Severe Thunderstorm Warning 122, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
255 AM CDT WED JUL 5 2000

LATEST SFC AND MSAS ANALYSIS INDICATE STAGNANT BOUNDARY CONTINUING TO
DROOP FROM NORTH CENTRAL NE INTO NORTHEAST MO...WITH MSAS INDICATING
MOISTURE POOLING ALONG AND SOUTH OF FEATURE ACRS NORTHERN MO INTO
SOUTH CENTRAL IL. SCTRD CONVECTION HAS DEVELOPED ON NORTHERN FRINGE OF
THIS AREA ACRS SOUTHEAST IA AND INTO WEST CENTRAL IL DUE TO LLVL
CONVERGENT FLOW...ESPECIALLY AT H85...LOOKING AT PLAN VIEW PROFILERS.
00Z UA ANALYSIS SHOWS H85 MOISTURE APLENTY ACRS THE PLAINS AND MIDWEST
AS LLVL SOUTHERLY FLOW ON WEST SIDE OF EAST GULF H85 HIGH CENTER
CONTINUES TO PUMP JUICE NORTHWARD.

LOOKING AT SYNOPTIC SCALE FEATURES/PROGS...RATHER STAGNANT PATTERN TO
CONTINUE THROUGH 48 HRS AS BOOKEND L/W TROUGHS ON BOTH COASTS FLANK
RIDGE CENTER ACRS THE CENTRAL CONUS. SHORT RANGE MODELS SIMILAR IN
AMPLIFYING THIS RIDGING UP ACRS THE NORTHERN REACHES OF MANITOBA
THROUGH 00Z FRI...INDUCING STEEP NORTHWEST FLOW JUST EAST OF THE REGION
ACRS THE GRT LKS. VORT IGNITING CURRENT CONVECTIVE SYSTEMS OVER THE
NORTHEAST PLAINS LOOKS TO CONTINUE TO PASS WELL NORTH OF THE LOCAL CWA
AS IT RIPPLES ACRS UPPER RIDGE NOSE TODAY. AM LEARY OF SD ACTIVITY'S
SOUTHEAST PROPAGATION...IF IT HOLDS TOGETHER...MAY AFFECT NORTHERN CWA
LATER TODAY...ALTHOUGH MODELS INDICATE IT WON/T. WILL LEAVE LOW POPS IN
FOR NORTHERN GROUPS WITH UNCERTAINTIES. POSSIBLE OUTFLOW BOUNDARIES
FROM MCS COULD ALSO SEEP SOUTHEAST AND INTERACT WITH LLVL CONFLUENT
FLOW NEAR CWA LATER TODAY...SUPPORTING GENERAL LOW POPS TO COVER
POSSIBILTY. AFTER THIS...MODELS VARY SOMEWHAT IN HANDLING NEXT VORT OF
CONSEQUENCE OUT OF WESTERN TROUGH AND ACRS UPPER MIDWEST TONIGHT AND THU
MORNING. FEATURE NOT REALLY EVIDENT ON W/V IMAGERY AND MUST BE BEING
MASKED BY DRY STREAK ACRS GRT BASIN INTO CENTRAL PLAINS. AVN LAGS NGM
AND ETA IN SPEED OF VORT...AND ACTUALLY THRUSTS MAIN VORT FURTHER NORTH
THU MORNING. WONDER WITH AMPLIFYING RIDGE AXIS...THIS FURTHER NORTH
SCENARIO MAY BE MORE CORRECT...BUT WITH MODEL UNCERTAINTIES AND ADJACENT
BOUNDARY AND BAROCLINICITY...WILL KEEP POPS GOING FOR ENTIRE CWA IN SOME
FASHION.

AT 06Z...MODELS WERE UNDERPLAYING THE DAKOTAS PRECIP...BUT DOING
DECENT WITH RATHER RECENT DEVELOPMENT OF SOUTHEAST IA-WEST IL
CONVECTION. MODELS EVENTUALLY WANE/WEAKEN ACTIVITY ACRS THE SOUTH CWA
AND SHIFT IT EAST AFTER 12Z THIS MORNING AS H85 WINDS VEER AND WEAKEN
ACRS THAT AREA THROUGH 18Z WED. WILL TREND PRECIP ACRS SOUTHERN ZONES
THIS WAY THIS MORNING. WITH NEXT MAIN VORT LATER THIS AFTERNOON AND
TONIGHT...NGM AND ETA INITIATE MCS OVER EASTERN SD AND NE THIS
AFTERNOON ON NOSE OF GOOD LOW TO MID LEVEL THTA-E ADVECTION AND
CONVERGENCE. VARIOUS MCS SPAWN PARAMETERS REALLY HINT AT CENTRAL NE.
ACTIVITY THEN LOOKS TO PROPAGATE EAST ALONG H85 BAROCLINICITY AND SFC-
H85 THTA-E GRADIENT ACRS IA OVERNIGHT. MODELS...ESPECIALLY THE ETA...
DO TEND IT INTO WEAKENING REMNANTS AS IT PUSHES ACRS THE CWA BY LATE
TONIGHT AND THU MORNING. LLVL INFLOW AND CONVERGENCE LOOK TO WEAKEN
BY 12Z THU ACRS SOUTHEAST IA AND WEST IL. ETA INDICATING ACTUALLY
H85 DIVERGENCE THU MORNING. BOTH NGM AND ETA DO KEEP LINGERING WEAKER
ACTIVITY GOING ALL DAY THU ACRS THE AREA THOUGH. INTERESTING HOW AVN
JUST IGNITES ACTIVITY ACRS THE WESTERN DAKOTAS AGAIN THIS AFTERNOON AND
SHIFTS IT EAST INTO MN AGAIN THROUGH THU...KEEPING DVN CWA DRY.

AS FOR TEMPS TODAY...TRICKY SITUATION WITH POSSIBILITY OF BUSTS. IF
HIGHER LLVL RH'S CONTINUE TO KEEP MOSTLY CLOUDY SKIES ACRS THE CWA
TODAY...COMBINED WITH EASTERLY SFC FLOW OFF THE WESTERN GRT LAKES...FWC
AND FAN VALUES WILL BE TOO HIGH. IF WE GET SOME INSOLATION BETWEEN THE
CLOUDS...TEMPS SHOULD STRIDE INTO THE 80S. WILL LEAN TOWARD MOSTLY
CLOUDY SCENARIO TODAY AND UNDERCUT GUIDANCE...BUT FEEL BREAKS IN CLOUD
COVER A GOOD POSSIBILITY...ESPECIALLY THIS AFTERNOON.

DAY FORECASTERS WILL HAVE TO MONITOR IF POTENTIAL MCS WILL STEAM-ROLL
ACRS THE CWA TONIGHT WITH MORE HYDROLOGIC VIGOR THAN NOW ANTICIPATED.
IF SO...A FLASH FLOOD WATCH SHOULD BE KEPT IN MIND WITH CWA'S
SATURATED SOILS.

.DVN...
IA...NONE.
IL...NONE.4
MO...NONE.

JDH