450
FXUS63 KDVN 042004
AFDDVN
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
300 PM CDT SAT JUL 4 2009
SYNOPSIS
IT HAS BEEN A MURKY FOURTH TODAY...WITH MUCH OF THE FORECAST AREA
SITTING UNDER CLOUDS AND LIGHT TO MODERATE RAINFALL MOST OF TODAY.
ACROSS THE SOUTH THIRD OF THE FORECAST AREA...A BACK EDGE TO THE
PRECIPITATION HAS BEEN WORKING EAST SINCE LATE MORNING...AND NOW
ONLY THE MACOMB AREA HAS ANY PRECIPITATION FOR AREAS SOUTH OF THE
HIGHWAY 34 CORRIDOR. HOWEVER...GENERALLY ALONG INTERSTATE 80 NORTH
TO ABOUT HIGHWAY 20 THERE IS A LINGERING AREA OF LIGHT RAIN...
BECOMING MORE SHOWERY OVER IOWA. THIS LIGHT RAIN AREA IS BEING
MAINTAINED BY SOME GOOD FRONTOGENETIC LIFT BASED IN THE 700-650MB
LAYER...AS DEPICTED ON THE NAM. MOST LOCATIONS ARE STILL SITTING IN
THE 65 TO 70 DEGREE RANGE...AND IF WE CANNOT PUT ON A FEW MORE
DEGREES IN THE NEXT FEW HOURS WE WILL HAVE RECORD LOW MAXIMUM
TEMPERATURES FOR TODAY. JUST FOR REFERENCE...DBQ RECORD LOW MAX IS
63 FROM 1967...AND MLI RECORD LOW MAX IS 67 ALSO IN 1967. THOUGH
THIS RECORD HAS NOT BEEN OFFICIALLY COMPILED FOR CID OR BRL...FROM
LOCAL RECORDS CID WOULD BE 65...AND BURLINGTON WOULD BE 69. ..LE..
SHORT TERM...TONIGHT AND SUNDAY
TONIGHT THE DIMINISHING TREND WITH PRECIPITATION MOVING OFF TO THE
EAST WILL CONTINUE...WITH THE AREA GENERALLY ALONG THE HIGHWAY 30
CORRIDOR LINGERING THE LONGEST WITH THE LIGHT RAINFALL. FOR AREAS
ALONG THIS CORRIDOR THOUGH...AREAS IN IOWA SHOULD SEE THE RAINFALL
END BY 7-8 PM...AND EAST OF THE RIVER IN THE 10-11 PM RANGE. HAVE
BASED THESE ESTIMATES ON THE AREA OF FRONTOGENESIS NOTED ON THE NAM
IN THE 650-750MB LAYER. BY MIDNIGHT ALL PRECIPITATION SHOULD HAVE
MOVED OFF TO THE EAST OF THE FORECAST AREA. CLOUDS ARE THE NEXT
CONCERN...WITH PLENTY OF MOISTURE AND CONVERGENCE LINGERING MOST OF
THE NIGHT TO KEEP US CLOUDY FOR AT LEAST THE SOUTHERN HALF OF THE
AREA...WITH GRADUAL CLEARING WORKING IN FROM THE NORTH. BY MORNING
ABOUT THEN NORTHERN HALF OF THE FORECAST AREA SHOULD HAVE MANAGED TO
BREAK OUT...BUT FEEL THAT LOW CLOUDS WILL BE LINGERING INTO SUNDAY
MORNING ALONG THE HIGHWAY 34 CORRIDOR. THIS WILL KEEP TEMPERATURES
WARM...IN THE UPPER 50S TO LOWER 60S. SUNDAY SHOULD BE QUIET IN
GENERAL. THERE ARE SOME INDICATIONS THAT SOME POP UP SHOWERS MAY
GENERATE ACROSS THE NORTH DURING THE LATE AFTERNOON...BUT THIS IS
LOOKING RATHER IFFY AT THE MOMENT WITH A FAIR AMOUNT OF DRY AIR AND
SUBSIDENCE MOVING IN AFTER SATURDAYS RAIN. HAVE LEFT OUT FOR
NOW...BUT WILL PASS ALONG TO THE NEXT SHIFT TO REEVALUATE.
OTHERWISE WE ARE LOOKING AT COOLER THAN NORMAL CONDITIONS WITH
PARTLY TO MOSTLY CLOUDY SKIES. ..LE..
LONG TERM
SUNDAY NIGHT THROUGH MONDAY NIGHT...AS AN UPPER LEVEL VORTEX SETTLES
OVER THE NORTHEASTERN GRT LKS THIS PERIOD...THE UPPER MS RVR VALLEY
WILL BE UNDER THE INFLUENCE OF BROAD CYCLONIC NW FLOW. THIS FLOW TO
BE EMBEDDED WITH OCCASIONAL WEAK VORTS THAT RIDGE-RIDE THE ROCKIES
UPPER RIDGE AXIS AND THEN GET SHUTTLED DOWN ACRS THE AREA. FIRST OF
ALL FOR SUNDAY EVENING...WILL LEAVE IT DRY BUT LATER SHIFTS MAY
HAVE TO INCLUDE AT LEAST AN ISOLATED THREAT FOR A SHOWER OR
STORM DURING THE EVENING ANYWAY IN LINGERING INSTABILITY PLUME AND
WEAK LLVL THTA-E CONVERGENT ZONE/SIMILAR TO WHAT IS CURRENTLY
OCCURRING ACRS SOUTHERN MN AND WI/. SUNDAY NIGHT LOWS SHOULD RANGE
FROM THE UPPER 50S TO LOWER 60S. ON MONDAY...FCST SOUNDINGS SUGGEST
VERY STEEP LLVL LAPSE RATES AND CAPES GROWING OVER 1K J/KG. IF DEEP
MIXING OVER H8 MB DOES NOT REDUCE SFC DPTS TOO GREATLY AND REDUCE
THESE POTENTIAL CAPES...THERE LOOKS TO BE A STE UP FOR AT LEAST
ISOLATED SHOWERS AND STORMS MON AFTERNOON AND EVENING IN DEEP
CONVECTIVE INDICE PLUME AND WILL EXPAND ON AREAL COVERAGE OF THIS
THREAT ALREADY INTRODUCED BY THE PREVIOUS SHIFT. WILL ALSO BANK OF
DEEP MIXING AND MODERATING THERMAL PROFILES TO SUPPORT WIDESPREAD
LOW TO MID 80 HIGH TEMPS FOR MON...WITH MORE MID 80S THAN LOW 80S
POSSIBLE IF LLVL MOISTURE REALLY MIXES OUT.
IN THE EXTENDED/TUE-SAT/...LATEST SUITE OF MEDIUM RANGE MODELS
CONTINUE TO ADVERTISE BUILDING UPPER RIDGE AND HEAT DOME CENTERED
ON THE SOUTHERN PLAINS AND WESTWARD TOWARD THE EASTERN GRT BSN.
DURING THE MID WEEK PERIOD...THIS SET-UP SHOULD SHUNT THE MAIN
ORGANIZED CONVECTION/MCS TRACK ACRS THE NORTHWEST HIGH PLAINS/SOUTH
CENTRAL CANADA...AND TOWARD THE NORTHWEST GRT LKS. AFTER A LOW
THREAT FOR SOME WAA TYPE SHOWERS AND STORMS AS LLVL WARM FRONT
TRIES TO RETREAT NORTHWARD LATER TUE AND TUE NIGHT...THE LOCAL CWA
LOOKS TO BE WARMING/POSSIBLY BACK TO THE 90S/ AND MAINLY CAPPED UNTIL
A LARGE PIECE OF ENERGY EJECTS OUT OF WESTERN CONUS L/W TROF AND
INTO THE NORTHERN STREAM LATE THU INTO FRI. THE MEDIUM RANGE MODEL
ARE ALL VARYING WITH RESPECT TO TIMING OF THIS PROCESS AS WELL AS
DAMPENING OF THE BROAD SCALE UPPER RIDGE AXIS...BUT THE 12Z RUN ECMWF
AND GFS BREAK IT DOWN ENOUGH TO SHUTTLE AN ASSOCIATED COLD FRONT DOWN
THROUGH THE CWA LATE THU NIGHT INTO FRI FOR THE NEXT MAIN CONVECTIVE
WINDOW. OF COURSE PLENTY OF CAPE EXPECTED BY THEN TO FUEL A SVR MCS
WITH EXPECTED WARMING AND LLVL MOISTURE RETURN. WILL KEEP LOW TO
MODERATE CHC POPS DURING THIS TIME FRAME AND AWAIT TO SEE IF LLVL
BAROCLINICITY CAN REALLY GET SHOVED THIS FAR SOUTH. THE MODELS
CONTINUE TO SHUNT THE MAIN SFC FRONT AND STORM TRACK TO THE SOUTH
OVER THE WEEKEND ACRS KS AND MO/SIMILAR TO WHAT JUST HAPPENED
THIS PAST THU INTO FRI/...BUT AM LEARY IF IT CAN MAKE IT THAT FAR
SOUTH DURING THIS TIME OF YEAR. OF COURSE A FURTHER NORTH PLACEMENT
THROUGH PORTIONS OF IA AND NORTHERN IL LIKE THE 06Z RUN GFS
ADVERTISED WOULD SPELL MCS TROUBLE FOR THE LOCAL AREA FOR NEXT
WEEKEND AND BEYOND. WILL KEEP LOW CHANCES GOING THROUGH SAT FOR NOW.
..12..
AVIATION
CLOUDS AND PRECIPITATION HAVE BEEN GRADUALLY LIFTING AND DIMINISHING
ACROSS THE AREA THIS MORNING. THIS TREND SHOULD CONTINUE INTO THE
LATE AFTERNOON AND EVENING...WITH THE CURRENT MIX OF LOW END MVFR
AND IFR CONDITIONS GRADUALLY LIFTING INTO MAINLY MVFR BY MID EVENING
FOR ALL SITES EXCEPT KBRL. THERE...THE IFR CIGS MAY LINGER UNTIL
08Z WITH SOME LIGHT DRIZZLE AS THE LIFT SLOWLY SHIFTS SOUTH ACROSS
THE AREA. WITH KDBQ KCID AND KMLI EXPECTED TO GO AT LEAST VFR BY
06Z...EXPECT SOME FOG DEVELOPMENT AFTERWARDS WITH THE RECENT
RAINFALL AND LIGHT WINDS. VISIBILITIES MAY DROP INTO THE IFR
CATEGORY AFTER 09Z WITH SOME ASSOCIATED LIFR STRATUS. ..LE..
DVN WATCHES/WARNINGS/ADVISORIES
IA...NONE
IL...NONE
MO...NONE
12/LE
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