Hail and Damaging Winds in Kansas, May 6 to 7, 2010

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TOPEKA KS
723 PM CDT THU MAY 6 2010

.UPDATE...

UPDATED FOR THE 00Z TAF ISSUANCE.

&&

.DISCUSSION...

SEE PREVIOUS DISCUSSION.

&&

.AVIATION...

EXPECT ELEVATED CONVECTION TO DEVELOP IN THE AREA THIS EVENING AS
LLVL JET INCREASES ACROSS THE SFC FRONT TO THE SOUTH. THEREFORE
WILL KEEP CB GOING WITH SCT CONVECTION SOUTH...WITH THE MORE
WIDESPREAD CONVECTION DEVELOPING/SPREADING EASTWARD INTO THE AREA
AFT MIDNIGHT...BUT MODELS KEEP THE MAIN AREA OF CONVECTION NORTH
OF THE TAF SITES SO WILL KEEP VCNTY FOR NOW ALL TAFS. POST FRONTAL MVFR
STRATUS PLUNGES SOUTHEAST ACROSS THE TAF SITES AFT 07Z WITH
INCREASING NORTH/NORTHWEST WINDS...THEN SCATTERS OUT TO VFR AFT 16Z/07.

&&

.PREV DISCUSSION... /ISSUED 316 PM CDT THU MAY 6 2010/

DISCUSSION...
AT 2 PM SFC OBS SHOW THE WARM FRONT JUST SOUTH OF THE FORECAST
AREA...GENERALLY FROM CHANUTE TO HUTCHINSON. MEANWHILE WATER VAPOR
IMAGERY WAS SHOWING A SHORTWAVE ROTATING THROUGH THE BASE OF AN
UPPER LOW ACROSS UT IN TO WY AND CO.

MAIN QUESTION WITH THE FORECAST IS WHEN AND WHERE WILL THUNDERSTORMS
OCCUR TONIGHT. A FEW HIGH RES MODELS ARE SHOWING ENOUGH MOISTENING
ACROSS EAST CENTRAL KS FOR ISOLATED CONVECTION TO FIRE BY 7 PM.
WHILE THERE IS STILL A DECENT AMOUNT IF CONVECTIVE INHIBITION FROM
THE CAPPING EML...RUC INDICATES SOME MID LEVEL COOLING AS THE LOW
LEVEL MOISTURE INCREASES TO REMOVE THE INHIBITION. FOR NOW AM IN A
WAIT AND SEE MODE. AM A LITTLE SKEPTICAL OF THE QUALITY OF MOISTURE
SINCE DEWPOINTS HAVE BEEN MIXING OUT AROUND THE ARKLATX REGION. IF A
STORM WERE TO DEVELOP THIS AFTERNOON ACROSS EAST CENTRAL KS...THE
LOW LEVEL SHEAR AND INSTABILITY WOULD SUGGEST THAT A TORNADO THREAT
WOULD EXIST. LATER TONIGHT...THE SHORTWAVE MOVING THROUGH THE
CENTRAL ROCKIES IS EXPECTED TO TRIGGER CONVECTION OVER THE HIGH
PLAINS. THEN WITH PERSISTENT LIFT OVER THE FRONT...AN MCS WOULD
PROPAGATE EAST ALONG THE KS/NEB STATE LINE. DAMAGING HAIL WOULD BE
MORE LIKELY GIVEN THE ELEVATED NATURE OF THE STORMS WITH SOME WIND
POTENTIAL IF DOWNDRAFTS WERE ABLE TO PENETRATE THE STABILIZING
BOUNDARY LAYER. CONFIDENCE IN THE OVERNIGHT STORMS IS A LITTLE HIGH
AND HAVE CONTINUED WITH CATEGORICAL POPS ACROSS THE NORTHERN
COUNTIES.

ANOTHER CONCERN OVERNIGHT IS AN INCREASING PRESSURE GRADIENT BEHIND
THE SFC LOW POSSIBLY CAUSING WINDS TO BE SUSTAINED AT OR ABOVE 30
MPH. THE NAM AND GFS KEEP THE STRONGEST PRESSURE GRADIENT AND
ISALLOBARIC FORCING TO THE SOUTH AND WEST OF THE FORECAST AREA.
CONSIDERED THE NEED FOR A WIND ADVISORY ACROSS THE SOUTHWESTERN
COUNTIES...BUT GIVEN THE OBJECTIVE GUIDANCE KEEPING SUSTAINED WINDS
BELOW 30 MPH WILL NOT ISSUE AN ADVISORY AT THIS TIME. NEVERTHELESS
IT WILL BE WINDY LATE TONIGHT AND INTO THE DAY FRIDAY. DRY AIR
ADVECTION AND INCREASING SUBSIDENCE WILL FAVOR A DRY DAY FRIDAY WITH
DECREASING CLOUDS DURING THE MORNING. CAA THROUGH THE DAY SHOULD
KEEP HIGHS IN THE 60S.

WOLTERS

STRONG COLD AIR ADVECTION TO PERSIST THROUGH FRIDAY NIGHT WITH 850MB
DROPPING TO AROUND 0C. DESPITE CLEAR SKIES...CAA AND ASSOCIATED WIND
ALOFT SHOULD KEEP FROST AND FREEZING TEMPS AT BAY. WINDS WILL
DIMINISH SATURDAY WITH BUILDING LOW LEVEL RIDGE AS HIGH CLOUDS SPILL
OVER THE ROCKIES IN FAST ZONAL FLOW ALOFT. WITH DECREASING MIXING
POTENTIAL AND THE CLOUD INCREASES...LOWERED HIGHS A TOUCH.
ISENTROPIC LIFT SLOWLY INCREASES AND DEEPENS FROM SATURDAY NIGHT
INTO SUNDAY. SOME MODEL DISCREPANCIES EXIST IN HOW DEEP THE COLUMN
WILL MOISTEN...AND SMALLER POPS WILL BE MAINTAINED SUNDAY. THE
POTENTIAL EXISTS FOR SUNDAY TO BE COOLER THAN SATURDAY IF CLOUDS AND
PRECIP ARE MORE EXTENSIVE THAN EXPECTED...AND WITH SURFACE
TRAJECTORIES SOURCED FROM THE ANTICYCLONE TO THE SOUTHEAST. DROPPED
TEMPS ABOUT 5 DEGREES FOR NOW.

DESPITE RATHER POOR DAY 5 SKILL SCORES FROM THE LATE APRIL
RUNS...THERE IS GOOD AGREEMENT IN THE RECENT MEDIUM RANGE MODELS.
WARM ADVECTION PATTERN WILL CONTINUE TO RULE SUNDAY NIGHT.
INSTABILITY WILL INCREASE WITH TIME AS THE LOW LEVEL ANTICYCLONE IS
DISPLACED EAST BY DEEPENING LEE LOW PRESSURE AHEAD OF THE NEXT
STRONG SHORTWAVE. A LOWER-BASED THUNDERSTORM CONCERN MONDAY
AFTERNOON INTO TUESDAY MORNING AS THIS SHORTWAVE PASSES...AND
SIMILAR TODAY...MUCH WILL DEPEND ON TIMING AND QUALITY OF MOISTURE
RETURN AND PERSISTENCE OF OVERNIGHT CONVECTION...BUT DYNAMICS OF THE
SETUP SUGGEST A DEFINITE SEVERE THREAT. NEXT UPPER WAVE WILL BE
CLOSE ON THE HEALS OF THIS ONE...KEEPING THE LOW LEVEL BAROCLINIC
ZONE FROM GETTING TOO FAR SOUTHEAST AND RETURNING MAINLY ELEVATED
SHOWER AND THUNDERSTORM CHANCES FOR WEDNESDAY INTO THURSDAY. WITH
COLD FRONTS REPEATED MOVING THROUGH AND DAYTIME PRECIPITATION
POTENTIAL...WILL KEEP TEMPERATURES NEAR TO SLIGHTLY BELOW NORMAL
WITH LARGE VARIATIONS ACROSS THE AREA POSSIBLE ON MULTIPLE DAYS.

65

&&

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

&&

63

HAZARDOUS WEATHER OUTLOOK...UPDATED
NATIONAL WEATHER SERVICE TOPEKA KS
818 PM CDT THU MAY 6 2010

KSZ008>012-020>024-026-034>040-054>056-058-059-080130-
REPUBLIC-WASHINGTON-MARSHALL-NEMAHA-BROWN-CLOUD-CLAY-RILEY-
POTTAWATOMIE-JACKSON-JEFFERSON-OTTAWA-DICKINSON-GEARY-MORRIS-
WABAUNSEE-SHAWNEE-DOUGLAS-LYON-OSAGE-FRANKLIN-COFFEY-ANDERSON-
818 PM CDT THU MAY 6 2010

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

.DAY ONE...TONIGHT

ISOLATED THUNDERSTORMS ARE STILL EXPECTED ACROSS EAST CENTRAL
AND NORTHEAST KANSAS THROUGH 9 PM. HAIL AND STRONG GUSTY WINDS
ARE POSSIBLE WITH THE STRONGER STORMS.

LATER THIS EVENING...ADDITIONAL STRONG TO SEVERE THUNDERSTORMS
ARE LIKELY TO MOVE INTO NORTH CENTRAL KANSAS. THESE STORMS COULD
THEN SPREAD INTO NORTHEAST AND EAST CENTRAL KANSAS DURING THE
OVERNIGHT HOURS. THESE STORMS ARE EXPECTED TO BE CAPABLE OF
DAMAGING WINDS AND LARGE HAIL AS THEY MOVE RAPIDLY EAST.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY

THUNDERSTORMS WILL BE POSSIBLE SUNDAY THROUGH TUESDAY. THE CHANCE
FOR SEVERE STORMS APPEARS TO BE GREATEST MONDAY NIGHT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY STILL BE NEEDED ACROSS EAST CENTRAL KANSAS
THIS EVENING AND IN NORTH CENTRAL AREAS AFTER 10 PM...THEN ACROSS
THE NORTHEAST AND EAST CENTRAL AFTER MIDNIGHT.