Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

000
FXUS63 KDVN 061201
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
701 AM CDT MON JUL 6 2015

.UPDATE...
ISSUED AT 701 AM CDT MON JUL 6 2015

COMPLEX OF THUNDERSTORMS WITH HEAVY RAIN HAS BECOME STALLED AND
WAS BACK-BUILDING JUST WEST OF THE FORECAST AREA...MAINLY WEST OF
A LINE FROM WATERLOO TO OTTUMWA. THESE WERE OCCURRING IN AN AREA
OF ELEVATED MOISTURE ADVECTION ALONG THE EDGE OF STEEP MID LEVEL
LAPSE RATES. FURTHER EAST...ISOLATED...MORE ELEVATED STORMS WERE
MAINLY NW OF A LINE FROM IOWA CITY TO DUBUQUE. HAVE UPDATED TO
INCREASE POPS TO COVER SCATTERED STORMS IN THIS AREA.

ALL INDICATIONS SUGGEST THE CENTRAL IA COMPLEX TO DISSIPATE
WITHIN A COUPLE HOURS AND NOT ADVANCE MUCH FURTHER EASTWARD AWAY
FROM THE BETTER UPSTREAM THETAE ADVECTION AND HIGHER INSTABILITY.
WITH HEAVY RAINFALL RATES OF 1 TO 2 INCHES ESTIMATED BY RADAR AND
CONTINUED UPSTREAM CLOUD TOP COOLING ON IR SATELLITE...WILL
CONTINUE TO MONITOR CLOSELY...BUT AT THIS TIME IT APPEARS THE
GREATEST HEAVY RAINFALL THREAT WILL BE JUST WEST OF THE FORECAST
AREA THIS MORNING.

&&

.SYNOPSIS...
ISSUED AT 349 AM CDT MON JUL 6 2015

AT 3 AM...A LARGE THUNDERSTORM COMPLEX WAS SITUATED FROM FAR WESTERN
WI W-SW ACROSS SOUTHERN WI...NW IA AND EASTERN NEB. THIS WAS
OCCURRING IN AN AREA OF DEEP MOISTURE CONVERGENCE AND WAVE OF LOW
PRESSURE ALONG A COLD FRONT THAT REACHED FROM WESTERN LAKE SUPERIOR
SW ACROSS MN...NEB INTO FAR WESTERN KS. AREA RADARS SHOWED
THUNDERSTORMS WELL OUT AHEAD OF THIS BOUNDARY OVER CENTRAL IA FROM
ABOUT MASON CITY SOUTH TO DES MOINES IN AN AREA OF STEEP MID LEVEL
LAPSE RATES AND APPARENT ELEVATED MOISTURE ADVECTION. OVER THE LOCAL
AREA...BACKING LIGHT S-SE WINDS WERE LEADING TO SLOWLY CLIMBING
DEWPOINTS IN UPPER 60S TO NEAR 70S W OF THE MS RIVER WITH MAINLY
LOWER 60S TO THE EAST.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 349 AM CDT MON JUL 6 2015

THUNDERSTORM TRENDS AND THE POTENTIAL FOR SEVERE WEATHER AND
HEAVY RAINFALL ARE THE PRIMARY FOCUS. EARLY THIS MORNING...THE
CENTRAL IA CONVECTION WILL BE MOVING INTO A LESS FAVORABLE
ENVIRONMENT AS ALL MODELS DEPICT MID LEVEL LAPSE RATES BECOMING
LESS UNSTABLE AFTER SUNRISE...ESPECIALLY OVER EASTERN IA.
HOWEVER...AT THE CURRENT RATE...THESE THUNDERSTORMS WILL LIKELY
REACH INTO THE FAR WESTERN COUNTIES AROUND SUNRISE BEFORE
WEAKENING. BEYOND...FORECAST CONFIDENCE WANES AS MODELS APPEAR TO
BE OVERDONE WITH PW VALUES COMPARED TO 00Z SOUNDINGS OVER THE
PLAINS AND THE ANOMALOUSLY HIGH FORECAST PW VALUES WELL OVER 2
INCHES PROGGED OVER THE FORECAST AREA TODAY ARE QUESTIONABLE...
ALONG WITH DEWPOINTS SHOWN REACHING INTO THE UPPER 70S BY THE WRF.
RECENT HIGH RES CONVECTIVE MODELS AND OPERATIONAL MODELS FROM 00Z
ARE ALL BEING CHALLENGED BY THIS SYSTEM...BOTH WITH RESPECT TO
CONVECTIVE COVERAGE THIS MORNING AND SHORT TERM TRENDS...THUS FORECAST
CONFIDENCE IN DETAILS IS BELOW AVERAGE.

THE OVERALL TRENDS SUGGEST A WEAKENING OF THE LEADING CONVECTION
WITH THE LARGE MCS TRENDING MAINLY NW OF THE FORECAST AREA THROUGH
THE DAY AS MID LEVEL LAPSE RATES BECOME LESS FAVORABLE AND EXTENSIVE
CLOUD COVER SEEN ON SATELLITE COVERING MOST OF THE CENTRAL AND
NORTHERN PLAINS FROM THIS COMPLEX WILL LIKELY LIMIT INSOLATION AS
IT OVERSPREAD THE FORECAST AREA. OUTSIDE THE NOW SLOWER WRF...THE
FRONT IS GENERALLY SHOWN MOVING INTO FAR EAST CENTRAL IA AROUND
00Z. THIS WILL HAVE CAPE OF AT LEAST 1500 TO 2000 TO WORK WITH AS
LOW LEVEL MOISTURE CONVERGENCE PUSHES DEWPOINTS INTO THE LOWER TO
POSSIBLY MID 70S AND TEMPERATURES REACH AT LEAST THE UPPER 70S TO
LOWER 80S AHEAD OF THE FRONT DUE TO WARM ADVECTION. MODELS
DISAGREE IN THE AMOUNT OF DEEP SHEAR...BUT GENERALLY SUGGEST 30
KTS PLUS IN A ZERO TO 3 KM LAYER OVER AT LEAST THE NORTH FOR THE
BOUNDARY TO WORK WITH. THIS COULD SUPPORT SOME BOWING COMPLEXES
AND POSSIBLE DAMAGING WINDS WHERE THE FRONT MOVES THROUGH DURING
THE MOST UNSTABLE LATE AFTERNOON AND EARLY EVENING PERIOD. SPC HAS
THE ENTIRE FORECAST AREA UNDER A SLIGHT RISK. OF A GREATER
POTENTIAL WILL BE HEAVY RAINFALL RATES AS PW VALUES ARE LIKELY TO
REACH AT LEAST A 1.5 TO 2 INCH RANGE. CONSIDERING THAT IT HAS BEEN
NEARLY A WEEK SINCE THE LAST WIDESPREAD RAIN EVENT...FLASH FLOOD
GUIDANCE VALUES ARE HIGH AND RIVERS ARE HAVE RETURNED TO WELL
BELOW FLOOD STAGE. THE MOST LIKELY HYDRO THREAT WILL BE URBAN AND
SMALL STREAM TYPE FLOODING IF STORMS BECOME SLOW MOVERS OR BACK
BUILD...WHICH WILL NEED TO BE MONITORED.

THUNDERSTORMS AND THE THREAT OF AT LEAST LOCALIZED SEVERE STORMS AND
HEAVY RAINFALL WILL CONTINUE INTO THE EARLY EVENING HOURS...SHIFTING
TO EAST OF THE MS RIVER AFTER 7 PM. CURRENT TIMING SUGGESTS STORMS
WILL END OVER MOST OF EASTERN IA BY MIDNIGHT...WITH THE BACK EDGE
OF SHOWERS EXITING THE IL COUNTIES BY 3 AM. HOWEVER...OUR
FORECAST WILL REMAIN A MORE GENEROUS WITH HOURLY POPS OVERNIGHT
THAT ACCOUNT FOR POSSIBLE FURTHER SLOWING OF THE FRONTAL SYSTEM.
FORECAST QPF AMOUNTS WERE PLACED IN A WIDESPREAD HALF TO 1 INCH
RANGE FOR THIS SYSTEM...BUT WITH THE HIGH AMOUNTS OF
MOISTURE...LOCALIZED 2 TO 3 INCH AMOUNTS WILL BE POSSIBLE.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 349 AM CDT MON JUL 6 2015

TUESDAY AND WEDNESDAY...A FEW POST-FRONTAL SHOWERS POSSIBLE IN THE
FAR SOUTH AND EASTERN CWA TUE MORNING...BUT WOULD THINK MORE
PROGRESSIVE SOLUTION PANS OUT WITH EVERYTHING OUT OF THE CWA BY 15Z
TUE. THEN CLOUDS CLEAR IN THE AFTERNOON ESPECIALLY ALONG AND NORTH
OF I80 AS SFC RIDGE PUSHES EASTWARD ACRS THE UPPER MS RVR VALLEY.
CLOUDS AND POST-FRONTAL LLVL COOL CONVEYOR TO MAKE FOR WELL BELOW
NORMAL TEMPS THIS PERIOD. FIRST HALF OF TUE NIGHT MAINLY CLEAR WITH
TEMPS COOLING INTO THE 50S...BEFORE HIGH CLOUDS START TO SPRAWL IN
FROM THE SOUTHERN PLAINS AHEAD OF THE NEXT INCOMING WAVE. LATEST 00Z
RUN MODEL SOLUTIONS ADVERTISE A TYPE OF LARGE SPLIT FLOW PATTERN
TAKING OVER MUCH OF THE CONUS BY MID WEEK...WITH A VIGOROUS WAVE
ROLLING OUT ALONG THE SOUTHERN EDGE OF THE SPLIT AND ALONG THE
NORTHWEST FLANK OF SOUTHEASTERN ATLANTIC BROAD UPPER RIDGE COMPLEX.

SOME MODEL DISCREPANCY STILL ON HOW ROBUST THIS WAVE WILL BE AS
WELL AS HOW FAR NORTH OR SOUTH THE TRAJECTORY PATH WILL OCCUR AS
THIS FEATURE RIPPLES OUT OF THE SOUTHERN PLAINS AND TOWARD THE
SOUTHERN GRT LKS BY THU MORNING. DEPENDING ON IT/S PATH...THIS
SYSTEM MAY BE OF SOME IMPACT ON THE LOCAL FCST AREA IF IT CAN INGEST
AN INCREASING GULF MOISTURE FEED AND INDUCE A TYPE OF HEAVY RAIN DEF
ZONE ACRS PORTIONS OF THE CWA. THE 00Z RUN GFS JUST CLIPS THE
SOUTHEASTERN THIRD OF THE CWA WITH SUCH A FEATURE...WHILE THE 00Z NAM
TAKES MORE OF A DIRECT HIT ACRS MUCH OF THE LOCAL AREA. THE 00Z EURO
TARGETS THE SOUTHEAST HALF OF THE CWA WITH A PAN HANDLE HOOKER TYPE
LOW AND 1 TO 2+ INCHES OF RAIN BY 12Z THU FROM THIS SYSTEM. DEEPENING
ON HOW MUCH RAIN OCCURS TODAY/TONIGHT TO PRIME SOILS...ANOTHER HEAVY
RAIN SYSTEM ON WED/WED EVENING COULD LEAD TO SOME HYDRO ISSUES.
PRECIP...CLOUD COVER AND INDUCED EAST-NORTHEAST LLVL FLOW TO THE LEE
OF THIS INCOMING SYSTEM MAY MAKE FOR SOME AREAS HAVING TROUBLE
GETTING OUT OF THE 60S FOR WED HIGHS. ANY STRONG TO SVR WX CONCERNS
WOULD BE ON THE SOUTHERN FLANK OF THE COMPRESSED LOW PRESSURE SYSTEM
ON WED.

THURSDAY AND FRIDAY...LATEST 00Z RUN MEDIUM RANGE MODEL TRENDS/MREF
SOLUTION PAINT THIS PERIOD AS POTENTIALLY MORE ACTIVE AND UNDER A
TYPE OF MCS WINDOW AS UPPER RIDGING ESTABLISHES ACRS MUCH OF THE
SOUTHEASTERN CONUS AND INTO THE SOUTHERN PLAINS. WARM MOIST CONVEYOR
ROTATING AROUND THIS FEATURE UP INTO A LLVL BOUNDARY GETTING STALLED
OUT SOMEWHERE ACRS THE CENTRAL PLAINS AND INTO THE SOUTHERN GRT LKS
TO OCCASIONALLY FOCUS ROUNDS OF CONVECTIVE DEVELOPMENT ON FROM LATE
THU THROUGH FRI NIGHT. THIS COULD MAKE FOR ANOTHER TEMPORARY WET
REGIME AND COMPOUNDED HEAVY RAIN EVENTS INTO THE START OF THE
WEEKEND FOR RENEWED RIVER FLOODING AS WELL AS URBAN/SMALL STREAM
FLOODING ISSUES IF THE BOUNDARY HAPPENS TO LAY OUT ALONG OR JUST
SOUTH OF THE DVN CWA. LARGE TEMP DISCREPANCIES POSSIBLE THIS PERIOD
AS WELL FROM NORTH TO SOUTH. WILL HAVE TO BLANKET THESE DAYS WITH
POPS AND GENERAL TEMP TRENDS.

NEXT SATURDAY AND SUNDAY...SOME LONGER RANGE SIGNS OF ENOUGH UPPER
RIDGE AMPLIFICATION TO SHUNT THE MAIN STORM TRACK TO THE NORTHERN
PLAINS ACRS TO THE GRT LKS THIS PERIOD AND THE DVN CWA INTO THE WARM
SIDE OF BUILDING THERMAL RIDGE. BUT MANY TIMES WHEN THE MODELS
ADVERTISE THIS FLUX...THE TRANSITION CAN BE STORMY AS WELL AND COULD
EASILY SEE THE FRONTAL RETREAT TO THE NORTH OF THE AREA GET HINDERED
BY CONVECTION ITSELF AND OUTFLOW. THUS LATE SAT AND SAT NIGHT WE
COULD SEE ANOTHER ROUND OF STORMS EITHER IN OR VERY CLOSE TO THE CWA
AND WILL HAVE TO MAINTAIN POPS. LONGER RANGE TRENDS SUGGEST RIDGE
RIDING WAVE ENERGY WILL LOOK TO TRY AND DIG DOWN ACRS THE GRT LKS
AND RE-CARVE OUT TROFFINESS AND NORTHWEST FLOW DOWN THE UPPER MIDWEST
AGAIN BY EARLY NEXT WEEK. ..12..

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 701 AM CDT MON JUL 6 2015

ISOLATED THUNDERSTORMS WILL LIKELY REMAIN WEST OF MOST OF THE
TERMINALS THIS MORNING. THE EXCEPTION IS CID...WHERE THUNDERSTORMS
OVER CENTRAL IA WILL LIKELY AFFECT THE TERMINAL IN A DISSIPATING
MODE FROM MID TO LATE MORNING. OTHERWISE...WIDESPREAD MVFR
CONDITIONS DUE TO FOG AND HAZE WILL GRADUALLY IMPROVE.
BEYOND...FORECAST CONFIDENCE IS LOW WITH THUNDERSTORM TRENDS THIS
AFTERNOON AS A COLD FRONT ADVANCES INTO THE AREA. THE MOST LIKELY
PERIOD FOR STORMS AT ALL TERMINALS IS ROUGHLY FROM 21Z TO
01Z...WHICH HAS BEEN TARGETED WITH TEMPO OR PREVAILING GROUPS FOR
RAIN AND THUNDERSTORMS WITH MVFR CONDITIONS. WHILE NOT IN THE
FORECASTS...PERIODS OF IFR CONDITIONS WILL BE POSSIBLE WITH THE
STRONGEST STORMS. OVERNIGHT...WINDS WILL VEER TO THE NW BEHIND THE
FRONT WITH STORMS ENDING IN THE EVENING...WITH ENOUGH DRY AIR TO
SUGGEST VFR CONDITIONS AT ALL SITES BY TUESDAY MORNING.

&&

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

$$

UPDATE...SHEETS
SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...12
AVIATION...SHEETS


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.