Flooding in Missouri, April 28 to 29, 2002

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
220 PM CDT SAT APR 27 2002

SAT IMAGERY AND UPPER AIR ANALYSIS SHOW VIGOROUS SHORTWAVE TROUGH
EJECTING ACROSS KS/NEB THIS AFTERNOON...WITH PRONOUNCED MID LEVEL
DRY SLOT ADVECTING ACROSS CWA. CURRENT VIS IMAGERY SHOWS PERSISTENT
STRATUS DECK ACROSS CWA...HOWEVER WESTERN EDGE OF STRATUS HAS BEEN
ERODING OVER PAST FEW HOURS ACROSS E KS...WITH SOME CLEARING
BECOMING EVIDENT NEAR KTOP OVER PAST HALF HOUR OR SO. AT THE
SFC...TRIPLE POINT LOW LOCATED ALONG KS/NEB BORDER NW OF KCNK...WITH
DRYLINE BEGINNING TO SURGE EWD NEAR I-35/135 CORRIDOR PER MSAS
ANALYSIS. WARM FRONT EXTENDS E OF SFC LOW ACROSS C MO...NEAR A
NEVADA MO TO KAIZ LINE...AND DESPITE ABUNDANT CLOUD COVER...THIS
FRONT HAS BEEN GRADUALLY LIFTING NORTH THROUGHOUT THE DAY. SEVERE
THREAT THIS AFTERNOON IS DEPENDENT ON HOW MUCH CLEARING IS ABLE TO
TAKE PLACE AHEAD OF APPROACHING DRYLINE...AND RESULTANT
DESTABOLIZATION. CONVERGENCE ALONG DRYLINE HAS APPEARED WEAK SO FAR
THIS AFTERNOON...AND LIMITED INSTABILITY SEEMS TO BE OVERWHELMED
THUS FAR BY IMPRESSIVE SHEAR PROFILES (WINDS AOA 50KTS JUST ABOVE H9
ON 18Z TOP SOUNDING WITH 80KT+ WINDS AT H5). NONETHELESS...EXPECT
CONVECTIVE DEVELOPMENT ACROSS NE KS THIS AFTERNOON...WITH BEST
CHANCE OF SEVERE ACROSS NW MO...NORTH OF A KSTJ TO BETHANY LINE.
META PROG SOUNDING INDICATE DRY-ADIABATIC BOUNDARY LAYER PROFILE TO
NEAR H7...WHICH MAY BE A LITTLE OVERDONE...BUT ALONG WITH
AFOREMENTIONED WINDS ALOFT EXPECT DESTRUCTIVE STRAIGHT LINE WINDS TO
BE PRIMARY THREAT...WITH POTENTIAL FOR A TORNADO TO TWO IFOV
RETREATING WARM FRONT.

CONVECTION SHOULD CLEAR CWA BY LATE THIS EVENING...AS SFC RIDGE
BUILDS INTO CWA SUN. HAVE STAYED RELATIVELY CLOSE TO FWC
GUIDANCE...AS SUFFICIENT SOLAR HEATING SHOULD ALLOW TEMPS TO RECOVER
INTO 60S. NORTHERN STREAM SHORTWAVE PROGGED TO PUSH COLD FRONT
INTO CWA DURING THE DAY MON...WITH BEST SYNOPTIC LIFT WELL N OF CWA.
CONV ALONG FRONT APPEARS WEAK...AND META PROG SOUNDINGS INDICATE
CAPE VALUES AOB 100 J/KG...SO NOT EXPECTING CONVECTIVE PRECIP ALONG
FRONT. OTHERWISE NEXT THREAT FOR PRECIP COMES TUES
AFTERNOON/NIGHT...AS MODELS PROG STRONG H85 THETA-E ADVECTION AHEAD
OF NEXT SHORTWAVE TROUGH. 84 HR ETA EXTENSION IS MUCH SLOWER WITH
THETA-E ADVECTION...SO WILL SLOW DOWN TIMING OF PRECIP TUES UNTIL
AFTERNOON HOURS.

ANOTHER FRONT TO MOVE THRU IN DAYS 4-5 TIMEFRAME.  WENT CLOSER TO
ECMWF TIMING ON IT.  HAVE INTRODUCED POPS INTO TUESDAY DAYTIME
FRAME.  LOOKS LIKE FRONT WILL END UP JUST TO THE SOUTH OF OUR CWA ON
WED/THURS. THUS HAVE REMOVED POPS FROM WED NITE.  THINK H8 TEMPS FOR
WED/THURS ARE A BIT ON THE COOL SIDE...BUT NEVERTHELESS HAVE DROPPED
TEMPS A BIT FM PREVIOUS FCST.

MS/LVQ

530 AM...
FORECASTING THE SKY CONDITION FOR THIS AFTERNOON IS THE MAJOR
FORECAST CONCERN FOR TODAY. THE AMOUNT OF CLOUD COVER OVER EASTERN
KANSAS AND NORTHERN MISSOURI WILL HAVE A CRITICAL ROLE IN THE
EVOLUTION AND STRENGTH OF THUNDERSTORMS THIS AFTERNOON.

WARM AIR ADVECTION THUNDERSTORMS SHOULD CONTINUE THROUGH THE MID
MORNING HOURS OVER MOST OF EAST CENTRAL KANSAS AND ALL OF MISSOURI.
HEAVY RAINS HAVE MOVED OVER THE AREA IN RESPONSE TO STORNG THETA-E
ADVECTION AT 850 MB EARLY THIS MORNING.  A SECOND ROUND OF
SIGNIFICANT RAINS WILL MOVE THROUGH THE AREA IN THE 12-15Z TIME
FRAME AS A SHORTWAVE OVER WESTERN OKALHOMA RAPIDLY TRAVERSES
THROUGH.  BEHIND THAT DISTURBANCE WATER VAPOR IMAGERY DEPICTS DRIER
MID LEVELS, AND TRAJECTORIES FROM THE ETA MODEL SHOW WINDS AT THE
700 MB AND 500 MB LEVEL BECOMING MORE WESTERLY THIS AFTERNOON.
VEERING IN THE MID LEVEL WINDS SHOULD AID TO SCOUR OUT CLOUD COVER
AFTER 18Z.  WITH SOME SUNSHINE THIS AFTERNOON...MID TO UPPER 70S
SHOULD BE REACHED YIELDING CAPES 1500 AND 2000 J/KG LATE THIS
AFTERNOON OVER EXTREME EAST KANSAS AND MUCH OF NORTHERN MISSOURI.
INSTABILITY OF THIS MAGNITUDE WILL BE ENOUGH TO SUSTAIN UPDRAFTS
DESPITE THE LARGE AMOUNTS OF DEEP LAYER SHEER PROGECTED BY THE ETA.
0-6KM SHEAR VALUES ARE PROGGED TO BE AROUND 70 KTS AND 0-1KM SHEAR
35 KTS.  LONG LIVED SUPERCELL STORMS ARE LIKELY IN THIS ENVIRONMENT
AND THE TORNADIC POTENTIAL WILL BE QUITE HIGH.

ANOTHER CONCERN FOR LATE IN THE DAY WILL BE THE POTENTIAL FOR STRONG
GRADIENT WINDS BEHIND THE DRY LINE.  MODEL SOUNDINGS SHOW LAPSE RATE
DRY ADIABATIC FROM 700MB TO THE SURFACE AT 00Z OVER EAST KANSAS AND
WEST MISSOURI.  WIND SPEEDS AT 850MB FROM THE ETA ARE 50KTS FROM THE
WEST INDICATING THE POTENTIAL FOR VERY STRONG GUSTS IN A PART OF A
SYNOPTIC SCALE STORM WHERE DOWNWARD TRANSPORT IS QUITE EFFICEINT.  A
WIND ADVISORY MAY BE NECESSARY FOR THREE OR FOUR HOURS LATE THIS
AFTERNOON AND EARLY THIS EVENING FOR MOST OF THE COUNTY WARNING
AREA.  AS THE SUN GOES DOWN AND LOW LEVEL LAPSE RATES DECREASE
CONDITIONS SHOULD BY 3Z OR 4Z.

.EAX...
KS...NONE
MO...NONE