD CONTRIBUTE TO ISOLD
STG-SVR TSTMS CAPABLE OF LARGE HAIL AND DMGG WIND GUSTS.
...W TX AND EXTREME SERN NM...
GENERAL HEIGHT FALLS ACROSS THE SRN ROCKIES ASSOCD WITH THE UPR LOW
MIGRATING SLOWLY NEWD FROM THE DESERT SW WILL INDUCE A MODEST SELY
LLVL FLOW ACROSS SWRN TX SUNDAY. SFC DEW POINTS WILL LIKELY MIX
INTO THE 50S DURING THE AFTN...BUT PERSISTENT UPSLOPE
FLOW/DIFFERENTIAL HEATING AND WEAK FORCING ALOFT WILL YIELD HIGH
BASED TSTMS OVER THE TRANSPECOS INTO SERN NM BY MID/LATE AFTN.
VERTICAL SHEAR WILL BE MEAGER...BUT MAGNITUDE OF MID-LVL LAPSE RATES
WILL BE FAVORABLE FOR ISOLD STORMS TO PRODUCE LARGE HAIL AND GUSTY
WINDS.
..RACY/HURLBUT.. 05/31/2009
CLICK TO GET WUUS01 PTSDY1 PRODUCT
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1300Z
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