Area Forecast Discussion
Issued by NWS Chicago, IL

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000
FXUS63 KLOT 010604
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
104 AM CDT SAT NOV 1 2014

.UPDATE...
958 PM CDT

COVERAGE AND INTENSITY OF THE LAKE EFFECT PRECIP IS
DIMINISHING...WHILE A WINTRY MIX IS STILL BEING OBSERVED. LOW
LEVEL VEERING WILL CONTINUE WITH THE BULK OF THIS PRECIP SHIFTING
MORE INTO NORTHEAST ILLINOIS OVER THE NEXT COUPLE OF HOURS. STILL
ANTICIPATE A TREND TOWARDS ALL SNOW IN THE NEAR TERM EVEN FOR
AREAS IMMEDIATELY NEAR THE LAKE...BUT DO EXPECT A CONTINUED
DIMINISHING TREND AS WELL DURING THIS TIME. IN THE NEAR
TERM...BRIEF REDUCTIONS IN VISIBILITY AND MINOR ACCUMULATIONS
MAINLY ON GRASSY SURFACES ARE STILL POSSIBLE UNDER THE MORE
INTENSE SNOWFALL.

RODRIGUEZ

&&

.SHORT TERM...
307 PM CDT

THROUGH TONIGHT...

NO CHANGES PLANNED WITH HEADLINES.

SEVERAL BANDS OF LAKE EFFECT SNOW HAVE DEVELOPED ACROSS SOUTHERN
LAKE MICHIGAN EARLY THIS AFTERNOON...WITH SOME OF THESE SNOW SHOWERS
IMPACTING PORTIONS OF THE NORTHEASTERN ILLINOIS SHORES.
HOWEVER...THE MOST SUBSTANTIAL AREA OF LAKE EFFECT RAIN AND SNOW HAS
BEEN OCCURRING ALONG THE SOUTHERN TIP OF LAKE MICHIGAN AND ACROSS THE
ADVISORY AREA OF NORTHWESTERN INDIANA. BASED ON NUMEROUS PHONE
CALLS ACROSS THIS AREA IT APPEARS AREAS NEAR THE LAKE ARE SLIGHTLY
WARMER...RESULTING IN A RAIN SNOW MIX. HOWEVER...AREAS ROUGHLY 20 TO
30 MILES INLAND (BASICALLY ALONG AND SOUTH OF A CROWN POINT TO
VALPARAISO INDIANA LINE) THE PRECIPITATION IS MAINLY IN THE FORM OF
SNOW. SEVERAL REPORTS OF ACCUMULATING SNOW HAVE BEEN RECEIVED SOUTH
OF THIS LINE...WITH LOW VISIBILITIES UNDER A MILE.

BASED ON CURRENT RADAR TRENDS AND SHORT RANGE HIRES GUIDANCE...IT
APPEARS THIS ACTIVITY WILL CONTINUE TO BE FOCUSED MAINLY ACROSS
NORTHWESTERN INDIANA FOR THE NEXT FEW HOURS...THROUGH LATE
AFTERNOON/EARLY THIS EVENING. HOWEVER...SOME OF THE LESS ORGANIZED LAKE
EFFECT SNOW SHOWERS WILL LIKELY IMPACT PORTIONS OF COOK AND LAKE
COUNTIES IN ILLINOIS AS WELL DURING THIS TIME. FINALLY...AS THE
SURFACE LOW SHIFTS SOUTHEAST OVER THE OHIO VALLEY INTO THIS EVENING
THE BOUNDARY LAYER FLOW WILL VEER AND WEAKEN A BIT. THIS SHOULD
ALLOW THE BETTER FOCUS FOR LAKE EFFECT SHOWERS TO SHIFT FARTHER WEST
ACROSS PORTIONS OF EASTERN ILLINOIS...INCLUDING THE CHICAGO METRO
AREA NEAR THE LAKE. WHILE THERE COULD BE A SHORT PERIOD OF SOME
MODERATE...OR EVEN BRIEFLY HEAVY SNOW SHOWERS INTO NORTHEASTERN
ILLINOIS INTO THIS EVENING...I HAVE CHOSEN NOT TO EXTEND THE WINTER
ADVISORIES FARTHER WEST INTO ILLINOIS. THIS IS MAINLY DUE TO THE
FACT THAT IT APPEARS THE THREAT FOR BETTER MORE ORGANIZED LAKE
EFFECT SNOW WILL BE OF SHORT DURATION...LIMITING OVERALL
ACCUMULATIONS. HEIGHT RISES AND WARMING TEMPERATURES IN THE MID
LEVELS SHOULD ALLOW INVERSION HEIGHTS TO DROP BELOW THE DENDRITIC
GROWTH ZONE BY LATER THIS EVENING/OVERNIGHT. THE MODELS HAVE BEEN
INSISTENT ON THIS FOR THE PAST FEW DAYS AND SEE NO REASON WHY THIS
WOULD NOT OCCUR AS THE UPPER RIDGE TO OUR WEST BEGINS TO BUILD
EASTWARD. THEREFORE...ANY LEFT OVER LAKE EFFECT SNOW SHOWERS WILL
LIKELY NOT BE EFFICIENT SNOWFALL PRODUCERS AND LIKELY BE LOOSELY
ORGANIZED...AND HENCE THE THREAT FOR ACCUMULATING SNOWFALL SHOULD
COME TO AN END BY LATER THIS EVENING.

THE WINDS WITH THIS SYSTEM HAVE BEEN IMPRESSIVE. KGYY HAS BEEN
EXPERIENCING GUSTS TO 58 KT FOR SEVERAL HOURS...WITH SIMILAR
MAGNITUDES NOTED ALONG THE LAKE SHORE. IT APPEARS THESE STRONG WINDS
WILL SLOWLY EASE TONIGHT AS THE SURFACE HIGH OVERSPREADS THE AREA ON
SATURDAY. THEREFORE...NO CHANGES ARE PLANNED WITH THE CURRENT WIND
ADVISORIES OR WARNINGS.

LAKE SHORE FLOODING CONTINUES TO BE AN ISSUE...ESPECIALLY IN
CHICAGO...WHERE WAVES HAVE BEEN GETTING WATER ONTO LAKE SHORE DRIVE.
WE CONSIDERED TO UPGRADE TO A LAKE SHORE FLOOD WARNING...BUT DECIDED
TO JUST BEEF UP THE WORDING IN THE CURRENT ADVISORY AS A WARNING
WOULD NOT DUE MUCH GOOD AT THIS STAGE OF THE GAME.

KJB

&&

.LONG TERM...
307 PM CDT

TOMORROW THROUGH THURSDAY...

SATURDAY AND SUNDAY...
THE UPPER LEVEL TROUGH PUSHES EAST ALLOWING A LARGE UPPER LEVEL
RIDGE TO MOVE OVERHEAD THROUGH THE WEEKEND. THE CORRESPONDING
SURFACE HIGH MOVES OVER THE REGION TOMORROW EVENING.

GUIDANCE CONTINUES TO FEATURE A NARROW CONVERGENCE BAND ALONG THE
SOUTHWEST END OF LAKE MICHIGAN EARLY SATURDAY MORNING.  KEPT A
SLIGHT CHANCE OF PRECIP IN FOR FAR NORTHEAST IL WITH THE BAND
DISSIPATING BY LATE MORNING/EARLY AFTERNOON AS FORCING AND MOISTURE
WEAKEN. NOT EXPECTING ANY ADDITIONAL SIGNIFICANT ACCUMULATION AND
THE PRECIP TYPE WILL BE A SNOW/RAIN MIX AS TEMPERATURES WILL BE
ABOVE FREEZING OVER THE LAKE.  HAVE MEDIUM CONFIDENCE IN THE BAND
PERSISTING UNTIL MORNING...MEDIUM HIGH CONFIDENCE IN THE BAND MAINLY
IMPACTING THE IL SIDE OF THE LAKE...AND HIGH CONFIDENCE IN LITTLE TO
NO ADDITIONAL ACCUMULATION.

WINDS DECREASE SATURDAY AS THE HIGH MOVES OVERHEAD.  WARMER AIR
BEGINS TO MOVE IN AS WELL WITH HIGHS IN THE LOW 40S TOMORROW. WINDS
TURN SOUTH BEHIND THE HIGH SUNDAY AND USHER IN EVEN WARMER AIR WITH
HIGHS IN THE UPPER 40S TO AROUND 50. SATURDAY AFTERNOON THROUGH
SUNDAY NIGHT WILL BE DRY.

MONDAY THROUGH THURSDAY...
THE RIDGE AXIS MOVES OVERHEAD MONDAY AS THE SURFACE LOW SLIDES OVER
THE SE U.S. THE WARM-UP CONTINUES WITH HIGHS IN THE UPPER 50S TO
AROUND 60 MONDAY...AND MID 50S EXPECTED THROUGH MID WEEK. OVERNIGHT
LOWS VARY FROM THE MID 40S MONDAY NIGHT TO THE MID TO LOWER 30S
THURSDAY NIGHT.

A SURFACE LOW MOVES INTO ONTARIO TUESDAY...AND IT DRAGS A COLD FRONT
ACROSS THE REGION TUESDAY. EXPECTING WIDESPREAD SHOWERS TUESDAY
MORNING WITH RAIN ENDING FROM WEST TO EAST AS THE FRONT SLIDES EAST
TUESDAY EVENING/NIGHT.  GUIDANCE DIFFERS ON HOW MUCH PRECIP WILL
FALL...BUT ITS LOOKING LIKE A GOOD WETTING RAIN IS EXPECTED.

A WEAKER LOW PASSES JUST TO OUR NORTH MID WEEK AND HAVE MEDIUM-LOW
CONFIDENCE IN PRECIP MAKING IT INTO NORTHERN IL WEDNESDAY. THINKING
PRECIP WILL REMAIN CLOSELY TIED TO THE LOW WHICH RIGHT NOW WILL BE
OVER SOUTHERN WI. IF THE LOW/S TRACK WERE TO DIP A BIT MORE
SOUTH...THERE WOULD BE A BETTER CHANCE FOR PRECIP ACROSS FAR
NORTHERN IL.

WINDS TURN NORTHWEST BEHIND THE LOW AND ANOTHER LAKE EFFECT PRECIP
SITUATION IS POSSIBLE FOR NW INDIANA WEDNESDAY NIGHT. ONLY HAVE RAIN
FOR NOW AS TEMPS WILL BE ABOVE FREEZING.  WINDS REMAIN OFF OF THE
LAKE THROUGH THURSDAY NIGHT AS ANOTHER HIGH PRESSURE SYSTEM
APPROACHES FROM THE WEST.

JEE

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 06Z...

* NORTH WINDS GUSTING 20-25 KT GRADUALLY DIMINISH OVERNIGHT.

* PERIODIC LIGHT SNOW SHOWERS OVERNIGHT WITH LITTLE IF ANY
  VISIBILITY REDUCTION.

* VFR CIGS EXPECTED TO PREVAIL BUT SOME MVFR LEVEL CLOUDS MAY
  DEVELOP OVERNIGHT. LOWERING TO MVFR POSSIBLE TOWARD DAYBREAK
  THEN LIFT AND SCATTER TO VFR LATE AFTERNOON.

MDB

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

HIGH PRESSURE CONTINUES TO APPROACH FROM THE WEST WHICH IS HELPING
NORTH WINDS TO SLOWLY DIMINISH ACROSS NORTHERN ILLINOIS AWAY FROM
THE LAKE. NORTHWEST INDIANA CONTINUES TO SEE HIGHER GUSTS AND
ALTHOUGH GYY HAS NOT REPORTED SUSPECT GUSTS AROUND 40 KT ARE
CONTINUING. THESE GUSTS WILL EASE OVERNIGHT AS WELL BUT WILL
PROBABLY REMAIN UP NEAR 30 KT. LAKE EFFECT SNOW BANDS HAVE WANED
OVER THE PAST FEW HOURS BUT WILL LIKELY SEE CONTINUED LIGHT SNOW
SHOWERS AT ORD/MDW/GYY BUT AT THIS POINT SEE LITTLE IN THE WAY OF
VSBY REDUCTION. THESE SHOULD COME TO AN END LATER THIS MORNING.
CIGS REMAIN MAINLY VFR BUT CANNOT RULE OUT SOME MVFR PATCHES. CIGS
MAY LOWER TO MVFR TOWARD DAYBREAK BUT THIS COULD END UP BEING A
LITTLE PESSIMISTIC.

NORTH TO NORTHEAST WINDS WILL GUST TO NEAR 20 KT DURING THE DAY
TODAY ACROSS NORTHEAST IL AND NW INDIANA WITH FEW GUSTS ACROSS
NORTH-CENTRAL ILLINOIS. ANY MVFR WILL GRADUALLY LIFT TO VFR WITH
SCATTERING FROM WEST TO EAST. HIGH PRESSURE WILL MOVE OVERHEAD
TONIGHT ALLOWING WINDS TO DROP OFF WITH SUNSET THIS EVENING.

MDB


//ORD AND MDW CONFIDENCE...UPDATED 06Z...

* HIGH CONFIDENCE IN WIND TRENDS.

* HIGH CONFIDENCE IN -SHSN PERSISTING OVERNIGHT WITH MINIMAL VSBY
  REDUCTION.

* MEDIUM-HIGH CONFIDENCE IN CIG TRENDS THROUGH SATURDAY MORNING.
  MEDIUM CONFIDENCE IN DURATION OF MVFR CIGS INTO THE AFTERNOON.

MDB

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

SUNDAY...DRY/VFR. SOUTH WINDS 10-15 KT.

MONDAY...DRY/VFR DURING THE DAY. SHRA LIKELY MONDAY NIGHT. GUSTY
SOUTHWEST WINDS 15-20 KT.

TUESDAY...SHRA/MVFR LIKELY. SOUTHWEST WINDS.

WEDNESDAY...DRY/VFR. SOUTHWEST WINDS.

THURSDAY...DRY/VFR. WEST-NORTHWEST WINDS.

RATZER

&&

.MARINE...
212 PM CDT

STORM FORCE WINDS WILL SLOWLY EASE TO GALES TONIGHT. NO CHANGES
PLANNED TO CURRENT HEADLINES.

FOR THE NEARSHORE ZONES...WILL NEED A PROLONGED SMALL CRAFT ADVISORY
THROUGH AT LEAST SATURDAY AS VERY LARGE WAVES SUBSIDE.  MAY FLIRT
WITH SMALL CRAFT ADVISORY CRITERIA WINDS AND WAVES SUNDAY AND
MONDAY. HAVE MEDIUM CONFIDENCE AS CONDITIONS MAY BE MARGINAL.

NORTH TO NORTHEAST WINDS TO 30 KT SLOWLY DIMINISH SATURDAY AND WINDS
TURN SOUTHWEST BEHIND A HIGH PRESSURE SYSTEM SUNDAY MORNING.  SOUTH
TO SOUTHWEST WINDS INCREASE TO 30 KT SUNDAY AFTERNOON AS THE
GRADIENT TIGHTENS BETWEEN THE DEPARTING HIGH AND AN APPROACHING
LOW.  SOUTH TO SOUTHWEST WINDS FINALLY DIMINISH TO UNDER 30 KT
MONDAY NIGHT...AND THEN WINDS TURN WEST 10-20 KT BEHIND THE LOWS
COLD FRONT TUESDAY. WEST WINDS INCREASE TO 20-25 KT AND BECOME
NORTHWEST WEDNESDAY NIGHT...AND MAY SEE 30 KT WINDS OVER THE
NORTHERN HALF OF THE LAKE THURSDAY.  WINDS DIMINISH THURSDAY NIGHT
AS HIGH PRESSURE MOVES OVER THE AREA.

KJB/JEE

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ014 UNTIL 4 AM SATURDAY.

IN...LAKESHORE FLOOD ADVISORY...INZ001-INZ002 UNTIL 4 AM SATURDAY.

LM...GALE WARNING...LMZ080-LMZ366-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779-LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 4 AM
     SATURDAY.

&&

$$

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