Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 070750
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
250 AM CDT TUE JUL 7 2015

.SHORT TERM...
252 PM CDT

THROUGH TONIGHT...

A LINE OF SHOWERS IS MOVING THROUGH NORTHEAST IL WITH ADDITIONAL
SHOWERS AND STORMS OVER SOUTHERN AND EASTERN IOWA.  THE LINE OF
SHOWERS WITH A FEW EMBEDDED THUNDERSTORMS WILL CONTINUE EAST AND MAY
WEAKEN FURTHER AS THE OUTFLOW BOUNDARY HAS STARTED TO SEPARATE
ITSELF FROM THE LINE OF SHOWERS.  HEAVY RAIN...A FEW GUSTS OF
WIND...AND A FEW FUNNEL CLOUDS HAVE BEEN REPORTED WITH THIS LINE OF
SHOWERS. THE FUNNEL CLOUDS ARE FORMING AS BOUNDARIES INTERSECT...BUT
THE FUNNELS ARE NOT LOCATED UNDER ANY UPDRAFTS SO TORNADOES ARE NOT
EXPECTED.

TEMPERATURES ARE FALLING INTO THE 70S BEHIND THE LINE OF SHOWERS AND
WITH THE THICK CLOUD COVER...RECOVERY IS VERY SLOW AT BEST.
THEREFORE LOCATIONS OVER NORTHWEST IL ACTUALLY SAW THEIR HIGH TEMPS
EARLY THIS MORNING AS THEY WILL STAY IN THE 70S. HAVE FALLING TEMPS
ALSO ACROSS NW INDIANA AS THE STORMS ROLL THROUGH...BUT IF THE LINE
FALLS APART...TEMPS WILL LIKELY STAY IN THE LOW TO MID 80S.

THE COLD FRONT STRETCHES ACROSS NORTHWEST WI THROUGH SOUTHERN MN AND
NW IA AND IS PROGGED TO SWING THROUGH NORTHERN IL AND NW INDIANA
OVERNIGHT.  ANOTHER ROUND OF SHOWERS ARE EXPECTED AHEAD OF THE COLD
FRONT...BUT NOT EXPECTING MUCH IF ANY SEVERE WEATHER.  THE LATEST
RAP ANALYSIS SHOWS 500-2000 J/KG OF CAPE BEHIND THE LINE OF STORMS
OVER NORTH CENTRAL IL...WITH THE VALUES DECREASING AS YOU GET CLOSER
TO THE MISSISSIPPI RIVER.  SHEAR VALUES ARE ALSO AROUND ZERO...SO
ORGANIZED STORMS ARE NOT EXPECTED.  EXPECTING THE NEXT ROUND OF
SHOWERS AND STORMS TO MOVE INTO NW ILLINOIS AFTER 5PM CDT AND
CONTINUE ACROSS NORTHERN IL AND NW INDIANA THROUGH THE NIGHT. THIS
ROUND WILL ALSO HAVE LIGHTNING...HEAVY RAIN...AND PROBABLY SOME
GUSTY WINDS...BUT WIDESPREAD SEVERE WEATHER IS NOT EXPECTED.

GIVEN THE LOWER THAN EXPECTED HIGH TEMPS TODAY...LOWERED LOW TEMPS
TONIGHT AS WELL. DEW POINTS WILL REMAIN IN THE MID 60S TO AROUND 70
SO LOW TEMPS SHOULD STICK PRETTY CLOSE TO THE DEW POINTS. EXPECTING
LOWS TO VARY FROM THE MID 60S AROUND RFD TO AROUND 70 IN NW INDIANA.

JEE

&&

.LONG TERM...
325 PM CDT

TUESDAY THROUGH MONDAY...

THE FRONT WILL CONTINUE SHIFTING SOUTH THROUGH TUESDAY MORNING
WITH NORTHERLY WINDS AND COLD ADVECTION ENVELOPING THE AREA. SUCH
AS HAS BEEN THE TREND WITH THE SYSTEM...DID ALSO SPEED UP THE END
OF RAIN CHANCES ON TUESDAY. THINK SHOWER COVERAGE IN THE MORNING
WILL BE SCATTERED WITHIN POST FRONTAL FORCING...AND ANY THUNDER
LIKELY EVEN MORE ISOLATED. STRATUS IS LIKELY TO LINGER LONGER THAN
THE RAIN CHANCES AS THE COOL AIR COLLIDES WITH THE MOIST BOUNDARY
LAYER. IT IS CERTAINLY POSSIBLE CLOUDS STICK AROUND FOR SOUTHERN
AREAS AS WELL AS LOCATIONS NEAR THE LAKE THROUGH THE AFTERNOON.
HIGH PRESSURE SHOULD KEEP THE AREA MAINLY DRY INTO WEDNESDAY
MORNING.

TEMPERATURES BOTH TUESDAY AND WEDNESDAY LOOK TO BE WELL BELOW
NORMAL WITH HIGHS PRIMARILY IN THE LOWER 70S...WITH MID-UPPER 60S
NEAR THE LAKE SHORE. THESE READINGS ACROSS THE FORECAST AREA ARE
10 TO 15 DEGREES BELOW NORMAL FOR EARLY JULY. IN-BETWEEN ON
TUESDAY NIGHT...ANY CLOUDS SHOULD BE CONFINED TO THE SOUTHERN CWA
WHICH WILL ALLOW NORTHERN COMMUNICATIONS TO DIP INTO THE
50S...EVEN LOWER 50S FOR OUTLYING LOCATIONS.

BEYOND...SHORT WAVE IMPULSES LOOK TO BE KEY TO RAIN CHANCES WITH
ONE BECOMING MORE CONSISTENTLY TARGETED ON GUIDANCE WEDNESDAY
NIGHT. THE WINDOW OF INSTABILITY RETURN LOOKS LIMITED...SO THIS
COULD BE MAINLY JUST SHOWERS ESPECIALLY NORTH OF I-80. EACH
SUCCESSIVE IMPULSE APPEARS TO BRING THE THETA-E GRADIENT ALOFT
MORE SO OVER THE AREA WHICH WARRANTS STORM CHANCES ALMOST DAILY
LATE IN THE WEEK INTO THE WEEKEND. TEMPERATURES ALSO LOOK TO
REBOUND BACK TO NORMAL BY THE WEEKEND.

MTF

&&

.AVIATION...

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

* OCCASIONAL RAIN THROUGH DAYBREAK.

* NORTHWEST WINDS QUICKLY FLIP TO NORTHEAST JUST AFTER DAYBREAK
  AND INCREASE WITH GUSTS TO 22KT POSSIBLE THROUGH EARLY
  AFTERNOON.

* MVFR CIGS THROUGH EARLY TUE...WITH OCCASIONAL IFR POSSIBLE.

KMD

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

MORE ORGANIZED SHOWER AND THUNDERSTORM ACTIVITY IS NOW ALONG A
LINE FROM KPNT TO KIKK AND NORTHEAST OF KGYY...WITH OCCASIONAL
LIGHTER THOUGH AT TIMES MODERATE RAIN DRIFTING THROUGH NORTHEAST
AND NORTH CENTRAL ILLINOIS. MEANWHILE...COLD FRONT IS KNOCKING AT
THE DOOR OF KRFD WITH A RAPID SHIFT TO NORTH-NORTHWEST WINDS
EXPECTED SOON. THIS SHOULD COME TO THE CHICAGOLAND TERMINALS
CLOSER TO 9Z. LIGHTER WINDS AHEAD OF THE FRONT AND A VERY MOIST
AIR MASS SUCH THAT MVFR CIGS SHOULD BEGIN TO MATERIALIZE IN THE
NEXT HOUR OR TWO. IFR MAY BRIEFLY AS WELL IN THE NEXT FEW
HOURS...THOUGH MVFR SHOULD BE MORE PREVAILING. WINDS WILL FLOP
OVER TO NORTHEAST JUST AFTER DAYBREAK AND REMAIN ELEVATED THROUGH
THE DAY. SKIES SHOULD SCATTER OUT DURING THE LATE MORNING HOURS.
NORTHEAST WINDS REMAIN ABOVE 10 KT THROUGH THE EARLY EVENING.

KMD

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

* HIGH IN OCCASIONAL RAIN...MEDIUM ON END TIMING. HIGH THAT
  THUNDER WILL REMAIN TO THE SOUTH OF THE TERMINALS.

* HIGH IN WIND DIR/SPEED...HIGH IN GUSTS DEVELOPING TUE MIDDAY.

* HIGH IN CIGS DIPPING TO MVFR CONDS...BUT LOW ON IF IFR OCCUR.
  MEDIUM ON DURATION OF MVFR CIGS.

KMD

//OUTLOOK FOR ORD/MDW FOR 12Z WEDNESDAY-12Z MONDAY...UPDATED 00Z...

WEDNESDAY...CHANCE OF SHRA SLIGHT CHANCE OF TSRA.

THURSDAY THROUGH SUNDAY...PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS.

BEACHLER

&&

.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...9 AM TUESDAY TO 4 AM
     WEDNESDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002...9 AM TUESDAY TO 4 AM
     WEDNESDAY.

LM...SMALL CRAFT ADVISORY...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...9 AM
     TUESDAY TO 4 AM WEDNESDAY.

&&

$$

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