Expires:No;;658734 FXUS63 KDVN 251202 AFDDVN AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE QUAD CITIES IA IL 702 AM CDT SAT MAY 25 2013 .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 12Z TAFS THROUGH 12Z SUNDAY MORNING) ISSUED AT 700 AM CDT SAT MAY 25 2013 A LARGE COMPLEX OF SHOWERS AND THUNDERSTORMS OVER CENTRAL AND WESTERN IA AT SUNRISE WILL MOVE THROUGH THE EASTERN IA TERMINALS THIS MORNING. THIS COMPLEX WILL GRADUALLY WEAKEN TO LIGHT RAIN AS IT TRANSITIONS EASTWARD...CAUSING THUNDERSTORMS TO DIMINISH TO LIGHT RAIN WITH PREVAILING MVFR CONDITIONS FROM LATE MORNING THROUGH EARLY AFTERNOON. LATEST FORECASTS THEN MAINTAIN A BREAK WITH VFR WEATHER BETWEEN SYSTEMS FROM MID AFTERNOON INTO EARLY EVENING... FOLLOWED BY ANOTHER NIGHTTIME COMPLEX OF THUNDERSTORMS. WHILE CONFIDENCE OF THUNDERSTORMS AFFECTING THE MLI AND BRL SITES IS HIGH FOR LATE TONIGHT...STORMS WILL NOT LIKELY AFFECT THE ENTIRE 6 TO 8 HOUR OUTLOOK PERIOD AS ADVERTISED. LIKEWISE...THE BROAD BRUSHED OUTLOOK PERIODS AT DBQ AND CID WILL LIKELY BE FURTHER REFINED IN LATER FORECASTS AND THUNDERSTORMS CANNOT BE RULED OUT AT THESE LOCATIONS. SHEETS && .DVN WATCHES/WARNINGS/ADVISORIES... IA...NONE. IL...NONE. MO...NONE. && $$ UPDATE...SHEETS SYNOPSIS...SHEETS SHORT TERM...SHEETS LONG TERM...WOLF AVIATION...SHEETS