Severe Thunderstorm Warning 145, NWS Kansas City, MO

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
1255 PM CDT SUN JUN 13 2010

...UPDATED AVIATION DISCUSSION...

.DISCUSSION...

/330 AM CDT SUN JUN 13 2010/
MIDLEVEL CIRCULATION CENTER CURRENTLY SPINNING NEARLY STATIONARY
OVER CNTRL UTAH HAS BEGUN THE FILLING AND SLOW LIFTING
STAGE...SPITTING NUMEROUS SHORTWAVES NORTHEAST INTO THE ERN FLANK OF
THE JET AXIS (AND EVEN OBTAINING A NARROW SUBTROPICAL TAP FROM
MEXICO AND THE WARMER EAST PACIFIC). ELONGATED SW-NE ORIENTED
CONVECTIVE BAND WAS ALIGNED FROM THE TX PANHANDLE THROUGH NERN
KANSAS...THOUGH ONLY A SMALL SEGMENT ON THE WRN PERIPHERY WAS
DISPLAYING MORE CLASSIC MCS STRUCTURE (UNLIKE THE PREVIOUS 2 NIGHTS
WHERE WELL DEVELOPED MATURE MCS/S HAD ALREADY FORMED). WOULD HAVE TO
SPECULATE THAT A SLIGHTLY WEAKER LLJ AXIS (AND ESPECIALLY VEERED
THROUGH THE ERN HALF OF KANSAS) AND PERHAPS SLIGHTLY MORE MERIDIONAL
FLOW ALOFT HAS KEPT THE THUNDERSTORM COMPLEX SOMEWHAT LESS
ORGANIZED. EASTWARD PROGRESSION OF THE CONVECTIVE COMPLEX HAS
STRUGGLED THUS FAR...MOST LIKELY DUE TO A MUCH MORE VEERED LLJ AXIS
AND WEAK SUBSIDENCE BEHIND AN OLD OUTFLOW BOUNDARY FROM THIS
MORNING. THIS BOUNDARY IS CURRENTLY WASHING OUT AND LIFTING
NORTH...WHICH SHOULD EVENTUALLY ALLOW A BETTER NORTHWARD MOISTURE
FLUX INTO NRN MISSOURI THROUGH THIS MORNING.

ONCE AGAIN TONIGHT...LARGER GRID SCALE MODELS WHILE CAPTURING MAIN
SYNOPTIC FEATURES FAIRLY ACCURATELY...HAVE STRUGGLED WITH ANY TYPE
OF MESOSCALE PROCESSES...WITH SIGNIFICANT ERRORS IN
TIMING...PLACEMENT...AND TRANSIENT NATURE OF THUNDERSTORMS. ONLY THE
HRRR (AND TO A LESSER EXTENT THE HIGH RESOLUTION WRF ARW AND NMM
CORES) HAVE A REALISTIC DEPICTION OF THE CURRENT SITUATION...AND
HAVE TAILORED SHORT TERM GRIDS STRONGLY TOWARDS THESE MODELS.
EASTWARD PROPAGATION AND NEW DOWNSTREAM DEVELOPMENT SHOULD BE
OCCURRING INTO NWRN MISSOURI BY DAYBREAK (GENERALLY ALONG AND NORTH
OF THE MISSOURI RIVER)...AND HAVE HIT THIS AREA WITH A CATEGORICAL
MENTION BEFORE 18Z. SHOULD SEE SOME MEASURE OF SUBSIDENCE AND
STABILIZATION BEHIND THIS ACTIVITY...HOWEVER ANOTHER E-W TYPE
BOUNDARY SHOULD BE GENERATED THROUGH THE AREA...AND ASSUMING SFC
BASED INSTABILITY CAN BE ATTAINED ACROSS SRN/CNTRL MISSOURI THIS
AFTERNOON...THIS BOUNDARY MAY BECOME THE FOCUS FOR DIURNALLY DRIVEN
DEEP CONVECTION. ALTHOUGH DEEP LAYER SHEAR PROFILES ARE STILL
SOMEWHAT MARGINAL FOR WIDESPREAD ORGANIZED SVR WX THIS FAR
EAST...THE POTENTIAL FOR ATTAINING STRONG INSTABILITY SUGGESTS THE
POSSIBILITY FOR PULSE-TYPE OR MULTICELL SEVERE STORMS.

OTHERWISE...MORE EXTENSIVE AND ORGANIZED THUNDERSTORMS SHOULD
RAPIDLY ERUPT ACROSS SWRN/SOUTH CNTRL KANSAS (CLOSER TO MORE
SUPPORTIVE JET ENERGY AND DEEP LAYER SHEAR) BY LATE AFTERNOON. EVEN
THE POORLY PERFORMING OPERATIONAL MODELS SUGGEST ROBUST
INTENSIFICATION INTO A FORWARD PROPAGATING MCS DURING THE OVERNIGHT
HOURS...HEADING SOMEWHERE TOWARDS ERN KANSAS/WRN MISSOURI (LARGER
UNCERTAINTY IN EXACT PLACEMENT UNDERSTOOD). WITH A LARGE RESERVOIR
OF PWATS IN EXCESS OF 1.75 INCHES RESIDING THROUGHOUT THE WARM
SECTOR FEEDING INTO ANY CONVECTIVE SYSTEM...FEEL FLOODING TYPE
RAINFALL WILL EASILY BE PROBABLE SOMEWHERE THROUGH MONDAY MORNING
(ESPECIALLY CONSIDERING FFG VALUES ARE AOB 1 INCH THROUGH MUCH OF
THE FORECAST AREA). HAVE EXTENDED FLASH FLOOD WATCH FOR THE ENTIRE
AREA THROUGH MONDAY MORNING...THOUGH REALISTICALLY MAY BE ABLE TO
DROP THE FAR NWRN COUNTIES EARLIER AS CONCEPTUALLY WOULD THINK THE
AXIS OF HEAVIEST RAINFALL MONDAY MORNING WOULD ALIGN CLOSER TO THE
I-70 CORRIDOR.

EXPECTING TO SEE THE EFFECTIVE BOUNDARY SINK FURTHER SOUTH TOWARDS
THE I-44 CORRIDOR MONDAY NIGHT AND TUESDAY...THOUGH RESIDUAL
PRECIPITATION ON THE NRN PERIPHERY OF ANY ADDITIONAL CONVECTIVE
SYSTEM(S) COULD EASILY WORK NORTH INTO CNTRL MISSOURI. BEST
PROSPECTS FOR DRIER AND LESS HUMID WEATHER WILL OCCUR ON WEDNESDAY
AND INTO THURSDAY...WITH MORE RIDGING ALOFT PROMOTING SFC PRESSURE
RISES. SOME MEASURE OF WRN CONUS TROUGHING SHOULD RELOAD BY THE END
OF THE WEEK WITH MODELS IN GENERALLY GOOD AGREEMENT CONCERNING THIS
EVOLUTION. MADE ONLY MINOR ADJUSTMENTS PAST WEDNESDAY...AND WILL
CONTINUE TO FEATURE A WARMING TREND WITH INCREASING PRECIPITATION
CHANCES BY THE END OF THE WEEK AND INTO THE WEEKEND.

21

&&

.AVIATION...

SEVERAL ROUNDS OF SHOWERS AND THUNDERSTORMS EXPECTED AT OR VICINITY
OF TAF SITES THROUGH THE TAF PERIOD. SLIGHT LULL IN TSRA AND SHRA
THIS MORNING MAY BE SHORT LIVED GIVEN UNSTABLE...UNCAPPED NATURE OF
ATMOSPHERE. MAIN FORCING MECHANISM WILL BE DIURNAL HEATING...THUS
HAVE HIGHLIGHTED GREATEST POTENTIAL FOR TSRA DURING EARLY TO MID
AFTERNOON...WITH ACTIVATING WANING DURING LATE AFTN/EARLY EVENING
HOURS.  AS LLJ STRENGTHENS MID-EVENING...IN COMBINATION WITH A WEAK
JET MAX APPROACHING...LIKELY WILL SEE STORMS REDEVELOP IN THE 02-05
UTC TIMEFRAME AND PERSIST MOST OF THE OVERNIGHT HOURS...WITH YET ANOTHER
THUNDERSTORM COMPLEX IS EXPECTED TO DEVELOP AND MOVE EAST ACROSS THE
REGION AFFECTING THE THREE TERMINALS.  DUE TO THE AMOUNT OF
UNCERTAINTY BEYOND THE OVERNIGHT PERIOD...DECIDED NOT TO PUT MUCH
DETAIL BEYOND 11 UTC...BUT LIKELY WILL AMEND LATER WHEN THERE IS MORE
TIME TO PERUSE GUIDANCE.

24

&&

.EAX WATCHES/WARNINGS/ADVISORIES...
MO...FLASH FLOOD WATCH THROUGH MONDAY AFTERNOON FOR MOZ001>008-
     011>017-020>025-028>033-037>040-043>046-053-054.

KS...FLASH FLOOD WATCH THROUGH MONDAY AFTERNOON FOR KSZ025-057-060-
     102>105.

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