Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 061953
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
253 PM CDT MON JUL 6 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...
303 AM CDT

TUESDAY NIGHT THROUGH SUNDAY...

LOOKS LIKE A BRIEF RESPITE TUESDAY NIGHT BEFORE THE FRONT GETS
SHIFTED BACK NORTHWARD AND BECOMES THE FOCUS FOR ADDITIONAL ROUNDS
OF PRECIPITATION THROUGH WEEKS END. THE UPPER AIR PATTERN FEATURES
HIGH PRESSURE OVER THE SE UNITED STATES EXTENDING OFFSHORE TO THE
ATLANTIC...WITH A TROUGH JUST OFF THE CALIFORNIA COAST. THE HIGH IN
THE EAST WILL SLOWLY RETROGRADE AND SHIFT INLAND TO THE WEST WHILE
THE TROUGH IN THE WEST SLOWLY MOVES EASTWARD ONSHORE INTO THE GREAT
BASIN. THIS KEEPS OUR AREA IN A SOMEWHAT MOIST WSW FLOW WITH
MULTIPLE WAVES PROPAGATING NE IN THIS FLOW PATTERN AND INTERSECTING
WITH THE STALLED OUT FRONTAL BOUNDARY. THIS PATTERN SUGGEST
OCCASIONAL PERIODS OF SHOWERS AND THUNDERSTORMS. FUTURE FORECASTS
WILL LIKELY NEED TO REFINE THE TIMING OF THESE CHANCES...WHICH
CURRENTLY LOOK TO OCCUR WEDNESDAY PM...FRIDAY...AND POSSIBLY INTO
SATURDAY. UPPER LEVEL HEIGHTS CONTINUE TO BUILD FROM THE EAST AS THE
HIGH EXPANDS OVER THE ENTIRE SOUTHERN UNITED STATES WHICH SHOULD
EVENTUALLY LIFT THE FRONTAL BOUNDARY NORTH OF THE AREA AT SOME
POINT BUT NOT UNTIL THE WEEKEND.

TEMPERATURES WILL BE MUCH COOLER THROUGH MID WEEK...WITH READINGS
BACK INTO THE 70S...WITH LAKESHORE AREAS STUCK IN THE 60S/NEAR 70
BEFORE HEIGHTS BUILD AND THE FRONT GETS LIFTED NORTHWARD.
TEMPERATURES AT THIS POINT CONTINUE TO RECOVER BACK WELL INTO THE
80S FOR THE WEEKEND.

KMD

&&

.AVIATION...

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

* THUNDERSTORMS THIS AFTERNOON AND AGAIN THIS EVENING.

* MVFR OR POSSIBLE IFR TUESDAY MORNING.

* NORTH-NORTHEAST WINDS OVER 10KT TUESDAY.

MM

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

PRE-FRONTAL THUNDERSTORMS ARE FIRING ACROSS NORTHERN ILLINOIS
THIS AFTERNOON WITH CONDITIONS FAVORABLE FOR CONTINUED EASTWARD
EXPANSION. TIME OF ARRIVAL TOOL PUTS FIRST ROUND OF THUNDER TO
ORD/MDW CLOSE TO 20Z. AS THESE STORMS LOOK TO BE OUTRUNNING THE
MAIN STORM COMPLEX...THEY ARE LOSING THEIR INTENSITY. FOLLOWING
THE BRIEF FIRST ROUND OF THUNDER...EXPECT VCSH ON AND OFF UNTIL
THE NEXT ROUND OF TSRA APPROACHES. MODEL CONSENSUS STARTS THUNDER
AT ORD/MDW AGAIN NEAR 02-03Z...LASTING FOR ABOUT 3 HOURS.

LOOK FOR A WIND SHIFT TO THE NORTH BEHIND THE COLD FRONT ALONG
WITH LOW CLOUDS...BR...AND OCCL SHOWERS. LOW-BASED INVERSION
EARLY TUESDAY WILL KEEP MVFR LIKELY WITH A CHANCE FOR CEILINGS
DROPPING UNDER 1KFT. THE INVERSION SHOULD MIX OUT JUST AFTER 12Z
BUT MVFR CONDITIONS WILL REMAIN THROUGH MOST OF THE MORNING.

MM

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

* HIGH THAT THUNDERSTORMS WILL OCCUR...MEDIUM ON TIMING.

* HIGH ON MVFR TUESDAY...MEDIUM LOW ON IFR OCCURRING.

* HIGH ON NORTH WINDS OVER 10KT.

MM

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

TUESDAY NIGHT...VFR.

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

THURSDAY...CHANCE OF TSRA.

FRIDAY...CHANCE OF TSRA.

SATURDAY...CHANCE OF TSRA.

SUNDAY...CHANCE OF TSRA.

RODRIGUEZ

&&

.MARINE...
252 PM CDT

WIND GUSTS WERE NOT AS STRONG AS EXPECTED ACROSS THE NEARSHORE
WATERS TODAY AS THICK CLOUD COVER LIMITED MIXING. A LINE OF SHOWERS
THAT HAS A HISTORY OF PRODUCING GUSTS UP TO 30 KT IS MOVING ACROSS
THE NEARSHORE WATERS SO WILL KEEP THE SMALL CRAFT GOING THROUGH
00Z/7PM CDT TO ACCOUNT FOR SHOWER RELATED GUSTS. WINDS WILL PICK
BACK UP TOMORROW AND A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR
POINTS SOUTH OF CHICAGO FROM 9AM CDT TUESDAY THROUGH 4AM CDT
WEDNESDAY.  FLOW WILL BE ON SHORE SO WAVE HEIGHTS ALONG THE INDIANA
SHORE WILL GROW TO 4-7 FT AND THEN COME DOWN TUESDAY EVENING AND
NIGHT.  WINDS DIMINISH AS HIGH PRESSURE SPREADS OVER THE LAKE
WEDNESDAY MORNING. WINDS WILL BE LIGHT AND VARIABLE OVER THE NORTH
HALF OF THE LAKE INTO WEDNESDAY EVENING WHILE A WEAK LOW PASSES JUST
SOUTH OF THE LAKE WEDNESDAY NIGHT. WINDS WILL BE NORTHEAST THEN
NORTH THURSDAY AFTERNOON.  WINDS REMAIN LESS THAN 10 KT AS THE HIGH
SLOWLY SHIFTS EAST THROUGH THE END OF THE WEEK WITH THE NEXT LOW
IMPACTING THE LAKE EARLY NEXT WEEK. THERE WILL BE ADDITIONAL
PERIODIC CHANCES OF THUNDERSTORMS WEDNESDAY NIGHT AND THEN FROM
EARLY FRIDAY MORNING THROUGH EARLY NEXT WEEK.

JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY...ILLINOIS NEARSHORE WATERS UNTIL 7 PM MONDAY.

&&

$$

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