River Flood Warning 117, NWS Quad Cities, IA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
349 PM CDT SAT JUL 30 2011

.SYNOPSIS...
HIGH PRESSURE WAS LOCATED OVER THE GREAT LAKES AND OHIO VALLEY WITH
RIDGE AXIS EXTENDING INTO NORTHERN CWA. MIXING OF DRY AIR ALOFT
HAS DROPPED DEWPTS INTO VERY COMFORTABLE L/M 60S MANY LOCATIONS IN
AREA BOUNDED BY KSFY-KCID-KMUT-KVYS DENOTED BY CLEAR WEDGE ON VISIBLE
SATL. ELSEWHERE IN CWA... STILL REMAINS HUMID WITH DEWPTS IN THE
L70S WHICH COUPLED WITH TEMPS CLIMBING INTO THE U80S TO L90S IS
PRODUCING HEAT INDICES IN THE U90S WITH COUPLE SITES JUST ABOVE 100
DEGS. MAIN CORE OF HEAT DOME EXTENDS FROM CENTRAL/SOUTHERN PLAINS
TO MID ATLANTIC WITH FAST ZONAL TO NORTHWEST FLOW PREVAILING OVER THE
NORTHERN TIER OF CONUS. LINEAR MCS OBSERVED MOVING ACROSS NORTHERN WI
THIS AFTN AHEAD OF MID LEVEL SHORTWAVE.   ..05..

&&

.SHORT TERM...TONIGHT AND SUNDAY...
FOG...HEAT HEADLINES AND SMALL PCPN CHCS MAIN FCST CHALLENGES.

MONITORING PORTIONS OF SOUTHEAST IA LATE THIS AFTN FOR ISOLD CONVECTION
WITH VISIBLE SATL SHOWING SOME ENHANCEMENT TO CU FIELD NEAR KOTM-KFFL-
KFSW LINE NEAR LLVL MOISTURE GRADIENT AND EAST OF WEAK DISTURBANCE
SEEN LIFTING NWD INTO SOUTHERN IA PER VISIBLE SATL LOOP. WITH COUPLE
MORE HRS OF HEATING MAY SEE DEVELOPMENT AS CONVECTIVE TEMPS IN THE L90S
PER FCST SOUNDINGS... BUT APPEARS ANY ACTIVITY FAR TOO ISOLD FOR ANY
INCLUSION OF POPS ATTIM. BEYOND... GENERALLY QUIET CONDITIONS WITH
WEAK SFC RIDGING IN CONTROL. WILL HOWEVER NEED TO KEEP EYE ON MN THIS
EVE FOR POTENTIAL CONVECTIVE DEVELOPMENT. SHOULD DEVELOPMENT OCCUR THEN
CORFIDI VECTORS FAVORABLE FOR ACTIVITY TO PROPAGATE SEWD... BUT WILL
BE RUNNING INTO RESEVOIR OF DRIER MID LEVEL AIR WITH 850 MB HIGH JUST
EAST OF CWA. GIVEN THIS AND WITH TIMING MAINLY LATER TNGT CONFIDENCE
TOO LOW FOR ANY PCPN MENTION ATTIM BUT PASS CONCERNS ON TO EVE SHIFT.
OVRNGT WITH LIGHT TO CALM WINDS AND BOUNDARY LAYER MOISTURE EXPECT PATCHY
TO AREAS OF FOG WHICH MAY BE DENSE... WITH TWO AREAS TO WATCH BEING
NORTHEAST IA INTO NORTHWEST IL DUE TO RECENT EXTREME RAINFALL AND SECOND
BEING ACROSS THE SOUTH WHERE HIGHER DEWPTS POOLING. AS FOR LOWS...
GIVEN THE LIGHT WINDS AND MAINLY CLEAR SKIES PROVIDING DECENT RADIATIONAL
COOLING SETUP... OPTED FOR NEAR TO JUST BELOW COOL SIDE OF GUIDANCE IN
MANY AREAS EXCEPT SOUTH WHERE SIDED WITH BLEND.

SUNDAY... ASIDE FROM ISOLD SHRA OR WEAK TSRA POSSIBLE FAR NORTH EARLY WITH
ANY REMNANTS OF MN CONVECTION... IT LOOKS DRY AS SUGGESTIONS OF FRONT
AND MAIN FORCING STAYING TO OUR NORTH FROM DAKOTAS INTO WI. AIRMASS
FAIRLY SIMILAR TO THAT OF TDY AND THUS EXPECT WIDESPREAD HIGHS IN THE U80S
TO L90S. DEWPT FCST CHALLENGING AGAIN AS STILL SUGGESTED DRAW/FETCH FROM
RETREATING 850 MB HIGH AND ATTENDANT DRY RESEVOIR WHICH WITH MIXING COULD
LOWER DEWPTS INTO THE 60S AGAIN ESPECIALLY EAST OF MISSISSIPPI RVR. EVEN
WITH HIGHS IN L90S AND DEWPTS L70S... MARGINAL FOR HEAT ADVISORY WITH HEAT
INDICES AROUND 100-102 AND MAY BE FOR ONLY HR OR TWO. FOR THESE REASONS
HAVE HELD OFF ON ANY HEAT HEADLINES.

.LONG TERM...SUNDAY NIGHT THROUGH NEXT SATURDAY...
SUNDAY NIGHT THROUGH MONDAY NIGHT...LATEST SUITE OF 12Z RUN MODEL
GUIDANCE IN GOOD AGREEMENT OF SUGGESTING UPPER RIDGE AMPLIFICATION
ACRS THE EASTERN PLAINS AND MO RVR VALLEY THIS PERIOD...WHILE A
BOUT OF SFC RIDGING CONTINUES ACRS THE WESTERN GRT LKS. THIS
SYNOPTIC SCALE/MASS FIELD PLACEMENT GENERALLY SUGGESTS A DRY FCST
LOCALLY OR A LOW CHANCE FOR AN ISOLATED POP-UP TYPE SHOWER/STORM
IN THE HEIGHT OF AFTERNOON HEATING. SOME SIGNALS IN THE LATEST RUNS
OF A WEAK INLAND LAKE ENHANCED BOUNDARY SETTING UP SOMEWHERE OVER
NORTHERN IL MONDAY AFTERNOON FOR A POSSIBLE CONVECTIVE FOCAL POINT...
BUT CURRENTLY NOT SURE IF IT WILL MAKE IT FAR ENOUGH WEST TO WARRANT
EVEN SLIGHT CHC POPS IN NORTHWEST IL AT THIS POINT. WILL GO WITH
WIDESPREAD LOWS IN THE LOWER 70S SUNDAY NIGHT...AND BUILDING THERMAL
RIDGE ACRS THE REGION ON MONDAY SUPPORTS HIGHS IN THE LOWER TO
MIDDLE 90S. FCST SOUNDINGS SUGGEST ANOTHER DRY DOWN MIXING OF SFC
DPT POTENTIAL ON MONDAY WHICH MAY KEEP THEM MORE IN THE REALM OF LOW
TO MID 70S. DESPITE THIS...STILL COMING UP WITH HEAT ADVISORY
CRITERIA OF 100-105 HEAT INDEX/S MON AFTERNOON OVER THE MAJORITY OF
THE DVN CWA EXCEPT MAYBE THE FAR NORTH AND NORTHEAST. STILL TIME TO
ASSESS AND HOLD OFF ANY KIND OF HEADLINES AT THIS JUNCTURE IN TIME.
WARM AND MUGGY CONDITIONS CONTINUE INTO MON NIGHT WITH SOME AREAS
POSSIBLY NOT DIPPING BELOW 77 DEGREES FOR OVERNIGHT LOWS TAKING
INTO ACCOUNT AN INCREASING SOUTHERLY BREEZE EVEN IN THE OVERNIGHT.

TUESDAY...THIS DAY POSSIBLY THE MOST VOLATILE ONE OF THE UPCOMING
WEEK OF WEATHER. THE MEDIUM RANGE MODELS CONTINUE TO SAG A
WEAKENING BOUNDARY FROM NORTHWEST-TO-SOUTHEAST THROUGH THE CWA TUE
AFTERNOON AND EVENING...WITH THE MODELS CONTINUING TO VARY IN
TIMING. BUT THE LATEST TREND WITH THE MAJORITY OF THE 12Z RUNS IS
MORE PROGRESSIVE WITH THE FROPA THROUGH MOST OF THE DVN CWA BY 06Z
WED. WITH BEST UPPER JET DYNAMICS ON SOUTHERN FRINGE OF HIGHER
SPEED MAX ACRS THE NORTHWEST HIGH PLAINS...ACRS TO THE NORTHERN GRT
LKS INTO THE MID WEEK...THUS IT APPEARS BEST FORCING AND DEEP LIFTING
MECHANISMS TO REMAIN TO THE NORTH OF THE DVN CWA. BUT THE PRE-
FRONTAL CAPE POOL COULD INCREASE TO 4K-6K J/KG BY LATE TUE AFTERNOON
ESPECIALLY WITH A SLOWER BOUNDARY ARRIVAL. PW/S PROJECTED TO INCREASE
TO AT LEAST 2 INCHES BY 00Z WED. THUS THERE IS A CHANCE FOR SOME HIGH
CAPE PULSE SVR STORMS ALONG THE FRONT LATE TUE AFTERNOON AND INTO THE
EVENING...OR THE POSSIBILITY OF A MORE ORGANIZED SVR THREAT IF A
PORTION OF AN MCS DROPS INTO THE AREA OUT OF MN OR WI AND FEEDS ON
THE HIGH CAPE AIRMASS WHILE DEVELOPING/MAINTAINING A COLD POOL FOR
A DAMAGING WIND THREAT. ANY ORGANIZED STORMS OR CLUSTERS WOULD
PRODUCE TORRENTIAL DOWNPOURS AND POSSIBLY IMPACT THE WATER SENSITIVE
NORTHERN CWA WITH RENEWED FLASH FLOODING. BUT STORM PLACEMENT AND
PROPAGATION SPEEDS FOR HIGH RAINFALL IMPACTS STILL VERY MUCH
UNCERTAIN AT THIS POINT. BEFORE THE STORMS ARRIVE...PRE-FRONTAL
THERMAL POOL COULD MIX OUT AND BOOST SFC TEMPS INTO THE MID AND UPPER
90S. EVEN IF SFC DPTS ARE HELD IN THE LOW TO MID 70S BY SAME MIXING
PROCESSES...THESE PARAMETERS STILL SUPPORT EXCESSIVE HEAT WARNING
CRITERIA ACRS AT LEAST THE SOUTH HALF OF THE CWA ON TUE. AT LEAST THE
INCOMING FRONT WILL EVENTUALLY BRING RELIEF FROM THE TRUE HEAT AND
HUMIDITY BY LATE TUE NIGHT.

WEDNESDAY AND THURSDAY...LATEST MEDIUM RANGE MODELS AGAIN IN DECENT
AGREEMENT OF SUGGESTING POST-FRONTAL SFC RIDGING ACRS THE WESTERN GRT
LKS AND MAIN SFC BOUNDARY GETTING SHUNTED ACRS MO AND BECOMING QUASI-
STATIONARY THIS PERIOD. THIS WOULD SUGGEST GENERALLY DRY WX REGIME
AND DECREASING LLVL HUMIDITY IN NORTH TO NORTHEASTERLY BOUNDARY LAYER
FETCH ESPECIALLY BY THU. HIGHS MAY BE HELD IN THE 80S...WITH LOWS AT
NIGHT POSSIBLY DIPPING DOWN INTO THE LOW 60S IN THE NORTHEASTERN CWA.
MIXED SIGNALS OF OVERRUNNING RAIN AND ELEVATED STORMS POSSIBLE LATE
THU AFTERNOON AND INTO THU NIGHT ESPECIALLY ACRS THE SOUTH HALF OF
THE DVN CWA IF A RIDGE-RIDING WAVE CAN ACT UPON THE KS-MO QUASI-
STATIONARY FRONTAL BOUNDARY.

FRIDAY THROUGH SATURDAY...LONGER RANGE TRENDS ON THE ENSEMBLES AND
12Z RUNS SUGGEST THAT ANY LINGERING OVERRUNNING RAIN ON FRI WILL
EXIT BY EVENING AND MAKE WAY FOR RE-ENFORCING SFC RIDGING ACRS THE
UPPER MS RVR VALLEY AND WESTERN GRT LKS FRI NIGHT INTO SAT. THIS
SCENARIO COULD OPEN THE DOOR TO A FAIR AND SEASONABLE WEEKEND FOR
THE LOCAL CWA.     ..12..

&&

.AVIATION...
GENERALLY VFR CONDITIONS EXPECTED FOR MOST OF THE PERIOD AT THE TAF
CYCLES AS SFC RIDGE OF HIGH PRESSURE REMAINS IN CONTROL. MAIN
CONCERN OVERNIGHT WILL BE WITH FOG AS LIGHT WINDS AND ABUNDANT LLVL
MOISTURE WITH MAINLY CLEAR SKIES PROVIDING EXCELLENT SETUP FOR FOG
WITH SHALLOW STEEP LLVL INVERSION CONDUCIVE FOR RAPID FLUCTUATIONS
IN VSBYS WITH POTENTIAL VARYING FROM LIFR TO MVFR FOR FEW HOURS.
FOG COULD BE DENSE... ESPECIALLY AT KBRL WHERE DEEPER LLVL MOISTURE
WILL RESIDE. VERY LOW POTENTIAL ALSO EXISTS FOR STRAY SHRA OR
WEAK TSRA TO DEVELOP OR DROP DOWN FROM MN OVERNIGHT INTO NORTHEAST
IA...MAINLY AFT 07Z TO 13Z... POSSIBLY NEAR KDBQ/KCID. DRIER AIR IN
THE MID LEVELS MAKES CHC OF PCPN FAR TOO LOW TO INCLUDE IN TERMINALS.
..05..

&&

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

05/12

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE QUAD CITIES IA IL
349 PM CDT SAT JUL 30 2011

IAZ040>042-051>054-063>068-076>078-087>089-098-099-ILZ001-002-007-
009-015>018-024>026-034-035-MOZ009-010-310930-
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-
349 PM CDT SAT JUL 30 2011

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

PATCHY TO AREAS OF FOG WILL DEVELOP OVERNIGHT. THE FOG COULD BE
DENSE IN SOME LOCATIONS... REDUCING VISIBILITIES TO LESS THAN
ONE QUARTER MILE.

THE MISSISSIPPI RIVER IS EXPERIENCING FLOODING. PLEASE SEE THE
LATEST FLOOD STATEMENTS AND FLOOD WARNINGS FOR DETAILS.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

TEMPERATURES WILL WARM THROUGH THE WEEKEND AND INTO NEXT WEEK...
REACHING POTENTIALLY DANGEROUS LEVELS IN SOME LOCATIONS. BY
SUNDAY...THE HEAT INDEX IS EXPECTED TO NEAR 100 DEGREES AND BY
NEXT TUESDAY COULD APPROACH 105 DEGREES. SOME AREAS SOUTH OF
INTERSTATE 80 MAY SEE HEAT INDEX READINGS OVER 100 DEGREES EACH
DAY FROM SUNDAY THROUGH TUESDAY.

LATE TUESDAY THROUGH NEXT THURSDAY...THERE WILL BE A CHANCE FOR
THUNDERSTORMS AS A FRONT LINGERS OVER THE REGION. IT IS TOO EARLY TO
DETERMINE WHETHER THESE STORMS WILL HAVE THE POTENTIAL TO BECOME
SEVERE.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NEEDED THIS AFTERNOON OR TONIGHT.