Severe Thunderstorm Warning 251, NWS Topeka, KS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
300 PM CDT TUE SEP 23 2008

.DISCUSSION...
LARGE SCALE UPPER WAVE MOVING EAST INTO THE NORTHERN PLAINS THIS
AFTERNOON...WITH RESPECTABLE SHORTER WAVELENGTH FEATURE MOVING INTO
KANSAS. FAIRLY RESPECTABLE LOW LEVEL MOISTURE HAS TAKEN RESIDENCE IN
CENTRAL AND EASTERN KANSAS...WITH MID 60S DEWPOINTS COMMONPLACE.
RECENT OBJECTIVE ANALYSIS INDICATES NEARLY 2000 J/KG CAPE..THOUGH
NEARLY UNIDIRECTIONAL AND MODERATE WINDS WERE LIMITING SHEAR.

APPEARS SURFACE COLD FRONT WILL STRUGGLE TO MAKE IT INTO THE CWA.
INSTABILITY WILL TAPER OFF THIS EVENING...AND VERY WEAK LOW LEVEL
WINDS SHOULD LIMIT PERSISTENT AND WIDESPREAD PRECIPITATION COVERAGE.
MAY SEE SOME LOCALIZED HEAVIER AMOUNTS INTO THE EVENING AS STORM
MOTIONS VEER. SOME DECENT MOISTURE CONVERGENCE IN THE 700-850 LAYER
WILL PERSIST THROUGH THE NIGHT AND INTO WEDNESDAY...SO SOME THREAT
OF CONVECTION WILL CONTINUE. INSTABILITY WILL AGAIN BECOME WEAK TO
MODERATE IF DECENT INSOLATION CAN DEVELOP. THE ONLY SIGNIFICANT
CHANGES TO THE FORECAST WERE TO INCREASE PRECIPITATION CHANCES THIS
EVENING AND ADD SOME TO THE WESTERN AREAS WEDNESDAY WHERE
CONVERGENCE IS STILL RESPECTABLE.

65

CONTINUED WITH A SLIGHT CHANCE OF THUNDERSTORMS ACROSS FAR NORTH
CENTRAL KANSAS WEDNESDAY EVENING AS MODELS CONTINUE TO SHOW
CONVECTION DEVELOPING ON THE BACK SIDE OF THE SFC RIDGE. THE GFS
LOOKS LIKE IT DEVELOPS SOME FEEDBACK ISSUES...BUT FOR THE MOST PART
THINK MOST IF NOT ALL OF THE CONVECTION WILL REMAIN NORTH OF THE
STATE LINE. BOTH THE GFS AND NAM INDICATE THE BETTER THETA-E
ADVECTION AND ISENTROPIC LIFT ACROSS SOUTHERN NEB...WITH THE SFC
RIDGE AND DOWN GLIDE OVER MUCH OF THE FORECAST AREA.

THURSDAY AND FRIDAY CONTINUE TO LOOK DRY WITH RIDGING AND DRY AIR IN
PLACE. OTHER THAN SOME MINOR TWEAKS...FORECAST IS PRETTY SIMILAR TO
PREVIOUS VERSION WITH HIGHS IN THE MID 80S AND LOWS IN THE LOWER
60S.

MEDIUM RANGE MODELS HAVE TRENDED TOWARDS DEVELOPING A LONGWAVE
TROUGH OVER THE UPPER MIDWEST AND NORTHEAST. IN RESPONSE TO
THIS...WEAK COLD FRONTS ARE PROGGED TO MOVE INTO THE AREA SATURDAY
AND AGAIN MONDAY. THIS FIRST FRONT APPEARS TO HAVE LIMITED MOISTURE
AHEAD OF IT SO THE FORECAST REMAINS DRY FOR SATURDAY. MAIN EFFECT
SHOULD BE TO TREND TEMPS DOWN. IF THERE IS A LITTLE MORE CLOUD COVER
AND SUSTAINED NORTHERLY WINDS...CURRENT HIGHS COULD BE SLIGHTLY TO
WARM. FOR THE SECOND FRONTAL BOUNDARY...THE ECMWF AND GFS BRING A
CLIPPER SHORTWAVE ACROSS THE NORTHERN PLAINS AND UPPER MS RIVER
VALLEY WHICH COULD PROVIDE BETTER DYNAMICS WITH THE FRONT. HOWEVER
THERE DOES NOT APPEAR TO BE A STRONG INFLUX OF MOISTURE AHEAD OF
THIS FRONT. BECAUSE OF THIS HAVE INTRODUCED SLIGHT CHANCE POPS FOR
SUNDAY NIGHT THROUGH MONDAY NIGHT. FORECAST SOUNDINGS SHOW
INSTABILITY TO BE LIMITED AT THIS TIME...SO HAVE NOT INCLUDED
THUNDER IN THE GRIDS. A COOLING TREND SEEMS LIKELY WITH TEMPS CLOSER
TO SEASONAL NORMS FOR TUESDAY AS MODIFIED CANADIAN AIR FILTERS
SOUTH.

WOLTERS

&&

.AVIATION...
VFR CONDITIONS EXPECTED FOR THE MOST PART THROUGH THE PERIOD. BREEZY
SOUTHERLY WINDS THIS AFTERNOON AHEAD OF A WEAK COLD FRONT AND LINE
OF TSRA THAT WILL SLOWLY PUSH EASTWARD THIS AFTERNOON AND THROUGH
THE NIGHT. FORCING ALOFT IS RELATIVELY WEAK...AND LOW LEVEL JET
DISPLACED MAINLY WEST...SO AM NOT TOTALLY CONFIDENT IN THE EXTENT OF
PRECIP...OR WITH TIMING AS TO WHEN IT MAY BEGIN TO AFFECT LOCAL
TERMINALS LATER TODAY. MAINTAINED CB GROUP FOR MAINLY THE LATER
EVENING HOURS. MODEST INSTABILITY WILL KEEP THE CHANCE FOR THUNDER
ALIVE DURING THIS TIME FRAME...AND ADDED VCTS AT MHK FOR A FEW HRS
AFTER 01Z. MAY SEE A BRIEF MVFR CIG/VIS WITH ANY PRECIP AREAS.

&&

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

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE TOPEKA KS
230 PM CDT TUE SEP 23 2008

KSZ008>012-020>024-026-034>040-054>056-058-059-241930-
REPUBLIC-WASHINGTON-MARSHALL-NEMAHA-BROWN-CLOUD-CLAY-RILEY-
POTTAWATOMIE-JACKSON-JEFFERSON-OTTAWA-DICKINSON-GEARY-MORRIS-
WABAUNSEE-SHAWNEE-DOUGLAS-LYON-OSAGE-FRANKLIN-COFFEY-ANDERSON-
230 PM CDT TUE SEP 23 2008

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL...NORTH
CENTRAL AND NORTHEAST KANSAS.

.DAY ONE...THIS AFTERNOON AND TONIGHT

SCATTERED THUNDERSTORMS WILL AFFECT NORTH CENTRAL AND PORTIONS OF
NORTHEAST KANSAS THIS AFTERNOON...GENERALLY NORTHWEST OF ALINE
FROM COUNCIL GROVE TO VALLEY FALLS. A FEW OF THESE STORMS MAY BE
SEVERE...WITH HAIL AROUND THE SIZE OF QUARTERS AND WIND GUSTS
AROUND 60 MPH BEING THE PRIMARY HAZARDS. THUNDERSTORM CHANCES WILL
SPREAD ACROSS THE REMAINDER OF THE AREA AS THE NIGHT PROGRESSES.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY

THERE IS A SLIGHT CHANCE OF THUNDERSTORMS FOR MAINLY NORTHEAST AND
EAST CENTRAL KANSAS WEDNESDAY...AND IN PORTIONS OF NORTH CENTRAL
KANSAS WEDNESDAY EVENING.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED THIS AFTERNOON.

SIGNIFICANT WEATHER ALERT
NATIONAL WEATHER SERVICE TOPEKA KS
500 PM CDT TUE SEP 23 2008

KSZ022-023-232230-
POTTAWATOMIE-RILEY-
500 PM CDT TUE SEP 23 2008

THROUGH 530 PM CDT...A STRONG THUNDERSTORM WILL MOVE NORTHEAST AT 25
MPH ACROSS PORTIONS OF NORTHERN RILEY INTO NORTHWEST POTTAWATOMIE
COUNTY. NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED THIS
STORM IS CAPABLE OF PRODUCING PENNY SIZE HAIL AND WINDS UP TO 40
MPH. SOME LOCATIONS THAT COULD BE AFFECTED INCLUDE RANDOLPH AND
NORTHERN PORTIONS OF TUTTLE CREEK LAKE.

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