Area Forecast Discussion
Issued by NWS Quad Cities, IA IL

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000
FXUS63 KDVN 251637
AFDDVN

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1137 AM CDT MON AUG 25 2014

.UPDATE...
ISSUED AT 1121 AM CDT MON AUG 25 2014

HAVE UPDATED TO BUMP UP POPS AND EXTEND THROUGH THE AFTERNOON AS
LOOKING LIKELY TO SEE AT LEAST SCATTERED ACTIVITY PERSIST ALL
DAY MOSTLY NORTH OF I-80 WITH MORE ISOLATED OVER SOUTHEAST IA.
THIS ACTIVITY WILL BE AIDED BY WEAK SURFACE LOW NORTHEAST OF
DES MOINES AND INTERACTING WITH OUTFLOW BOUNDARIES...WITH MAIN
BOUNDARY OF NOTE ARCING JUST SOUTH OF I-80. WITH LINGERING
CONVECTION AND DEBRIS CLOUDS HAVE TWEAKED HIGHS DOWN OVER PORTIONS
OF NORTHEAST IA AND FAR NORTHWEST IL INTO THE MID 80S... BUT
WITH DUBUQUE STILL AT 71 DEGS AT 11 AM WOULD NOT BE SURPRISED TO
SEE SOME AREAS STRUGGLE TO HIT 80 OR LOWER 80S FAR NORTH. OTHERWISE
CURRENT HEAT ADVISORY HEADLINE ON TRACK FROM AROUND QUAD CITIES
SOUTH/EAST WITH FEW LOCATIONS ALREADY AT 90 DEGS AND HEAT INDEX
READINGS APPROACHING 100.

LOOKING FURTHER AHEAD TO TONIGHT AND TUESDAY... COLD FRONT THROUGH
NORTHWEST IA MOVING A BIT FASTER THAN MODELS AND LIKELY TO BE
LOCATED SOUTH OF THE CWA TUESDAY MORNING. ANTICIPATE POTENTIAL FOR
MORE ORGANIZED CONVECTION MOVING ACROSS NORTH 1/3-1/2 LATER
TONIGHT INTO TUE AM. IF TRENDS PERSIST THEN GOING FORECAST HIGHS
TOMORROW ARE LIKELY TOO WARM...POSSIBLY BY AS MUCH AS 5-10 DEGS
NOTING THAT AS WE ARE APPROACHING THE NOON HOUR TEMPS ARE IN THE
UPPER 60S TO LOWER 70S IN NORTHWEST IA POST FRONTAL WITH SUNSHINE.
THUS WITH CLOUDS AND RAIN COULD EASILY SEE AREAS STUCK IN THE 70S
ALL DAY TOMORROW. HAVE NOT MADE CHANGES YET AS STILL EVALUATING
MODEL SUITE... AND WILL HAVE MORE ON THIS WITH AFTERNOON DISCO.
UPDATED GRIDS/ZFP/PFM HAVE BEEN ISSUED.

&&

.SYNOPSIS...
ISSUED AT 334 AM CDT MON AUG 25 2014

THUNDERSTORMS HAVE DEVELOPED EARLY THIS MORNING ALONG AND AHEAD OF
THE SURFACE FRONT EXTENDING ROUGHLY FROM WESTERN LAKE SUPERIOR SW
ACROSS WESTERN WI...SW MN...INTO W CENTRAL IA. THIS WAS ALONG AN
AXIS OF HIGH THETAE INDICATED BY 850 MB DEWPOINTS OF 14 TO 16 C FROM
NORTHEAST KS INTO SW ONTARIO AT 00Z...WITH CONVERGENCE ASSISTED
BY 35KT TO 40 KT SW WINDS AT 850 MB. THIS MOISTURE WAS BEING
PULLED NORTHWARD BY A STRONG SURFACE AND UPPER LEVEL LOW SEEN ON
WV IMAGERY ALONG THE ND/MANITOBA BORDER. AT 3 AM...THE LEADING
LINE OF SCATTERED THUNDERSTORMS WAS MOVING INTO BUCHANAN AND
BENTON COUNTIES...INTO A VERY HUMID AIRMASS WITH DEWPOINTS IN THE
LOWER TO MID 70S AND AIR TEMPERATURES IN THE MID TO UPPER 70S.

&&

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 334 AM CDT MON AUG 25 2014

FORECAST CHALLENGES CENTER ON THUNDERSTORMS THIS MORNING AND AGAIN
TONIGHT...AND HEAT HEADLINES TODAY AS THE HOT AND HUMID CONDITIONS
PERSIST OVER THE REGION. IN THE NEAR TERM...A SEMI-LINEAR MCS WILL
LIKELY MOVE ACROSS THE FORECAST AREA MAINLY NORTH OF I-80...DRIVEN
BY A WEAK SHORTWAVE FLOW IN THE NW FLOW ALOFT. WHILE NO INDIVIDUAL
FORECAST MODEL HAS HAD A GOOD HANDLE ON TRENDS OVERNIGHT...THE
HIGH RES WRF AND RAP MODELS APPEAR TO HAVE THE BEST HANDLE ON THE
CONVECTION ENTERING THE NORTH. THESE HAVE THE THUNDERSTORMS ADVANCING
THROUGH THE NORTH OVER THE NEXT SEVERAL HOURS AND THEN DISSIPATING
BY NOON...AND HAVE TRENDED THE FORECAST ACCORDINGLY. THE LATEST
RAP IS ALONE WITH DEVELOPING THUNDERSTORMS IN THE HIGH MUCAPE
AXIS FURTHER SE...OVER 4000 J/KG...OVER W CENTRAL IL TOWARD
SUNRISE...WHICH WHILE NOT IN THE CURRENT FORECAST CANNOT BE
ENTIRELY RULED AND WILL WATCH TRENDS CLOSELY.

OTHERWISE...THIS SHOULD BE FOLLOWED BY CLEARING SKIES AND A RETURN
TO THE HEAT AND HUMIDITY SEEN OVER THE AREA YESTERDAY. DUE TO
UNCERTAINTIES IN THE TIMING OF THE DISSIPATING MCS IN THE NORTH AND
POSSIBLE DEBRIS CLOUDS FROM STORMS IN THE PLAINS...ALONG WITH 850 MB
TEMPERATURES PROGGED ABOUT 1 DEGREE COOLER...HAVE TRENDED HIGHS A
DEGREE OR TWO COOLER THAN SUNDAY...WITH UPPER 80S NW TO LOWER 90S
CENTRAL AND SOUTH. DEWPOINTS WILL HOLD IN THE LOWER TO MID 70S AND
POSSIBLY TOUCH THE UPPER 70S AT TIMES LATE IN THE DAY. THIS
COMBINATION WILL SEND HEAT INDEX VALUES TO JUST ABOVE 100 ACROSS
THE SOUTH AND WILL KEEP THE PREVIOUS HEAT ADVISORY CONFIGURATION
IN PLACE.

TONIGHT...THE SETUP WILL BE FAVORABLE FOR ANOTHER MCS AS THE SURFACE
FRONT SLOWLY ADVANCES THROUGH THE FORECAST AREA AND MODEST
CONVERGENCE OCCURS IN THE 850 MB THETAE AXIS AS IT SHIFTS OVERHEAD.
HAVE KEPT LIKELY POPS IN THE NORTH WITH SLIGHT TO LOW END CHANCE
POPS IN THE SOUTH TOWARD MORNING. THE MAIN THREAT WILL BE LOCALLY
HEAVY RAINFALL. IT WILL BE ANOTHER WARM AND VERY HUMID NIGHT WITH
TEMPERATURES AND DEWPOINTS IN THE 70S...EXCEPT IN THE FAR NW...WHERE
THE CURRENT FRONTAL TIMING SUGGESTS READINGS LOWERING INTO THE
UPPER 60S.

.LONG TERM...(TUESDAY THROUGH SUNDAY)
ISSUED AT 334 AM CDT MON AUG 25 2014

AN ORGANIZED THUNDERSTORM COMPLEX SHOULD MOVE INTO THE AREA TUESDAY
MORNING AND DISSIPATE DURING THE MORNING. BOUNDARIES LEFT OVER FROM
THIS COMPLEX COMBINED WITH A WEAK FRONT MOVING THROUGH THE AREA WILL
PROVIDE THE FOCUS FOR NEW CONVECTION TUESDAY AFTERNOON AND EVENING.
HIGH MOISTURE LEVELS IN THE LOWER ATMOSPHERE MEANS ANY STORM WILL BE
CAPABLE OF PRODUCING LOCALLY HEAVY RAINFALL.

CLOUD COVER AND RAIN WILL PLAY INTO HOW WARM IT WILL GET ON TUESDAY.
THE SOUTHEAST HALF MAY SEE TEMPERATURES AROUND 90 WITH HEAT INDEX
READINGS IN THE UPPER 90S TO JUST OVER 100.

ANOTHER THUNDERSTORM COMPLEX IS EXPECTED TO DEVELOP IN WESTERN IOWA
TUESDAY EVENING AND THEN MOVE MAINLY EAST OVERNIGHT INTO WEDNESDAY
MORNING. THIS STORM COMPLEX SHOULD ARRIVE IN THE WESTERN THIRD OF
THE CWFA IN THE PRE-DAWN HOURS AND SLOWLY DISSIPATE ACROSS THE AREA
WEDNESDAY MORNING. LOCALLY HEAVY RAINFALL WILL BE POSSIBLE FROM THE
STORMS DUE TO HIGH MOISTURE LEVELS.

LIKE TUESDAY...BOUNDARIES LEFT OVER FROM THE WEDNESDAY STORM COMPLEX
WILL PROVIDE THE FOCUS FOR NEW CONVECTION WEDNESDAY AFTERNOON AND
EVENING.

SIGNALS FROM THE MODELS SUGGEST YET ANOTHER THUNDERSTORM COMPLEX
WILL DEVELOP IN WESTERN IOWA WEDNESDAY EVENING AND MOVE GENERALLY
EAST OVERNIGHT AND ARRIVE IN THE WESTERN THIRD OF THE AREA IN THE
PRE-DAWN HOURS. LOCALLY HEAVY RAINFALL MAY BE POSSIBLE FROM SOME OF
THE STRONGER STORMS.

THURSDAY ON...
THE MODEL CONSENSUS HAS CHANCE POPS IN EACH 12 HOUR PERIOD FROM
THURSDAY THROUGH SATURDAY NIGHT. TEMPERATURES SHOULD BE NEAR NORMAL.
ON SUNDAY...THE MODEL CONSENSUS HAS SLIGHT CHANCE TO LOW CHANCE POPS.

THE LARGE SCALE PICTURE SUGGESTS THE WEATHER PATTERN WILL REMAIN
FAIRLY ACTIVE WITH A FRONT STALLED OUT JUST SOUTH OF THE AREA. IT
WILL NOT RAIN CONTINUOUSLY THE ENTIRE TIME. THERE WILL BE PERIODS OF
DRY WEATHER THAT MAY LAST 6 OR 12 HOURS.

&&

.AVIATION...(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)
ISSUED AT 645 AM CDT MON AUG 25 2014

A SLOW MOVING AXIS OF THUNDERSTORMS OVER NORTHEAST IOWA MAY
BRIEFLY IMPACT THE CID AND DBQ TERMINALS EARLY THIS MORNING. FOG
AND A FEW AREAS OF LOW CLOUDS WILL IMPACT MOST OF THE TERMINALS
WITH PERIODS OF MVFR CONDITIONS UNTIL MID MORNING.
OTHERWISE...TODAY WILL BE MAINLY VFR WITH VERY HUMID CONDITIONS.
ANOTHER ROUND OF THUNDERSTORMS IS EXPECTED TO MOVE THROUGH EASTERN
IOWA AND NORTHWEST ILLINOIS LATE TONIGHT AS A COOL FRONT SLOWLY
DROPS SOUTH THROUGH THE AREA. THIS IS MOST LIKELY TO AFFECT THE
CID...DBQ AND MLI TERMINALS...WHERE PROB30 GROUPS COVER THE
POTENTIAL FOR NOW. ALSO...LIGHT WINDS AND LINGERING LOW LEVEL
MOISTURE WILL ALSO LEAD TO MVFR FOG...WHICH IS ALSO INCLUDED FOR
THE LATE NIGHT AND EARLY MORNING PERIODS.


&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR LOUISA-MUSCATINE-
     SCOTT.

     HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR DES MOINES-HENRY
     IA-LEE-VAN BUREN.

IL...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR BUREAU-HENRY IL-
     MERCER-PUTNAM-ROCK ISLAND-WHITESIDE.

     HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR HANCOCK-HENDERSON-
     MCDONOUGH-WARREN.

MO...HEAT ADVISORY UNTIL 8 PM CDT THIS EVENING FOR CLARK-SCOTLAND.

&&

$$

UPDATE...05
SYNOPSIS...SHEETS
SHORT TERM...SHEETS
LONG TERM...08
AVIATION...SHEETS





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