Severe Thunderstorm Warning 115, NWS Topeka, KS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
307 PM CDT TUE JUN 3 2008

.DISCUSSION...

MAIN CONCERN OVR THE NEXT COUPLE OF DAYS IS CONVECTIVE THREAT. 19Z
SFC ANLYS INDCD SFC CDFNT EXTNDD FM NR KICL TO KFNB TO KMHK TO KHUT.
SWD PROGRESS OF THIS BOUNDARY HAS BEEN SLOW TODAY AND WITH LITTLE
PRES FALLS NOTED BEHIND THE BOUNDARY...THIS TREND SHLD CONT THRU THE
EVNG. DEEPEST MOISTURE THIS AFTN RESIDES JUST BEHIND THE SFC
BOUNDARY WHERE THE H85 MOISTURE REMAINS LOCKED INTO PLACE. SOUTH OF
THE BOUNDARY...SOME MOISTENING HAS BEEN TAKING PLACE PER INCREASE IN
CU DVLPMNT OVR ERN KS...BUT SAMPLING OF THIS AIR PER THE 18Z TOP
SPECIAL SOUNDING INCS A STRONG CAPPING INVERSION IN PLACE. THUS MAIN
INITIAL CONCERN WL BE FOR CONVECTION ALNG AND JUST BEHIND THE
BOUNDARY THRU THE REMAINDER OF THE AFTN. MODIFIED 18Z SOUNDING FOR
AIRMASS BEHIND THE BOUNDARY INDCS A MUCH WEAKER CAP...BUT STILL ARND
-80 J/KG OF MLCIN. CONTINUED HEATING AND MOISTENING OF THE BOUNDARY
THRU THE REST OF THE AFTN THOUGH MAY LEAD TO AN ISO STORM ON THE
COOL SIDE OF THE BOUNDARY. OTHERWISE CONVECTION IS EXPECTED TO DVLP
OVR SW KS AND THE OK PANHANDLE LATE THIS AFTN AND TRACK EWD ACRS SRN
KS THIS EVNG. SOME OF THIS ACTIVITY WL LIKELY CROSS OUR SRN COUNTIES
BY LATE EVNG. OTHER CHANCE FOR CONVECTION TONIGHT APPEARS TO TAKE
PLACE AFTER MIDNIGHT AS THETA-E ADVECTION INCREASES WITH THE
INCREASE IN THE NOCTURNAL LLJ FM CNTRL OK INTO CNTRL KS. THIS IS
LIKELY TO FUEL AND MCS TONIGHT...BUT MOST OF THIS SHOULD TRACK ACRS
NEB BUT MAY DIP INTO OUR NRN COUNTIES.

AREA PROFILERS INDC MID LVL FLOW IS INCREASING ACRS THE WRN HI
PLAINS AND ALSO FLOW ACRS THE CWA IS FAIRLY WEAK ATTM...DEEP LAYER
SHEAR SHOULD INCREASE THRU THE EVNG AND THUS SVR WX STILL SEEMS
POSSIBLE WITH ANY OF THE 3 POSSIBLE CONVECTIVE CHANCES.
AGAIN...LARGE HAIL /SOME VERY LARGE GIVEN THE LAPSE RATES/ AND
DAMAGING WINDS /GIVEN THE >30 K H6 TO SFC THETA-E DIFF/ WILL BE THE
MAIN THREATS. OTHERWISE...DID INCREASE GOING LOWS FOR TONIGHT WITH
RECENT PERFORMANCE OF OPERATIONAL GUIDANCE BEING ON THE COOL SIDE
OVR THE LAST WEEK.

ANY CONVECTION SHLD BE EXITING THE CWA BY EARLY MRNG WED AND HAVE
ADDED A SMALL POP TO WED MRNG...BUT MOST OF THE AREA SHOULD START
DRY ON WED. SFC WRMFNT SHLD DVLP NWD THRU THE DAY AS LOW PRES
STRENGTHENS OVR THE WRN HI PLAINS IN RESPONSE TO STRONG HEIGHT
FALLS MOVES INTO THE GREAT BASIN. EML WILL ALSO INCREASE THROUGH
THE DAY ON WED AND SFC-BASED CONVECTIVE INITIATION IS IN QUESTION
DURING THE AFTN PERIOD. FNT LOOKS TO LINE UP BY 00Z FM SE NEB INTO
CNTRL KS. ATMOSPHERE BY LATE AFTN DOES BECOMING EXTREMELY UNSTABLE
TO THE SOUTH OF THE BOUNDARY AND SHEAR CERTAINLY SUPPORTS SIG SVR
IF STORMS CAN DVLP. HAVE LOWERED GOING POPS DURING THE AFTN PERIOD
WITH STRONG CAPPING INVERSION WITH BETTER CHANCES OCCURRING AFTER
00Z.

BOUSTEAD

WEDNESDAY NIGHT...MODELS CONSISTENT IN SHOWING WARM FRONT LIFTING
NORTH DURING THE OVERNIGHT HOURS. MOISTURE CONVERGENCE LOOKS TO
INCREASE ALONG THE RETREATING WARM FRONT...SO IF THUNDERSTORMS
HAVE NOT INITIATED DURING PEAK HEATING HOURS OF THE
DAY...STRENGTHENING LOW LVL MOISTURE CONVERGENCE DOES MAKE IT
POSSIBLE TO INITIATE STORMS NEAR THE WARM FRONT AS CAP ERODES. ALL
INGREDIENTS PRESENT FOR SEVERE THUNDERSTORMS IF ANYTHING INITIATES
ACROSS THE TOP CWA. AS TSTM CHANCES LOOK GREATEST ALONG THE WARM
FRONT...FEEL THAT BEST CHANCE TO SEE SVR WX WILL EXIST IN NORTH
CENTRAL KS. TSTMS SHOULD MOVE NORTHEAST ALONG THE WARM FRONT AS IT
CONTINUES TO LIFT NORTH...SO COULD SEE MOST TSTM ACTIVITY PUSH
NORTHEAST INTO EASTERN NE DURING THE EARLY MORNING HOURS THURSDAY.

THURSDAY AND THURSDAY NIGHT...POWERFUL UPPER LEVEL TROUGH FOR JUNE
IS ALREADY PUSHING ONSHORE THE WESTERN CONUS. MODELS CONSISTENT IN
BRINGING STRONG EMBEDDED SHORTWAVE TROUGH THROUGH LONGER WAVE
TROUGH AXIS THURSDAY MORNING OVER THE GREAT BASIN...ROTATING
NORTHEAST INTO THE CENTRAL PLAINS THURSDAY AFTERNOON/EVENING.
MODELS INDICATING 60-70 KT H500 JET WITH H250 JET OF AROUND 100
KTS EMBEDDED WITHIN THIS SHORTWAVE TROUGH. MODELS INDICATE
SECONDARY SFC LOW DEVELOPING OVER WESTERN KS THURSDAY
AFTERNOON...WITH DRYLINE MIXING EAST INTO CENTRAL KS BY 00Z FRI.
MODELS INDICATE 2500-3000 J/KG OF SBCAPE BUILDING UP DUE TO EML IN
PLACE OVER MUCH OF THE CWA. INITIALLY THURSDAY AFTERNOON...WITH
UPPER JET CORE OVER CENTRAL KS ALONG WITH DRYLINE...FEEL THIS IS
THE MOST LIKELY PLACE FOR TSTM INITIATION BEFORE 00Z AS MODELS
FAIRLY CONSISTENT IN KEEPING AT LEAST MODEST EML CAP OVER MUCH OF
THE CWA THRU 00Z FRI. GOOD LOW LVL CONVERGENCE ALONG THE DRYLINE
AND LARGE SCALE ASCENT ASSOCIATED WITH SHORTWAVE TROUGH ENTERING
THE REGION SHOULD BE SUFFICIENT TO LIFT THROUGH THIS
CAP...ALLOWING ISOLATED SUPERCELL TSTMS TO INITIATE IN CENTRAL KS.
THESE TSTMS ARE EXPECTED TO MOVE NORTHEAST INTO THE TOP CWA...AND
TSTMS WILL LIKELY INCREASE IN COVERAGE AFT 00Z AS LARGE SCALE
ASCENT INCREASES THROUGH THE CENTRAL PLAINS. GIVEN STRENGTH OF THE
SHORTWAVE TROUGH AND WINDS ALOFT...A WIDESPREAD SEVERE WEATHER
OUTBREAK IS BECOMING MORE LIKELY. MESOSCALE ENVIRONMENT WILL
MODULATE POTENTIAL FOR TORNADOES...BUT THE PRESENCE OF SFC LOW
OVER WESTERN KS MAKES BACKED LOW LVL WINDS MORE LIKELY...WHICH
WOULD GENERALLY ENHANCE TORNADO POTENTIAL ASSOCIATED WITH ANY
SUPERCELL TSTM. TOO EARLY TO TELL EXACT TORNADO POTENTIAL...BUT A
SITUATION TO WATCH VERY CLOSELY AS IT BECOMES MORE OF A SHORT TERM
CONCERN.

EXTENDED...NO SIGNIFICANT CHANGES MADE TO GOING FORECAST PACKAGE.
WITH VERY ACTIVE SHORT TERM PATTERN...DECIDED TO SIDE WITH HPC
GUIDANCE FOR THE VERY END OF THE FORECAST PACKAGE. IN
GENERAL...GFS/ECMWF SEEM TO AGREE IN UPPER RIDGE OVER THE EASTERN
CONUS WITH AN UPPER TROUGH OVER THE WESTERN CONUS. THIS PATTERN
WILL KEEP SOUTHWEST FLOW THROUGH THE CENTRAL PLAINS WHICH WILL
MAKE FOR A CONTINUED ACTIVE WEATHER PATTERN FOR MUCH OF THE
EXTENDED FORECAST PACKAGE. CAN SEE SOUTHWEST FLOW ALLOWING
PERSISTENT EML TO REMAIN OVER REGION BUILDING UP LARGE INSTABILITY
DURING THE DAYTIME HOURS AND THUS A POTENTIAL FOR TSTMS DURING
PEAK HEATING HOURS. ANY AMBIENT BOUNDARY IN THE CENTRAL PLAINS
WOULD TEND TO FAVOR NOCTURNAL CONVECTION. MANY CHANGES WILL BE
MADE TO THE EXTENDED FORECAST PACKAGE AS SMALL SCARE FEATURES ARE
RESOLVED IN THE SHORT TERM.

CAVANAUGH

&&

.AVIATION...

VFR CONDS EXPECTED TO CONT AT ALL 3 TAFS SITES THRU THE PERIOD. AFTN
CU DVLPMNT WL DISSIPATE THIS EVNG EITHER FM STORMS DEVELOPING IN THE
AREA OR FM LOSS OF DIURNAL MIXING. ISO/SCT STORMS ARE POSSIBLE
DURING THE EVNG...BUT GIVEN THE SCT NATURE OF THE EVNT...ONLY
INCLUDED A CB IN THE TAFS AND ONCE TIMING BECOMES MORE CLR...TSRA
CAN BE ADDED. OTHERWISE...WK SFC BOUNDARY WILL CONT IN THE TAF SITES
THRU THE EVNG BEFORE FLOW BECOMES INCREASINGLY SRLY LATE TONIGHT AND
CONTS THRU THE DAY ON WED WITH DRY WX EXPECTED.

BOUSTEAD

&&

.TOP WATCHES/WARNINGS/ADVISORIES...NONE.

&&

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