Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 272203
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
503 PM CDT SUN JUL 27 2014

.DISCUSSION...
250 PM CDT

COMPACT UPPER LOW OVER WISCONSIN THIS AFTERNOON CONTINUES TO DIG
SOUTHEAST ACROSS THE WESTERN GREAT LAKES REGION. A COLD FRONT
TRAILING FROM ASSOCIATED SURFACE LOW OVER LOWER MICHIGAN...TRAILS
SOUTHWEST ACROSS NORTHWEST INDIANA INTO CENTRAL IL AND WAS JUST
ABOUT TO CLEAR THE SOUTHEAST CORNER OF THE CWA AT 1930Z. GUSTY
WEST-NORTHWEST WINDS UP TO 35 MPH AT TIMES WERE SPREADING DRIER AIR
INTO THE FORECAST AREA...THOUGH COLD POOL ASSOCIATED WITH UPPER LOW
WILL BRING THE POTENTIAL FOR ISOLATED TO SCATTERED SHOWERS AND
POSSIBLY A THUNDERSTORM INTO THE NORTHEAST THIRD OR SO OF THE
FORECAST AREA THROUGH THE REMAINDER OF THE AFTERNOON AND EARLY
EVENING HOURS. MID-LEVEL CIRCULATION MOVES OFF TO THE SOUTHEAST THIS
EVENING AND A DECREASE IN DIURNAL STRATOCU IS EXPECTED TO ACCOMPANY
COOLER WEATHER OVERNIGHT...WITH TEMPERATURES FALLING OFF INTO THE
50S FROM THE NORTHWEST.

UPPER PATTERN IS IN THE PROCESS OF EVOLVING INTO A DEEP LONG WAVE
TROUGH ACROSS EASTERN NORTH AMERICA...AND AN UPPER RIDGE IN THE
WEST. THIS SETS UP A PROLONGED PERIOD OF SLIGHTLY COOLER THAN NORMAL
WEATHER...WITH HIGHS IN THE MID-70S MONDAY...THEN GENERALLY IN THE
MID-UPPER 70S THROUGH THE REMAINDER OF THE WEEK. SOME LAKE COOLING
EXPECTED INTO NORTHWEST INDIANA AND ALONG THE IMMEDIATE IL SHORE
MONDAY WITH NORTH WINDS BECOMING SLIGHTLY NORTHEAST AS GRADIENT
WEAKENS MONDAY AFTERNOON. LOW LEVEL FLOW THEN BECOMES MORE
WEST-NORTHWEST OVER THE NEXT SEVERAL DAYS AS SURFACE HIGH PRESSURE
BUILDS THROUGH THE MISSOURI...MID-MISSISSIPPI AND OHIO VALLEYS...AND
A SERIES OF WEAK TROUGHS ROTATE THROUGH THE GREAT LAKES REGION.

SUBSIDENCE BEHIND DEPARTING UPPER LOW AND WEST OF DEEPENING LONG
WAVE TROUGH AXIS IS EXPECTED TO SUPPRESS ANY SHOWER POTENTIAL
MONDAY. GUIDANCE DEPICTS A SERIES OF MINOR SHORT WAVES ROTATING
THROUGH THE WESTERN GREAT LAKES REGION WITHIN THE WESTERN PERIPHERY
OF THE CORE OF THE UPPER TROUGH THROUGH THE WEEK HOWEVER...WITH SOME
THREAT OF SCATTERED DIURNAL SHOWERS/THUNDERSTORMS EACH DAY FROM
TUESDAY INTO SATURDAY. MODELS MAY BE A LITTLE TOO MOIST IN LOW
LEVELS GIVEN NORTH-NORTHWEST FLOW NEAR THE SURFACE THROUGH THE
PERIOD...HAVE GENERALLY MAINTAINED 20-30 PERCENT POPS FOR DAILY
SHOWER TRENDS. SOME INDICATION OF A DEEPER MID-LEVEL SHORT WAVE
FRIDAY WITH SLIGHTLY HIGHER BLENDED MODEL POPS AT THAT TIME. TROUGH
AXIS DRIFTS EAST WITH WEAK SURFACE HIGH DEPICTED OVER NEXT
WEEKEND...WITH DRY FORECAST SATURDAY NIGHT-SUNDAY.

RATZER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 22Z...

* STRONG/GUSTY WEST/NORTHWEST WINDS THRU EARLY EVENING
* ISOLD OF SHRA THROUGH SUNSET
* WINDS BECOME MORE NORTHERLY THIS EVENING
* CHANCE OF MVFR CIGS LATE EVENING/OVERNIGHT
* GUSTY NORTH/NORTHEAST WINDS MONDAY

IZZI

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

FRONTAL BOUNDARY JUST EAST OF ORD/MDW WITH A FEW CELLS DEVELOPING
OVER THE LAKE AND ADDITIONAL DEVELOPMENT SHOULD REMAIN EAST OF
ORD/MDW BUT MAY STILL IMPACT GYY THROUGH 19Z OR SO UNTIL THE FRONT
PUSHES EAST OF THERE. AS COOLER AIR ALOFT SPREADS ACROSS THE AREA
THIS AFTERNOON...THERE COULD BE SOME INSTABILITY SHOWERS...
PERHAPS ISOLATED THUNDER...FROM MID AFTERNOON THROUGH EARLY
EVENING.

WEST/NORTHWEST WINDS HAVE INCREASED INTO THE 15-20KT RANGE WITH
GUSTS INTO THE MID 20KT RANGE. WITH COOLER AND DRIER AIR ADVECTING
INTO THE REGION...LOW LEVEL MIXING WILL BE FAIRLY EFFICIENT
BRINGING STRONGER WINDS TO THE SURFACE AND BUMPED SPEEDS/GUSTS UP
JUST A BIT WITH GUSTS INTO THE UPPER 20KT RANGE POSSIBLE FOR MUCH
OF THE AFTERNOON/EARLY EVENING.

ANOTHER COLD FRONT/WIND SHIFT IS EXPECTED THIS EVENING WHICH WILL
LIKELY SHIFT WINDS TO THE NORTH/NORTHEAST. CHANGES TO TIMING MAY
BE NEEDED WITH FUTURE UPDATES BUT CONFIDENCE FOR A SHIFT TO THE
NORTH/NORTHEAST IS INCREASING. IN ADDITION...THERE COULD BE A
PERIOD OF MVFR CIGS BEHIND THIS FRONT. WINDS WILL TEND TO SHIFT
BACK NORTH/NORTHWEST OVERNIGHT...THEN SHIFT BACK NORTH/NORTHEAST
MONDAY MORNING AND REMAIN GUSTY FOR MUCH OF MONDAY. CMS

//ORD AND MDW CONFIDENCE...UPDATED 22Z...

* HIGH FOR WINDS THIS AFTERNOON...MEDIUM FOR THE REST OF THE
  PERIOD
* HIGH CONFIDENCE IN LOW COVERAGE ISOLD FOR SHRA INTO EARLY
  EVENING
* LOW CONFIDENCE FOR MVFR CIGS LATE EVENING/OVERNIGHT

IZZI

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

MONDAY NIGHT...VFR.
TUESDAY...SLIGHT CHANCE OF AFTERNOON TSRA.
WEDNESDAY...SLIGHT CHANCE OF TSRA.
THURSDAY-SATURDAY...SLIGHT CHANCES OF TSRA. NORTHEAST WINDS.

MTF

&&

.MARINE...
210 PM CDT

AN ACTIVE PERIOD OF WEATHER IN UNDERWAY OVER LAKE MICHIGAN.
DEEPENING LOW PRESSURE HAS PASSED ACROSS NORTHERN LAKE MICHIGAN
AND IS MOVING THROUGH LOWER MICHIGAN THIS AFTERNOON TO THE EASTERN
GREAT LAKES THIS EVENING. FOLLOWING THE PASSAGE OF THIS LOW AND AN
ASSOCIATED COLD FRONT...STRENGTHENING NORTHWEST WINDS ARE
FILTERING ACROSS THE LAKE AND QUICKLY INCREASING TO 20-25KT WITH
OCNL GUSTS TO 30KT AND SCATTERED THUNDERSTORMS. THE SCATTERED
THUNDERSTORMS SHOULD CONTINUE INTO THE EVENING WHILE WINDS
GRADUALLY VEER MORE NORTHERLY AND INCREASE TO PREVAILING 30KT.
OCNL GALE FORCE GUSTS TO 35 KT ARE POSSIBLE...BUT SHOULD NOT BE
PERSISTENT ENOUGH TO NECESSITATE A GALE WARNING. SMALL CRAFT
ADVISORIES HAVE ALREADY BEEN HOISTED FOR THE ILLINOIS AND INDIANA
NEARSHORE WATERS AND NO CHANGE HAS BEEN MADE TO THE TIMING
DETAILS. HIGH PRESSURE BUILDING ACROSS THE NORTHERN PLAINS THIS
AFTERNOON AND SHOULD BEGIN TO SPREAD ACROSS THE WESTERN GREAT
LAKES MONDAY. AS THE HIGH SPREADS ACROSS THE LAKE LATE
MONDAY...WINDS SHOULD DIMINISH QUICKLY. ON TUESDAY...A SFC TROUGH
OR OR WEAK COLD FRONT TRACKING SOUTH DOWN THE LAKE WILL BRING A
REINFORCING SHOT OF COOLER AIR...BRINGING A BRIEF INCREASE TO NWLY
WINDS TUESDAY MORNING. FOLLOWING THE PASSAGE OF THIS WEAK
TROUGH/COLD FRONT...THE HIGH PRESSURE WILL SPREAD ACROSS THE
WESTERN GREAT LAKES TO THE OHIO VALLEY BY WEDNESDAY. HIGH PRESSURE
WILL BE THE DOMINANT FEATURE OVER THE GREAT LAKES REGION FROM MID
WEEK INTO THE WEEKEND...SETTING UP A PERIOD OF QUIET WEATHER WITH
LIGHT AND VARIABLE WINDS AND MINIMAL WAVE ACTION.

KREIN

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...BEACH HAZARDS STATEMENT...ILZ014...10 PM SUNDAY TO 4 AM TUESDAY.

     BEACH HAZARDS STATEMENT...ILZ006...10 PM SUNDAY TO 10 PM MONDAY.

IN...BEACH HAZARDS STATEMENT...INZ001-INZ002 UNTIL 4 AM TUESDAY.

LM...SMALL CRAFT ADVISORY...NEARSHORE WINTHROP HARBOR TO NORTHERLY IS UNTIL 10 PM MONDAY.

     SMALL CRAFT ADVISORY...NEARSHORE NORTHERLY IS TO MICHIGAN CITY IN UNTIL 4 AM
     TUESDAY.

&&

$$

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