Special Weather Statement, NWS Kansas City, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
620 PM CDT WED MAY 11 2011

...UPDATED AVIATION DISCUSSION...

.DISCUSSION...

WEAK SHORTWAVE WHICH INITIATED THE CONVECTION THIS MORNING HAS
DEPARTED THE FORECAST AREA. A WEAK SUBSIDENCE INVERSION WAS NOTED IN
THE WAKE OF THE WAVE ON THE TOPEKA 18Z SOUNDING. REGARDLESS...THE CAP
IS RATHER WEAK WITH INSTABILITY AROUND 2500 J/KG-3500 J/KG. DUE TO
THE HIGH INSTABILITY...WIDELY SCATTERED SHOWERS AND THUNDERSTORMS
WERE DEVELOPING THIS AFTERNOON. GIVEN THE WEAK SHEAR
ENVIRONMENT...THE PRIMARY THREATS ARE LARGE HAIL AND DAMAGING WINDS.

NEXT CONCERN IS THE CONVECTION UPSTREAM IN OKLAHOMA AND SOUTH CENTRAL
KANSAS...AHEAD OF A NEARLY STATIONARY UPPER LEVEL LOW IN SOUTHERN
COLORADO. CONVECTION WAS GENERALLY MOVING NORTH NORTHEAST AS MID
LEVEL WINDS BACK AHEAD OF THE LOW. DUE TO THE SLOW MOVEMENT AND
BACKING WINDS...THE CONVECTION TO THE SOUTHWEST IN KANSAS AND
OKLAHOMA WILL BE SLOW TO MOVE SUFFICIENTLY EAST...NOT LIKELY
ARRIVING INTO EXTREME WESTERN MISSOURI UNTIL AT LEAST 7 OR 8 PM. THE
ONLY EXCEPTION MAY IN EXTREME NORTHWEST MISSOURI...JUST TO THE SOUTH
OF THE STATIONARY FRONT IN SOUTHEASTERN NEBRASKA. SBCAPES WILL BE
AROUND 2500-3000 J/KG THIS EVENING...BUT LOW AND DEEP LAYER SHEAR
WILL BE WEAK. DESPITE THE WEAK SHEAR...LARGE HAIL AND DAMAGING WINDS
ARE POSSIBLE DUE TO THE HIGH INSTABILITY.

MODELS CONTINUE TO SUGGEST THAT THE UPPER LEVEL LOW WILL BE VERY SLOW
TO MOVE EAST. THIS APPEARS REASONABLE GIVEN THE BLOCK OFF THE EAST
COAST. THE INSTABILITY WILL SIGNIFICANTLY DIMINISH AFTER SUNSET WITH
THE INTENSITY OF THE CONVECTION DECREASING AS IT MOVES EAST.

ON THURSDAY...THE UPPER LEVEL LOW DRIFTS INTO CENTRAL AND WESTERN
KANSAS WITH THE ATTENDANT SURFACE LOW SHIFTING EAST INTO EASTERN
KANSAS WITH THE FRONT SAGGING INTO NORTHWEST MISSOURI. THESE FEATURES ALONG
WITH ANY WEAK SHORTWAVES WILL TRIGGER SCATTERED THUNDERSTORMS ONCE
AGAIN IN A HIGH INSTABILITY AND LOW SHEAR ENVIRONMENT. LARGE
HAIL...DAMAGING WINDS AND LOCALLY HEAVY RAINFALL ARE POSSIBLE.

ON THURSDAY NIGHT AND FRIDAY...THE NAM AND GFS ARE CONSISTENT IN
SHIFTING THE UPPER LEVEL LOW EAST SOUTHEAST INTO SOUTHERN MISSOURI.
THE PRECIPITATION WILL GRADUALLY END FROM THE NORTHWEST DURING THIS PERIOD.

DB

MEDIUM RANGE (SATURDAY THROUGH WEDNESDAY)...

MODELS HAVE COME INTO BETTER AGREEMENT WITH THE HANDLING OF UPPER
DOUBLE LOW EVOLUTION AS THEY PRETTY MUCH AGREE WITH SWINGING THE
NORTHERN ONE THROUGH THE UPPER MIDWEST AS THE FIRST ONE SLOWLY SWINGS
THROUGH TO THE EAST. THIS FIRST WAVE SHOULD HAVE MOVED ON BY THE
EXTENDED AND THE SECOND WAVE WILL PROVIDE SOME INSTABILITY SHOWERS
POTENTIALLY ON SATURDAY AND MORE LIKELY ON SUNDAY. AFTER THAT SURFACE
RIDGING WILL BRING QUIET AND CONTINUED SLIGHTLY COOL THROUGH
WEDNESDAY.

BAILEY

&&

.AVIATION...

FOR THE 00Z TAFS...TOUGH FORECAST THROUGH THURSDAY WITH THE FORECAST
REVOLVING AROUND THE TIMING OF CONVECTION. AN UPPER LOW WAS NEARLY
STATIONARY IN SOUTHERN COLORADO WITH THE CONVECTION AHEAD OF THE LOW
IN SOUTHEAST KANSAS INTO NORTHEAST OKLAHOMA. THIS CONVECTION SHOULD
REACH THE TERMINALS IN A COUPLE OF HOURS. THE STORMS WILL GRADUALLY
DIMINISH TO A COUPLE OF HOURS OF RAIN AFTER 03Z AS INSTABILITY DIMINISHES.
NUMERICAL GUIDANCE SUGGEST THAT AN MVFR DECK MAY FORM LATE TONIGHT
DUE TO SATURATION OF THE LOWER LEVELS AND NOCTURNAL COOLING. CANNOT
ARGUE WITH THE GUIDANCE AT THIS TIME...BUT CONFIDENCE IS NOT HIGH.
OTHERWISE...THE UPPER LEVEL LOW WILL APPROACH THE TERMINALS LATE
THURSDAY AFTERNOON WITH A GOOD THREAT OF CONVECTION.

DB

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...NONE.
KS...NONE.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
501 PM CDT WED MAY 11 2011

KSZ025-057-060-102>105-MOZ001>008-011>017-020>025-028>033-037>040-
043>046-053-054-121130-
ATCHISON KS-MIAMI-LINN KS-DONIPHAN-LEAVENWORTH-WYANDOTTE-JOHNSON KS-
ATCHISON MO-NODAWAY-WORTH-GENTRY-HARRISON-MERCER-PUTNAM-SCHUYLER-
HOLT-ANDREW-DE KALB-DAVIESS-GRUNDY-SULLIVAN-ADAIR-BUCHANAN-CLINTON-
CALDWELL-LIVINGSTON-LINN MO-MACON-PLATTE-CLAY-RAY-CARROLL-CHARITON-
RANDOLPH-JACKSON-LAFAYETTE-SALINE-HOWARD-CASS-JOHNSON MO-PETTIS-
COOPER-BATES-HENRY-
501 PM CDT WED MAY 11 2011

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTHWEST...NORTH CENTRAL AND
WEST CENTRAL MISSOURI...AS WELL AS EXTREME EASTERN KANSAS.

.DAY ONE...TONIGHT

SCATTERED THUNDERSTORMS CONTINUED LATE THIS AFTERNOON FROM NORTHWEST
MISSOURI SOUTHWEST INTO SOUTHEAST AND SOUTH CENTRAL KANSAS. DUE TO
THE HIGH INSTABILITY...ADDITIONAL THUNDERSTORMS MAY DEVELOP THIS
EVENING FURTHER EAST ACROSS REST OF THE OUTLOOK AREA. THE PRIMARY
THREATS ARE LARGE HAIL...DAMAGING WINDS AND LOCALLY HEAVY RAINFALL.
BY LATE THIS EVENING...INSTABILITY WILL DECREASE WITH THE THREAT OF
SEVERE STORMS DIMINISHING.

.DAYS TWO THROUGH SEVEN...THURSDAY THROUGH TUESDAY

THUNDERSTORMS ARE POSSIBLE THURSDAY AS THE UPPER LEVEL SYSTEM MOVES
OVER THE REGION. SEVERE THUNDERSTORMS ARE POSSIBLE... ESPECIALLY
DURING THE AFTERNOON AND EARLY EVENING. ALTHOUGH AN ISOLATED TORNADO
IS POSSIBLE...THE PRIMARY THREATS ARE LARGE HAIL...DAMAGING WINDS
AND LOCALLY HEAVY RAINFALL.

A FEW THUNDERSTORMS ARE POSSIBLE ON FRIDAY...BUT ARE NOT EXPECTED TO BE
SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS EVENING.

DB

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