Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 281803
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
103 PM CDT FRI AUG 28 2015

.SYNOPSIS...
ISSUED AT 304 AM CDT FRI AUG 28 2015

TROPICAL...MONSOON MOISTURE WAS LOCATED OVER THE HIGH PLAINS THIS
MORNING. AN UPPER LEVEL FEATURE WAS AIDING IN CYCLOGENESIS OVER
NEBRASKA. A SFC LOW WAS LOCATED IN CENTRAL NEBRASKA. SHOWERS AND
THUNDERSTORMS WERE ONGOING ACROSS THE MID MISSOURI RIVER VALLEY
ASSOCIATED WITH THESE FEATURES. THE SFC LOW AND MONSOON MOISTURE
FROM THE DESERT SOUTHWEST ARE FORECAST TO SLOWLY MOVE EAST THROUGH
THE DAY AND OVERNIGHT TODAY.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 304 AM CDT FRI AUG 28 2015

MAIN FORECAST CONCERN FOR THE SHORT TERM FORECAST ARE WHERE THE
BEST CHANCES OF RAIN AND THUNDERSTORMS ARE TODAY THROUGH TONIGHT.
CURRENT RADAR AND GUIDANCE SUGGESTS THAT WE WILL SEE APPRECIABLE
RAIN IN THE CWA TODAY AND TONIGHT.

MONSOONAL MOISTURE ADVECTING INTO THE AREA HAS SATURATED THE
ATMOSPHERE ACCORDING TO THE 00Z DVN SOUNDING. DEEPER SFC MOISTURE
WILL ADVECT INTO THE AREA THROUGH THE DAY TODAY AS LOW PRESSURE
MOVES THROUGH THE AREA. TWO DAYS AGO THE AMERICAN MODELS HAD
PEGGED AREAS TO OUR SOUTH AND ECMWF WAS FURTHER NORTH. TODAYS RUNS
ARE SOMEWHAT REVERSED. THE ECMWF IS EVEN FURTHER NORTH AND THE
AMERICAN MODELS SEEM TO BE BETTER AT RESOLVING WHAT IS GOING TO
HAPPEN. GUIDANCE SUGGESTS THAT AREAS JUST NORTH OF THE CWA WILL
SEE THE HEAVIEST RAIN.

DECIDED TO BRING THE BETTER RAIN CHANCES FURTHER SOUTH IN LINE
WITH 4KM NAM AND TRENDS FROM THIS YEAR THAT SUGGEST IF LSE IS
PEGGED WITH QPF THEN IT IS USUALLY FURTHER SOUTH. THIS SOUTHERN
TREND WAS BROUGHT UP IN THE DAY SHIFTS AFD AND I THINK THAT A
SOUTHERN PUSH IS MORE REALISTIC. THE H5 WAVE IS RATHER OPEN AND
DOESNT SUGGEST THAT THE SFC LOW MOVES THAT FURTHER NORTH. H85 FLOW
PEGS THE NORTHERN ROW OF COUNTIES FOR THE BEST MASS CONVERGENCE.
THIS PAIRED WITH PWATS NEAR OR EXCEEDING 2 INCHES...WILL RESULT IN
THE HEAVIEST RAIN FALLING FROM HIGHWAY 30 NORTH. 6Z WPC QPF ALSO
PULLS THE BEST QPF SOUTH ACROSS OUR NORTHERN HALF. HAVE GONE WITH
A BLEND WITH 00Z AND 06Z QPF...THIS RESULTS IN UP TO 2 INCHES
ACROSS THE NORTH TO NEAR HALF AN INCH IN THE QCA.. CAPE VALUES ARE
LOW...MOSTLY DUE TO LOW TEMPERATURES. AS A RESULT....HIGH
PRECIPITATION EFFICIENCY IS NOT FORECAST. DECIDED TO HOLD OFF ON A
FFA. MY GUT TELLS ME THAT CATEGORICAL POPS MAY NEEDED TO BE PULLED
EVEN FURTHER SOUTH. WILL MONITOR AND ADVISE THE DAY SHIFT ON THIS.

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 304 AM CDT FRI AUG 28 2015

WARMING TREND TO ABOVE NORMAL TEMPERATURES AND DRY.

LONG TERM FORECAST CONFIDENCE ASSESSMENT...FAIR OR AVERAGE WITH
LIMITED SENSIBLE WEATHER ISSUES.  TWO MAIN ISSUES...ONE IS THE NEED
TO ADD POSSIBLE ISOLATED PRECIPITATION AS FLOW PATTERN SUPPORTS THIS
MAY OCCUR MID TO LATE NEXT WEEK.  THE SECOND ISSUE IS TEMPERATURES
AS LOCAL TOOLS SUGGESTS HIGHS SATURDAY AND SUNDAY MAY BE A FEW
DEGREES TOO HIGH IF CLOUDS HANG AROUND.  LOWS INTO MONDAY AM ALSO
MAY BE TOO MILD IF BL DECOUPLING AND FAIR SKIES OCCUR.

OVERVIEW...INITIALIZATION AND VERIFICATION AT 06Z INDICATE POOR
MODEL QPF (TOO FAR NORTH) AND BL MOISTURE ISSUES TOO DRY FOR A
CHANGE.  TRENDS SUGGEST A 75/25 MIX OF HI-RES ECMWF TO THE TOO
UNSTABLE RUN TO RUN OF THE GFS.

SATURDAY AND SUNDAY...SLOWLY CLEARING SKIES SATURDAY BY LATE
AFTERNOON WITH LINGERING CHANCE OF SHOWERS INTO MID DAY.  HIGHS A
CHALLENGE WITH MOST LOCATIONS RISING INTO THE UPPER 70S WITH SOME
SUNSHINE BY MID PM.  SATURDAY NIGHT...WINDS TO BECOME LIGHT WITH
MINS POSSIBLY STILL A FEW DEGREES TOO MILD WITH PATCHY LIGHT FOG A
RISK FOR LATER SHIFTS.  SUNDAY...MOSTLY SUNNY AND WARMER WITH HIGHS
IN THE LOWER 80S AND LIGHT WINDS AND SEASONABLY HUMID.  SUNDAY NIGHT
SUGGEST WITH LIGHT WINDS GOOD DECOUPLING AND FOR LOWS TO BE A FEW
DEGREES COOLER THAN FORECAST WITH A DECENT RISK OF FOG FOR LATER
SHIFTS TO REASSESS.

MONDAY THROUGH THURSDAY...RIDGING AND SOUTH WINDS OF 5 TO 10 KTS AND
LOTS OF SUNSHINE SUGGESTS VERY WARM TO HOT AND HUMID.  HIGHS SHOULD
PER LOCAL TOOLS BE MOSTLY IN THE UPPER 80S WITH SOME READINGS AROUND
90 DEGREES.  HEAT INDEX VALUES MAY REACH INTO THE LOWER 90S FOR AT
LAST A FEW HOURS.  MINS MOSTLY IN THE MID 60S WITH RISK OF FOG
TOWARD SUNRISE.  FLOW PATTERN MAY ALLOW FOR MOISTURE TO KICK OF SOME
PATCHY PRECIPITATION OF SHOWERS OR A STORM FOR LATER SHIFTS TO
RECONSIDER.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1255 PM CDT FRI AUG 28 2015

STORM SYSTEM OVER IA WILL SHIFT EAST TOWARD LAKE MICHIGAN BY THE
END OF THE TAF CYCLE. THIS SYSTEM WILL BRING WIDESPREAD
RAIN/SHOWERS TO AREAS NORTH OF I-80...WITH PERIODIC BANDS OF
SHOWERS SOUTH OF I-80. ISOLD STORMS WILL ALSO BE POSSIBLE.
CONDITIONS WILL GENERALLY RANGE FROM VFR TO MVFR IN THE
PRECIPITATION...WITH ISOLD IFR VSBYS POSSIBLE IN STRONGER SHOWERS
AND ISOLD STORMS. TONIGHT...WILL CONTINUE WITH WIDESPREAD RAIN
OR SHOWERS NORTH OF I-80 AND PERIODIC BANDS OF SHOWERS SOUTH OF
I-80... WITH GENERALLY VFR TO MVFR CONDITIONS. WITH CONTINUED
MOISTENING AND BL COOLING AND LIGHT WINDS DO ANTICIPATE
DEVELOPMENT OF MORE WIDESPREAD MVFR TO IFR CONDITIONS IN LOW
CLOUDS AND FOG OVERNIGHT AND SATURDAY AM...ESPECIALLY WEST OF THE
MISSISSIPPI RIVER.

&&

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

$$

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


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