Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 300508
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1208 AM CDT SUN AUG 30 2015

.SYNOPSIS...
ISSUED AT 349 PM CDT SAT AUG 29 2015

WEAK SURFACE LOW EARLIER IN THE VICINITY OF THE QUAD CITIES
CONTINUES TO WEAKEN EVOLVING INTO ELONGATED TROUGH AT MID
AFTERNOON. ABUNDANT LOW LEVEL MOISTURE (AIDED BY RECENT HEAVY
RAINFALL NORTH OF I-80) COUPLED WITH WEAK LOW LEVEL FLOW AND
INVERSION HAS MAINTAINED WIDESPREAD STRATUS DECK. THIS CLOUD
COVER WAS HOLDING TEMPS DOWN IN THE 70S MOST LOCATIONS...WITH
A FEW SITES AROUND 80 FAR SOUTH WHERE SOME PEEKS OF SUNSHINE
HAVE BEEN OBSERVED. DEPARTING WEAK SURFACE TROUGH WILL GIVE WAY
TO WEAK RIDGE OF HIGH PRESSURE OVER THE NEXT 24 HOURS... WHICH
WILL MEAN A RETURN OF DRY CONDITIONS AND SUNSHINE FOR SUNDAY WITH
TEMPS REBOUNDING TO NEAR NORMAL.

&&

.SHORT TERM...(THIS EVENING THROUGH SUNDAY)
ISSUED AT 349 PM CDT SAT AUG 29 2015

MAIN FOCUS IS WITH CLOUD TRENDS AND IMPACT ON TEMPS...AND
POTENTIAL FOR DENSE FOG.

MAINTAINED SOME SMALL PRECIP CHANCES REST OF THIS AFTERNOON
THROUGH SUNSET FOR AREAS S/E OF QUAD CITIES WITHIN WEAK LOW LEVEL
CONVERGENCE AXIS.

THE WEAK SURFACE TROUGH WILL SLOWLY DEPART AND BE REPLACED BY
SURFACE RIDGING FROM THE GREAT LAKES OVER THE NEXT 24 HOURS.
WEAK SURFACE FLOW AND ABUNDANT MOISTURE COUPLED WITH
STRENGTHENING SUBSIDENCE INVERSION GENERALLY SUPPORT MORE
CLOUDS THAN CLEARING FOR TONIGHT AND HAVE ADJUSTED TOWARD THIS
SCENARIO AND ALSO NUDGED UP MINS WITH GENERALLY LOWER TO MIDDLE
60S. SATELLITE AND OBS DO SHOW SOME HOLES CONTINUING TO DEVELOP
IN THE CLOUDS OVER PORTIONS OF MN AND NORTHERN IA WITH THIS
LIKELY BEING SUBSIDENCE INDUCED CLEARING IN WAKE OF PASSING
UPPER LEVEL DISTURBANCE INTO EASTERN IA ATTIM. BUT BEING LATE
PM AND NO REAL DRY PUSH NOT CONFIDENT WILL SEE MUCH OF THIS
CLEARING INTO CWA... BUT WILL NEED TO BE WATCHED AS WILL ALSO
HAVE IMPACT ON TEMPS. WITH THE WEAK FLOW AND ABUNDANT LOW LEVEL
MOISTURE DO ANTICIPATE AREAS OF FOG DEVELOPING LATE THIS EVENING
AND OVERNIGHT... WITH POTENTIAL FOR SOME DENSE FOG THOUGH
COVERAGE AND MAGNITUDE OF FOG COULD BE FUNCTION OF CLOUD COVER/
TRENDS.

SUNDAY...EXPECT GRADUAL BURNING OFF OF ANY FOG AND STRATUS WITH
SKIES BECOMING MOSTLY SUNNY DURING THE AFTERNOON. THIS WILL LEAD
TO A WARMER DAY WITH NOTICEABLE HUMIDITY... WITH HIGHS IN THE
LOWER TO MIDDLE 80S.

.LONG TERM...(SUNDAY NIGHT THROUGH SATURDAY)
ISSUED AT 349 PM CDT SAT AUG 29 2015

OVERVIEW...BUILDING AND PERSISTENT UPPER-LEVEL RIDGE OVER THE
CENTRAL U.S. WILL LEAD TO ABOVE AVERAGE TEMPERATURES AND HUMID
CONDITIONS THROUGH THE EXTENDED PERIOD. OVERALL CHANCES FOR RAIN
ARE VERY LOW.

SUNDAY NIGHT...LIGHT WINDS AND RESIDUAL LOW-LEVEL MOISTURE IN AREAS
THAT RECEIVED RAIN LAST FRIDAY/FRIDAY NIGHT HAVE A CHANCE FOR FOG
DEVELOPMENT. TOO EARLY TO DETERMINE EXTENT AND SEVERITY AT THIS
POINT SO HAVE MENTION OF PATCHY FOG IN THE FORECAST FOR NOW.

MONDAY AND TUESDAY...EXPECT WARMER TEMPS INTO THE MIDDLE/UPPER 80S
AS UPPER-LEVEL RIDGE BUILDS OVER THE MIDWEST. 1000-500MB THICKNESS
VALUES ARE FORECAST TO HOVER NEAR 576 DAM WITH 850MB TEMPS IN THE
UPPER TEENS/NEAR 20 C.

WEDNESDAY...A SHORTWAVE TROUGH FROM REMNANT MONSOONAL CONVECTION MAY
TRAVERSE THE MIDWEST BUT MODELS HAVE TRENDED IT A LITTLE FURTHER
NORTH OVER PAST FEW RUNS. REMOVED SLIGHT CHANCE POPS FROM THE
FORECAST. NO SIGNIFICANT CHANGE IN 1000-500MB THICKNESSES OR 850MB
TEMPS MEANS HIGHS SHOULD STILL AVG IN THE MID/UPPER 80S.

THURSDAY AND FRIDAY...MODELS AGAIN INDICATE 850MB TEMPS IN THE UPPER
TEENS CELSIUS. CURRENT FORECAST HAS MID/UPPER 80S ON AVG ACROSS THE
CWA. RAW MODELS SUCH AS THE ECMWF/GFS HAVE COME DOWN TO THE LOWER
90S WHICH MAKES MORE SENSE BASED ON 850MB TEMPS BUT STILL MAY BE TOO
HIGH. HUMID CONDITIONS AND A LOWER SEPTEMBER SUN ANGLE SUPPORT A
TEMP FORECAST SLIGHTLY BELOW THE HIGHER RAW MODEL DATA.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1207 PM CDT SAT AUG 29 2015

LINGERING LOW LEVEL MOISTURE AND LIGHT WINDS UNDER AN APPROACHING
SURFACE RIDGE WAS LEADING TO WIDESPREAD LOW CLOUDS AND DENSE FOG
OVER THE REGION THIS EVENING. WIDESPREAD IFR CONDITIONS ARE
LIKELY TO DETERIORATE TO VLIFR AT MOST SITES BY 07Z TO 08Z...AND
PERSIST UNTIL WELL AFTER SUNRISE. THE CURRENT TIMING OF CONDITIONS
IMPROVING TO IFR AS CIGS LIFT AND VISIBILITIES IMPROVE AROUND MID
MORNING IS LOW CONFIDENCE...BUT ALL SITES SHOULD SEE VFR
CONDITIONS BY EARLY AFTERNOON WITH CLEARING SKIES AND VERY LIGHT
SOUTHEAST WINDS. CONDITIONS WILL BE FAVORABLE FOR FOG AGAIN SUNDAY
EVENING....BUT THERE IS NOT ENOUGH CERTAINTY IN TIMING OR
INTENSITY TO INCLUDED IN THE CURRENT FORECASTS.

&&

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

$$

SYNOPSIS...MCCLURE
SHORT TERM...MCCLURE
LONG TERM...UTTECH
AVIATION...SHEETS



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