Flood and Hail in Kansas, June 26 to 27, 2011

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
642 PM CDT SUN JUN 26 2011

...UPDATE TO AVIATION...

.DISCUSSION...

SHORT RANGE FORECAST (TODAY-MONDAY)...

COMPLICATED FORECAST ONGOING FOR THE NEXT FEW HOURS. THE MAIN
CONCERN WILL BE THE FORMATION OF STRONG TO SEVERE THUNDERSTORMS
LATER THIS AFTERNOON INTO THIS EVENING. THE UPPER LEVEL PATTERN IS
CHARACTERIZED BY A LARGE TROUGH OVER SOUTHERN CANADA AND A FLATTENED
UPPER RIDGE SITUATED OVER WESTERN TEXAS WITH SSW 500 MB WINDS OVER
THE FORECAST AREA. AT THE SURFACE A WARM FRONTAL BOUNDARY HAS
GRADUALLY CREPT NORTHWARD AHEAD OF A DEEPENING LEE SIDE SURFACE
TROUGH. STRONG SOUTHERLY SURFACE WINDS HAVE AIDED IN ACCELERATING
THE PROGRESS OF THE FRONT NORTHWARD. EXPECT THE WARM FRONT TO
FINALLY SET UP NEAR THE KS/NE BORDER BY THE MID AFTERNOON HOURS. ON
VISIBLE SATELLITE IMAGERY AT 19Z AN AGITATED CUMULUS FIELD SHOWED UP
ALONG THE STRONG CONVERGENCE ZONE RIGHT ALONG THE WARM FRONT. VISUAL
OBSERVATION OF THE CU FIELD NEAR THE WARM FRONT INDICATES THAT THE
CU FIELD HAS LITTLE VERTICAL EXTENT WHICH INFERS THAT THE MID LEVELS
ARE SUFFICIENTLY WARM TO MITIGATE CONVECTIVE DEVELOPMENT. 18Z RUC
SHOWS 700 MB TEMPS REACHING 15 C ALONG THE NS/NE BORDER WITH WARMER
TEMPS FURTHER TO THE SOUTH. SHOULD THIS BE THE CASE THE GOING
THOUGHT IS THAT THE WARM MID LEVELS WILL KEEP CONVECTION FROM
OCCURRING...ESPECIALLY IN THE ABSENCE OF ANY CONSIDERABLE UPPER
LEVEL FORCING. NAM AND RUC ALSO SHOWING A SPLIT IN THE 300 MB JET
OVER CENTRAL NEBRASKA WHICH GIVEN THE STRONG UPPER LEVEL DIVERGENCE
ASSOCIATED WITH THAT SPLIT SHOULD ALLOW FOR BETTER CONVECTIVE
CHANCES FURTHER NORTH UNDER THE DIFFLUENT FLOW ALOFT. SHOULD THE
UPPER JET NOSE INTO NORTHEAST KANSAS THAT WOULD BE ONE MORE
MITIGATING FACTOR TO CONVECTIVE DEVELOPMENT THIS AFTERNOON. SHOULD
STORMS BE ABLE TO OVERCOME THE MID LEVEL CAP AND UPPER CONVERGENCE
THEY WILL BE ABLE TO BECOME SEVERE VERY QUICKLY GIVEN THE
CONSIDERABLE INSTABILITY (APPROXIMATELY 5000 J/KG SBCAPE) AND 50 TO
60 KTS OF DEEP LAYER SHEAR...WITH SUPERCELLS BEING THE LIKELY
CONVECTIVE MODE. THE WARM FRONTAL BOUNDARY IS ALSO A FOCUS OF
CONCERN SHOULD STORMS INITIATE AS THE BOUNDARY WILL AID IN LOW LEVEL
HELICITY AND BRING THE POTENTIAL FOR A TORNADO WITH ANY STRONG
STORM.

AS THE STORM SYSTEM CURRENTLY ONGOING IN NW NEBRASKA MERGES WITH ANY
AFTERNOON CONVECTION WHICH GETS GOING IN EASTERN NEBRASKA IT IS
EXPECTED TO CONGEAL INTO AN MCS WHICH LOOKS TO DIVE SOUTHEASTWARD.
FORWARD PROPAGATING CORFIDI VECTORS SHOW THAT THE CLUSTER OF
THUNDERSTORMS WOULD MOVE SE INTO OUR NE COUNTIES DURING THE
OVERNIGHT HOURS. THE MAIN CONCERN WITH THESE STORMS WILL BE DAMAGING
WINDS...AND POSSIBLY SOME LARGE HAIL. HEAVY RAIN IS ALSO POSSIBLE
WITH THIS COMPLEX WHICH COULD RESULT IN SOME ISOLATED FLASH FLOODING.

FOR MONDAY THE MCS SHOULD BE CLEARED OUT OF THE AREA BY THE MID TO
LATE MORNING HOURS. DURING THE DAY ON MONDAY A SURFACE FRONT WILL
SLOWLY PUSH SOUTHEASTWARD THROUGH THE CWA BRINGING COOLER CONDITIONS
TO THE WESTERN ZONES. DON'T EXPECT MUCH IN THE WAY OF CONVECTION
ALONG THE FRONT AS THE CAP CONTINUES TO GAIN STRENGTH OVERNIGHT.
WILL KEEP LOW END CHANCE POPS IN THE NORTHEAST ZONES WHERE THE MID
LEVEL TEMPS DON'T LOOK QUITE AS WARM. ELSEWHERE WILL KEEP SLIGHT
CHANCE POPS THROUGHOUT THE DAY ON MONDAY.

JL

LONG TERM...FRONTAL BOUNDARY WILL SHIFT SOUTH MON NIGHT WITH
RETURN FLOW ALOFT EXPECTED BY TUES NIGHT INTO EARLY WEDS AS THE
UPPER RIDGE BUILDS IN. BY WEDS PM EXPECT EML TO CAP THE ATMOSPHERE
WITH HOT...HUMID AND MAINLY DRY CONDS EXPECTED INTO THU AT LEAST. RIDGE
AXIS DOES SHIFT SE WITH TIME AS A UPPER WAVE MOVES ACROSS THE
NORTHERN PLAINS. REMNANT FRONT WILL SAG INTO THE REGION WITH SOME
SMALL CHC FOR PRECIP BY THE END OF THE WEEK INTO THE WEEKEND AS
THE UPPER FLOW BECOMES MORE ZONAL.

CO

&&

.AVIATION...

FOR THE 00Z TAF ISSUANCE...A WARM FRONT HAS LIFTED NORTH OF THE
TERMINALS WITH THUNDERSTORMS FOCUED OVER CENTRAL AND NORTHEAST
NEBRASKA NEAR A COLD FRONT. BASED UPON THE 00Z KTOP
SOUNDING...WHICH SHOWS THE CAPPING INVERSION HAS STRENGTHENED
FURTHER SINCE THE 20Z KTOP SOUNDING...WILL NOT MENTION CB UNTIL
AROUND 11Z WITH THE ARRIVAL OF THE COLD FRONT. THIS FRONT WILL
BRING A WIND SHIFT TO THE NORTHWEST WITH GUSTS NEAR 20 KNOTS
POSSIBLE AFTER 18Z FROM INCREASED MIXING. HAVE INCLUDED LOW LEVEL
WIND SHEAR IN THE TAFS DUE TO AN INCREASING NOCTURANAL LOW LEVEL
JET NEAR 50 KTS FROM AROUND 04-11Z.

ANGLE

&&

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

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE TOPEKA KS
919 PM CDT SUN JUN 26 2011

KSZ008>012-020>024-026-034>040-054>056-058-059-280230-
REPUBLIC-WASHINGTON-MARSHALL-NEMAHA-BROWN-CLOUD-CLAY-RILEY-
POTTAWATOMIE-JACKSON-JEFFERSON-OTTAWA-DICKINSON-GEARY-MORRIS-
WABAUNSEE-SHAWNEE-DOUGLAS-LYON-OSAGE-FRANKLIN-COFFEY-ANDERSON-
919 PM CDT SUN JUN 26 2011

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

.DAY ONE...TONIGHT.

STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE AFTER 10 PM INTO
EARLY MONDAY MORNING. THUNDERSTORMS AHEAD OF A COLD FRONT IN
NEBRASKA WILL PROPAGATE INTO NORTHERN KANSAS. WHILE MOST
THUNDERSTORMS ARE EXPECTED TO REMAIN BELOW SEVERE THRESHOLDS...A
FEW THUNDERSTORMS COULD PRODUCE HAIL UP THE SIZE OF
QUARTERS...WIND GUSTS UP TO 60 MPH AND HEAVY RAIN.

.DAYS TWO THROUGH SEVEN...MONDAY THROUGH SATURDAY.

THUNDERSTORMS MAY CONTINUE INTO MONDAY...AND LINGER INTO MONDAY
EVENING SOUTH OF INTERSTATE 35. THUNDERSTORM CHANCES RETURN TO
THE AREA TUESDAY NIGHT INTO WEDNESDAY MORNING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS POSSIBLE LATE TONIGHT NEAR THE STATE LINE
OF KANSAS AND NEBRASKA.