Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 272331
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
631 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 00Z...

* STRONG WNW WINDS EASE EARLY THIS EVENING...THEN BECOME MORE
  NORTHERLY TOWARD MIDNIGHT
* GUSTY NORTH TO NORTHEAST WINDS LIKELY MONDAY
* CHANCE OF MVFR CIGS OVERNIGHT/MONDAY MORNING

IZZI

//DISCUSSION...UPDATED 00Z...

STRONG/GUSTY NORTHWEST WINDS WILL SUBSIDE WITH SUNSET. SECONDARY
TROUGH/COLD FRONT DROPPING SOUTH SHOULD RESULT IN WINDS SHIFTING
NORTH LATE THIS EVENING WITH DIRECTION LIKELY VARYING SOME BETWEEN
340-010. POCKETS OF MVFR CIGS OVER NORTHERN WISCONSIN AND NORTHERN
LAKE MICHIGAN BEHIND THIS TROUGH COULD TRANSLATE SOUTHWARD
BRINGING THE THREAT OF AT LEAST TEMPORARY MVFR CIGS OVERNIGHT INTO
MONDAY MORNING...BUT CONFIDENCE IS NOT OVERLY HIGH SO WILL MONITOR
TRENDS EARLY THIS EVENING. GRADIENT LOOKS TO SUPPORT NORTHERLY
WINDS 350-020 DURING THE DAY MONDAY...THOUGH THERE COULD BE SOME
LAKE INFLUENCE IN THE AFTERNOON RESULTING IN WINDS FAVORING MORE A
SLIGHTLY MORE EASTERLY COMPONENT.

IZZI


//ORD AND MDW CONFIDENCE...UPDATED 00Z...

* MEDIUM CONFIDENCE IN WIND TRENDS THROUGH THE TAF PERIOD
* LOW-MEDIUM CONFIDENCE IN CIGS FORECAST OVERNIGHT INTO EARLY
  MONDAY

IZZI

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

TUESDAY THROUGH SATURDAY...PREDOMINANTLY VFR.

IZZI

&&

.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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