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000
FXUS63 KDVN 251817
AFDDVN

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

.UPDATE...
ISSUED AT 101 PM CDT SAT MAY 25 2013

SENT UPDATE A LITTLE WHILE BACK TO LOWER HIGHS TO MOSTLY IN THE
50S BENEATH EXTENSIVE CLOUD CANOPY AND EASTERLY LOW LEVEL WINDS.
OTHERWISE... ADJUSTED POPS FOR ARCING RAIN SHIELD AS IT
CONTINUES TO SLIDE EAST SLOWLY AHEAD OF SHORTWAVE MOVING INTO
EASTERN IOWA ATTIM. WILL CONTINUE TO UPDATE/AMEND AS NEEDED.

UPDATE ISSUED AT 700 AM CDT SAT MAY 25 2013

MCS THAT DEVELOPED OVER NEB LAST NIGHT HAS MOVED INTO W CENTRAL
IA AT 6 AM. OUT AHEAD OF THIS...A LARGE WING OF WARM ADVECTION
SHOWERS AND THUNDERSTORMS CONTINUED TO PERCULATE OVER CENTRAL
INTO SE IA...REACHING INTO THE FORECAST AREA WEST OF A KCID TO
KBRL LINE. LATEST SATELLITE IR IMAGERY SHOWED A LARGE AREA OF COLD
CLOUD TOPS BEING MAINTAINED OVER WESTERN IA...BUT STILL EXPECTING
DIURNAL WEAKENING AS THE COMPLEX PUSHES EAST ACROSS THE SOUTHERN
2/3RDS OF THE FORECAST AREA OVER THE NEXT 4 TO 6 HOURS. WIDESPREAD
QUARTER TO HALF INCH RAINFALL AMOUNTS LOOK REASONABLE AND THERE COULD
STILL AT LEAST A FEW HOURS OF DRY WEATHER IN THE AFTERNOON AND
POSSIBLY EARLY EVENING BEFORE THE NEXT STORM COMPLEX DEVELOPS.

&&

.SYNOPSIS...
ISSUED AT 330 AM CDT SAT MAY 25 2013

RIDGE RIDING SHORTWAVES INTERACTING WITH A FEED OF GULF MOISTURE AT
850 MB WERE PRODUCING SEVERAL MCS COMPLEXES EARLY THIS MORNING. THE
LEAD COMPLEX THAT FORMED OVER THE EASTERN DAKOTAS FRIDAY AFTERNOON
HAD DISSIPATED INTO MAINLY HIGH BASED SPRINKLES...EXTENDING FROM
WESTERN WI INTO FAR EASTERN IA AND NW IL AT 08Z...AS IT WAS MOVING
AWAY FROM ITS MOISTURE SOURCE AND INTO THE SURFACE RIDGE IN PLACE
OVER THE GREAT LAKES. FURTHER UPSTREAM...SCATTERED HIGH BASED
SHOWERS WERE POPPING UP OVER EASTERN IA AHEAD OF A LOOSELY ORGANIZED
MCS TRYING TO DEVELOP OVER CENTRAL IA ALONG THE NOSE OF A 35-40 KT
LOW LEVEL JET. THE STRONGEST...AND MOST ORGANIZED MCS BY FAR...
ENCOMPASSED MUCH OF EASTERN AND CENTRAL NEB WHERE IT WAS PRODUCING
HEAVY RAIN AS IT WAS PROPAGATING EAST AROUND 30 MPH.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 330 AM CDT SAT MAY 25 2013

THE PRIMARY FOCUS IS TRYING TO PIN DOWN THE TIMING OF INTENSITY OF
RAIN AND THUNDERSTORMS THROUGHOUT. THIS MORNING...SHORT TERM
TRENDS INDICATE WIDESPREAD SHOWERS AND THUNDERSTORMS DEVELOPING OVER
CENTRAL AND S CENTRAL IA TO SPREAD INTO ESPECIALLY THE CENTRAL AND
SOUTHERN FORECAST AREA THROUGH LATE MORNING. THESE WILL LIKELY BE
UNDERGOING A DIURNAL WEAKENING TREND WITH THE WANING OF THE LOW
LEVEL JET AND ASSOCIATED THETAE ADVECTION. THE NEBRASKA COMPLEX AND
POSSIBLE MCV WOULD THEN ARRIVE INTO THE SOUTHERN THIRD OF THE
FORECAST AREA AROUND NOON. THE GFS...NAM AND GEM REFLECT THIS WITH
VORT MAX PUSHING THROUGH THE SOUTHERN HALF OF THE AREA AROUND
MIDDAY...WHICH WOULD BE SUFFICIENT TO CONTINUE WIDESPREAD RAIN AND A
FEW THUNDERSTORMS THERE THROUGH AT LEAST MID AFTERNOON. THIS TIMING
MAY THEN PROVIDE A SEVERAL HOUR PERIOD BREAK BETWEEN SYSTEMS FROM
LATE AFTERNOON THROUGH EARLY EVENING...WHEN THE LOWEST HOURLY POPS
ARE MAINTAINED. LIKELY TO CATEGORICAL POPS ARE THUS CARRIED FOR ALL
BUT THE FAR NORTH AND NORTHEAST FORECAST AREA THAT WILL LIKELY BE ON
THE EDGE OF THESE SYSTEMS TODAY. ANTICIPATING CLOUDS AND WET
CONDITIONS TO PREVAIL...HAVE LIMITED HIGHS TO THE UPPER 50S NORTH TO
MID AND POSSIBLY UPPER 60S IN THE FAR SOUTH.

TONIGHT...THE PRIMARY LOW LEVEL JET IS SHOWN AGAIN FOCUSING TO THE
WEST IN THE PLAINS. HOWEVER...A BROAD BUT SOMEWHAT WEAK SW FLOW AT
850 MB IS SHOWN CONVERGING OVER THE FORECAST AREA TO SUPPORT
SCATTERED SHOWERS AND THUNDERSTORMS THAT WOULD DEVELOP IN THE
EVENING. WILL THEN HAVE A SIMILAR SETUP WHERE ANY MCS THAT DEVELOPS
TO THE WEST MAY MOVE IN LATE AND WILL CARRY CATEGORICAL POPS IN THE
WEST AND SOUTH...DIMINISHING TO HIGH CHANCES IN THE FAR NORTHEAST. A
FEED OF SOMEWHAT HIGHER PW VALUES MAY LEAD TO MORE WIDESPREAD
HEAVIER RAINFALL TOTALS AND HAVE GONE WITH OVERNIGHT QPF IN A RANGE
OF A QUARTER TO HALF OVER MUCH OF THE FORECAST AREA. SOUTHEAST
SURFACE WINDS OUT OF THE GREAT LAKES RIDGE WILL LEAD TO SOME
EVAPORATIVE COOLING...CAUSING TEMPERATURES TO DROP TO LOWS FROM THE
UPPER 40S TO MID 50S. SHEETS

.LONG TERM...(SUNDAY THROUGH FRIDAY)
ISSUED AT 330 AM CDT SAT MAY 25 2013

A RATHER REPETITIVE PATTERN IS SETTING UP THROUGH EARLY TUESDAY
WITH WEAK TROUGHS RIPPLING THROUGH THE UPPER LEVEL RIDGE SETTING
OFF SHOWERS AND THUNDERSTORMS WHICH WILL FOCUS ALONG THE SURFACE
AND 850MB WARM FRONTAL BOUNDARIES. DETAILS ARE RATHER MUDDLED IN
THE MODELS WITH SUBTLE FEATURES...BUT THE FOCUS SEEMS TO BE ON
NOCTURNAL SYSTEMS. THERE IS POSSIBILITY OF REDEVELOPMENT DURING
THE AFTERNOON HOURS...THOUGH DAYTIME PRECIP CHANCES WILL MOST
LIKELY COME FROM LINGERING/DECAYING MCS ACTIVITY.

WHILE PRECIP FROM ANY ONE SYSTEM SHOULD NOT BE TOO SIGNIFICANT...
SOME LOCATIONS COULD SEE 2 INCH 4-DAY TOTALS BY TUESDAY MORNING.
HOWEVER...THERE WILL BE PLENTY OF DRY HOURS IN BETWEEN STORMS.
THE SEVERE THREAT SHOULD BE LIMITED DUE TO LACK OF INSTABILITY AND
STRONG SHEAR...AT LEAST UNTIL MONDAY NIGHT AND TUESDAY WHEN THE
THERMAL-MOISTURE AXIS CENTERS OVER THE AREA PUSHING CAPES UP TO
AROUND 2000 J/KG UNDER INCREASING SHEAR.

FLOW AT THE SURFACE AND ALOFT BECOMES SOUTH-SOUTHWEST DURING THE
DAY TUESDAY AS THE WARM FRONT LIFTS NORTH LEAVING US IN THE WARM
SECTOR THROUGH LATE WEEK. TEMPS WILL WARM NICELY REACHING ABOVE
NORMAL VALUES FOR THIS TIME OF YEAR. IN THE THURSDAY-FRIDAY
TIME...THE GFS AND ECMWF DIFFER SOMEWHAT ON THE DETAILS...BUT A
DEVELOPING PACIFIC TROUGH WILL PUSH INTO THE NORTHERN PLAINS OR
UPPER MIDWEST DRAGGING A COLD FRONT INTO OUR AREA. WITH PLENTY OF
MOISTURE AND INSTABILITY IN PLACE AND LOW-LEVEL CONVERGENCE ALONG
THE FRONT APPEARING PRETTY DECENT IN BOTH MODELS...STORM CHANCES
WILL AGAIN INCREASE.  WOLF

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 101 PM CDT SAT MAY 25 2013

RAIN WILL SLOWLY DIMINISH IN COVERAGE THIS AFTERNOON BUT LIKELY
KEEP SOME RAIN AROUND INTO EARLY EVENING AS UPPER DISTURBANCE
MOVES THROUGH EASTERN IOWA. PERIODS OF MVFR VSBYS 3-5SM POSSIBLE
IN THE RAIN. OTHERWISE...VFR CIGS REST OF THIS AFTN INTO EVE AT
KDBQ AND KMLI... WHILE IFR TO MVFR CIGS AT KBRL AND KCID WHERE
BETTER LOW LEVEL MOISTURE EXISTS. ADDITIONAL SHOWERS AND STORMS
EXPECTED TO REDEVELOP BY MID TO LATE EVENING INTO SUNDAY MORNING
WHICH WILL IMPACT TERMINALS WITH WIDESPREAD IFR TO MVFR CONDITIONS.
WINDS GENERALLY E/SE AROUND 10-15 KTS AND GUSTY.

&&

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

$$

UPDATE...05
SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...WOLF
AVIATION...05