Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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FXUS63 KDVN 241132 AAA
AFDDVN

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
632 AM CDT SUN MAY 24 2015

.UPDATE...
ISSUED AT 631 AM CDT SUN MAY 24 2015

RAIN HAS OVERSPREAD THE CWA FASTER THAN PREVIOUSLY THOUGHT. THE
LINE OF SHOWERS MATCHES WELL TO THE MOISTURE TRANSPORT VECTOR.
BELIEVE THAT WESTERN ZONES WILL SEE THE MOST RAIN THIS MORNING.
THE RAIN BAND WILL SLOWLY MOVE TO THE EAST.M HRRR MODEL RUNS
SUGGESTS THAT THIS AREA OF PRECIP WILL MOVE EAST THROUGH THE DAY
UNTIL THIS AFTERNOON. AS SUCH...HAVE INCREASED PRECIP CHANCES AND
TRIED TO BETTER TIME THE MOVEMENT OF THE RAIN THROUGH THE CWA AND
TAF SITES.

&&

.SYNOPSIS...
ISSUED AT 359 AM CDT SUN MAY 24 2015

EARLY THIS MORNING...A HEAVY RAINFALL EVENT WITH SIGNIFICANT FLASH
FLOODING AND SEVERE WEATHER IS OCCURRING ACROSS PORTIONS OF THE
CENTRAL AND SOUTHERN GREAT PLAINS. A WIDE OPEN GULF AND WEAK
UPPER LEVEL FLOW WAS LEADING TO THE DEVELOPMENT OF RAIN AND
THUNDERSTORMS ACROSS THAT AREA. CLOSER TO HOME...RAIN ASSOCIATED
WITH THE STORMS TO OUR SOUTH IS FINALLY MAKING ITS WAY INTO OUR
AREA. THIS RAIN SHOULD CONTINUE TO SPREAD ACROSS THE AREA THIS
MORNING.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 359 AM CDT SUN MAY 24 2015

MAIN FORECAST CONCERN FOR THE SHORT TERM IS THE RAIN AND IMPACTS
ASSOCIATED WITH POTENTIAL HEAVY RAIN ACROSS THE AREA.

OVERALL...THE GULF IS OPEN AND H5 FLOW IS PERFECT FOR ADVECTING
LARGE AMOUNTS OF PW INTO THE AREA. GEFS M-CLIMATE DATA SUGGESTS
THAT PROGGED PWATS WILL BE IN THE 99 PERCENTILE. THERE WILL BE NO
LACK OF MOISTURE WITH THIS SYSTEM. THE MAIN FORECAST CHALLENGE IS
TIMING AND DETERMINING THE AREAS THAT HAVE THE BEST CHANCES FOR
POSSIBLE FLOODING.

CURRENT THINKING IS THAT WE WILL HAVE RAIN THROUGH THE EARLY
AFTERNOON HOURS. HIRES GUIDANCE SUGGESTS THAT WE HAVE SOME DOWN
TIME THIS AFTERNOON BEFORE A WAVE MOVES THROUGH THE AREA AND LEADS
TO THE DEVELOPMENT OF SHOWERS AND ISOLATED THUNDERSTORMS THIS
AFTERNOON AND EVENING.

MOISTURE TRANSPORT VECTORS FAVOR AREAS TO OUR WEST THROUGH LATE
MORNING. THE VECTORS THEN SHIFT TO THE EAST AND PAINT OUR WESTERN
ZONES FOR SIGNIFICANT MOISTURE TRANSPORT. THROUGH THE REST OF THE
SHORT TERM. THESE VECTORS SLOWLY TRANSLATE THE BULLS THROUGH OUR
CWA.

UNCERTAINTY REMAINS IN OVERALL FLASH FLOODING COVERAGE. WITH PW
VALUES AT THE TOP OF THE SPECTRUM...ANY CONVECTIVE ELEMENTS THAT
FORM WILL BE VERY EFFICIENT AT PUMPING OUT HEAVY RAIN. AREAS TO
OUR SOUTH IN THE STRATIFORM SHIELD ARE SEEING OVER AN INCH OF RAIN
FROM THOSE SHIELDS. WHAT MAKES THIS A TRICKY FORECAST IS THE
OVERALL LACK OF INSTABILITY. WITHOUT INSTABILITY OVERALL RAINFALL
RATES SHOULD STAY LOW ENOUGH THAT RUNOFF DOES NOT BECOME A
CONCERN. I CANNOT RULE OUT THUNDER COMPLETELY...THIS MEANS THAT
ANY THUNDERSTORM THAT CAN FORM WILL HAVE THE POTENTIAL TO LEAD TO
HEAVY RAINFALL AND RAIN RATES THAT COULD LEAD TO FLOODING. IF
MODELS ARE UNDER FORECASTING THE INSTABILITY...OUR THREAT FOR
FLASH FLOODING WILL GO UP. ANTECEDENT CONDITIONS DO NOT LEND
THEMSEMLVES WELL TO FLASH FLOODING AS WELL. OVERALL THUNDERSTORM
COVERAGE WILL BE LOW...SO A FLASH FLOOD WATCH WILL NOT BE ISSUED
ON THIS SHIFT.

THIS FORECAST IS FLUID...ANY CHANGES IN HOURLY TRENDS COULD LEAD
TO A DIFFERENT OUTCOME. TODAY IS A DAY TO NOT IGNORE THE WEATHER
AS ANY CHANGES COULD LEAD TO AN INCREASED OR DECREASED THREAT OF
FLASH FLOODING.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 359 AM CDT SUN MAY 24 2015

CONTINUED ACTIVE/UNSETTLED WITH PERIODIC BOUTS OF PCPN AND TEMPS
NEAR TO SLIGHTLY ABOVE NORMAL.

MEMORIAL DAY AND MONDAY NIGHT... PCPN CHANCES WILL BE DIMINISHING
FROM SOUTHWEST TO NORTHEAST IN THE MORNING AS AN UPPER LEVEL
SHORTWAVE LIFTS INTO THE GREAT LAKES REGION. FOR MEMORIAL DAY
AFTERNOON MODELS SHOW HEIGHTS ALOFT INCREASING AND THIS COMBINED
WITH DRY ADVECTION ON VEERED SOUTHWEST FLOW AND SOME SUGGESTION
OF A BIT OF AN ELEVATED EML PER NAM/GFS BUFR SOUNDINGS SHOULD
MEAN A GENERALLY DRY AFTERNOON. WINDS SHOULD BE RATHER GUSTY FROM
SOUTHWEST AT 15-30+ MPH DUE TO SOME TIGHTENING OF PRESSURE GRADIENT
AND MIX DOWN OF DRYING COLUMN. WITH THE GUSTY SOUTHWEST WINDS AND AT
LEAST PARTIAL SUNSHINE EXPECT HIGHS WIDESPREAD AROUND 80 OR IN THE
LOWER 80S... WITH POTENTIAL FOR FEW MID 80S SOUTHWEST CWA IF MORE
SOLAR INSOLATION. MONDAY NIGHT... PCPN CHANCES WILL BE INCREASING
AHEAD OF WEAK COOL FRONT AND PLAINS SHORTWAVE. BULK SHEAR 0-6 KM OF
30-35 KTS WITH 0-4 KM MUCAPE 1500-2000+ J/KG PARAMETERS SUPPORTIVE
OF AT LEAST ISOLD SEVERE STORM POTENTIAL. THE CHALLENGE IS WHETHER
CONVECTION CAN GROW UPSCALE IN MCS AS SOME MODELS DEPICT SEVERAL MCS
PARAMETERS/INGREDIENTS TO AT LEAST ENTERTAIN POSSIBILITY OF
UPSCALE GROWTH FROM WESTERN INTO CENTRAL IA WHICH IF OCCURS WOULD
PROPAGATE EASTWARD INTO PORTIONS OF CWA LATE MONDAY EVENING AND
OVERNIGHT WITH ROUND OF HEAVY RAIN AS LAYER PWATS SURGE TO OVER 1.5
INCHES. ENOUGH UNCERTAINTY ON THIS OCCURRING TO CAP POPS IN HIGH
CHANCE CATEGORY ATTIM FOR MONDAY NIGHT.

TUESDAY AND TUESDAY NIGHT... CONTINUE TO FOCUS ON TUESDAY AS WET DAY
WITH UPPER LEVEL SHORTWAVE LIFTING THROUGH THE UPPER MIDWEST IN
SOMEWHAT OF A NEGATIVE TILT FASHION. AT LEAST SOME ISOLD SEVERE
POTENTIAL POSSIBLE EASTERN CWA AHEAD OF WEAK FRONT WITH 0-6 KM BULK
SHEAR 30-35 KTS. THE MAIN CHALLENGE WILL BE HOW MUCH INSTABILITY
WILL DEVELOP DURING THE AFTERNOON AND EVENING IN PRESENCE OF LIKELY
CONVECTIVE DEBRIS.

WEDNESDAY AND WEDNESDAY NIGHT... THIS PERIOD IS TRENDING DRIER WITH
WEAK COOL FRONT SETTLING SOUTH OF CWA AND WEAK SURFACE RIDGING
BUILDING IN. HIGHS A BIT WARMER AND MAINLY UPPER 70S TO NEAR 80 WITH
AT LEAST PARTIAL SUNSHINE.

THURSDAY THROUGH SATURDAY... ACTIVE PATTERN APPEARS SET TO RETURN
DURING THE LATTER HALF OF THE WEEK INTO NEXT WEEKEND AS SOUTHEAST
ATLANTIC RIDGE STRENGTHENS WITH GULF MOISTURE INCREASING ON WESTERN
PERIPHERY AHEAD OF NEXT ROUND OF LEE SIDE TROUGHING AND SOUTHWEST
FLOW ALOFT. DUE TO TIMING UNCERTAINTIES UNFORTUNATELY HAVE SEVERAL
PERIODS OF HIGH CHANCE POPS FROM THURSDAY NIGHT THROUGH SATURDAY.

OVERALL... WITH ACTIVE REGIME FEATURING POTENTIAL FOR A FEW PERIODS
OF HEAVY RAIN DURING THE PERIOD WILL HAVE TO WATCH AREA RIVERS IN
THE COMING WEEK AHEAD. ALSO...WILL NEED TO KEEP EYE ON ANY HEAVY
RAINS INTO CENTRAL IA FOR POSSIBLY SOME RISES ON A FEW EASTERN IA
TRIBS DUE TO ROUTING OF SOME WATER. NCRFC ENSEMBLE QPF SCENARIOS
SHOW POTENTIAL FOR SOME TRIBUTARY LOCATIONS NEARING FLOOD STAGE
TOWARD LATE IN THE WEEK AND NEXT WEEKEND...MAINLY THE WAPSIPINICON
AT DEWITT...IOWA RIVER AT MARENGO...SKUNK AT SIGOURNEY.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)
ISSUED AT 631AM CDT SUN MAY 24 2015

MESSY DAY ON THE AVIATION DESK TODAY. IN THE NEXT SIX HOURS MOST
OF THE SITES WILL SEE RAIN AND THEN IT START TO TAPER OFF. AT THAT
TIME SOME BR COULD DEVELOP AT THE TAF SITES. SOME SITES TO THE
WEST ARE ALREADY SHOWING IFR CEILINGS THIS AM. WILL TEMPO IF IFR
SHOWS UP AT CID AS I THINK IT WILL BE TEMPORARY. LATER THIS
AFTERNOON THUNDERSTORMS COULD RETURN WITH THE RAIN. WESTERN TAF
SITES ARE FORECAST TO HAVE CIGS CRASH TO IFR AND POSSIBLY LIFR.
RAIN SHOULD CONTINUE OVERNIGHT THROUGH THE TAF PERIOD.

&&

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

$$

UPDATE...GIBBS
SYNOPSIS...GIBBS
SHORT TERM...GIBBS
LONG TERM...05
AVIATION...GIBBS


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