Severe Thunderstorm Warning 335, NWS Kansas City, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1231 AM CDT SUN SEP 19 2010

...UPDATED AVIATION DISCUSSION...

.UPDATE...

STORMS CONTINUE TO REGENERATE ACROSS EXTREME EAST CENTRAL KANSAS AND
WEST CENTRAL MISSOURI LATE THIS EVENING...GENERALLY ACROSS THE
NORTHERN 2/3 OF THE GREATER KANSAS CITY METROPOLITAN AREA. SOUTHWEST
H8 WINDS CONTINUE TO ADVECT WARM UNSTABLE AIR ACROSS A WEAK BOUNDARY
LEFT ACROSS THE METRO FROM THE EARLIER STORM ACTIVITY AND A FRONT
THAT SAGGED SOUTH SATURDAY. WITH MLCAPE VALUES OF 2000+ J/KG STILL
PREVAILING SOUTH OF THE BOUNDARY AS OF 11 PM...SEVERAL MORE HOURS OF
SEVERE THUNDERSTORM ACTIVITY LOOK TO REMAIN POSSIBLE AS THE H8 WIND
IS NOT GOING TO VEER OFF TO THE WEST TILL EARLY SUNDAY MORNING AS A
VERY WEAK AND SUBTLE SHORTWAVE MOVES THROUGH IOWA. ADD IN 0-6KM SHEAR
VALUES OF 35 KNOTS...AND THESE STORMS LOOK TO HAVE THE JUICE TO
CONTINUE PRODUCING SEVERE WEATHER INTO THE EARLY MORNING HOURS OF
SUNDAY. AS A RESULT...HAVE EXPANDED THE GOING SEVERE THUNDERSTORM
WATCH 673 FOR NORTHERN MISSOURI BACK TO THE SOUTHWEST TO INCLUDE THE
KANSAS CITY METROPOLITAN AREA. PRIMARY THREATS WITH THESE STORMS WILL
BE LARGE HAIL AND DAMAGING WINDS. ADDITIONALLY...HEAVY RAIN LEADING
TO FLOODING WILL ALSO CONTINUE TO BE A CONCERN.

FARTHER NORTH...NEAR THE IOWA BORDER...STORMS ARE NEARER THE UPPER
LEVEL SUPPORT FROM THE STRONGER WESTERLIES. THAT ACTIVITY IS ALSO
EXPECTED TO PERSIST INTO THE EARLY MORNING HOURS OF SUNDAY.

CUTTER

&&

.DISCUSSION...

OLD OUTFLOW BOUNDARY HAS PUSHED WELL INTO CNTRL MISSOURI THIS
AFTERNOON...AND ESSENTIALLY WASHED OUT WITH DIURNAL HEATING...WHILE
TRUE SHALLOW SYNOPTIC FRONT/DENSITY CURRENT HAS NEARLY STALLED ALONG
A KHYS-KCNK-KFNB-KLWD LINE. BETWEEN THESE TWO
BOUNDARIES...CONVERGENCE HAS BEEN RATHER LIMITED...WITH THE BEST
MOISTURE FLUX AND SFC CONVERGENCE FOCUSED THROUGH CNTRL KANSAS AS
EVIDENCED BY THE ENHANCED CU FIELD ON VISIBLE SATELLITE.
HOWEVER...SPECIAL 18Z KTOP SOUNDING INDICATES RATHER MINIMAL
INHIBITION LEFT WITH MLCAPES ON THE ORDER OF 3000 J/KG...COINCIDENT
WITH BULK SHEAR VALUES IN THE 30-40KT RANGE ON THE SRN PERIPHERY OF
THE STRONGER JET AXIS NORTH OF THE SYNOPTIC FRONT. INVESTIGATION OF
WV IMAGERY AND PROFILERS (WITH SUPPORT FROM OBJECTIVE RUC GUIDANCE)
HINTS AT A SUBTLE WAVE EJECTING ACROSS SWRN NEBRASKA TOWARDS THE
WARM SECTOR...WHICH MAY PROVIDE JUST ENOUGH LIFT IN THE NEXT COUPLE
HOURS TO SUPPORT DEEPER CONVECTIVE OVERTURNING. WITH DEEP LAYER
SHEAR JUST SUFFICIENT TO SUPPORT SUPERCELLULAR STRUCTURE AND 0-1KM
SHEAR LARGELY RELEGATED TO THE COLD SECTOR...EXPECTING STORMS THAT
DO FORM TO CONGEAL INTO CLUSTERS AND BECOME OUTFLOW DOMINATED BY THE
EARLY EVENING. HOWEVER...BEFORE THAT TIME...LARGE HAIL AND DAMAGING
WINDS WILL BE THE PRIMARY THREATS...THOUGH A BRIEF ISOLATED TORNADO
CANNOT BE ENTIRELY DISCOUNTED UPON INITIAL ROBUST THUNDERSTORM
UPDRAFT FORMATION...ESPECIALLY FROM THE KC METRO AREA WEST ALONG
I-70 WHERE LOW LEVEL VORTICITY HAS BEEN MAXIMIZED AND WOULD
CONCEIVABLY BE INGESTED AND ENHANCE LOW LEVEL STRETCHING.
OVERALL...PREFERRED AN EVOLUTION SIMILAR TO THE HI-RES 00Z NSSL WRF
(WHICH HANDLED EARLY MORNING OUTFLOW MOST ACCURATELY)...WITH
SUPPLEMENTAL INPUT FROM RECENT HRRR RENDITIONS.

OUTFLOW ENHANCED CONVECTION SHOULD MOVE SOUTH OF THE FORECAST AREA
THIS EVENING...HOWEVER WITH THE SHALLOW BOUNDARY LIKELY RESUMING A
SLIGHT SOUTHWARD PUSH AND WEAK LLJ AXIS IMPINGING ACROSS THIS
FRONT...HAVE DECENT CONFIDENCE OF ELEVATED SHRA AND ISOLD TSTMS
REFORMING ACROSS NRN MISSOURI THROUGH THE MORNING HOURS.
THEREAFTER...SIGNIFICANT UNCERTAINTY EXISTS REGARDING THE EXTENT TO
WHICH THE FRONTAL BOUNDARY LIFTS BACK NORTH TOMORROW...WITH THE
OPERATIONAL NAM-WRF ALMOST COMPLETELY SCOURING OUT THE SHALLOW COLD
AIRMASS...WITH THE OPERATIONAL GFS AND ECMWF FAR MORE PESSIMISTIC.
CANNOT COMPLETELY IGNORE THE NAM SOLUTION GIVEN ITS BETTER BOUNDARY
LAYER RESOLUTION...YET THIS MODEL HAS LITTLE OTHER SUPPORT...AND
HAVE HEDGED MORE TOWARDS AN SREF MEAN SOLUTION ONLY BRINGING
LOCATIONS SOUTH OF HIGHWAY 36 BACK INTO THE TRUE WARM SECTOR.

WARM AND WINDY CONDITIONS CAN BE EXPECTED ON MONDAY AS THE OLD
FRONTAL BOUNDARY WASHES OUT AND REFORMS NORTH WITH BUILDING HEIGHTS
ALOFT AND RENEWED LEE SFC PRESSURE FALLS. THIS BOUNDARY WILL
EVENTUALLY TAKE THE FORM OF A COLD FRONT...PUSHING BACK INTO THE
REGION ON TUESDAY AFTERNOON AND EVENING. CURRENT SUITE OF MODELS
INDICATES THE POSSIBILITY OF ANOTHER EPISODE OF STRONG TO SEVERE
STORMS WITH THIS FRONT. ONLY MINOR CHANGES MADE THEREAFTER...WITH A
SIMILAR PATTERN OF QUASI-ZONAL FLOW AND REGULAR FRONTAL PASSAGES.

&&

.AVIATION...

FOR THE 06Z TAFS...ONGOING THUNDERSTORM DEVELOPMENT ACROSS EAST
CENTRAL KANSAS AND WEST CENTRAL MISSOURI WILL KEEP AT LEAST VICINITY
MENTION OF STORMS AT THE TERMINALS THROUGH THE REMAINDER OF THE
OVERNIGHT HOURS. TERMINAL MOST UNDER THREAT FROM THESE STORMS IS THE
INTERNATIONAL AIRPORT ON THE NORTH SIDE OF KANSAS CITY...KMCI. MVFR
CONDITIONS WITH THESE STRONG THUNDERSTORMS...WITH BRIEF PERIODS OF
IFR...WILL PERSIST TILL THE STORMS SHIFT A LITTLE FARTHER EAST AROUND
07Z. AFTER 07Z/19 THE STRONG TO SEVERE THUNDERSTORMS SHOULD HAVE
MOVED OFF TO THE EAST OF THE TERMINALS...BUT SOME LINGERING SHOWERS
MAY STILL PERSIST TILL JUST BEFORE SUNRISE. ANTICIPATE NUMEROUS
AMENDMENTS TO THE TAFS THIS MORNING.

OTHERWISE...LOW CLOUDS /IFR/ HAVE ADVECTED SOUTH INTO THE KSTJ
TERMINAL BEHIND THE FRONT THAT SAGGED SOUTH SATURDAY. PREVAILING IFR
CLOUDS ARE NOT ANTICIPATED TO MAKE IT AS FAR SOUTH AS KANSAS CITY DUE
TO THE RESIDUAL STORM ACTIVITY NEAR THE BOUNDARY. THESE CLOUDS SHOULD
LIFT BACK INTO THE MVFR RANGE BY MID-MORNING AS THE FRONTAL BOUNDARY
LIFTS BACK TO THE NORTH.

CUTTER

&&

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

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1055 PM CDT SAT SEP 18 2010

KSZ025-057-060-102>105-MOZ001>008-011>017-020>025-028>033-037>040-
043>046-053-054-191100-
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-
1055 PM CDT SAT SEP 18 2010

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

.DAY ONE...OVERNIGHT

 AN UNSTABLE ENVIRONMENT COUPLED WITH STRONG VERTICAL WIND SHEAR
 REMAINS IN PLACE ACROSS THE REGION LATE THIS EVENING. SCATTERED
 THUNDERSTORMS CAPABLE OF PRODUCING VERY LARGE HAIL AND TORRENTIAL
 RAINFALL WILL REMAIN POSSIBLE THROUGH THE OVERNIGHT HOURS.
 THE MOST INTENSE STORMS WILL BE FOCUSED JUST NORTH OF INTERSTATE
 70...GRADUALLY SHIFTING NORTHWARD OVERNIGHT TO INCLUDE MOST OF
 NORTHERN MISSOURI.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

 A LINGERING FRONT WILL CONTINUE TO PROVIDE SCATTERED THUNDERSTORM
 CHANCES THROUGH SUNDAY...ALTHOUGH THE THREAT FOR RENEWED SEVERE
 WEATHER APPEARS LOW AT THIS TIME.

 THUNDERSTORM CHANCES WILL RETURN TO THE OUTLOOK AREA TUESDAY
 AFTERNOON AND TUESDAY NIGHT AS A COLD FRONT PUSH SOUTH. SOME OF
 THESE STORM COULD REACH STRONG TO SEVERE LIMITS...WITH HEAVY
 RAINFALL ALSO POSSIBLE.

 ANOTHER FRONT IS FORECAST TO REACH THE AREA THURSDAY NIGHT...THOUGH
 IT IS TOO EARLY TO DETERMINE WHETHER SEVERE WEATHER WOULD BE
 POSSIBLE.

.SPOTTER INFORMATION STATEMENT...

 SPOTTERS WILL BE REQUIRED OVERNIGHT...PRIMARILY NORTH OF INTERSTATE
 70 FOR THE THREAT OF LARGE HAIL AND FLASH FLOODING.

BOOKBINDER

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