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000
FXUS63 KDVN 201630
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1130 AM CDT MON MAY 20 2013

.UPDATE...
ISSUED AT 1104 AM CDT MON MAY 20 2013

QUICK ASSESSMENT ON THIS MORNINGS UPPER AIR ANALYSIS AND WHAT IS
TAKING PACE CURRENTLY...SEEMS THERE MAY BE A DELAY TO LATER THIS
AFTERNOON AND EARLY EVENING. CURRENT TEMPS IN THE LOW TO MID 70S
WITH SFC DPTS MAINLY IN THE LOW 60S WILL STILL TAKE TIME TO
IMPROVE UPON...ESPECIALLY WITH BETTER SFC MOISTURE POOLED ALONG
OUTFLOW BOUNDARY ACRS CENTRAL MO ATTM. THE LOCAL AREA UNDER A H85
MB AND H7 MB LULL IN MOISTURE AS WELL. MID AND UPPER JET MAX/S
ACRS THE GRT BSN AND SHIFTING INTO THE SOUTHWESTERN PLAINS THIS
MORNING WILL NOT NOSE UP ACRS THE CWA UNTIL AFTER 20Z-21Z THIS
AFTERNOON. IF SFC DPTS ONLY RECOVER INTO THE MID 60S...THE 12Z NAM
AND GFS PROGGED CAPES OF 1500-2000 J/KG MAY BE TOO HIGH. ALSO HIGH
TEMPS MAY BE MORE IN THE WAY OF LOW TO MID 80S AS OPPOSED TO MID
TO UPPER 80S THIS AFTERNOON. SFC WINDS CURRENTLY SOUTH AND MAINLY
SOUTHWESTERLY...THUS WITHOUT AND LLVL BACKING TO THE SOUTHEAST THE
LOWER LEVEL HELICITIES AND SHEAR DON/T APPEAR AS IMPRESSIVE AS
WHAT MAY BE EARLIER THOUGHT. BUT THERE APPEARS TO BE DECENT DEEPER
LAYER SPEED SHEAR WITH UNIFORM VERTICAL PROFILES. LCL LEVELS MAY
NOT BE AS LOW AS WHAT THE SHORT RANGE MODELS DEPICT IN THE
SOUTHEAST THIRD/1500-2000 FT AGL/ THIS AFTERNOON AS WELL LIMITING
A POSSIBLE TORNADIC THREAT. THUS ALL IN ALL...LESS INSTABILITY
BUT STILL STRONG KINEMATICS/SHEAR SUGGEST A THREAT FOR LARGE HAIL
AND DAMAGING DOWNBURST WINDS WITH STILL THE POSSIBILITY OF
SUPERCELL TYPE DISCRETE STORMS THIS AFTERNOON...BUT MAY BE LESS
WIDESPREAD THEN YESTERDAY. THE SOUTHEAST THIRD OF THE CWA MOST AT
RISK OF SVR STORMS THIS AFTERNOON. STILL CAN/T RULE OUT ISOLATED
TORNADOES AND ANY WATCH THAT DOES COME OUT WILL PROBABLY STILL BE
A TOR WATCH FOR THE LOCAL AREA. SECOND ROUND OF STORMS ALONG THE
MAIN FRONT ITSELF...CURRENTLY ACRS FAR WESTERN IA...MAY SWEEP ACRS
THE AREA FROM THE WEST NOT UNTIL MID EVENING. WILL STILL HAVE TO
BE VERY MUCH ON GUARD AND WATCH TRENDS THROUGH THE AFTERNOON.

12

UPDATE ISSUED AT 624 AM CDT MON MAY 20 2013

THE NOCTURNAL MCS WILL CONTINUE TO SLOWLY DISSIPATE THROUGH MID
MORNING AND MOST OF THE AREA SHOULD SEE DRY CONDITIONS THROUGH MID
DAY. AFTER MID DAY NEW CONVECTION WILL RAPIDLY DEVELOP ONCE
CONVECTIVE TEMPERATURE IS ACHIEVED.

DATA INDICATES DISCRETE CELLS WILL INITIALLY DEVELOP THAT EVOLVE
INTO ONE OR MORE LINEAR MCS EVENTS BY EARLY EVENING AND WILL
CONTINUE INTO THE LATE EVENING.

THERE IS STILL A GOOD POTENTIAL FOR SEVERE STORMS THIS AFTERNOON
AND EVENING. THE MORNING UA FLIGHT THAT IS UNDERWAY SHOWS
CONSIDERABLE SPEED SHEAR UP THROUGH 2KFT AGL. THE KEY TO
EVERYTHING WILL BE HOW THE UPPER JET ROTATING UP FROM THE SOUTHERN
PLAINS WILL INTERACT WITH LOWER LEVEL FEATURES.

BASED ON THE PROGGED PLACEMENT OF THE JET STRUCTURE AND
INSTABILITY AXIS...SEVERE STORMS APPEAR TO BE PROBABLE DURING THE
AFTERNOON AND EVENING HOURS. IF SEVERE STORMS OCCUR...DAMAGING
WINDS AND LARGE HAIL ARE A GIVEN. BASED ON PROGGED SHEAR PROFILES
AND BUOYANCY WITH INPUT FROM THE IN PROGRESS 12Z UA FLIGHT...
TORNADOES ARE ALSO POSSIBLE. IF TORNADOES DEVELOP WITH THE
DISCRETE CELLS...SIGNIFICANT TORNADOES MAY BE POSSIBLE.   ..08..

&&

.SYNOPSIS...
ISSUED AT 304 AM CDT MON MAY 20 2013

06Z SFC ANALYSIS HAS A SYNOPTIC LOW NEAR KMBG WITH THE STATIONARY
FRONT RUNNING EAST THROUGH WISCONSIN AND LOWER MICHIGAN. MESOSCALE
LOWS WERE NEAR KFSD...KBVN...AND KCSM. NUMEROUS OUTFLOW BOUNDARIES
RAN FROM ILLINOIS BACK THROUGH MISSOURI. DEW POINTS WERE IN THE 50S
AND 60S ACROSS THE MIDWEST.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 304 AM CDT MON MAY 20 2013

TODAY WILL BE QUITE INTERESTING. MESOSCALE PROCESSES WILL DRIVE THE
SENSIBLE WX AND CONCEPTUALLY...THERE IS A GOOD PROBABILITY OF SEEING
SEVERE STORMS THIS AFTERNOON AND EVENING.

MCS AND LIFT TOOLS SUGGEST THE BULK OF THE MCS MOVING ACROSS MISSOURI
WILL REMAIN SOUTH OF THE AREA. HOWEVER...VORT MAXES HELPING TO DRIVE
THIS MCS WILL PUSH DECAYING SHRA AND SOME TSRA INTO THE CWFA THROUGH
SUNRISE WITH ACTIVITY DISSIPATING DURING THE MORNING.

THERE SHOULD BE A FEW HOURS OF QUIET WX FROM MID TO LATE MORNING
UNTIL CONVECTIVE TEMPERATURE IS ACHIEVED. ONCE THIS OCCURS...NEW
CONVECTION WILL DEVELOP DURING THE AFTERNOON AND BUILD INTO ONE OR
MORE SEVERE MESOSCALE CONVECTIVE COMPLEXES BY EARLY EVENING.

THE OVERALL PLACEMENT OF THE JET STRUCTURE AND INSTABILITY AXIS
POINT TO SEVERE STORMS DEVELOPING DURING THE AFTERNOON. LARGE HAIL
AND DAMAGING WINDS ARE A GIVEN. THE SHEAR PROFILES AND BUOYANCY IS
ALSO FAVORABLE FOR TORNADOES...POSSIBLY SIGNIFICANT.

BY LATE EVENING AND OVERNIGHT...STORM ACTIVITY WILL BE ON THE
DECREASE AS THE ATMOSPHERE COOLS.

08

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 304 AM CDT MON MAY 20 2013

TURNING COOLER AND UNSETTLED WITH PROBABLY COOL RAINS AGAIN THIS NEXT
WEEKEND.

OVERVIEW...INITIALIZATION AND VERIFICATION ON LARGER SCALES...OR
SYNOPTIC SCALE ARE GOOD BUT ALL SOLUTIONS POOR TO VERY POOR ON
PRECIPITATION/MOISTURE/CLOUDS. AGAIN HEAVY USE OF CONCEPTUAL FORCING
TOOLS WHICH HAS AIDED PAST SEVERAL DAYS. THIS SUPPORTS MORE SHOWERS
AND STORMS TUESDAY TURNING COOLER WITH CLOUDS AND SHOWERS WEDNESDAY.
RISK OF SEVERE TUESDAY IS QUESTIONABLE BASED ON CONVECTION AND NEXT
WAVE INTERACTIONS LATER ON TUESDAY. PREFER A 60/40 MIX OF FORCING
OF HI-RES ECMWF AND NAM-WRF INTO DAY 4...THEN A 50/50 OF HI-RES
ECMWF AND GFS DAY 4 AND BEYOND.

TUESDAY...POOR CONFIDENCE IN FORECAST POPS AS NEXT 24 HOURS WILL
IMPACT EVOLUTION OF UPPER LOW AND PROGRESS OF COOL FRONT AND
ASSOCIATED AMOUNT OF CLEARING/CLOUDS. UPPER JET SUPPORTS LIGHTER AND
LOWER POPS WEST WITH RISK OF LINGERING WAVE OF SHOWERS AND STORMS
THAT SHOULD TEND TO STAY BELOW SEVERE LEVELS. HIGHS 75 TO 80 FROM
NW TO SE. MINS MID 50S NW TO THE LOWER 60S SE SECTIONS.

WEDNESDAY...CLOUDY AND COOLER WITH RAIN OR RAIN SHOWERS. HIGHS IN
THE NORTH MAY NEED LOWERING WITH LOW CLOUDS AND POSSIBLY EVEN
DRIZZLE WITH COOL NORTH WINDS ARRIVING FROM NORTH TO SOUTH DURING
THE DAY A BIT EARLIER IN THE FORECAST FOR LATER SHIFTS. WEDNESDAY
NIGHT...LOW CLOUDS AND POSSIBLY LIGHT RAIN AND PROBABLY AREAS OF
DRIZZLE WITH MINS IN THE 50S.

THURSDAY AND FRIDAY...BELOW NORMAL TEMPERATURES MOSTLY IN 65 TO
72 DEGREE RANGE. CLOUDS WILL CLEAR IN THE AFTERNOON FROM NORTH TO
SOUTH AS CANADIAN HIGH PRESSURE MOVES IN. THURSDAY NIGHT...CLEAR
AND COOL WITH MINS PROBABLY MANY LOCATIONS 3+ DEGREES TOO MILD WITH
LOWER TO MIDDLE 40S SUGGESTED OVER NORTH SECTIONS. FRIDAY...SUNNY
AND COOL WITH LIGHT NE WINDS.

SATURDAY AND SUNDAY...WESTERLY WINDS TO UPGLIDE OVER COOL AIRMASS
THAT PRIMES THE REGION FOR COOL HIGHS DUE TO GOOD EVAPORATIVE
COOLING AND LIKELY RAIN AND ISOLATED STORMS POSSIBLE IN SOUTH AND
WEST SECTIONS. CHANCE POPS FOR NOW WILL LIKELY BE RAISED WITH
TIMING ISSUES BETTER CLARIFIED. ANOTHER MODERATE TO LOCALLY LOWER
END HEAVY RAIN EVENT WITH MOST AREAS PICKING UP .5 TO 1+ INCHES.

NICHOLS

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 624 AM CDT MON MAY 20 2013

NOCTURNAL CONVECTION IS DISSIPATING ACRS IOWA/ILLINOIS AND SHOULD
BE GONE BY 15Z/20. MORNING UPPER AIR FLIGHT HAS 40 KTS JUST OFF
THE SURFACE SO LLWS WAS INCLUDED IN ALL TAFS UNTIL THE INVERSION
BREAKS AROUND 15Z/20. OTHERWISE VFR CONDITIONS WILL BE SEEN
THROUGH 18Z/20. AFT 18Z/20 NEW CONVECTION WILL DVLP RAPIDLY WITH
SEVERE STORMS POSSIBLE. PROBABILITY IS HIGH THAT MVFR/IFR
CONDITIONS WITH G40 KTS WILL BE SEEN IF A TSRA AFFECTS A TAF SITE.
CONVECTION WILL CONTINUE PAST 00Z/21 WITH INCREASING PROBABILITY
OF MVFR CONDITIONS.                       ..08..


&&

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

$$

UPDATE...12
SYNOPSIS...08
SHORT TERM...08
LONG TERM...NICHOLS
AVIATION...08