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000
FXUS63 KLOT 190744
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
244 AM CDT WED JUN 19 2013

.DISCUSSION...
849 PM CDT

VERY LITTLE CHANGE MADE TO THE GOING FORECAST FOR THE REST OF
TONIGHT. THE HIGH PRESSURE RIDGE CONTINUES TO BUILD DOWN THE LAKE
RESULTING IN A PRESSURE GRADIENT ACROSS NE IL AND NW IN. THIS
COUPLED WITH THE LONG NNE FETCH OF THE WINDS OVER THE LAKE HAS
CONTINUED TO ALLOW FOR 20+ MPH GUSTS EARLY THIS EVE. THESE LOOK
SLOW TO SUBSIDE PER OBSERVATIONAL TRENDS AND THE RAP BUFKIT
SOUNDINGS. SO THESE WILL ADD A LITTLE NIP IN THE AIR...BY JUNE
STANDARDS...ACROSS CHICAGO WITH TEMPS FALLING SLOWLY THROUGH THE
MID-UPPER 50S. THE COOLEST TEMPS TONIGHT STILL LOOK TO BE ALONG
THE STATE LINE WHERE CONDITIONS SHOULD DECOUPLE. UPPER 40S SHOULD
BE REALIZED THERE.

MTF

//PREV DISCUSSION...
239 PM CDT

STRATUS LAYER THAT WAS ANCHORED OVER FAR NORTHEAST IL/NORTHWEST IN
THIS MORNING HAS ERODED WITH THE WARM AIR HEATING THE SFC. VISIBLE
IMAGERY INDICATES A FEW AREAS OF CUMULUS CLOUDS THAT HAVE DEVELOPED
THIS AFTERNOON ACROSS NORTHERN IL. IN ADDITION SOME BUILDING CUMULUS
CLOUDS WERE NOTED ALONG A PONTIAC TO KANKAKEE LINE...IN AN AREA OF A
STRONGER THERMAL DIFFERENTIAL. HOWEVER THE LIFT MECHANISM IN THIS
AREA IS MINIMAL...AND SO A FEW ISOLATED SHOWERS/THUNDERSTORMS MAY
DEVELOP BUT QUICKLY DISSIPATE. ALL PRECIPITATION OVER THE CWFA WILL
BE DIURNALLY DRIVEN...THUS BY SUNSET OR IMMEDIATELY AFTER SUNSET
PRECIP WILL COME TO AN END. FURTHER SOUTH STRONGER INSTABILITY WAS
POSITIONED ACROSS CENTRAL IL STRETCHING WEST THROUGH NORTHERN
MISSOURI. MID-LVL WAVE CONTINUES TO PIVOT EAST ACROSS FAR NORTHWEST
IL THIS AFTERNOON...AND WILL MAINTAIN THE NORTHEAST FLOW ACROSS MUCH
OF THE CWFA. AS A RESULT COOL TEMPS WILL PERSIST THIS EVENING...WITH
MINIMAL CLOUD COVER FROM THE DIFFLUENT FLOW ALOFT. SKIES WILL BECOME
MOSTLY CLEAR TONIGHT...WITH THE LLVL FLOW WEAKENING. THIS SHOULD
PROVIDE DECENT RADIATIONAL COOLING WITH TEMPS OVERNIGHT EXPECTED TO
BE IN THE MID 50S SOUTH OF I-80. FURTHER NORTH TEMPS WILL BE MUCH
COOLER TO ARND 50...POSSIBLY THE UPR 40S FOR AREAS ALONG AND NORTH
OF A ROCKFORD...AURORA...WAUKEGAN LINE.

CONFIDENCE...HIGH.

WEDNESDAY THROUGH THURSDAY...

500MB TROUGH AXIS SLOWLY PIVOTS TO THE EASTERN GREAT LAKES WED...AND
WILL CONTINUE TO PUSH EAST THUR. THE SFC RIDGE WILL ALSO BEGIN TO
PUSH EAST...HOWEVER AN ONSHORE OR NORTHEAST TO EAST FLOW WILL
PERSIST INTO WED FOR MUCH OF NORTHERN IL. THE DIFFERENCE FOR WED
WILL BE THAT THE 850MB THERMAL TROUGH WILL LINGER OVERHEAD. WITH
ABUNDANT SUNSHINE AND SFC HEATING...TEMPS SHUD WARM INTO THE MID/UPR
70S OR POSSIBLY THE LOW 80S FROM LASALLE TO IROQUOIS COUNTY.

FOR THUR 500MB HEIGHTS WILL BEGIN TO RISE WITH FLOW BEGINNING TO
TURN TO THE SOUTHEAST IN THE LLVLS. A WEAK LAKE BREEZE MAY DEVELOP
AND PUSH INTO LAKE COUNTY IL...WHICH WOULD MOST LIKELY PROVIDE A
COOLING TREND IN THE AFTN HOURS. 850MB TEMPS WILL STEADILY WARM FOR
THUR TO ARND 14 TO 16 DEG C...WITH CONTINUED THIN CLOUD COVER. THIS
WILL ALLOW TEMPS TO WARM INTO THE LOW/MID 80S. THE CAVEAT WILL BE
AREAS OF LAKE COUNTY IL POST FRONTAL PASSAGE THAT WILL ALLOW TEMPS
TO FALL INTO THE 60S IN THE AFTN.

IT DOES APPEAR THAT ENOUGH DRY AIR WILL LINGER THRU THUR
AFTN/EVE...THUS HAVE HELD ONTO A DRY FORECAST IN THIS TIMEFRAME.
THIS PATTERN WILL BE CHANGING AS WE MIGRATE INTO THE EXTENDED
PERIODS.

CONFIDENCE IN TEMPERATURE FORECAST...HIGH.
CONFIDENCE IN DRY WEATHER THROUGH THUR...MEDIUM/HIGH.

FRIDAY THROUGH MONDAY...
MINIMAL CHANGES FROM PREVIOUS FORECAST IN REGARDS TO THE EXTENDED
PERIODS. POSSIBLY THE FIRST STRETCH OF 90 DEG DAYS IS UPON US FOR
SUN/MON/TUE.

GUIDANCE HAS A WARM FRONTAL BOUNDARY LIFTING OVERHEAD FRI WITH
SOUTHERLY FLOW USHERING IN ADDTL LLVL MOISTURE. IT DOES APPEAR A
WAVE WILL ALSO PUSH OVER THE CWFA FRI...WITH POTENTIAL FOR
SHOWERS/THUNDERSTORMS. TEMPS WILL BE SLIGHTLY WARM FOR FRI INTO THE
UPR 80S...WITH A FEW 90 DEGREE POINTS ACROSS THE CWFA.

ENSEMBLES FOR SEVERAL DAYS HAVE CONTINUED TO INDICATE THAT A 500MB
RIDGE ACROSS THE CENTRAL CONUS WILL ADVECT EAST AND BECOME ANCHORED
ACROSS THE EASTERN HALF OF THE CONUS BY THE WEEKEND AND POSSIBLY
PERSIST THROUGH EARLY NEXT WEEK. ADDITIONALLY...GUIDANCE HAS PROGGED
850MB TEMPS TO RISE TO ARND 20-22 DEG C FOR THE WEEKEND THRU EARLY
NEXT WEEK. CONSISTENCY FROM PREVIOUS RUNS SUGGESTS HIGH CONFIDENCE
IN THIS WARM STRETCH ARRIVING. THEN SUN/MON/TUE APPEAR TO BE NEAR
CARBON COPIES WITH TEMPS EASILY WARMING TO 90 DEGREES...POSSIBLY THE
LOW 90S. CLIMATOLOGY BASED ON THE 850MB TEMPS PROGGED AND TIME OF
YEAR WOULD SUGGEST TEMPS TO BE WARMER AS FORECASTED. A COUPLE
LIMITING FACTORS MIGHT BE THE POTENTIAL FOR A SERIES OF WAVES
BRINGING INSTABILITY AND THUNDERSTORM POTENTIAL EACH DAY OF THE
EXTENDED...ALONG WITH DEW PTS PROGGED TO BE ARND 70 DEG.
THIS COULD POTENTIALLY KEEP TEMPS IN CHECK IN THE MID/UPR 80S.

CONFIDENCE IN TEMPERATURE FORECAST...HIGH.
CONFIDENCE IN PRECIP/CONVECTIVE FORECAST...MEDIUM/HIGH.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* LAKE BREEZE WEDNESDAY AFTERNOON.

BMD

//DISCUSSION...UPDATED 06Z...

HIGH PRESSURE SPANS THE GREAT LAKES REGION TONIGHT WITH LIGHT FLOW
EXPECTED THROUGH THE TAF PERIOD. WINDS SHOULD SYNOPTICALLY VEER EAST
THEN SOUTHEAST...BUT A LAKE BREEZE MAY INTERRUPT THIS PROCESS
WEDNESDAY AFTERNOON TURNING WINDS BACK TO NORTHEAST FOR A PERIOD.
WITH SUNSET...WINDS SHOULD THEN VEER AGAIN TO THE SOUTHEAST AS THE
HIGH CONTINUES TO SETTLE SOUTHEAST TOWARDS THE MID ATLANTIC COAST.
OUTSIDE OF THE INFLUENCE OF THE LAKE BREEZE WEDNESDAY
AFTERNOON...EXPECT WINDS TO REMAIN LESS THAN 10 KT. VFR CONDITIONS
ARE ALSO EXPECTED TO PREVAIL THROUGH THE PERIOD.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* MEDIUM CONFIDENCE IN WIND DIRECTION FORECAST...HIGH CONFIDENCE
  IN WIND SPEEDS.
* HIGH CONFIDENCE IN ALL OTHER FORECAST ELEMENTS.

BMD

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

THURSDAY...VFR.

FRIDAY THROUGH MONDAY...PERIODIC CHANCES FOR TSRA...OTHERWISE VFR.

LENNING

&&

.MARINE...
243 AM CDT

HIGH PRESSURE IS CENTERED OVER THE CENTRAL GREAT LAKES REGION EARLY
THIS MORNING AND IS FORECAST TO MOVE SOUTHEAST TOWARDS THE MID
ATLANTIC COAST BY THURSDAY. MEANWHILE...WINDS AND WAVES HAVE ALREADY
DIMINISHED UNDER THE INFLUDENCE OF THE HIGH...THUS WILL ALLOW
REMAINING SMALL CRAFT ADVISORIES TO EXPIRE WITH THE MORNING FORECAST
PACKAGE. WITH LIGHT FLOW IN PLACE TODAY...WINDS WILL BECOME OFFSHORE
THIS AFTERNOON AS LAKE BREEZES DEVELOP ACROSS THE ENTIRE LAKE. AS
THE HIGH SETTLES TO OUR EAST THURSDAY...AND LOW PRESSURE OVER THE
PLAINS...WINDS WILL BEGIN TO TURN SOUTHERLY...AND FRESHEN UP FRIDAY
AS THE LOW LIFTS INTO THE UPPER MIDWEST. SOUTHERLY FLOW WILL
DOMINATE THE REMAINDER OF THE WEEKEND INTO EARLY NEXT WEEK. BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 4 AM WEDNESDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 4 AM WEDNESDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 4 AM WEDNESDAY.

&&

$$

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