Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 081824
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
124 PM CDT TUE JUL 8 2014

.DISCUSSION...
325 AM CDT

ONCE SHOWERS/T-STORMS END EARLY THIS MORNING SHOULD SEE SEVERAL DAYS
OF DRY/MILD WEATHER BEFORE A RETURN TO WARMER/MORE HUMID AND
POTENTIALLY UNSETTLED PATTERN LATE IN THE WEEK INTO THE WEEKEND.

WATCHING A COUPLE OF FEATURES FOR CONVECTIVE CHANCES THE NEXT
SEVERAL HOURS. FIRST...SHORTWAVE TROUGH AND ASSOCIATED COLD FRONT
WILL CONTINUED TO KICK OFF WDLY SCTD TSTORMS THIS MORNING ACROSS
NORTHERN PORTIONS OF THE CWA. INSTABILITY IS RELATIVELY MEAGER BUT
SHORT RANGE GUIDANCE SUGGESTS SOME WEAK ELEVATED INSTABILITY WILL
CONTINUE TO TRANSLATE EASTWARD WITH THE FRONT SUPPORTING AT LEAST
SCTD STORMS INTO THE CHICAGO AREA THROUGH EARLY MORNING. SECOND
FEATURE IS MCV ASSOCIATED WITH LARGE MCS THAT MOVED ACROSS MISSOURI
AND DOWNSTATE ILLINOIS MON EVENING. NORTHERN EXTENT OF ITS PRECIP
SHIELD AND CONVECTION WILL AFFECT AREAS MAINLY SOUTH OF THE KANKAKEE
RIVER EARLY THIS MORNING. PRECIP SHOULD GENERALLY SHIFT
EAST/SOUTHEAST OF THE AREA BY 14 OR 15Z THIS MORNING WITH INCREASING
WEST/NORTHWEST WINDS SLOWLY ADVECTING IN DRIER AIR MASS INTO THE
AREA. GUIDANCE IS GENERALLY IN GOOD AGREEMENT IN DEPICTING WEAK
UNCAPPED INSTABILITY DEVELOPING THIS AFTERNOON WITH SBCAPE OF
500-1000 J/KG DEVELOPING THIS AFTERNOON. STILL IN A CYCLONIC FLOW
ALOFT WITH UPPER TROUGH OVER THE AREA SO PLAUSIBLE THAT ISOLD SHRA
OR TSTM COULD POP UP THIS AFTERNOON...PARTICULARLY CLOSER TO
LAND/LAKE BREEZE CONVERGENCE ZONE OVER EASTERN CWA...BUT COVERAGE
SHOULD REMAIN LIMITED AT BEST SO KEEPING POPS VERY SMALL.

CANADIAN HIGH PRESSURE WILL BUILD INTO THE AREA WEDNESDAY AND
THURSDAY PROVIDING FOR LOW HUMIDITY AND MILD DAYS AND MOSTLY CLEAR
AND SEASONABLY COOL NIGHTS. LAKE BREEZES BOTH DAYS WILL KEEP TEMPS
COOLER NEAR THE LAKE WITH MID 70S TO AROUND 80 EXPECTED INLAND AND
UPPER 60S/NEAR 70 LAKESIDE.

UPPER TROUGH WILL BEGIN MOVING OUT BY END OF THE WEEK WITH UPPER
FLOW FLATTENING OUT A BIT ALLOWING FOR WARMER/MORE HUMID AIR MASS TO
BEGIN TO SPILL BACK EASTWARD TOWARD THE AREA. MEDIUM RANGE GUIDANCE
SUGGESTS THAT OUR AREA WILL BE POSITIONED UNDER A MODERATELY ACTIVE
NW FLOW ALOFT ON THE FRINGE OF THE HOT/HUMID AIR OVER THE CENTRAL
CONUS. GENERALLY LOOKS TO BE A POTENTIALLY UNSETTLED PERIOD WITH ONE
OR MORE MCS`S POTENTIALLY AFFECTING THE AREA. TEMPS WILL HINGE
LARGELY ON CLOUD COVER AND PRECIP TRENDS WHICH JUST CAN`T BE
PINPOINTED THIS FAR OUT...BUT A GENERAL TREND TOWARD WARMER AND MORE
HUMID CONDITIONS IS EXPECTED.

IZZI

&&

.AVIATION...

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

* ISOL -SHRA NEAR THE TERMINALS THIS AFTERNOON.

* LAKE BREEZE WEDNESDAY AFTERNOON.

RODRIGUEZ

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

WHILE FRONTAL BOUNDARY CONTINUES TO SLIDE SOUTHEAST OF THE
TERMINALS THIS AFTERNOON...ANOTHER SURFACE TROUGH/BOUNDARY IS
SITUATED FURTHER NORTH OVER WISCONSIN. IN BETWEEN...A STEADY
WEST/NORTHWEST WIND WITH LOW 20KT GUSTS IS OCCURRING WHILE DIURNAL
CU/STRATO CU DEVELOP OVERHEAD. THIS IS RESULTING IN VFR
CEILINGS...WITH CONDITIONS TO REMAIN VFR THROUGH THE AFTERNOON AND
FOR THE REST OF THE FORECAST PERIOD. WHILE MID/UPPER LEVEL FORCING
WILL HELP PROVIDE ISOLATED SHOWERS NEAR THE TERMINALS THIS
AFTERNOON...BETTER FORCING/FOCUS WILL REMAIN FURTHER NORTH IN
WISCONSIN WHERE BETTER COVERAGE OF SHOWERS AND EVEN THUNDERSTORMS
WILL OCCUR. DESPITE THE POSSIBILITY FOR ISOLATED SHOWERS THIS
AFTERNOON...DID LEAVE THE TAFS DRY AS ONCE AGAIN ANY DEVELOPMENT
WILL BE LIMITED NEAR THE TERMINALS. THE WEST/NORTHWEST WINDS WILL
PERSIST THROUGH THIS EVENING BUT WITH GUSTS DIMINISHING. EXPECT
WINDS TO BEGIN OUT OF THE NORTH/NORTHWEST WEDNESDAY BEFORE LAKE
BREEZE INTERACTION IN THE AFTERNOON SHIFTS THEM TO THE NORTHEAST.

RODRIGUEZ

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

* HIGH CONFIDENCE OF -SHRA THIS AFTERNOON...MEDIUM CONFIDENCE THAT
  -SHRA WILL REMAIN NORTHEAST OF THE TERMINALS.

* HIGH CONFIDENCE OF LAKE BREEZE IMPACTING THE TERMINALS WEDNESDAY
  AFTERNOON...LOW MEDIUM CONFIDENCE OF EXACT TIMING.

RODRIGUEZ

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

WEDNESDAY NIGHT AND THURSDAY...VFR

FRIDAY THROUGH SUNDAY...GENERALLY VFR WITH A CHANCE OF SHOWERS
AND THUNDERSTORMS EACH DAY.

MONDAY...VFR.

KJB

&&

.MARINE...
123 PM CDT

SURFACE LOW PRESSURE CONTINUES TO PULL AWAY TO THE NORTHEAST ACROSS
NORTHEASTERN ONTARIO THIS AFTERNOON...WITH A WEAK COLD FRONT
TRAILING JUST SOUTH OF LAKE MICHIGAN. WINDS HAVE SHIFTED GENERALLY
TO THE WEST-NORTHWEST ACROSS THE LAKE WITH GUSTS AROUND 20 KT
ESPECIALLY NEAR SHORE WHERE LAND-BASED MIXED LAYER WAS HELPING TO
TRANSPORT MOMENTUM TO THE WATER...THOUGH BUOYS IN THE CENTER OF THE
LAKE WERE GENERALLY BELOW 10 KT. WIND WILL REMAIN FROM AN OVERALL
WEST-NORTHWEST DIRECTION TONIGHT INTO WEDNESDAY WITH SOME MINOR
BACKING AND VEERING AHEAD OF ANOTHER WEAK COLD FRONTAL TROUGH
TONIGHT...BEFORE THE GRADIENT REALLY BEGINS TO WEAKEN LATER
WEDNESDAY AS HIGH PRESSURE RIDGE SLIDES EAST TOWARD THE LAKE. LIGHT
VARIABLE WINDS ARE EXPECTED AS LAKE BREEZE CIRCULATIONS DEVELOP
AROUND THE PERIMETER OF THE LAKE WEDNESDAY AFTERNOON...WITH LIGHT
WINDS CONTINUING THROUGH EARLY THURSDAY WITH THE SURFACE RIDGE AXIS
IN THE VICINITY. WINDS WILL THEN BECOME SOUTH-SOUTHEAST BY THURSDAY
AFTERNOON AS THE RIDGE DRIFTS OFF TO THE EAST AND A TROUGH DEVELOPS
OVER THE PLAINS TO THE WEST. SOUTH WINDS WILL INCREASE IN SPEED INTO
THE 20 KT RANGE ESPECIALLY ACROSS THE NORTHERN PORTION OF THE LAKE
LATER FRIDAY AND FRIDAY NIGHT AHEAD OF THE APPROACHING SURFACE
TROUGH. WITH THE SOUTH WINDS...AN INCREASE IN LOW LEVEL MOISTURE
WILL ALSO BRING WITH IT AN INCREASING CHANCE OF SHOWERS AND
THUNDERSTORMS LATE FRIDAY INTO THE WEEKEND.

RATZER

&&

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

$$

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