Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 131137
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
637 AM CDT SAT SEP 13 2014

.DISCUSSION...
331 AM CDT

PRETTY REMARKABLE TRANSITION FROM A 3 WEEK PERIOD OF ABOVE AVERAGE
TEMPERATURES INTO LATE FALL-LIKE TEMPERATURES.

UPPER TROUGH IS MOVING EAST AND SKIES ARE QUICKLY CLEARING FROM WEST
TO EAST EARLY THIS MORNING. WHERE SKIES HAVE CLEARED TEMPS HAVE
FALLEN INTO THE 30S THIS MORNING. HEART OF THE COLD AIR MASS WILL
MOVE OVER THE AREA TODAY AND TONIGHT...SO DESPITE THE SUNSHINE
EXPECT TEMPERATURES TO STRUGGLE TO REACH 60 TODAY. SURFACE HIGH
SHOULD BE NEARLY OVERHEAD TONIGHT...SO WITH CLEAR SKIES AND WINDS
LIKELY TO GO CALM ANTICIPATE TEMPS TO BOTTOM OUT AGAIN WITH 30S MOST
AREAS OUTSIDE OF URBAN HEAT ISLAND LOCATIONS. SOME OF THE COLDEST
VALLEYS AND LOW LYING AREAS COULD DIP INTO THE LOW TO MID 30S SO
FROST IS ACTUALLY A CONSIDERATION FOR MAINLY RURAL AND COLD AIR
DRAINAGE AREAS. HAVE INTRODUCED SOME PATCHY FROST INTO THE GRIDS
FOR PORTIONS OF FAR WEST SUBURBS INTO NORTH CENTRAL ILLINOIS AND
THIS FROST MENTION COULD NEED TO BE EXPANDED A BIT...THOUGH LIKELY
TOO MARGINAL FOR ANY HEADLINES.

TEMPS SHOULD RECOVER A BIT ON SUNDAY IN ADVANCE OF THE NEXT UPPER
TROUGH AND ASSOCIATED COLD FRONT WHICH SHOULD BRING A PRETTY GOOD
THREAT OF A PERIOD OF SHOWERS TO THE AREA MONDAY. HAVE TRIMMED A
COUPLE DEGREES OFF HIGHS MONDAY AND THIS COULD STILL BE TOO WARM
DEPENDING ON EXTENT OF CLOUD COVER AND SHOWERS. FOLLOWING THAT
TROUGH LOOKS TO BE ANOTHER HEALTHY SHOT OF UNSEASONABLY COLD AIR FOR
TUESDAY WITH THE POTENTIAL FOR MORE 30S IN OUTLYING AREAS MON NIGHT
ASSUMING SKIES CLEAR. A VERY SLOW MODERATING TREND SHOULD THEN TAKE
PLACE TUESDAY THROUGH FRIDAY WITH AMPLE SUNSHINE...NO PRECIP AND
WHAT WOULD BE IDEAL WEATHER FOR MID OCTOBER.

IZZI

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 12Z...

* PATCHY MVFR/IFR CIGS THIS MORNING.

BMD

//DISCUSSION...UPDATED 12Z...

HIGH PRESSURE WILL BUILD ACROSS THE REGION TODAY AND SHOULD PROVIDE
PRIMARILY VFR CONDITIONS OUTSIDE OF SOME PATCHY FOG/LOWER CIGS THIS
MORNING. THERE MAY BE A BRIEF WINDOW OF WINDS GUSTING INTO THE MID
TO HIGH TEENS LATE MORNING TO EARLY AFTERNOON DUE TO DEEP
MIXING...BUT THE GRADIENT IS PROGGED TO CONTINUE TO RELAX THROUGH
THE DAY ALLOWING WINDS TO DIMINISH...AND EVENTUALLY BECOME LIGHT AND
VARIABLE THIS EVENING...AND POSSIBLY CALM FOR A FEW HOURS TONIGHT.
WINDS WILL TURN AROUND TO THE SOUTHWEST SUNDAY AS THE HIGH STARTS TO
MOVE TO THE EAST.

BMD


//ORD AND MDW CONFIDENCE...UPDATED 12Z...

* HIGH.

BMD

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

SUNDAY NIGHT...VFR.
MONDAY...SHOWERS LIKELY.
TUESDAY THROUGH FRIDAY...VFR.

BMD

&&

.MARINE...
316 AM CDT

A TIGHT PRESSURE GRADIENT IS IN PLACE OVER SOUTHERN LAKE MICHIGAN
BETWEEN LOW PRESSURE NEAR LAKE ERIE AND EXPANSIVE HIGH OVER THE
PLAINS AND UPPER MIDWEST. IN ADDITION...AN UNSEASONABLY COOL AIRMASS
HAS RESULTED IN STRONG INSTABILITY OVER LAKE MICHIGAN CAUSING A
PLUME OF LAKE EFFECT SHOWERS AND ENHANCING THE LOW LEVEL
CONVERGENCE. THIS HAS RESULTING IN NORTHWEST WINDS TO AROUND 30 KT
ACROSS SOUTHERN LAKE MICHIGAN. WINDS ARE EXPECTED TO SLOWLY TAPER
THROUGH THE DAY AS THE HIGH BEGINS TO BUILD OVER THE SOUTH END OF
THE LAKE BY TONIGHT. WINDS WILL TURN SOUTHWEST AND FRESHEN UP...OVER
THE NORTH HALF OF THE LAKE INITIALLY AS THE HIGH SLIDES EAST LATE IN
THE WEEKEND AND LOW PRESSURE TRANSLATES EAST ACROSS THE CANADIAN
PRAIRIES. THIS LOW WILL DRAG A COLD FRONT ACROSS LAKE MICHIGAN ON
MONDAY. FLOW SHOULD REMAIN RELATIVELY MODEST FROM MIDWEEK ON AS HIGH
PRESSURE BUILDS BACK OVER THE GREAT LAKES.

BMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ006-ILZ014 UNTIL 10 PM SATURDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 10 PM SATURDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WATERS
     UNTIL 10 PM SATURDAY.

&&

$$

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