Tornado Warning 22, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
309 PM CDT TUE JUN 1 1999

...GLOBALLY...
LONGWAVE PATTERN HAS BEEN AMPLIFYING OVER THE PAST SEVERAL DAYS FROM
A SEMI ZONAL FLOW WITH ENERGY STARTING TO BE DIVIDED BETWEEN BOTH
THE NORTHERN AND SOUTHERN STREAM. THE CURRENT RIDGE/TROF/RIDGE ACROSS
NORTH AMERICA IS UNDERGOING A CHANGE WITH RETROGRESSION OF THE TROF
BACK INTO THE WESTERN PART OF THE CONTINENT. WATER VAPOR SHOWS
SEVERAL POWERFUL SHORTWAVES (-250+ DEKAMETER FALLS IN THE PAC NW)
THAT WILL DIG SOUTH AMPLIFYING AND RETROGRESSING THE TROF TO THE
INTERMOUNTAIN REGION. THIS PATTERN SHOULD HOLD THROUGH NEXT WEEKEND
BEFORE THE UNSTABLE 5 WAVE PATTERN IN THE MID LATITUDES FORCES
ANOTHER CHANGE AROUND THE SECOND HALF OF NEXT WEEK. THE END RESULT
MEANS WARMER THAN NORMAL TEMPERATURES BEGINNING LATE THIS WEEK AND
INTO THE FIRST PART OF NEXT WEEK.

...LOCALLY...
VERY IMPRESSIVE SHORTWAVE DROPPING SOUTHEAST OUT OF THE PACIFIC
NORTHWEST WITH ANOTHER IMPRESSIVE SHORTWAVE IN WATER VAPOR/PROFILER
DATA OVER SOUTHWEST IOWA AT 18Z. LLJ STARTING TO STRENGTHEN ACROSS
MISSOURI WITH 30 KNOTS NOTED WHILE 50- 60 KNOTSPEED MAX IS MOVING
ACROSS KANSAS/MISSOURI AT 500 MB. SURFACE ANALYSIS HAS THE LOW NEAR
DSM AT 18Z WITH THE WARM FRONT RUNNING ROUGHLY EAST ALONG I80 WHILE
COLD FRONT EXTENDS SOUTH INTO SOUTHEAST KANSAS. SEVERAL PREFRONTAL
TROFS EXIST ACROSS MISSOURI WITH THE MAIN ONE RUNNING FROM DSM TO
IRK AND THEN TO SGF. THIS TROF IS SUPPORTING THE SQUALL LINE ACROSS
MISSOURI/SOUTHERN IOWA WITH CAPES AHEAD OF THE TROF RUNNING 1500-
2500 J/KG. MOISTURE ANALYSIS HAS LOW TO MID 60 DEWPOINTS ACROSS THE
AREA WITH 70 DEW POINTS AS NEARBY AS I70 IN MISSOURI. DVN 88D HAS
WAA PRECIPITATION ACROSS NORTHEAST IOWA WITH CLEARING SKIES AHEAD OF
THE TROF AND COLD FRONT.

PROBLEMS THIS PACKAGE ARE MANY WITH VERY SHORT TERM BEING SEVERE
WEATHER...THEN RAIN/TEMPERATURES/CLOUD COVER.

12Z MODELS APPEAR TO HAVE INITIALIZED OK WITH THE AVN/NGM DOING
BETTER THAN THE ETA STRENGTH WISE AT 18Z. THE ETA IS WEAKENING THE
IOWA SHORTWAVE AND PAC NORTWEST SHORTWAVE BY 18Z WHILE THE AVN/NGM
MAINTAIN THE STRENGTH. THIS IS REAFFIRMED BY THE INITIALIZATION OF
THE 12/15/18Z RUC WHICH MAINTAIN THE STRENGTH OF THE SHORTWAVES.
THEREFORE OVERALL PERFORMANCE OF THE ETA IS HIGHLY SUSPECT AND
QUESTIONABLE.

BELIEVE FOR THE NEAR SHORT TERM THE RUC IS HANDLING THE SITUATION
THE BEST WITH A TRANSLATION INTO THE AVN/NGM FOR LATER PERIODS. RUC
MOVES IOWA SHORTWAVE INTO EASTERN IOWA BY 06Z WITH AVN/NGM
CONTINUING TREND OF DOWNWARD MOTION AND DRYING OUT THE AREA AFTER
MIDNIGHT. THUS RAIN THROUGH MIDNIGHT WITH RAIN ENDING FROM WEST TO
EAST AFTER MIDNIGHT LOOKS GOOD. ON WEDNESDAY CLOUDS SHOULD CONTINUE
TO BREAK UP BUT SOME RESIDUAL MOISTURE/CYCLONIC FLOW ALOFT SHOULD BE
ENOUGH TO POP SC/CU. ANOTHER RIPPLE COMES THROUGH DURING THE DAY
WEDNESDAY WHICH MIGHT BE ENOUGH TO POP A SHOWER BUT COVERAGE WOULD
BE 10 PERCENT AT BEST AND WILL LEAVE OUT FOR NOW. RIDGE HOLDS IN
PLACE ACROSS THE AREA WEDNESDAY NIGHT THROUGH THURSDAY WITH DRY
CONDITIONS. RETURN FLOW THURSDAY NIGHT BRINGS INCREASING MOISTURE
WITH SOME LIFT ACROSS THE AREA. THIS COMBINED WITH A THETA E RIDGE
MAY BE ENOUGH TO MENTION LOW POPS.

...EXTENDED...
EXTENDED LOOKS WARMER AND MORE ACTIVE AS SOUTHWEST LOW EJECTS OUT
PIECES OF ENERGY. INITIAL THOUGHTS ARE A CHANCE OF RAIN EACH DAY.

.DVN...NONE.

NC