Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 071948
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
248 PM CDT TUE JUL 7 2015

.SHORT TERM...
234 PM CDT

THROUGH WEDNESDAY...

THE COLD FRONT THAT MOVED THROUGH EARLY TODAY NOW LIES ACROSS
CENTRAL INDIANA AND SOUTHERN IL WITH THE RAIN ALSO LOCATED OVER
THOSE REGIONS. EXPECTING THE DRY CONDITIONS TO CONTINUE OVERNIGHT
AS HIGH PRESSURE MOVES OVER CENTRAL LAKE MI LATE TONIGHT. GUSTY
NORTH WINDS WILL DIMINISH FIRST FOR AREAS WEST OF I-55 AS THE
GRADIENT WILL WEAKEN QUICKEST THERE. GUSTY WINDS ALONG THE LAKE
WILL TAKE THE LONGEST TO DIMINISH BUT THINKING GUSTS WILL FINALLY
BE BELOW 20 MPH LATE THIS EVENING.

CUMULUS CLOUDS HAVE FORMED IN THE COOL AIR AS THE STRATUS ASSOCIATED
WITH THE FRONT SHIFTS TO THE SOUTHEAST. THE CU WILL BE DIURNAL IN
NATURE SO EXPECTING SKIES TO CLEAR OVERNIGHT ALLOWING TEMPS TO FALL
INTO THE LOW TO MID 50S. SOME LOCATIONS ALONG THE IL/WI STATE LINE
MAY EVEN DROP INTO THE UPPER 40S.  CHICAGO AND THE INDIANA SHORE
LINE WILL BE THE WARMEST WITH LOWS AROUND 60 DUE TO FLOW OFF OF
THE LAKE.

ATTENTION THEN SHIFTS TO TOMORROW/S RAINFALL. SOME AREAS SOUTH OF
I-80 RECEIVED UP TO 3 INCHES OF RAIN MONDAY AND MONDAY
NIGHT...AND WHEN THAT IS COMBINED WITH THE RECENT WET PATTERN WE
ARE IN...THERE ARE CONCERNS ABOUT FLOODING TOMORROW. BOTTOM LINE
UP FRONT...ISSUED A FLASH FLOOD WATCH FOR LASALLE
COUNTY...KANKAKEE COUNTY...THROUGH JASPER COUNTY SOUTH FROM
WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT.

A LOW PRESSURE SYSTEM WILL FORM OVER OKLAHOMA LATE THIS EVENING AND
DEEPEN AS IT MOVES OVER THE MID IL/IN STATE LINE WEDNESDAY EVENING.
AN UPPER LEVEL VORT STREAMER ASSOCIATED WITH THE LOW SHIFTS NORTH
INTO NORTHERN IL AND INDIANA WEDNESDAY MORNING...AND THEN PARKS OVER
THE AREA WEDNESDAY AFTERNOON. 12Z GUIDANCE IS IN BETTER AGREEMENT
THAN 06Z RUNS ABOUT PRECIP FALLING ALONG AND SOUTH OF THE I-88
CORRIDOR...SO HAVE MEDIUM-HIGH CONFIDENCE IN HOW FAR NORTH PRECIP
GETS WEDNESDAY. THE NAM IS THE MAIN OUTLIER WITH MUCH LESS PRECIP
THAN THE GFS AND ECMWF. PWAT VALUES INCREASE TO 1.5-2 INCHES
DURING THE DAY WEDNESDAY. HOWEVER...MODEL SOUNDINGS FEATURE A LOT
OF DRY AIR ALOFT THAT THE RAIN WILL HAVE TO OVERCOME...SO HAVE
MEDIUM CONFIDENCE IN HOW QUICKLY SHOWERS PUSH NORTH WEDNESDAY.
GUIDANCE ALSO FEATURES VERY LITTLE CAPE...SO ONLY HAVE A SLIGHT
CHANCE OF THUNDERSTORMS IN THE FORECAST.

THINKING THE MAJORITY OF PRECIP WILL FALL AS STRATIFORM RAIN WITH A
FEW EMBEDDED STRONGER RAIN SHOWERS OR THUNDERSTORMS. THE TOTAL
AMOUNT OF RAIN IS THE CONCERN...WITH 0.75 TO AN INCH OF ADDITIONAL
RAIN FORECAST FOR AREAS ALONG AND SOUTH OF I-80. LOCALLY HIGHER
AMOUNTS ARE POSSIBLE. ONCE AGAIN...WE ISSUED A FLASH FLOOD WATCH
FOR THE SOUTHERN PORTION OF THE CWA SINCE SIGNIFICANT RAINFALL
AMOUNTS ARE POSSIBLE OVER AREAS THAT ALREADY RECIEVED AMPLE
AMOUNTS OF RAIN FOR WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT.

WITH THE INCREASED CLOUD COVER...LOWERED HIGH TEMPS FOR WEDNESDAY BY
A DEGREE OR TWO. EXPECTING HIGH TEMPS AROUND 70 WITH UPPER 60S ALONG
THE LAKE.

JEE

&&

.LONG TERM...
330 AM CDT

FRIDAY THROUGH MONDAY...

THE EXTENDED PERIOD CONTINUES TO LOOK WARMER AND MORE
ACTIVE...WITH CHANCES FOR THUNDER THROUGHOUT MUCH OF THE PERIOD.
THIS WILL BEGIN ON FRIDAY WITH FAIRLY ENERGETIC FLOW RIDING ALONG
RISING HEIGHTS ACROSS THE REGION WITH A GOOD WARM/MOIST ADVECTION
PUSH...WITH AT LEAST SCATTERED THUNDERSTORM DEVELOPMENT LIKELY.
THUNDERSTORM DEVELOPMENT APPEARS TO BE LIKELY AGAIN FRIDAY NIGHT
INTO SATURDAY...WHILE STRONG LLJ PUMPS HIGHER MOISTURE CONTENT AIR
OVER THE REGION. THUNDERSTORMS MAY LINGER SATURDAY MORNING...BUT
SHOULD PUSH NORTH OF THE CWA THROUGH EARLY AFTERNOON. WITH THIS
LIKELY OCCURRING...ABOVE NORMAL TEMPS ARE EXPECTED SATURDAY...WITH
SIMILAR TEMPS EXPECTED SUNDAY.

RODRIGUEZ

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 20Z...

* NORTHEAST WINDS GUSTING TO 25KT THROUGH THIS AFTERNOON AND OVER
  10KT THROUGH 02Z.

MM

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

POST FRONTAL AIRMASS HAS SUPPORTED CUMULUS DEVELOPMENT ACROSS
WISCONSIN. ANY SUNNY AREAS CURRENTLY WILL BE FILLED IN WITH CLOUDS
BASED AROUND 3500 FEET THROUGH THE AFTERNOON. EXPECTING CLOUDS TO
SCATTER OUT THIS EVENING WITH THE LOSS OF DAYTIME HEATING. WINDS
HAVE CONTINUED TO BE GUSTY THIS AFTERNOON...BUT WILL ALSO SUBSIDE
AS THE PRESSURE GRADIENT RELAXES SOME AND AS WE LOSE HEATING.

INVERSION FORECASTED AT RFD MAY ALLOW FOR BRIEF MVFR FOG WED
AM...BUT LACK OF SURFACE MOISTURE HAS PRECLUDED MENTION IN TAF.
REPEAT DAYTIME CONDITIONS ARE EXPECTED WEDNESDAY WITH DIURNAL
CYCLE PROVIDING FAIR WEATHER CLOUDS. OVERCAST CANOPY WILL INCREASE
THROUGH THE DAY AHEAD OF LOW PRESSURE ADVANCING FROM THE MID-
MISSISSIPPI VALLEY. BETTER CHANCE FOR RAIN ASSOCIATED WITH THIS
SYSTEM LIES AFTER 00Z TOMORROW.

MM

//ORD AND MDW CONFIDENCE...UPDATED 20Z...

* HIGH IN WINDS.

* HIGH IN ALL OTHER FORECAST ELEMENTS.

MM

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

WEDNESDAY NIGHT...CHC SHRA...SCHC TSRA.

THURSDAY...VFR. EAST-NORTHEAST WINDS.

FRIDAY THROUGH MONDAY...PERIODS OF SHOWERS AND THUNDERSTORMS.

KMD

&&

.MARINE...
250 AM CDT

LOW PRESSURE PASSING OVER SOUTHERN LAKE MICHIGAN WILL CONTINUE OFF
TO THE NORTHEAST THIS MORNING...ALLOWING A COLD FRONT TO CLEAR THE
SOUTHERN TIP OF THE LAKE JUST AFTER DAYBREAK. WAVES WILL QUICKLY
BUILD ON THE SOUTHERN HALF/THIRD OF THE LAKE AS THIS
OCCURS...REACHING 7-8 FT ON THE INDIANA SHORELINE...MAYBE A TOUCH
LOWER ON THE ILLINOIS SHORELINE. EXPANSIVE HIGH PRESSURE OVER THE
UPPER MIDWEST WILL BUILD EAST ACROSS THE CENTRAL GREAT
LAKES...BECOMING CENTERED OVER NORTHERN LAKE MICHIGAN WEDNESDAY.
SEVERAL LOWS WILL CONTINUE TO PROGRESS SOUTH AND EAST OF THE LAKE
THROUGH FRIDAY.

KMD

&&

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

     BEACH HAZARDS STATEMENT...ILZ006 UNTIL 7 PM TUESDAY.

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

LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP TO WILMETTE HARBORS UNTIL 7 PM TUESDAY.

     SMALL CRAFT ADVISORY...NEARSHORE WILMETTE HARBOR TO MICHIGAN CITY IN UNTIL
     4 AM WEDNESDAY.

&&

$$

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