Hail and Damaging Winds in Kansas, August 19, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
326 PM CDT WED AUG 19 2009

.DISCUSSION...
20Z WATER VAPOR IMAGERY SHOWS A LONGWAVE TROUGH OVER THE NORTHERN
AND CENTRAL PLAINS...WITH A SHORTWAVE MOVING SOUTH ACROSS SD AND
WESTERN NEB. SFC OBS INDICATED A TROUGH STRETCHING FROM SOUTHWESTERN
KS TO EAST CENTRAL NEB WITH A COLD FRONT FROM NORTHWEST CO INTO
WESTERN NEB. LINE OF CONVECTION OVER EAST CENTRAL KS APPEARS TO BE
GENERATING OFF OF AN OLD OUTFLOW BOUNDARY.

FOR TONIGHT THINK THE WAVE MOVING THROUGH THE NORTHERN PLAINS WILL
BE THE MAIN FORCING MECHANISM FOR CONVECTION THROUGH THE EVENING.
MODELS KEEP THE FRONT PROGRESSIVE AND PUSH IT SOUTHEAST OF THE
FORECAST AREA BY 12Z THU. WHILE TEMPS AND DEWPOINTS HAVE BEEN A
LITTLE COOLER THAN EARLIER MODELS PROJECTED...THERE IS STILL AROUND
2000 J/KM OF CAPE ALONG AND JUST AHEAD OF THE SFC TROUGH.
ADDITIONALLY DEEP LAYER SHEAR AROUND 40 KTS SHOULD BE ENOUGH FOR A
FEW SUPERCELL STORMS. THINK THAT WITH STEEP MID LEVEL LAPSE RATES
LARGE HAIL WILL BE THE PRIMARY CONCERN WITH THE THUNDERSTORMS.
EARLIER OUTLOOKS MENTIONED A TORNADO THREAT DUE TO MESO BOUNDARIES
WHERE LOCAL SFC WINDS COULD REMAIN BACKED. HOWEVER MOST OF THE
BOUNDARIES HAVE WASHED OUT AND SFC WINDS ACROSS THE FORECAST AREA
HAVE VEERED TO THE SOUTH AND SOUTHWEST. THEREFORE THE TORNADO THREAT
APPEARS TO HAVE DIMINISHED SLIGHTLY. PWS ARE STILL PROGGED TO BE
GREATER THAN 1.5 INCHES SO HEAVY RAIN AND LOCALIZED FLOODING WILL
REMAIN A CONCERN. PROGRESSIVE NATURE OF THE FRONT IS EXPECTED TO
KEEP STORMS MOVING ALONG...SO THINK FLASH FLOODING WOULD BE FAIRLY
LOCALIZED AND HAVE DECIDED NOT TO ISSUE A FLASH FLOOD WATCH AT THIS
TIME.

FOR THURSDAY DRY AIR AND INCREASING SUBSIDENCE SHOULD BRING AN END
TO THE PRECIP. HOWEVER MODELS FORECAST SOUNDINGS SHOW LOW LEVEL
LAPSE RATES STEEPENING UP PRETTY GOOD THROUGH THE AFTERNOON. THERE
COULD EVEN BE SOME AFTERNOON INSTABILITY FOR ACROSS FAR NORTHEAST
KS. CAN NOT RULE OUT AN ISOLATED SHOWER DEVELOPING DURING THE
AFTERNOON...BUT THIS LOOKS TO BE RELATIVELY ISOLATED AND SINCE
PREVIOUS SHIFT REMOVED POPS WILL LET LATER SHIFTS SEE IF MODELS SHOW
SOME CONSISTENCY WITH THIS RATHER THAN ADDING POPS BACK IN. HIGHS
SHOULD END UP AROUND 80 WITH NEUTRAL TEMP ADVECTION ON NORTHWEST
WINDS EXPECTED THROUGH THE DAY.

WOLTERS

EXTENDED FORECAST...NOT MUCH CHANGE TO THE PREVIOUS FORECAST.
MODELS IN FAIRLY GOOD AGREEMENT AND SHOW AN UPPER LOW OVER THE
NORTHERN TIER STATES/SOUTHERN CANADA THAT PUSHES TAIL END OF TROF
OVER NE SECTIONS OF THE CWA DURING THE DAY FRIDAY. EXPECT ONLY
CLOUDS WITH THIS FEATURE AS BETTER MOISTURE AND LIFT REMAIN OVER
IOWA. CLOUDS SHOULD CLEAR BY FRIDAY EVENING AS A BROAD H5 AND SFC
RIDGE BUILD IN. WITH NORTHERLY WINDS...AFTERNOON CONDITIONS ON
SATURDAY SHOULD BE QUITE PLEASANT. SFC WINDS VEER BACK TO THE SOUTH
AS SFC HIGH PUSHES SE SATURDAY NIGHT. EXPECT A WARMING TREND
BEGINNING SUNDAY INTO TUESDAY WITH TEMPS IN THE UPPER 80S AND LOWER
90S. NEXT CHANCE OF PRECIP DOES NOT LOOK TO RETURN UNTIL NEXT
WEDNESDAY.

BYRNE

&&

.AVIATION...
THERE IS STILL ENOUGH UNCERTAINTY IN TS INITIATION TO KEEP TAFS VFR
WITH ONLY MENTION AS VC ATTM. HARD TO DISCERN WHETHER THERE IS A
SHORTWAVES ACROSS EASTERN CO WITHIN WATER VAPOR AND CONVECTION
ACROSS SOUTHERN KS MAY MODIFY AND DELAY AMOUNT OF DESTABILIZATION
THIS AFTERNOON. THINK THE BEST WINDOW FOR CONVECTION WILL BE BETWEEN
21Z AND 04Z. IF/WHEN CONVECTION MOVES INTO THE TERMINALS...HEAVY
RAINFALL WILL LIKELY CAUSE TEMPO IFR VSBY WITH CIGS LOWERING TO
AROUND 2 KFT. OTHERWISE EXPECT VFR TO PREVAIL WITH A WIND SHIFT TO
THE NORTHWEST AROUND 07-08Z.

WOLTERS

&&

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

&&

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE TOPEKA KS
306 PM CDT WED AUG 19 2009

KSZ008>012-020>024-026-034>040-054>056-058-059-202015-
REPUBLIC-WASHINGTON-MARSHALL-NEMAHA-BROWN-CLOUD-CLAY-RILEY-
POTTAWATOMIE-JACKSON-JEFFERSON-OTTAWA-DICKINSON-GEARY-MORRIS-
WABAUNSEE-SHAWNEE-DOUGLAS-LYON-OSAGE-FRANKLIN-COFFEY-ANDERSON-
306 PM CDT WED AUG 19 2009

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

.DAY ONE...THIS AFTERNOON AND TONIGHT

THERE IS A CHANCE FOR SEVERE THUNDERSTORMS THROUGH THE AFTERNOON
AND EVENING HOURS...MAINLY ACROSS EAST CENTRAL AND NORTHEAST
KANSAS. THE GREATEST HAZARDS WOULD BE LARGE HAIL...TORRENTIAL
RAINFALL AND STRONG STRAIGHT LINE WINDS. THUNDERSTORMS THAT TRAIN
OVER THE SAME AREAS COULD ALSO PRODUCE LOCALIZED FLASH FLOODING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.SPOTTER INFORMATION STATEMENT...

SPOTTERS MAY BE NEEDED AFTER 3 PM AND INTO THE EVENING HOURS
ACROSS EAST CENTRAL AND NORTHEAST KANSAS.

WOLTERS

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE TOPEKA KS
230 PM CDT WED AUG 19 2009

KSZ054-058-192000-
COFFEY-LYON-
230 PM CDT WED AUG 19 2009

...SIGNIFICANT WEATHER ALERT FOR SOUTHEASTERN LYON AND WESTERN
COFFEY COUNTIES...

THROUGH 300 PM CDT...A THUNDERSTORM WILL MOVE EAST AT 50 MPH ACROSS
PORTIONS OF SOUTHEASTERN LYON AND WESTERN COFFEY COUNTIES. NATIONAL
WEATHER SERVICE DOPPLER RADAR INDICATED THIS STORM IS CAPABLE OF
PRODUCING NICKEL SIZE HAIL...WINDS UP TO 40 MPH AND TORRENTIAL
RAINFALL. SOME LOCATIONS THAT COULD BE AFFECTED INCLUDE NEOSHO
RAPIDS...HARTFORD...JOHN REDMOND RESERVOIR...LEBO AND NEW STRAWN.
MOTORISTS ALONG INTERSTATE 35 BETWEEN MILE MARKERS 141 AND 155 COULD
ALSO BE AFFECTED.

STAY ALERT TO THE WEATHER IN CASE A WARNING IS ISSUED.