000
FXUS63 KDVN 040823
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
320 AM CDT SAT SEP 4 2010

.SYNOPSIS...
LATEST SFC ANALYSIS WAS INDICATING LARGE RIDGE COMPLEX OCCUPYING
MUCH OF THE PLAINS AND WESTERN FRINGES OF THE MS RVR VALLEY...WHILE
STILL RATHER TIGHT CYCLONIC FLOW PATTERN CONTINUED ACRS THE GRT
LKS. PATTERN OF SFC PRESSURE RISES AND FALLS AS WELL AS SOME WIND
SHIFTS SUGGEST EMBEDDED TROFS SLIPPING SOUTHEASTWARD IN THIS FLOW
ALONG AND EAST OF THE LOCAL FCST AREA. MIXING NORTHWEST WINDS
MAINTAINING AT 7-13 MPH OVERNIGHT STILL KEEPING MOST OF THE CWA IN
THE 50S...BUT MID 40S PERCHED JUST UPSTREAM ACRS NORTH CENTRAL IA
CLOSER TO INCOMING RIDGE AXIS. IR LOOP AND W/V IMAGERY INDICATING
PASSING VORT SPOKE IN CYCLONIC FLOW PATTERN ALOFT RIPPLING RIGHT
OVER THE NORTHEASTERN CWA ATTM...WITH ANOTHER ONE LOCATES ACRS
NORTHWEST ONTARIO.

&&

.SHORT TERM...TODAY AND TONIGHT...
TODAY...EDGE OF LLVL COOL POOL TO CONTINUE ACRS THE CWA TODAY...WITH
VERY DEEP MIXING UP TO H825 OR EVEN CLOSE TO H8 MB NEEDED TO ATTAIN
PROJECTED FCST HIGHS TODAY OF WIDESPREAD MID 60S TO LOWER 70S. ALSO
EXPECT A MID MORNING TO EARLY AFTERNOON WIND MIX DOWN/MOMENTUM
TRANSFER TO GENERATE WIND GUSTS UP TO 20 KTS...BEFORE GRADIENT
RELAXES AGAIN TOWARD LATE AFTERNOON. FCST SOUNDINGS AND CU RULE
SUGGEST CU DEVELOPMENT TO SCTRD AND PUSHING BKN LEVELS ACRS THE
NORTHEASTERN 2/3S OF THE CWA...BUT DRY DOWN MIXING TO BRING ABOUT
EROSION AGAIN BY LATE AFTERNOON.

TONIGHT...CLEAR SKIES INITIALLY AND SFC WIND DECOUPLE TO BRING ABOUT
A QUICK TEMP DROP OFF RIGHT AFTER SUNSET UNDER PASSING RIDGE AXIS.
LIGHT RETURN FLOW TO INITIATE AFTER 07Z SUNDAY AND PRODUCE A STEADY
OUT OR EVEN A SLOW RISE TOWARD SUNRISE IN TEMP TRENDS ACRS THE
SOUTHWESTERN THIRD OR HALF OF THE LOCAL FCST AREA. OTHERWISE ONGOING
WIDESPREAD LOWS IN THE UPPER 40SD TO LOWER 50S LOOK ON TARGET...WITH
COOLEST READINGS OCCURRING EAST OF THE MS RVR IN LINGERING RIDGE
VCNTY. ALONG WITH THE RETURN FLOW HOLDING TEMPS UP...MOST OF THE
SHORT RANGE MODELS SUGGEST A CONVERGENT WAA WING IN THE H9-H850 MB
LAYER MAY INITIATE A BAND OF STRATUS OR AC ACRS THE WESTERN CWA LATE
TONIGHT. DRY SUB-LAYER SHOULD PREVENT ANY SPRINKLES FROM REACHING THE
SFC...IF EVEN THE LOW CHC THAT ANY ELEVATED PRECIP GETS GENERATED.
..12..


.LONG TERM...SUNDAY THROUGH NEXT FRIDAY...
WE RETURN TO A MORE ACTIVE PERIOD WITH A STRING OF DAYS WITH SLIGHT
OR LOW END CHANCE POPS EACH DAY.  BEGINNING VERY LATE TONIGHT WARM
AIR ADVECTION SETS IN...AND CONTINUES THROUGH MOST OF MONDAY.  THIS
FLOW STARTS OUT VERY DRY...BUT OVER TIME WE GETS SOME SURGES OF
ADDITIONAL WARMTH AND MOISTURE.  SUNDAY NIGHT THROUGH MONDAY NIGHT
WE MAY HAVE SOME WARM AIR ADVECTION WING TYPE SHOWERS AFFECT THE
AREA...MAINLY ACROSS ABOUT THE NORTH HALF. THE WARM FRONT ITSELF
WILL BE WELL NORTH OF THE AREA...SO WE ARE ON THE FRINGES OF MUCH
HIGHER PRECIPITATION CHANCES...AND HAVE KEPT POPS MAINLY IN THE
SLIGHT CHANCE CATEGORY TO ACCOUNT FOR DRY AIR CONCERNS AND BEING ON
THE EDGES OF THE FORCING.  MONDAY NIGHT AND TUESDAY THE COLD FRONT
ITSELF COMES PLOWING THROUGH THE AREA.  THE TIMING AND LACK OF
MOISTURE ARE NOT ESPECIALLY FAVORABLE FOR PRECIPITATION...THOUGH THE
BOUNDARY ITSELF IS A RESPECTABLE COLD FRONT WITH A FAIRLY SIGNIFICANT
AIRMASS CHANGE COMING INTO THE AREA.  MAX TEMPERATURES AHEAD OF THE
FRONT WILL BE WELL UP INTO THE 80S ON MONDAY...THEN DROPPING INTO THE
MID 70S TO LOW 80S FOR TUESDAY.  THIS BOUNDARY SAGS TO THE SOUTH OF
THE FORECAST AREA FOR WEDNESDAY.  THE MODELS ARE NOT IN AGREEMENT
ABOUT HOW FAR SOUTH IT WILL GO...WHICH OF COURSE AFFECTS POPS FOR
LATER IN THE WEEK.  THE ECWMF FAVORS A MORE SOUTHERLY SOLUTION...THE
GFS MORE NORTH.  HAVE TRIED TO PLAY A MIDDLE OF THE ROAD FORECAST FOR
NOW WITH SLIGHT CHANCE POPS...AND WE CAN WAIT AND SEE HOW LATER RUNS
HANDLE THIS.  TEMPERATURES WILL BE CLOSE TO NORMAL DURING THIS PERIOD
BUT MAY NEED TO BE COOLED OFF IF THE FRONT SETTLES FARTHER SOUTH.
..LE..

&&

.AVIATION...
MVFR STRATUS WILL REMAIN LARGELY EAST OF THE TERMINALS THROUGH 15Z
THIS MORNING...BUT SCTRD TO BKN CU WILL DEVELOP FROM 3500-4000 FT AGL
BY LATE MORNING AGAIN IN THE VCNTY OF CID...DBQ AND MLI. WIND GUSTS
UP TO 20 KTS FROM 290-310 DEGREES EXPECTED FROM 15Z THROUGH 20Z
BEFORE SFC GRADIENT RELAXES WITH INCOMING RIDGE. LIGHT WINDS AND
CLEAR SKIES THIS EVENING...BUT WILL HAVE TO WATCH FOR NOCTURNAL AC
DEVELOPING FROM 5K-9K FT LATE TONIGHT ALONG AND WEST OF THE MS RVR.
..12..

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...NONE.
IL...NONE.
MO...NONE.

&&

$$

12/LE

NWS DVN Office Area Forecast Discussion