SPC AC 011254
DAY 1 CONVECTIVE OUTLOOK
NWS STORM PREDICTION CENTER NORMAN OK
0754 AM CDT THU MAY 01 2008
VALID 011300Z - 021200Z
...THERE IS A MDT RISK OF SVR TSTMS OVER PARTS OF ERN KS THIS
EVENING INTO TONIGHT...
...THERE IS A SLGT RISK OF SVR TSTMS FROM THE SRN PLNS INTO WRN
AR...
...SYNOPSIS...
STRONG CO UPR LOW EXPECTED TO EDGE SLOWLY E INTO S CNTRL NEB THIS
PERIOD AS 80+ KT MID LVL JET STREAK NOW CROSSING THE SRN GRT BASIN
AND FOUR CORNERS REGION REDEVELOPS E ACROSS OK/SRN KS. AT LWR
LVLS...EXPECT DEEP SFC LOW NOW OVER S CNTRL NEB TO LIFT NE INTO SE
SD AND WEAKEN BY THIS EVENING AS A NEW CENTER FORMS OVER SW/S CNTRL
KS IN RESPONSE TO APPROACHING JET STREAK. THIS LOW SHOULD...IN
TURN...LIFT NNE TO NEAR OMA BY THE END OF THE PERIOD AS ASSOCIATED
COLD FRONT ACCELERATES E/SE TO A WRN MO/NE OK/CNTRL TX LINE BY
FRIDAY MORNING. THE COLD FRONT WILL OVERTAKE DRYLINE IN CNTRL KS
THIS AFTN...OVER OK TONIGHT...AND OVER NE TX EARLY FRIDAY.
...KS INTO LWR MO VLY...
UNCERTAINTIES REGARDING QUALITY AND TIME OF ARRIVAL OF MOISTURE
RETURN...AND TIMING OF UPR LVL VORT MAXIMA...MAKE THIS A MORE
DIFFICULT FCST THAN USUAL FOR SUCH A POTENT KINEMATIC/DYNAMIC SETUP.
REGARDING THE MOISTURE ISSUE...REGIONAL VWP AND PROFILER DATA SHOW
BROAD SSWLY LLJ IN PLACE ACROSS THE SRN HALF OF THE PLNS/MS VLY.
BUT SATELLITE-DERIVED AND GPS PW DATA SHOW THAT LEADING EDGE OF 1
INCH ISOLINE ATTM HAS ADVANCED NWD ONLY TO A TPL/LFK LINE IN E CNTRL
TX. ASSUMING THIS RATE OF MOISTURE RETURN IS MAINTAINED...1 INCH
PWS SHOULD REACH THE I-40 CORRIDOR IN CNTRL OK BY 21Z...AND W CNTRL
MO BY 09Z FRIDAY. IN CONTRAST...PW FIELD FROM THE 00Z ECMWF SHOWS
THE 1 INCH PW ALREADY INTO SRN OK THIS MORNING...WITH VALUES AOA 1
INCH EXPECTED NWD INTO ERN KS/NW MO AND SW IA BY THIS EVENING.
CONSIDERING THE OVERALL PICTURE...AND THE FACT THAT THE 65F SFC
ISODROSOTHERM IS STILL WELL S IN CNTRL TX...BELIEVE THAT THE RICHEST
SFC MOISTURE LIKELY WILL REMAIN S AND E OF ERN KS AND ADJACENT PARTS
OF SE NEB/NW MO/SW IA THROUGH THE PERIOD. IN ADDITION...MUCH OF THE
REGION MAY REMAIN UNDER SLIGHT NVA THROUGH THE DAY IN WAKE OF LEAD
UPR IMPULSE NOW LIFTING N INTO NEB. BUT GIVEN STRENGTHENING
CONVERGENCE/ASCENT DOWNSTREAM FROM DEVELOPING SFC LOW...SUFFICIENT
MOISTURE LIKELY WILL BE AVAILABLE TO SUPPORT SVR STORM DEVELOPMENT
BY VERY LATE TODAY OR EARLY TONIGHT INVOF COLD FRONT AND/OR DRYLINE
FROM ERN KS E AND NE INTO SE NEB/NW MO AND SW IA...ON W SIDE OF
LOW-LVL MOISTURE RETURN.
THE INITIAL STORMS SHOULD BE SUPERCELLS...A FEW OF WHICH MAY BE
HIGH-BASED. INCREASING FRONTAL UPLIFT AND BACKING UPR FLOW SHOULD
FAVOR STORM MERGERS AND SQLN DEVELOPMENT LATER TONIGHT /EARLY FRIDAY
AS THE CONVECTION CONTINUES E INTO MO. STRENGTH OF LOW- TO
DEEP-LAYER SHEAR AND STEEP MID LVL LAPSE RATES SUGGEST POTENTIAL FOR
LARGE HAIL...HIGH WIND AND PERHAPS A COUPLE TORNADOES.
...SRN PLNS INTO WRN AR...
FARTHER S...BROAD AND STRONG EML CAP WILL KEEP ANY DAYTIME SVR
THREAT MUCH MORE CONDITIONAL ALONG DRY LINE FROM S CNTRL KS INTO OK
AND N TX. NEVERTHELESS...ANY ISOLD STORMS THAT DO FORM LATE THIS
AFTN OR EARLY TONIGHT WILL POSE A THREAT FOR VERY LARGE HAIL AND
TORNADOES. THE DRY LINE...AND ASSOCIATED ISOLD SVR THREAT ...MAY
RETREAT A BIT W ACROSS CNTRL OK THIS EVENING IN RESPONSE TO PRESSURE
FALLS AHEAD OF APPROACHING JET STREAK.
PROBABILISTICALLY...THE GREATEST SVR THREAT OVER THE SRN PLNS SHOULD
EVOLVE TONIGHT AS THE ERN KS SQLN DEVELOPS SWD ALONG MERGING COLD
FRONT/DRYLINE INTO ERN OK AND NW AR. EMBEDDED STORMS COULD POSE A
CONTINUING THREAT FOR HIGH WIND/LARGE HAIL AND PERHAPS AN ISOLATED
TORNADO THROUGH 12Z FRIDAY GIVEN INCREASING MOISTURE INFLOW AND
PROGRESSIVE NATURE OF UPR TROUGH.
..CORFIDI/CROSBIE/CARBIN.. 05/01/2008
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