Severe Thunderstorm Warning 116, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
644 PM CDT FRI AUG 30 2013

.UPDATE...
ISSUED AT 636 PM CDT FRI AUG 30 2013

CONVECTION IS SHOWING GROWING SIGNS OF CAPPING IN EASTERN IOWA...WHILE
THE AIRMASS OVER ILLINOIS CONTINUES TO SUPPORT CONVECTION...MAINLY
EAST OF THE CWA BORDER. THIS SHOULD ALLOW FOR STORMS NORTH OF
MONTICELLO IOWA TO DIE SLOWLY IN THE NEXT HOUR OR TWO...WITH THE
VAST MAJORITY OF THE CWA REMAINING DRY. POPS HAVE BEEN TIED TO THE
FRONTAL BOUNDARY IN AN HOURLY BASIS. THEY REMAIN LOW...BUT WILL BE
WATCHED TO SEE IF ANY NEW DEVELOPMENT CAN OCCUR LATE EVENING WHEN
A WEAK VORT AFFECTS THE REGION. BY THEN...THE FRONT WILL BE SOUTH
OF INTERSTATE 80...AND SURFACE CAP SHOULD BE CAPPED OFF THROUGH
NOCTURNAL INVERSION PROCESSES. THE HEAT ADVISORY CONDITIONS MAY
LINGER THROUGH 9 PM...BUT WILL LEAVE THE CANCELLATION AT 7 PM...AS
TO NOT CONFUSE THE ISSUE OF THIS EVENING BEING THE END OF THE HEAT
LOCALLY.

&&

.SYNOPSIS...
ISSUED AT 135 PM CDT FRI AUG 30 2013

LATEST SFC ANALYSIS SHOWS THE COLD FRONT JUST NORTH OF THE CWFA
ACROSS NE IA INTO SOUTHERN WI.  THUNDERSTORMS HAVE DEVELOPED ACROSS
SOUTHERN WI...WITH ONE CELL PROMPTING A SEVERE THUNDERSTORM WARNING
NW OF MKE.  HOT...HUMID AND SUNNY SKIES CURRENTLY PREVAIL OVER THE
DVN CWA...WITH TEMPERATURES MAINLY IN THE MIDDLE AND UPPER 90S...AND
HEAT INDICES IN THE 100-108 RANGE.

&&

.SHORT TERM...(THIS EVENING THROUGH SATURDAY)
ISSUED AT 135 PM CDT FRI AUG 30 2013

FOCUS WAS ON CONVECTION/SEVERE CHANCES LATE THIS AFTERNOON AND THIS
EVENING. THE SPC HAS ISSUED A SVR TSTORM WATCH FOR PARTS OF NW IL
AND SW WI AND POINTS EASTWARD THROUGH MID EVENING.  WILL NEED TO
CLOSELY WATCH POTENTIAL FOR ONGOING STORMS TO ZIPPER DOWN
SOUTHWESTWARD INTO NE IA AND THEN PROPAGATE INTO THE DVN CWA.
LATEST CELLS TO DEVELOP ARE ACROSS NORTHERN GRANT COUNTY WI...JUST N
OF DBQ.  CUMULUS FIELD ALONG BOUNDARY EXTENDS WESTWARD TO JUST N OF
ALO AND WESTWARD GENERALLY ALONG AND N OF HIGHWAY 20.  MOISTURE AND
INSTABILITY ARE SUFFICIENT GIVEN DEW POINTS IN THE 70S...WITH EVEN
SOME UPPER 70S AT TIMES ACROSS THE NE 2/3 OF THE CWFA.  SOME LOWER
MID 60 DEW POINTS HAVE NUDGED NE INTO THE SW CWFA.  MLCAPES OF
2500-3500 J/KG ARE OVER NW PART OF CWA AND NORTHWARD ALONG
FRONT...BUT EFFECTIVE SHEAR IS 20-25KTS. ANY SEVERE STORMS WILL BE
CAPABLE OF DAMAGING WINDS AND LARGE HAIL. HEAVY RAINS WILL ALSO BE
LIKELY WITH ANY STORMS...AS PWS ARE ON THE ORDER OF 1.6-1.8 INCHES
ACROSS THE ENTIRE AREA. MAIN ACTIVITY MAY COME WHEN AN UPPER LEVEL
VORT ENTERING NW IA MOVES INTO THE LOCAL AREA THIS EVENING. ALL IN
ALL ONLY HAVE SLIGHT TO LOW CHANCE POPS /20-30/ FOR THIS FRONTAL
PASSAGE.

STORM ACTIVITY SHOULD QUICKLY WANE BY LATE EVENING...AS WINDS
BECOME N-NE BEHIND THE FRONT. A LOW STRATUS DECK MAY DEVELOP LATE
TONIGHT AND DRIFT SOUTHWARD OVER THE AREA OVERNIGHT. LATER SHIFTS
WILL NEED TO MONITOR THIS AS WELL AS THE POTENTIAL FOR THE
DEVELOPMENT OF ANY FOG. FOR NOW ONLY HAVE AVIATION 4SM FOG FOR
TAFS...WHICH MAY BE LOWER IF ANY DECENT RAINS DO OCCUR.

TEMPS TONIGHT AND SAT LOOK TO BE ON TRACK...THUS NOT MUCH CHANGE.
SATURDAY LOOKS TO BE DRY WITH CLEARING SKIES AND HIGHS IN LOW 80S
NE...TO LOW 90S SW.

.LONG TERM...(SATURDAY NIGHT THROUGH FRIDAY) ISSUED AT 135 PM CDT
FRI AUG 30 2013

STRONG COLD FRONT TO PASS THROUGH THE AREA ON SUNDAY AND WILL BE
ACCOMPANIED BY CHANCE OF SHOWERS AND STORMS. SUGGESTION FROM
SEVERAL MODELS OF ONE OR MORE CONVECTIVE COMPLEXES FORMING
AHEAD OF THE FRONT TO OUR W/NW SAT EVE AND PROPAGATING TOWARD
CWA OVRNGT SAT-SUN AM WHILE WEAKENING. HAVE NUDGED UP POPS BUT
STILL IN CHANCE CATEGORY LATE SAT NGT-SUN... AS STILL SOME
CONCERNS ABOUT CONVECTION SPLITTING AND FOCUSING MORE TO OUR
NORTHEAST WITH MAIN DYNAMICS AND ALSO TO OUR WEST/SOUTHWEST WITHIN
AXIS OF BETTER MOISTURE AND INSTABILITY. LOWS MAINLY IN THE 60S
SAT NGT. HIGHS ON SUNDAY WILL BE CHALLENGING WITH CLOUDS AND SOME
PCPN AROUND. SIDED NEAR OR ON COOL SIDE OF GUIDANCE BLEND WITH
MID 80S TO FEW LOWER 90S FAR SOUTH. GUSTY NORTHWEST WINDS POST
FRONTAL BY SUN EVE TO USHER IN REFRESHING AND NOTICEABLY COOLER
AIR AND HAVE NUDGED LOWS DOWN 1-2 DEGS WITH MAINLY MID 50S TO
LOWER 60S.

MON-TUE... GORGEOUS WEATHER FOR THE LABOR DAY HOLIDAY AND THROUGH
TUE WITH CANADIAN SFC HIGH IN CONTROL PROVIDING VERY COMFORTABLE
CONDITIONS WITH BELOW NORMAL TEMPS AND LOW HUMIDITY. HIGHS IN
THE 70S TO AROUND 80F AND LOWS MAINLY IN THE 50S WITH SOME 40S
POSSIBLE ESPECIALLY IN SHELTERED OR FAVORED COOL DRAINAGE SITES
WHERE WINDS COULD DROP OFF TO ALLOW FOR EXCELLENT RADIATIONAL COOLING.

WED-FRI... REBOUND ON TEMPS TO AROUND NORMAL. NEXT FRONT SUGGESTED
SOMETIME LATER WED OR THU. KEPT WITH CONSENSUS MODEL AND POPS
REMAIN BELOW MENTION FOR NOW WITH UNCERTAINTIES ON TIMING... BUT
LIKELY NEED TO BE ADDED IN LATER SHIFTS WHEN TIMING CAN BE PINNED DOWN.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 636 PM CDT FRI AUG 30 2013

TONIGHTS AVIATION WILL INITIALLY DEAL WITH AN ISOLATED
THUNDERSTORM THREAT NEAR DBQ...THEN NEAR MLI AND BRL TOWARD 04Z AS
A COLD FRONT MOVES SOUTH THROUGH THE AREA. SINCE IT REMAINS
EXTREMELY ISOLATED...I HAVE REMOVED ALL VCTS AND TEMPO THUNDER
FROM FORECASTS. SHOULD ANY STORM DEVELOP...IT MAY PRODUCE MVFR
VISIBILITIES IN RAIN. OTHERWISE...AN AREA OF MVFR STRATUS IS
POSSIBLE OVERNIGHT AS NORTHEAST WINDS DEVELOP OFF LAKE MICHIGAN
BEHIND THE FRONT. I HAVE RETAINED THIS THREAT FROM EARLIER
TAFS...BUT INTRODUCED IMPROVING CIGS TO VFR BETWEEN 14Z AND 17Z IN
TAFS. VISIBILITIES COULD ALSO DIP TO MVFR DURING THIS STRATUS
PERIOD. AFTER 18Z SATURDAY...VFR WEATHER WILL BE WIDESPREAD.
ERVIN

&&

.CLIMATE...
ISSUED AT 135 PM CDT FRI AUG 30 2013

RECORD HIGHS FOR AUGUST 30...

MOLINE.........98 IN 1953
CEDAR RAPIDS...100 IN 1953
DUBUQUE........94 IN 1941
BURLINGTON.....102 IN 1947

&&

.DVN WATCHES/WARNINGS/ADVISORIES...
IA...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR BENTON-BUCHANAN-
     CEDAR-CLINTON-DELAWARE-DES MOINES-DUBUQUE-HENRY IA-IOWA-
     JACKSON-JEFFERSON-JOHNSON-JONES-KEOKUK-LEE-LINN-LOUISA-
     MUSCATINE-SCOTT-VAN BUREN-WASHINGTON.

IL...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR BUREAU-CARROLL-
     HANCOCK-HENDERSON-HENRY IL-JO DAVIESS-MCDONOUGH-MERCER-
     PUTNAM-ROCK ISLAND-STEPHENSON-WARREN-WHITESIDE.

MO...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR CLARK-SCOTLAND.

&&

UPDATE...ERVIN
SYNOPSIS...14
SHORT TERM...14
LONG TERM...05
AVIATION...ERVIN
CLIMATE...14

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
1141 AM CDT FRI AUG 30 2013

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-311645-
BUCHANAN-DELAWARE-DUBUQUE-BENTON-LINN-JONES-JACKSON-IOWA-JOHNSON-
CEDAR-CLINTON-MUSCATINE-SCOTT-KEOKUK-WASHINGTON-LOUISA-JEFFERSON-
HENRY IA-DES MOINES-VAN BUREN-LEE-JO DAVIESS-STEPHENSON-CARROLL-
WHITESIDE-ROCK ISLAND-HENRY IL-BUREAU-PUTNAM-MERCER-HENDERSON-
WARREN-HANCOCK-MCDONOUGH-SCOTLAND-CLARK-
1141 AM CDT FRI AUG 30 2013

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
ILLINOIS...NORTHWEST ILLINOIS...WEST CENTRAL ILLINOIS...EAST
CENTRAL IOWA...NORTHEAST IOWA...SOUTHEAST IOWA AND NORTHEAST
MISSOURI.

.DAY ONE...THIS AFTERNOON AND TONIGHT

A HEAT ADVISORY IS IN EFFECT THROUGH 7 PM FOR THE ENTIRE OUTLOOK
AREA. AFTERNOON HEAT INDEX READINGS WILL REACH 100 TO AROUND 105.
PLEASE SEE THE OFFICIAL HEAT ADVISORY MESSAGES FOR MORE DETAILS
AND PREPAREDNESS INFORMATION.

A FRONTAL SYSTEM PUSHING IN FROM THE NORTH WILL BRING A CHANCE FOR
THUNDERSTORMS THIS AFTERNOON AND EVENING. A FEW OF THESE STORMS
MAY BE SEVERE...PRODUCING DAMAGING WIND GUSTS AND LARGE HAIL. LOCALLY
HEAVY DOWNPOURS ARE ALSO POSSIBLE WITH THE STRONGEST STORMS.

THE STORM PREDICTION CENTER HAS A SLIGHT RISK FOR SEVERE STORMS
ACROSS PARTS OF EAST CENTRAL IOWA AND NORTHWEST ILLINOIS.

.DAYS TWO THROUGH SEVEN...SATURDAY THROUGH THURSDAY

SATURDAY AND SUNDAY...HOT AND HUMID CONDITIONS WILL CONTINUE SOUTH OF
INTERSTATE 80 WHERE AFTERNOON HEAT INDEX READINGS WILL RISE INTO THE
LOWER TO MIDDLE 90S.

SUNDAY...THERE IS A CHANCE OF THUNDERSTORMS. ANY STORMS IN THE
AFTERNOON INTO THE EARLY EVENING HOURS MAY APPROACH SEVERE LEVELS
WITH STRONG GUSTY WINDS THE MAIN THREAT.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION MAY BE NEEDED THIS AFTERNOON AND EVENING.

14/05/12/NICHOLS

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