Area Forecast Discussion
Issued by NWS Chicago, IL

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FXUS63 KLOT 070831
AFDLOT

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

.SHORT TERM...
330 AM CDT

THROUGH THURSDAY...

MAIN FORECAST CONCERNS/CHALLENGES IN THE NEAR TERM ARE WITH
PRECIP TRENDS THROUGH MIDDAY WITH PRECIP LIKELY LINGERING ACROSS
THE SOUTHEAST HALF OF THE CWA...AND THEN WITH MUCH COOLER TEMPS
EXPECTED TODAY.

LATEST RADAR IMAGERY DEPICTING PRECIP STILL PERSISTING OVER MUCH
OF THE AREA THIS MORNING WITH HEAVIER SHOWERS AND ISOLATED THUNDER
CONFINED PRIMARILY TO THE SOUTHEAST THIRD OF THE CWA...ALONG AND
SOUTH OF INTERSTATE 80. THIS BETTER DEVELOPMENT IS OCCURRING SOUTH
OF THE FRONT EARLY THIS MORNING WHERE HIGH MOISTURE CONTENT AIR
CONTINUES TO BE TRANSPORTED NORTHEASTWARD. ALTHOUGH INSTABILITY IS
LIMITED WITH THE HIGHEST INSTABILITY JUST SOUTH OF THE CWA...HIGH
PWAT AIR IN EXCESS OF TWO INCHES REMAINS SITUATED OVER MUCH OF THE
REGION. THIS IS ALLOWING FOR CONTINUED HEAVY DOWNPOURS WITH THE
STRONGER PRECIP...WITH HIGH INSTANTANEOUS PRECIP RATES STILL NOTED
ON DUAL POL. HOWEVER...THESE HEAVIER SHOWERS REMAIN FAIRLY
PROGRESSIVE AND CONTINUE TO STEADILY LIFT NORTHEAST THROUGH THE
REGION. LOOKING UPSTREAM...IT WOULD APPEAR THAT PRECIP WILL LIKELY
MOVE OVER MUCH OF THE CWA THROUGH THE 12-14Z TIME FRAME WITH SHORT
TERM GUIDANCE SUPPORTING THIS...BUT WITH THE HEAVIER RAIN AND
ISOLATED THUNDER PUSHING FURTHER SOUTH THROUGHOUT THIS TIME.
CONDITIONS SHOULD BE DRY FOR MUCH OF THE CWA BY MIDDAY...AND
ESPECIALLY BY EARLY AFTERNOON.

THIS WILL BE SUPPORTED WITH MUCH DRIER AND COOLER AIR ADVECTING
ACROSS THE REGION POST FROPA EARLY THIS MORNING. EARLY MORNING
SURFACE ANALYSIS WOULD PUT THE FRONT ACROSS A MENDOTA TO
STREAMWOOD...TO LAKE FOREST LINE ACROSS NORTHERN ILLINOIS. OVER
THE NEXT TWO TO THREE HOURS...THIS FRONT WILL CONTINUE THROUGH
REMAINING AREAS IN NORTHERN ILLINOIS WITH REMAINING AREAS IN EAST
CENTRAL ILLINOIS AND NORTHWEST INDIANA NOT OBSERVING FROPA UNTIL
CLOSER TO MID MORNING. BEHIND THIS FRONT...NORTHERLY WINDS ARE
RAMPING UP RATHER QUICKLY WHILE TEMPS FALL TO THE LOWER 60S. THIS
WILL SET THE STAGE FOR A RATHER COOL AND BREEZY DAY TODAY WITH
WELL BELOW NORMAL TEMPS EXPECTED FOR ALL AREAS. AREAS ACROSS NORTH
CENTRAL ILLINOIS MAY OBSERVE SOMEWHAT OF A RECOVERY THROUGH
MIDDAY...AS CLOUDS BEGIN TO SCATTER OUT.

BY THIS AFTERNOON AND ESPECIALLY THIS EVENING AND OVERNIGHT...DRY
CONDITIONS LIKELY IN PLACE WITH FRONT WELL SOUTH OF THE CWA AND
WITH MORE ZONAL FLOW IN PLACE ACROSS THE REGION. TONIGHT THROUGH
EARLY WEDNESDAY MORNING WILL BE DRY BUT THEN TURN ATTENTION
TOWARDS SHORTWAVE ENERGY LIFTING NORTHEAST THROUGH THE CENTRAL
PLAINS. THIS ENERGY AND ASSOCIATED SURFACE REFLECTION WILL LIFT TO
THE MID MISSISSIPPI VALLEY ON WEDNESDAY...WITH ASSOCIATED PRECIP
SPREADING NORTHWARD OUT AHEAD OF IT. DO BRING CHANCE POPS BACK
OVER THE SOUTHERN HALF OF THE CWA ON WEDNESDAY AND DID KEEP
MENTION OF SLIGHT CHANCE THUNDER AS WELL. HOWEVER...BEST
INSTABILITY LOOKS TO BE SITUATED TO THE SOUTH OF THE CWA DURING
THIS TIME AND AM NOT OVERLY EXCITED ABOUT THUNDER DURING THIS
TIME. BEST CHANCES FOR PRECIP FOR THE CWA WILL ARRIVE WEDNESDAY
NIGHT INTO EARLY THURSDAY MORNING WITH THE APPROACH OF THIS
SYSTEM. HOWEVER...GUIDANCE DOES VARY WITH PLACEMENT/TRACK OF THIS
SYSTEM...BUT WITH AREAS SOUTH OF INTERSTATE 88 HAVING THE BETTER
CHANCES OF OBSERVING PRECIP. INCREASING MOISTURE/INSTABILITY OUT
AHEAD OF A STRENGTHENING LLJ SHOULD ALLOW FOR BETTER CHANCES FOR
THUNDER.

RODRIGUEZ

&&

.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 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.

     BEACH HAZARDS STATEMENT...ILZ006...9 AM TUESDAY TO 7 PM TUESDAY.

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

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

     SMALL CRAFT ADVISORY...LMZ741-LMZ742-LMZ743-LMZ744-LMZ745...7 AM
     TUESDAY TO 4 AM WEDNESDAY.

&&

$$

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