Severe Thunderstorm Warning 102, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
219 PM CDT SUN AUG 4 2002

SYNOPTIC PICTURE THIS AFTERNOON SHOWS 110KT JET OVER SOUTHERN ONTARIO.
AT 500H...A STRONG HIGH EXTENDS FROM EASTERN KANSAS TO SOUTHERN
INDIANA...WITH STRONG FLOW ACROSS THE NORTHERN TIER...AND A SHORT
WAVE MOVING THRU SOUTHERN ONTARIO.  AT THE SURFACE...TWO QUASI-
STATIONARY FRONTS EXTEND FROM A WESTERN KANSAS LOW...ONE TO THE IA-MN
LINE AND THE OTHER TO THE IA-MO LINE.  CONVECTION OVERNIGHT WAS
ASSOCIATED WITH THE SOUTHERN OF THESE TWO...AS IT SANK ACROSS THE AREA
OVERNIGHT.  CURRENTLY...ALL PRECIPITATION HAS DIED OUT WITHIN A FEW
HUNDRED MILES OF THE FORECAST AREA...ALTHOUGH SHOWING SIGNS OF
REDEVELOPING ACROSS NORTHEAST AND EAST CENTRAL IOWA.  CLOUD COVER HAS
HELD TEMPS BELOW ADVERTISED LEVELS.

PRIMARY FORECAST CONCERNS THIS PACKAGE ARE TWO-FOLD.  FIRST IS PRECIP
OVER THE NEXT 24 HOURS ASSOCIATED WITH THE TWO FRONTS...WHICH WILL
RECOMBINE AND SINK SOUTH THROUGH THE AREA TONIGHT...AND THEN SOUTH OF
THE AREA AS A COLD FRONT ON MONDAY.  THE SECOND CONCERN IS TEMPS THRU
AT LEAST MID WEEK...WHICH WILL BE DRY AND COOL DUE TO AN EASTERLY
FLOW...ESPECIALLY FOR MONDAY AFTERNOON THROUGH TUESDAY NIGHT WHEN
LAKE EFFECT OFF LAKE MICHIGAN WILL BE QUITE PRONOUNCED.

THE MODELS HAD A HARD TIME HANDLING THE FRONTS ACROSS THE AREA THIS
MORNING...ALTHOUGH THEY DID MODERATELY WELL WITH 12Z-18Z QPF NORTHWEST
QUARTER OF FORECAST AREA.  THE MODELS RECOMBINE THE FRONTS AND PUSH
THEM SOUTH TONIGHT AND MONDAY.  THE AVN IS FASTEST...WITH THE COLD
FRONT TO JUST SOUTH OF THE CWA BY 12Z MONDAY...THE ETA BY 15Z...AND
THE NGM BY 18Z.  THEN THE FRONT CONTINUES SOUTH AT A SLOW TO MODERATE
RATE THROUGH MONDAY NIGHT AND TUESDAY.  HINTS OF AN INVERTED TROF INTO
SOUTHWEST IOWA INTO TUESDAY COULD KEEP A CHANCE OF PRECIP SOUTHEAST.

THE SHORT-TERM MODELS ALL POUND THE NORTHERN HALF OF THE FORECAST AREA
THIS EVENING WITH .50-1.00 QPF IN RESPONSE TO STRONG VVS.  PRECIP CAN
NOT BE RULED OUT SOUTH EITHER...AS INDICATIONS ON DMX RADAR ALREADY OF
POTENTIAL PRECIP ALONG THE SOUTHERN FRONT.  OVERNIGHT WILL BE MORE
PROBLEMATIC...BUT BEST INDICATIONS ARE THAT LOW-LEVEL JET WILL FOCUS
AROUND INTERSTATE 80 FROM AFTER MIDNIGHT THRU MID-MORNING...WITH MORE
PRECIP SOUTH TO BRL THAN NORTH TO DBQ.  PRECIP MAY LINGER SOUTHWEST
MONDAY NIGHT DUE TO INVERTED TROF...AND MAYBE INTO TUESDAY.

HIGH PRESSURE BUILDING IN FROM EAST CENTRAL CANADA INTO THE GREAT LAKES
WILL BRING A NORTHEAST FETCH DOWN LAKE MICHIGAN INTO THE FORECAST AREA
MONDAY EVENING THROUGH TUESDAY NIGHT. ON WEDNESDAY...THE FLOW BECOMES
STRAIGHT EAST...THEN LIGHT SOUTHEAST THURSDAY AND SOUTH FRIDAY.  THE
NEXT TROF MOVES INTO WESTERN IOWA SATURDAY...AND APPEARS TO DISSIPATE
OVER THE FORECAST AREA SUNDAY.

AT 500H...HIGH PRESSURE WILL BE OVER THE AREA THRU THURSDAY...WITH
NORTHWEST FLOW INTO THE EASTERN STATES. A STRONG SHORT WAVE APPROACHES
FROM THE WEST SUNDAY.  ALL OF THE MEDIUM-RANGE MODELS ARE IN MODERATE
AGREEMENT ON THIS SCENARIO.

WILL KEEP CLOSE TO CURRENT FORECAST...PERHAPS RAISING POPS A BIT FOR
THIS EVENING AND OVERNIGHT...AND ALSO MONDAY NIGHT SOUTHWEST. TEMPS ARE
ON TRACK.  NUMERICAL GUIDANCE IN GENERAL AGREEMENT ON TEMPS AND POPS AND
AGREE WITH FORECAST...EXCEPT MAV POPS TOO LOW FOR SOME REASON.

.DVN...
IA...NONE.
IL...NONE.
MO...NONE.

REA

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
619 PM CDT SUN AUG 04 2002

TIME(CDT)  .....CITY LOCATION..... STATE  ...EVENT/REMARKS...
           ....COUNTY LOCATION....

0600 PM    LE CLAIR                  IA   .75 INCH HAIL
08/04/02   SCOTT                          REPORTED BY STORM
                                          SPOTTER.