SWODY2
SPC AC 240557
DAY 2 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
1257 AM CDT FRI APR 24 2009
VALID 251200Z - 261200Z
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN AND CNTRL PLAINS
THROUGH THE MID MS VALLEY AND GREAT LAKES REGION...
...SYNOPSIS...
MODEL CONSENSUS IS THAT UPPER PATTERN WILL EVOLVE INTO A SPLIT FLOW
REGIME BY SATURDAY. POSITIVE TILTED UPPER TROUGH OVER THE PACIFIC NW
WILL MOVE THROUGH THE NRN PLAINS...UPPER MS VALLEY AND GREAT LAKES.
CONCURRENTLY...SECONDARY VORT LOBE OFF THE OREGON COAST WILL ADVANCE
SEWD...REACHING THE FOUR CORNERS AREA SATURDAY EVENING. PASSAGE OF
NRN STREAM SHORTWAVE TROUGH WILL PROVIDE IMPETUS FOR A COLD FRONT TO
CONTINUE SEWD THROUGH THE GREAT LAKES...MS VALLEY AND SRN PLAINS.
TRAILING END FRONT WILL LIKELY STALL FROM NW OK INTO THE TX
PANHANDLE OR NW TX AND MAY BEGIN TO RETREAT NWD SATURDAY NIGHT AS
SURFACE RIDGE SHIFTS FARTHER EAST. DURING THE AFTERNOON A DRYLINE
WILL EXTEND THROUGH WRN TX NWD WHERE IT WILL INTERSECT THE COLD
FRONT.
SHORTWAVE TROUGH NOW MOVING THROUGH WRN TX WILL ADVANCE SLOWLY ENEWD
INTO THE LOWER MS VALLEY REGION.
...CNTRL AND SRN PLAINS AREA...
COLD FRONT WILL LIKELY ADVANCE INTO SRN KS...PARTS OF NRN OK AND THE
TX PANHANDLE BY SATURDAY EVENING. RICHER LOW LEVEL MOISTURE WILL
ADVECT NWD THROUGH PRE-FRONTAL WARM SECTOR WITH DEWPOINTS IN THE MID
60S AS FAR NORTH AS OK. SWLY FLOW ALOFT WILL EXIST OVER THE CNTRL
AND SRN PLAINS DOWNSTREAM FROM SHORTWAVE TROUGH BOTTOMING OUT NEAR
THE FOUR CORNERS REGION. THIS WILL RESULT IN EWD TRANSPORT OF STEEP
MID LEVEL LAPSE ABOVE THE MOIST WARM SECTOR. THESE PROCESSES AND
DIABATIC HEATING WILL CONTRIBUTE TO MODERATE SURFACE BASED
INSTABILITY FROM TX NWD THROUGH OK SATURDAY AFTERNOON. HOWEVER...EWD
ADVECTION OF THE EML WILL LIKELY CONTRIBUTE TO A CAP OVER MUCH OF
THE WARM SECTOR DURING THE DAY.
NAM AND GFS BOTH SUGGEST A WEAK LEAD WAVE WILL EJECT ENEWD THROUGH
KS EARLY IN THE PERIOD. HOWEVER...TIMING OF ANY SUCH FEATURE AT THIS
POINT WOULD BE DIFFICULT. GIVEN PRESENCE OF CAP AND WEAK LARGE SCALE
FORCING...THUNDERSTORM INITIATION DURING THE DAY IS SOMEWHAT
UNCERTAIN. HOWEVER...INITIATION IS MOST LIKELY TO OCCUR NEAR TRIPLE
POINT OVER SW OK OR NW TX WHERE THE DRYLINE INTERSECTS THE COLD
FRONT AS WELL AS OVER SRN KS ALONG SWD ADVANCING COLD FRONT. LOW
LEVEL HODOGRAPHS WILL INITIALLY NOT BE PARTICULARLY LARGE IN WARM
SECTOR...BUT WILL INCREASE DURING THE EVENING AS THE LOW LEVEL JET
STRENGTHENS. BULK SHEAR WILL SUPPORT SUPERCELLS WITH LARGE HAIL
LIKELY AND ISOLATED TORNADOES POSSIBLE DURING THE EARLY
EVENING...ESPECIALLY WITH ANY STORM THAT CAN INITIATE NEAR TRIPLE
POINT.
OVERNIGHT...THE STRENGTHENING SLY LOW LEVEL JET WILL AUGMENT
DESTABILIZATION AND ISENTROPIC LIFT NORTH OF FRONTAL BOUNDARY
RESULTING IN AN INCREASE IN ELEVATED STORMS ACROSS KS. LARGE HAIL
WILL BE THE MAIN THREAT WITH THIS ACTIVITY.
...MID MS VALLEY THROUGH GREAT LAKES REGION...
MOIST AXIS WILL ADVECT NEWD THROUGH THE MID MS VALLEY AND GREAT
LAKES REGION. DEWPOINTS WILL RANGE FROM THE LOW 60S OVER THE MID MS
VALLEY TO UPPER 50S OVER THE GREAT LAKES. PRE-FRONTAL DIABATIC
HEATING WILL CONTRIBUTE TO DESTABILIZATION DURING THE
AFTERNOON...BUT MODEST MID LEVEL LAPSE RATES WILL LIKELY LIMIT
MLCAPE TO AOB 1000 J/KG WITH CAPE INCREASINGLY MARGINAL TOWARD THE
GREAT LAKES. STORMS WILL LIKELY BE ONGOING EARLY SATURDAY ALONG THE
COLD FRONT...BUT WILL LIKELY INTENSIFY AS THIS BOUNDARY ADVANCES
SEWD THROUGH THE DESTABILIZING WARM SECTOR. VERTICAL SHEAR IS NOT
FORECAST TO BE PARTICULARLY STRONG...AROUND 30 KT IN WARM SECTOR.
HOWEVER...MODERATE TO STRONG UNIDIRECTIONAL SWLY FLOW WILL EXIST IN
VICINITY OF THE FRONT. PRIMARY THREAT APPEARS TO BE ISOLATED
DAMAGING WIND AND POSSIBLY SOME HAIL.
...SRN AND CNTRL APPALACHIANS...
ISOLATED MULTICELL STORMS THAT DEVELOP OVER THE HIGHER TERRAIN
DURING THE AFTERNOON MAY BECOME CAPABLE OF PRODUCING MARGINALLY
SEVERE HAIL AND STRONG WIND GUSTS. ACTIVITY WILL DIMINISH WITH LOSS
OF HEATING.
..DIAL.. 04/24/2009
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
To unsubscribe from WX-STORM send e-mail to LISTSERV@LISTSERV.ILLINOIS.EDU with
"unsub wx-storm" in the body of your message. For more information write cnovy@cox.net.
No comments:
Post a Comment