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000
FXUS63 KDVN 260444
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1144 PM CDT SAT MAY 25 2013

.UPDATE...
ISSUED AT 636 PM CDT SAT MAY 25 2013

I HAVE DONE SOME MINOR ADJUSTMENTS TO HOURLY POPS AND
WEATHER...AS THE FOREVER LINGERING CONVERGENCE ON THE WEST FLANK
OF THE DISSIPATING MCS NARROWS AND WEAKENS ALONG JUST SOUTH OF THE
INTERSTATE 80 CORRIDOR EARLY THIS EVENING. OTHERWISE...OUR
FORECAST REMAINS WATCH AND WAIT. AS OF NOW...TOWERING CUMULUS IS
WIDESPREAD IN EASTERN NEBRASKA...AND NORTHWEST MISSOURI.
HOWEVER...SINCE 4 PM...THIS SIGNAL HAS BEEN CHANGING LITTLE...WITH
ONLY A FEW SKINNY TURKEY TOWER ECHOES SHOWING UP ON RADAR.
THUS...THIS AREA CONTINUES TO SHOW CAPPED POTENTIAL FOR NOW. IF IT
GOES BIG...WE WILL SEE OUR THREAT DIMINISH FOR HEAVY RAIN AS
PREVIOUS SHIFT NOTES. HOWEVER...THE LATEST HOUR OF VISIBLE
SATELLITE SHOWS NEW ACCAS TURRETS GROWING ALONG THE ELEVATED
FRONTAL ZONE WHICH HAD BEEN QUIET UNTIL THEN. THIS IS FROM THE
NORTHWEST CORNER OF IOWA THROUGH OTTUMWA. WE WILL WATCH THIS LINE
FOR THE NEW DEVELOPMENT OF STORMS THIS EVENING.
ERVIN

&&

.SYNOPSIS...
ISSUED AT 309 PM CDT SAT MAY 25 2013

UPPER LEVEL DISTURBANCE MOVING THROUGH EASTERN IA NORTH OF I-80 ATTIM
WITH LARGE RAIN SHIELD PERSISTING ON N/E FLANK OF SYSTEM... WHILE
FEW SHOWERS AND POSSIBLY RUMBLE OF THUNDER RECENTLY HAVING DEVELOPED
OVER PORTIONS OF WEST CENTRAL IL. WELL DEFINED FRONTAL ZONE ENHANCED
BY RAIN COOLED AIR EXTENDS FROM SOUTHEAST NE THROUGH NORTHERN MO
NEAR I-70 CORRIDOR. TEMPS OVER CWA MOSTLY IN THE 50S... WELL BELOW
NORMAL AND NEAR RECORD COOL MAX TERRITORY IN A FEW LOCATIONS.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 309 PM CDT SAT MAY 25 2013

FOCUS REMAINS WITH TRYING TO PIN DOWN MAGNITUDE AND LOCATION OF
CONVECTION... AND POTENTIAL FOR HEAVY RAIN AND FLASH FLOODING.

FRONTAL ZONE LIKELY NOT GOING TO MOVE ALL THAT MUCH NEXT 24 HRS
BENEATH FLATTENING RIDGE ALOFT AND WITH ELEVATED CONVECTION TO
NORTH OF FRONT. DO EXPECT REDEVELOPMENT OF AT LEAST SCATTERED
SHOWERS AND STORMS LATER THIS EVENING INTO OVERNIGHT... WITH
BRANCH OF LOW LEVEL JET AND ATTENDANT MOISTURE ADVECTION AND
CONVERGENCE.... WITH ACTIVITY CONTINUING SUNDAY. POTENTIAL TO
SEE SOME UPSCALE GROWTH INTO MCS MAINLY TO OUR WEST OVERNIGHT
POSSIBLY ROLLING ACROSS PORTIONS OF THE CWA LATE TONIGHT AND
SUNDAY. THIS NOT CERTAIN AS COULD SEE ANY MCS TRACK FURTHER
SOUTH/WEST COINCIDENT WITH BOUNDARY AND EXPANSIVE CU FIELD FROM NE
TO NORTHERN MO. THIS WOULD PLACE HEAVIEST AMOUNTS JUST SOUTH OF
CWA. DESPITE UNCERTAINTY WITH POTENTIAL MCS AND HEAVY RAIN
AMOUNTS... WILL CONTINUE LIKELY TO CATEGORICAL POPS LATER
TONIGHT INTO SUNDAY. FAR WESTERN AND SOUTHERN COUNTIES RECEIVED
AROUND 1 TO JUST OVER 2 INCHES IN FEW SPOTS... AND SO THESE AREAS
WOULD BE MOST SUSCEPTIBLE TO FLASH FLOODING... BUT 3-6 HR FFG
VALUES 2-2.5+ INCHES AND UNCERTAINTY WITH EVOLUTION TO MCS AND
TRACK SUPPORTIVE OF WIDESPREAD 1-3 INCH AMOUNTS PRECLUDES ANY HYDRO
HEADLINES ATTIM. TEMPS NOT FALLING MUCH TONIGHT AND STAYED NEAR TO
BELOW COOLEST GUIDANCE TOMORROW FOR HIGHS.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 309 PM CDT SAT MAY 25 2013

FORECAST FOCUS ON PROLONGED PERIOD OF ACTIVE WEATHER WITH HEAVY RAIN
POTENTIAL THEN SEVERE WEATHER THREAT INCREASES LATE IN THE WEEK.

SUNDAY NIGHT THROUGH TUESDAY NIGHT...DEEP TROUGH IN THE WESTERN
UNITED STATES WITH RIDGE IN THE SOUTHEAST WILL PUMP COPIOUS MOISTURE
NORTHWARD FROM THE GULF. PRECIPITABLE WATERS INCREASE TO OVER 1.60
INCHES WHICH IS WELL ABOVE NORMAL FOR THE END OF MAY. EAST-WEST
FRONTAL BOUNDARY WILL CONTINUE TO MEANDER AROUND THE DVN CWA DURING
THIS PERIOD WITH PERIODIC ROUNDS OF SHOWERS AND THUNDERSTORMS.
REPEATED ROUNDS OF HEAVY RAINFALL ADDING UP TO AT LEAST SEVERAL
INCHES OF RAIN CERTAINLY WOULD LEAD TO INCREASING POTENTIAL FOR
FLASH FLOODING AND SIGNIFICANT RISES IN RIVER LEVELS.

WEDNESDAY AND WEDNESDAY NIGHT...PACIFIC FLOW SHOULD BEGIN TO AMPLIFY IN
RESPONSE TO TROUGHING SOUTH OF THE ALEUTIANS...LEADING TO A SHARPER
TROUGH NEAR THE WEST COAST. THIS WILL INCREASE THE SOUTHERLY FLOW
PUSHING THE FRONTAL BOUNDARY WELL TO OUR NORTH. THIS SHOULD PUT THE
CWA IN THE CAPPED WARM SECTOR IMPLYING A BRIEF LULL IN THE ACTION.
HOWEVER WILL BE VERY WARM AND HUMID WITH AFTERNOON TEMPERATURES
PUSHING WELL INTO THE 80S AND DEW POINTS INTO THE 60S TO AROUND 70.

THURSDAY THROUGH SATURDAY...OPERATIONAL MODELS SIMILAR IN CARVING
OUT A MAJOR TROUGH IN THE ROCKIES/PLAINS. INCREASING DYNAMICS/
COLDER AIR ALOFT COMBINED WITH A VERY UNSTABLE AIRMASS SHOULD
TRIGGER MORE THUNDERSTORMS DURING THIS TIME FRAME. THE SYSTEM
EVENTUALLY WEAKENS/FILLS AS IT PUSHES ACROSS THE UPPER MIDWEST NEXT
WEEKEND. THE CURRENT DATA SUGGESTS SEVERE THUNDERSTORMS MAY BECOME A
THREAT LATE NEXT WEEK (THURSDAY/FRIDAY) AS DEEP LAYER SHEAR ARRIVES
AHEAD OF MAIN TROUGH AND SLOW MOVING COLD FRONT.

HAASE

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1139 PM CDT SAT MAY 25 2013

A CHALLENGING SET OF AVIATION FORECAST IS EXPECTED THE NEXT 24
HOURS AND BEYOND...AS A WARM FRONT OVER NORTHERN MISSOURI SENDS
SEVERAL WAVES OF WIDESPREAD SHOWERS AND THUNDERSTORMS OVER IOWA
AND ILLINOIS. THUS...WIDESPREAD VARIABLE MVFR/IFR CIGS WILL
CONTINUE THROUGH SUNDAY NIGHT...WITH ADDITIONAL PERIODS OF LOW
VISIBILITY IN ANY SHOWER OR THUNDERSTORM ACTIVITY. THE MAIN PERIOD
OF WIDESPREAD THUNDERSTORMS THROUGH MID DAY SUNDAY...THEN
POSSIBLY AGAIN SUNDAY NIGHT. THIS AREA IS ALREADY DEVELOPING OVER
IOWA AT THIS TIME...AND WILL CONTINUE TO SPREAD EAST SLOWLY
OVERSPREADING ALL OF EASTERN IOWA AND NORTHWEST ILLINOIS BY 12Z.
AFTER 12Z...THUNDERSTORMS WILL BECOME LESS OF A THREAT...BUT RAIN
SHOULD CONTINUE TO BE WIDESPREAD.  BEFORE CONSIDERING ANY
FLIGHT...A CHECK OF RADAR WOULD BE HELPFUL AS LINES OF STORMS WILL
CERTAINLY AFFECT ROUTES...AS WELL AS LANDING CONDITIONS. IN
ADDITION...THE VARIABILITY OF WEATHER CONDITIONS WILL BE HIGH AT
TERMINALS THROUGH SUNDAY NIGHT...AND UPDATES WILL MOST CERTAINLY
BE MORE FREQUENT THAN NORMAL. ERVIN

&&

.HYDROLOGY...
ISSUED AT 309 PM CDT SAT MAY 25 2013

RAINFALL REPORTS OF 1-2.5 INCHES WERE OBSERVED PAST 24 HRS OVER
FAR WESTERN AND SOUTHERN SECTIONS OF CWA. ANOTHER ROUND OF
SHOWERS AND STORMS IS LIKELY LATER TONIGHT AND SUNDAY. EACH
ROUND WILL INCREASE POTENTIAL FOR FLOODING WITH GROUND BECOMING
SATURATED... BUT CONFIDENCE LOW ON FLASH FLOODING WITH 3-6 HR FFG
VALUES 2-2.5 INCHES AND UNCERTAINTY WITH EVOLUTION AND MAGNITUDE
OF CONVECTION TONIGHT...AS SOME SUGGESTION MORE WIDESPREAD
SIGNIFICANT RAINFALL COULD END UP OCCURRING FURTHER SOUTHWEST OF
CWA. THIS WILL NEED TO BE MONITORED THIS EVENING WITH THE POTENTIAL
FOR HEADLINES IF INDEED LOOKS LIKE WIDESPREAD HEAVY RAINS OF 1-2+
INCHES WILL MOVE BACK ACROSS WESTERN/SOUTHERN CWA. AS THE RAINFALL
GOES...SO GOES RIVERS... AND DEPENDING ON HEAVY RAIN COULD SEE
RENEWED RISES AND FLOODING DEVELOP IN THE NEXT FEW DAYS... ESPECIALLY
ON THE IOWA...CEDAR...SKUNK AND WAPSIPINICON RIVERS.

&&

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

$$

UPDATE...ERVIN
SYNOPSIS...05
SHORT TERM...05
LONG TERM...HAASE
AVIATION...ERVIN