Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 011756
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
1256 PM CDT TUE SEP 1 2015

.SHORT TERM...
311 AM CDT

THROUGH TONIGHT...

PRIMARY FORECAST CHALLENGE TODAY IS POTENTIAL FOR ISOLATED
CONVECTION OVER MAINLY SE THIRD OF CWA...POSSIBLE WEAK LAKE
BREEZE...AND HIGH TEMPS.

WATER VAPOR IMAGERY THIS MORNING SHOWS A WELL DEFINED UPPER LOW OVER
CENTRAL INDIANA WITH A NARROW PLUME OF MID-UPPER LEVEL MOISTURE
WRAPPING AROUND THE NW FLANK OF THE SMALL CIRCULATION IN OUR
SOUTHEAST CWA. GUIDANCE HAS BEEN PRETTY AGGRESSIVE IN BREAKING OUT
ISOLD-SCTD CONVECTION WITH THIS FEATURE...EVEN NOW INTO EARLY THIS
MORNING...WHICH THUS FAR HAS BEEN ABSENT. 11-3.9U GOES IMAGERY DOES
SHOW SOME ACAS BUBBLING UP OVER EAST CENTRAL ILLINOIS...BUT THUS FAR
NO PRECIP. ONE CAMP OF GUIDANCE BREAK OUT CONVECTION THIS MORNING
WITH CONTINUED DEVELOPMENT ON THE OUTFLOW FLANK FROM THIS (YET TO
DEVELOP CONVECTION) MAKING FAIRLY FAR NORTH INTO OUR CWA THIS
AFTERNOON. ANOTHER CAMP OF MODELS IS MORE AGGRESSIVE IN BREAKING OUT
AFTERNOON CONVECTION AND FOCUSING IT MAINLY IN SE CWA. MAJORITY OF
GUIDANCE HAS DEWPOINTS IN THE MID 70S THIS AFTERNOON...WHICH LEADS
TO VERY HIGH CAPE AND NO CAP. THINK MORE REALISTICALLY DEWPOINTS
WILL BE AROUND 70 TO LOW 70S WITH WEAKER CAPE AND SOME INHIBITION.
THE MEMBERS OF THE HOP-WRF ENSEMBLE WITH LOWER TDS BREAK OUT LITTLE
TO NO CONVECTION THIS AFTERNOON WHILE THE MEMBER WITH MID 70 TDS IS
CONVECTIVELY MUCH MORE ACTIVE.

WILL KEEP AN EYE ON SATELLITE TREND NEXT HOUR OR SO AND MAKE SOME
FINAL TWEAKS TO POPS BASED ON TRENDS...BUT GENERALLY THINKING OF
MAINTAINING LOW (20-30) POPS THROUGH THE DAY SE COUNTIES WITH
LESSER...THOUGH NONE ZERO CHANCES FARTHER NORTH.

EXPECT SMOKE TO BE FAIRLY PREVALENT AGAIN TODAY AND HAVE MAINTAINED
HAZE IN THE GRIDS TO COVER THE MILKY/HAZY LOOK TO THE SKY THAT IS
ANTICIPATED. EVEN WITH THE SMOKE...TEMPS STILL MANAGED TO WARM
NICELY MONDAY...SO WITH 925MB TEMPS PROGGED TO BE A COUPLE DEGREES C
WARMER TODAY THINK GOING FORECAST HIGHS IN THE UPPER 80S/AROUND 90
LOOK REASONABLE. WEAK LAKE BREEZE COULD FORM RIGHT ALONG THE
ILLINOIS SHORE...POSSIBLY LEADING TO SOME LAKE COOLING AT TIMES THIS
AFTERNOON...BUT CONFIDENCE IS NOT HIGH AND KEPT LAKEFRONT TEMPS IN
THE SAME BALLPARK AS INLAND.

IZZI

&&

.LONG TERM...
311 AM CDT

WEDNESDAY THROUGH LABOR DAY...

WEAK UPPER LOW OVER INDIANA IS PROGGED TO CONTINUE TO
WEAKEN/DISSIPATE...SO AFTER TODAY PRECIP CHANCES LOOK TO BE SLIM AT
BEST ACROSS THE AREA THROUGH THE UPCOMING HOLIDAY WEEKEND.
UNSEASONABLY STRONG UPPER RIDGE IS FORECAST TO HOLD STRONG THROUGH
THE HOLIDAY WEEKEND WITH ABNORMALLY WARM AND RATHER HUMID CONDITIONS
LIKELY TO PERSIST. DAYTIME HIGHS LOOK TO REMAIN IN THE UPPER
80S/LOWER 90S EACH DAY THROUGH THE REST OF THE WEEK AND OVER THE
HOLIDAY WEEKEND. AFTERNOON LAKE BREEZES LOOK FAIRLY LIKELY EACH
DAY...ESPECIALLY THUR-SAT...PROVIDING A BIT OF NATURAL AIR
CONDITIONING FOR LAKE ADJACENT AREAS. MEDIUM RANGE MODELS SUGGEST
A STRONGER GRADIENT BY SUNDAY AND ESPECIALLY MONDAY WHICH SHOULD
SEND THE HEAT RIGHT UP TO THE LAKEFRONT. IN FACT...IF CURRENT
MODELS END UP BEING PERFECT PROGS THEN HIGHS BY MONDAY COULD CLIMB
INTO THE MID 90S AS 925MB TEMPS REACH 27C.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* LOW POSSIBLITY OF ISOLATED SHRA/TSRA THIS AFTERNOON

KMD

//DISCUSSION...UPDATED 18Z...

STORMS TO THE SOUTHEAST OF THE TERMINALS ARE IN A WEAKENING
PHASE...BUT ARE SENDING AN OUTFLOW NORTHWARD. LITTLE ACTIVITY IS
OCCURRING ALONG THE OUTFLOW FARTHER NORTH...THOUGH WE ARE SEEING
SOUTHERLY WINDS GUSTING TO THE UPPER TEENS AND SOME BRIEF MVFR
CIGS. CLEARING BEHIND THE OUTFLOW SUGGESTS THIS WILL NOT LAST
LONG...BUT THE ATMOSPHERE IN NE AND NC ILLINOIS IS MOIST AND
PRETTY UNSTABLE...SO EXPECT AT LEAST SCATTERED CUMULUS THIS
AFTERNOON. WINDS SHOULD FALL BACK TO A STEADIER SSW WIND IN THE
LOWER TEENS.

WITH THE UNSTABLE ENVIRONMENT IN PLACE...MODEL GUIDANCE IS MIXED
IN ADDITIONAL CONVECTIVE DEVELOPMENT THIS AFTERNOON. THERE IS NO
REAL TRIGGER IN WATER VAPOR IMAGERY AND THE UPPER LOW TRIGGERING
THIS MORNINGS ACTIVITY IS MOVING EAST...SO HAVE HELD ONTO DRY
TAFS AS ANYTHING THAT GOES WOULD NEED TO BE TRIGGERED BY SUBTLE
FORCING. NO REAL IMPACTS TONIGHT OTHER THAN SOME PATCHY FOG.

SHORTWAVE ENERGY TO THE WEST MOVES OVERHEAD ON WEDNESDAY...THOUGH
SOUNDINGS ARE LARGELY DRY. A WEAKENING LOW LEVEL WIND FIELD
SUGGESTS A LAKE BREEZE DEVELOPS...BUT AT THIS POINT CONFIDENCE IS
NOT HIGH THAT IS GETS WEST OF THE LAKESHORE AREAS.

KMD


//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM-HIGH THAT TERMINALS REMAIN DRY THIS AFTERNOON.
* HIGH WITH WIND SPEED AND DIRECTION

KMD

//OUTLOOK FOR ORD/MDW FOR 00Z THURSDAY-12Z TUESDAY...UPDATED 12Z...

WEDNESDAY NIGHT...VFR.

THURSDAY...VFR.

FRIDAY...VFR.

SATURDAY...VFR.

SUNDAY...VFR.

MONDAY...SLIGHT CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
218 AM CDT

HIGH PRESSURE WILL CONTINUE TO BE A DOMINATE FEATURE ACROSS THE
EASTERN THIRD OF THE COUNTRY THIS WEEK...WHILE THE BULK OF ANY
SYSTEMS CONTINUE TO STAY AWAY FROM THE REGION. SOUTHERLY FLOW WILL
CONTINUE TODAY INTO TONIGHT...WITH WINDS TURNING MORE NORTHERLY AS
A WEAK BOUNDARY PUSHES ACROSS THE NORTHERN PORTION OF THE LAKE
LATE TONIGHT INTO WEDNESDAY. DESPITE THIS TURNING WIND
FIELD...SPEEDS LOOK TO REMAIN ON THE LIGHTER SIDE. WINDS WILL
RETURN TO MORE OF A SOUTHERLY DIRECTION BY THE END OF THE WORK
WEEK. FOG IS ONCE AGAIN PRESENT OVER THE OPEN WATERS EARLY THIS
MORNING AND AFFECTING PRIMARILY THE ILLINOIS NEARSHORE
WATERS...WITH DENSE FOG LIKELY. DENSE FOG ADVISORY WILL REMAIN
THROUGH THE MORNING...BUT WILL NEED TO MONITOR POSSIBLE EXTENSION
AND EXPANSION INTO THE REMAINING AREAS OF THE NEARSHORE WATERS.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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