Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 041407
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
907 AM CDT SAT JUL 4 2015

.SHORT TERM...
305 AM CDT

THROUGH SUNDAY...

OTHER THAN A SLIM (ABOUT 10%) CHANCE OF A SHOWER OR STORM POPPING ON
THE LAKE BREEZE LATE THIS AFTERNOON...LOOK FOR WARM WEATHER WITH A
GOOD DEAL OF SUNSHINE TODAY. RATHER SHALLOW/WEAK FORCING ALONG THE
LAKE BREEZE ALONG WITH VERY WEAK INSTABILITY SUGGESTS THE THREAT OF
ANYTHING POPPING IS LOW AND WITH THE MODELS THAT DO CONVECTIVE
MOSTLY KEEPING ACTIVITY OVER WISCONSIN...HAVE OPTED TO KEEP POPS
BELOW MENTIONABLE LEVELS TODAY. LAKE BREEZE SHOULD SEND KNOCK TEMPS
DOWN SEVERAL DEGREES BY EARLY AFTERNOON ALONG THE LAKE BUT SHOULD
SEE TEMPS REACH INTO THE 70S ALONG THE LAKE FIRST BEFORE SETTLING
BACK DOWN TO THE UPPER 60S/LOWER 70S BEHIND THE LAKE BREEZE.
SLIGHTLY WARMER SUNDAY WITH TEMPS LIKELY REACHING INTO THE MID-UPPER
80S AND POSSIBLY REACHING 90 IN A FEW LOCATIONS...THOUGH ONCE AGAIN
A WEAK LAKE BREEZE IS EXPECTED ALONG THE ILLINOIS SHORE KNOCKING
TEMPS BACK SEVERAL DEGREES IN THE AFTERNOON.

IZZI

&&

.LONG TERM...
305 AM CDT

SUNDAY NIGHT THROUGH FRIDAY...
SOUTHERLY WINDS INCREASE MONDAY IN ADVANCE OF COLD FRONT AND COULD
SET THE STAGE FOR TEMPS TO REACH 90...ESPECIALLY EASTERN/SOUTHERN
CWA. DEBRIS CLOUDINESS FROM SUNDAY`S CONVECTION IS A BIT OF A WILD
CARD...BUT IF IT ISNT TOO EXTENSIVE THEN LOWER 90S WOULD BE
ATTAINABLE. SHOWERS/STORMS COULD MAKE IT INTO OUR NW CWA BY LATER IN
THE AFTERNOON...BUT BEST CHANCE OF STORMS WITH THE FRONT APPEARS TO
BE MONDAY NIGHT SPREADING SOUTHEAST ACROSS CWA. FRONT SHOULD CLEAR
SE CWA BY EARLY-MIDDAY TUESDAY WITH SOME THREAT OF STORMS
POTENTIALLY LINGERING INTO TUESDAY...MAINLY SE CWA. SOME GUIDANCE
CONTINUES TO INDICATE THAT THE FRONT WILL HANG UP AND COULD BE CLOSE
ENOUGH TO PROVIDE SOME THREAT OF SHOWERS AND STORMS WED NIGHT
ONWARD...THOUGH TENDENCY USUALLY IS FOR THESE FRONTS TO GET SHAVED
FURTHER SOUTH THAN GUIDANCE INDICATES SO QUITE POSSIBLY COULD REMAIN
DRY FOR THE REMAINDER OF THE WEEK FOLLOWING THE MON NIGHT/TUES
FROPA. COOLER/LESS HUMID CONDITIONS EXPECTED BEHIND THE FRONT WITH A
RETURN TO BELOW AVERAGE TEMPS AND EVEN COOLER WEATHER NEAR THE LAKE.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 14Z...

* LIKELY LAKE BREEZE WIND SHIFT TO EAST WITH SPEEDS POSSIBLY
  APPROACHING 8-10KT THIS AFTERNOON.

RC

//DISCUSSION...UPDATED 14Z...

LACK OF PRESSURE GRADIENT HAS ALLOWED FOR EARLY LAKE BREEZE
DEVELOPMENT IN DOWNTOWN CHICAGO...SO TREND ON NEAR TERM GUIDANCE
FOR EARLIER WIND SHIFT TO EAST AT ORD/MDW SEEMS REASONABLE AND
BUMPED UP TIMING TO 20Z IN TAF. WILL MONITOR LAKE BREEZE
PROGRESSION ON RADAR FOR SPECIFIC TIMING UPDATES. PREVAILING
SPEEDS SHOULD END UP LESS THAN 10 KT BUT THERE COULD BE A WINDOW
SHORTLY AFTER LAKE BREEZE PASSAGE FOR SPEEDS AROUND 10 KT.

RC

FROM 12Z...

PATCHY EARLY MORNING FOG HAS DEVELOPED ACROSS THE AREA BUT EXPECT
THIS FOG TO DIMINISH OVER THE NEXT ONE TO TWO HOURS WITH LITTLE IF
ANY IMPACTS. VFR CONDITIONS WILL THEN CONTINUE TO PREVAIL FOR THE
REMAINING FORECAST PERIOD. STILL MONITORING WIND SHIFT WITH LAKE
BREEZE THIS AFTERNOON AND STILL THINK SPEEDS IN THE 6-8KT RANGE
ARE A MORE LIKELY SCENARIO. WILL STILL NEED TO MONITOR THE
POTENTIAL FOR A BRIEF WINDOW OF SLIGHLY HIGHER SPEEDS...AS WELL
AS A SLIGHLY SOONER WIND SHIFT.

RODRIGUEZ

//ORD AND MDW CONFIDENCE...UPDATED 14Z...

* HIGH IN OVERALL WIND TRENDS...MEDIUM IN TIMING OF LAKE BREEZE
  SHIFT AND SPEEDS BEHIND SHIFT.

* HIGH IN REMAINING ELEMENTS.

RC

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

SUNDAY NIGHT...VFR.

MONDAY...TSRA LIKELY MONDAY NIGHT. BREEZY SOUTH WINDS.

TUESDAY...CHANCE OF MORNING TSRA.

WEDNESDAY...VFR...CHANCE SHRA/TSRA WED NIGHT.

THURSDAY...SLIGHT CHANCE TSRA.

FRIDAY...SLIGHT CHANCE TSRA.

RODRIGUEZ

&&

.MARINE...
313 AM CDT

HIGH PRESSURE SPANNING THE REGION WILL MOVE LITTLE TODAY INTO
TONIGHT...BUT WITH A WEAKENING SOUTHWARD MOVING FRONTAL BOUNDARY
EXPECTED TO PUSH INTO NORTHERN LAKE MICHIGAN THIS MORNING.
HOWEVER...THIS FRONT WILL CONTINUE TO WEAKEN AS IT MOVES OVER THE
LAKE BUT WITH THE CURRENT SOUTHERLY WINDS TURNING MORE NORTHERLY
OVER THE NORTH HALF. WINDS WILL GENERALLY STAY SOUTHERLY ACROSS
THE SOUTH HALF TODAY...WITH WINDS OVER THE ENTIRE LAKE RETURNING
TO THE SOUTH LATER TONIGHT INTO SUNDAY. SOUTHERLY SPEEDS WILL
INCREASE SUNDAY AND SUNDAY NIGHT AS A TROUGH OF LOW PRESSURE
APPROACHES FROM THE WEST. WINDS REALLY RAMP UP ON MONDAY WITH THE
ARRIVAL OF THIS SYSTEM WITH WINDS OVER THE OPEN WATERS...MAINLY
THE NORTH HALF LIKELY APPROACHING 30KT WHILE THE SOUTH HALF STAYS
IN THE 15 TO 25 KT RANGE. HAZARDOUS WINDS FOR SMALL CRAFT APPEAR
POSSIBLE BY MIDDAY MONDAY WITH SPEEDS INCREASING INTO THE
AFTERNOON...AND WITH SPEEDS POSSIBLY APPROACHING 30KT DURING THIS
TIME.

RODRIGUEZ

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...NONE.
IN...NONE.
LM...NONE.
&&

$$

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