SPC AC 291716
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1216 PM CDT THU MAY 29 2008
VALID 301200Z - 311200Z
...THERE IS A MDT RISK OF SVR TSTMS FRI AFTN/EVE ACROSS PARTS OF SE
IOWA...NE/E CNTRL MO...SRN WI...MUCH OF NRN AND CNTRL IL...AND WRN
IND....
...THERE IS A SLGT RISK OF SVR TSTMS SURROUNDING THE MDT RISK
AREA...FROM THE S CNTRL PLAINS THROUGH THE GREAT LAKES REGION....
...SYNOPSIS...
UPPER FLOW WILL BECOME INCREASINGLY ZONAL LATER TODAY THROUGH
FRIDAY...AS A STRONG MID/HIGH LEVEL JET...WHICH HAS EMANATED FROM
THE PACIFIC...CONTINUES TO TRAVERSE THE NATION. MODELS INDICATE
THAT BROAD UPPER TROUGHING OVER THE INTERMOUNTAIN WEST AND ROCKIES
WILL TRANSITION TO LOW AMPLITUDE RIDGING ON FRIDAY...AS ANOTHER
SOUTHERN STREAM SHORT WAVE IMPULSE APPROACHES THE CALIFORNIA
COAST...AND A MORE SIGNIFICANT...CONSOLIDATING TROUGH SHIFTS EAST OF
THE NORTHERN ROCKIES/NORTHERN PLAINS REGION. THE LATTER FEATURE IS
PROGGED TO MAINTAIN A MORE OR LESS EASTWARD MOTION INTO THE GREAT
LAKES/OHIO VALLEY BY 12Z SATURDAY...TO THE SOUTH OF RIDGING BETWEEN
SHORT WAVE IMPULSES WITHIN A SIGNIFICANT BELT OF WESTERLIES ACROSS
THE NORTHERN CANADIAN PROVINCES.
...MID MS VLY INTO THE GREAT LAKES REGION...
FAVORABLE LARGE SCALE FORCING AND SHEAR PROVIDES POTENTIAL FOR THE
CONTINUATION OF A WIDESPREAD...SIGNIFICANT SEVERE WEATHER OUTBREAK
...ANTICIPATED TO COMMENCE LATER TODAY/TONIGHT ACROSS THE NORTH
CENTRAL PLAINS AND MID MISSOURI VALLEY. HOWEVER...AN INITIALLY
COOL/DRY/STABLE BOUNDARY LAYER ASSOCIATED WITH A LINGERING
WEAKENING/RETREATING SURFACE RIDGE OVER THE GREAT LAKES REGION IS A
SOURCE OF UNCERTAINTY FOR THIS PERIOD. AND...IT APPEARS POSSIBLE
THAT AT LEAST THE REMNANTS OF A LARGE NOCTURNAL MESOSCALE CONVECTIVE
SYSTEM WILL OVERSPREAD SOUTHERN PORTIONS OF THE UPPER GREAT LAKES
INTO THE LOWER GREAT LAKES DURING THE DAY FRIDAY. THIS PROBABLY
WILL INHIBIT DESTABILIZATION TO THE LEE OF THE LOWER GREAT
LAKES...PERHAPS EVEN LOWER MICHIGAN...WITH A POSSIBLE CONVECTIVELY
GENERATED BOUNDARY SETTING UP TO THE SOUTH/SOUTHEAST OF A FAIRLY
DEEP FRONTAL WAVE PROGGED TO MIGRATE ACROSS WISCONSIN AND MICHIGAN
BY 31/03Z.
MODERATE TO STRONG DESTABILIZATION SEEMS MUCH MORE CERTAIN TO THE
SOUTH/WEST OF THE POSSIBLE CONVECTIVE BOUNDARY...AND AHEAD OF THE
COLD FRONT TRAILING SOUTHWESTWARD FROM THE LOW...ACROSS PARTS OF
SOUTHERN WISCONSIN/SOUTHEAST IOWA/NORTHEAST MISSOURI AND NORTHERN/
CENTRAL ILLINOIS. THIS IS WHERE MID-LEVEL HEIGHT FALLS AND DEEP
LAYER SHEAR BENEATH 50-70 KT 500 MB FLOW ON THE SOUTHERN/EASTERN
PERIPHERY OF THE APPROACHING UPPER TROUGH AXIS ARE EXPECTED TO
CONTRIBUTE TO SEVERE THUNDERSTORM DEVELOPMENT...PARTICULARLY FROM
SHORTLY AFTER PEAK HEATING INTO THE EVENING HOURS. ALTHOUGH THE 50+
KT SOUTHWESTERLY 850 MB JET CORE MAY ALREADY BE IN THE PROCESS OF
SHIFTING INTO THE LOWER GREAT LAKES REGION BY THAT TIME...LOW- LEVEL
HODOGRAPHS ARE STILL EXPECTED TO REMAIN SIZABLE...AND SUPPORTIVE OF
TORNADIC POTENTIAL. THIS THREAT SHOULD BE HIGHEST IN THE MORE
DISCRETE EARLY STORMS...BEFORE PROBABLE UPSCALE GROWTH INTO ANOTHER
LARGE MESOSCALE CONVECTIVE SYSTEM OCCURS...WITHIN AN ENVIRONMENT
WITH MIXED LAYER CAPE ON THE ORDER OF 2000-3000 J/KG.
HAIL...SOME QUITE LARGE...IS ALSO LIKELY IN MOST STORMS. AND...
DAMAGING WIND GUSTS WILL BECOME A PROMINENT THREAT IN ORGANIZED
STORM CLUSTERS.
IF IT TURNS OUT LOWER MICHIGAN IS NOT SUBSTANTIALLY IMPACTED BY
EARLY DAY CONVECTION...A MORE SIGNIFICANT SEVERE THREAT MAY EXIST
ACROSS THIS REGION THAN CURRENTLY INDICATED.
...SOUTH CENTRAL PLAINS INTO OZARKS...
STORMS ARE EXPECTED TO BE MORE SCATTERED FRIDAY AFTERNOON AND
EVENING SOUTHWARD ACROSS THE MISSOURI OZARKS INTO THE SOUTH CENTRAL
PLAINS. BUT...A STRENGTHENING ZONE OF LOWER/MID TROPOSPHERIC WARM
ADVECTION ON THE NORTHEASTERN PERIPHERY OF THE SUBTROPICAL RIDGE MAY
AID THE DEVELOPMENT OF ANOTHER STORM CLUSTER SOMEWHERE NEAR THE
KANSAS/OKLAHOMA BORDER INTO SOUTHWEST MISSOURI DURING THE OVERNIGHT
HOURS. DEEP LAYER SHEAR AND INSTABILITY SHOULD BE SUFFICIENT ACROSS
THIS REGION TO SUPPORT THE RISK FOR LARGE HAIL/DAMAGING WIND
GUSTS...IN ADDITION TO LOCALLY HEAVY RAIN ASSOCIATED WITH
PERSISTENT/TRAINING CONVECTION.
..KERR.. 05/29/2008
CLICK TO GET WUUS02 PTSDY2 PRODUCT
NOTE: THE NEXT DAY 2 OUTLOOK IS SCHEDULED BY 0800Z
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