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000
FXUS63 KLOT 170904
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
404 AM CDT MON JUN 17 2013

.DISCUSSION...
329 AM CDT

PRIMARY FORECAST CHALLENGE IS TEMPS AHEAD OF AND BEHIND BACK DOOR
FRONT COMING IN OFF THE LAKE THIS EVENING...THEN THUNDERSTORM
CHANCES LATE THIS AFTERNOON/EVENING AND AGAIN TUESDAY...FOLLOWED BY
LATE WEEK WARM UP.

STAGE APPEARS TO BE SET FOR A PRETTY SUMMER-LIKE DAY WITH A GOOD
DEAL OF SUNSHINE AND WARM TEMPERATURES. SECONDARY COLD FRONT OVER
THE NORTHERN LAKES WILL DROP SOUTH TODAY...ACCELERATING DOWN THE
LAKE AS IT GETS A BOOST FROM THE STILL CHILLY LAKE MICHIGAN WATERS.
AHEAD OF THE FRONT...H8 TEMPS IN THE MID-UPPER TEENS AND 925MB TEMPS
AOA 20C WITH WEST WINDS AND A GOOD DEAL OF SUNSHINE SHOULD ALLOW
HIGHS TO GET WELL INTO THE 80S AND MAYBE MAKE A RUN AT 90 IN A FEW
OF THE HOT SPOTS. LAKE ENHANCED COLD FRONT WILL MAKE ITS PRESENCE
WELL KNOWN EARLY THIS EVENING...ESPECIALLY ALONG THE IMMEDIATE LAKE
FRONT WHERE TEMPS COULD DROP 20F IN A MATTER OF MINUTES AS WINDS
SHIFT TO NE BEHIND THE FRONT. AM CONCERNED THAT FRONT MAY MOVE MORE
QUICKLY THAN RUC/HRRR ARE SUGGESTING...POSSIBLY ARRIVING IN THE
NORTH SHORE AREA LATE THIS AFTERNOON.

GUIDANCE HAS BACKED OFF ON THE STRENGTH OF THE PUSH OF COOLER
CANADIAN AIR INTO THE REGION BEHIND THE FRONT TUESDAY. IN FACT...NOW
LOOKS LIKE FRONT MAY BE LURKING NOT TOO FAR SOUTH AND WEST OF CWA
WITH MANY MODELS NOW SUGGESTING THAT SOME CONVECTION COULD DEVELOP
IN THE AFTERNOON TUESDAY AS NW FLOW SHORTWAVE DROPS INTO THE AREA.
NEAR AND DOWN WIND OF THE LAKE PRECIP CHANCES WILL BE LOWER AND
SHOULD BE DRY AND MUCH COOLER AS MARINE LAYER SEEPS INLAND.

LOOKS LIKE THE MIDDLE AND END OF THE UPCOMING WORK WEEK SHOULD BE
DRY WITH A WARMING TREND...THOUGH ONSHORE FLOW SHOULD KEEP LAKE SIDE
AREAS COOLER...PARTICULARLY WEDNESDAY AND THURSDAY. BY FRIDAY AND
INTO NEXT WEEKEND MEDIUM RANGE MODELS BRING STRONG UPPER LOW OFF THE
PAC NW COAST INLAND INTO THE NORTHERN ROCKIES WHICH SHOULD HELP POP
A RIDGE IN THE NATIONS MID SECTION AND LIKELY RESULT IN ANOTHER
TASTE OF SUMMER BY FRIDAY AND INTO NEXT WEEKEND. JUST HOW HOT IT
GETS WILL DEPEND ON WHERE RING OF FIRE SETS UP...IF THE CONVECTION
TRAIN REMAINS MAINLY TO OUR NORTH THEN MANY AREAS IN OUR CWA WILL
PROBABLY BREAK THE 90 DEGREE MARK. CONVERSELY...SHOULD CONVECTION
AND/OR ITS DEBRIS/OUTFLOW END UP FESTERING IN OUR AREA THAT TEMPS
MAY HOLD IN THE 80S. HAVE HEDGED TOWARD THE WARMER SOLUTION GIVEN
THE PROGGED STRENGTH OF THE H5 RIDGE...BUT OBVIOUSLY THIS WILL NEED
TO BE FINE TUNED AS WE GET CLOSER.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 09Z...

* WIND SHIFT MONDAY AFTERNOON.
* POTENTIAL FOR THUNDERSTORMS MONDAY AFTERNOON.

BMD

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

A WEAK PRESSURE GRADIENT IS IN PLACE LATE THIS EVENING AS A BROAD
FRONTAL TROUGH SLOWLY SAGS SOUTH ACROSS THE GREAT LAKES REGION.
WINDS WILL REMAIN FAIRLY LIGHT OVERNIGHT AND MAY GO VARIABLE AT
TIMES...BUT SHOULD GENERALLY KEEP A WESTERLY COMPONENT. DEEP MIXING
ON MONDAY WILL ALLOW WINDS TO PICK UP DURING THE DAYTIME AHEAD OF
THE FRONT...AND A FEW GUSTS INTO THE TEENS WILL BE POSSIBLE. THE
COLD FRONT IS EXPECTED TO MOVE FASTER DOWN THE LAKE AND THEN ONSHORE
AS AN ENHANCED LAKE BREEZE. IT SHOULD PASS OVER THE TERMINALS EARLY
TO MID EVENING WITH A SHARP SHIFT IN WINDS FROM W OR WNW TO NE.
MODEST INSTABILITY AHEAD OF THE FRONT MAY ALLOW A FEW THUNDERSTORMS
TO DEVELOP...BUT COVERAGE APPEARS TO REMAIN LOW AND MAY NOT IMPACT
THE TERMINALS. WILL MAINTAIN THE PROB30 FOR TSRA NOW BUT AT THIS
POINT SEE LITTLE CHANCE FOR UPGRADING THAT TO TEMPO/PREVAILING
LINE. STABLE AIR BEHIND THE FRONT SHOULD QUICKLY END THE THREAT
FOR PRECIP.

BMD

//ORD AND MDW CONFIDENCE...UPDATED 09Z...

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS/TIMING.
* LOW CONFIDENCE IN THUNDERSTORMS IMPACTING TERMINALS.

BMD

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

TUESDAY THROUGH THURSDAY...VFR. NO SIGNIFICANT WEATHER.

FRIDAY AND SATURDAY...SLIGHT CHANCE OF TSRA.

LENNING

&&

.MARINE...
232 AM CDT

A STRETCH OF RELATIVELY QUIET WEATHER IS STILL IN THE FORECAST
FOR LAKE MICHIGAN OVER MUCH OF THE UPCOMING WEAK. THE PRESSURE
GRADIENT REMAINS WEAK AS A BROAD FRONTAL TROUGH SLOWLY SAGS SOUTH
ACROSS LAKE MICHIGAN TODAY TURNING WINDS TO NORTHERLY. WHILE THERE
MAY BE A PERIOD OF 10 TO 20 KT WINDS BEHIND THE FRONT THROUGH
TUESDAY...WINDS WILL DIMINISH MID WEEK AS HIGH PRESSURE BUILDS
OVER THE LAKES. WINDS SHOULD THEN REMAIN LIGHT THROUGH
FRIDAY...WHEN WINDS FRESHEN UP SLIGHTLY AS LOW PRESSURE LIFTS
NORTHEAST FROM THE PLAINS INTO THE WESTERN LAKES REGION THIS
WEEKEND. BMD

&&

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

$$

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