Severe Thunderstorm Warning 51, NWS Des Moines, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE DES MOINES IA
313 PM CDT TUE MAY 30 2000

CHALLENGES TO INCLUDE TIMING AND PLACEMENT OF THUNDERSTORMS DURING
FORECAST AND HOW CLOUDS WL MESS WITH TEMPS.  CURRENTLY...CLOUDS WITH
ISOLD SHRA CONTINUE TO MOVE ACRS MUCH OF CWA.  AREAS IN THE SW WHICH
HAVE CLEARED HAVE SEEN TEMPS JUMP TO NEAR 90.  MOISTURE CONVERGENCE
HAS PERSISTED IN W CENTRAL ZONES AS WEAK WAVE IN S CENTRAL NEBRASKA
MOVES EAST.  MAIN QUESTION IS STRENGTH OF CAP AND IF IT WL HOLD.
18Z RUC HAS THE CAP BREAKING BY 00Z WITH ANY THUNDERSTORMS MOVING
RAPIDLY TO THE EAST.  MDT RISK IN LARGE SWATH ACRS CENTRAL IA AND WL
HAVE SEVERE WORDING IN ZONES AS ANY STORMS THAT FORM SHOULD RAPIDLY
INTENSIFY WITH DAMAGING WINDS AND LARGE HAIL THE MAIN THREAT.

MODELS STILL A BIT DIFFERENT TODAY WITH FRONTAL POSITIONING THROUGH
FRIDAY MORNING WITH A COMPROMISE THE BEST AT THIS POINT.  SO...FOR THE
BIG PICTURE...THE FRONT HEADS A BIT FARTHER SOUTH OVERNIGHT BEFORE
RETREATING BACK NORTH BY WEDNESDAY EVENING.  IT WL THEN MOVE
SOUTHEAST ACRS THE CWA BY LATER ON THURSDAY.  MOST CONVECTION WL
REMAIN ALONG AND NORTH OF THE FRONT AT THE EDGE OF THE CAP.  TIMING
OF CONVECTIVE SYSTEMS THROUGH CWA A BIG PROBLEMS BUT KNOWING THAT
FRONT WL BE IN CENTRAL OR NORTHERN IA LEAVES BEST PCPN CHANCES ACRS
THE NORTH.  TEMPS WL AGAIN BE TRICKY WITH RESIDUAL CLOUD COVER LEFT
OVER FROM CONVECTIVE SYSTEMS WL INHIBIT SOLAR INSOLATION.  WL AGAIN
KEEP IT ON THE WARM SIDE IN THE SOUTH LEANING TOWARDS COOLER
GUIDANCE IN THE NORTH.

IN THE EXTENDED...WL SEE FRONT PUSH SOUTHWARD ON FRIDAY WITH NORTH
DRYING OUT BUT SHOWERS CONTINUING SOUTH.  SATURDAY 9MAY SEE A BRIEF
BREAK BUT EXPECT WAA TO ONCE AGAIN INCREASE CHC FOR PCPN BY LATER IN
THE DAY.  SUNDAY APPEARS TO HAVE A DECENT CHC FOR THUNDERSTORMS
THROUGH THE DAY.

.DSM...NONE.

COGIL