000
FXUS63 KLOT 012022
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
222 PM CST SUN FEB 1 2015


.SHORT TERM...
220 PM CST

THROUGH TONIGHT...

ONLY CHANGES TO THE GOING HEADLINES WAS TO ADD PORTER COUNTY INDIANA
TO THE BLIZZARD WARNING. THIS WAS DONE AS IT APPEARS THEY WILL BE
GETTING A PERIOD OF STRONGER WINDS OFF THE LAKE THIS EVENING...WHICH
WILL PRODUCE SIGNIFICANT VIS RESTRICTIONS.

THE 19 UTC OBJECTIVE SURFACE ANALYSIS PLACES THE CENTER OF A 1003 MB
LOW ABOUT 50 MILES NORTHEAST OF KSTL...WITH A SURFACE BOUNDARY
DRAPED EASTWARD OVER THE SOUTHERN FRINGE OF MY CENTRAL ILLINOIS AND
INDIANA COUNTIES. TO THE NORTH OF THIS FRONT...WINDS HAVE BECOME
GUSTY OUT OF THE NORTHEAST...AND THIS IS BEGINNING TO LEAD TO
SIGNIFICANT BLOWING SNOW AS WE ARE NOW TRANSITIONING TO A DRYER
SNOWFALL AS COLDER AIR FILTERS SOUTHWARD. THIS TREND WILL CONTINUE
THIS EVENING AS STRONG WIND GUSTS OF 40 TO 45 MPH SET UP OVER
NORTHERN ILLINOIS/NORTHWESTERN INDIANA. THE COMBINATION OF FALLING
SNOW AND BLOWING SNOW WILL RESULT IN WHITE OUT CONDITIONS AT
TIMES...ESPECIALLY IN OPEN AREAS.

THE SNOW IS EXPECTED TO FINALLY BEGIN TO ABATE FROM WEST TO EAST
LATER THIS EVENING AND INTO THE OVERNIGHT HOURS. THE THREAT OF
SIGNIFICANT LAKE EFFECT SNOW SHOWERS LOOKS LOW ON THE BACK SIDE OF
THIS SYSTEM...AS THE THERMODYNAMIC SETUP OVER THE LAKE IS NOT LOOKING
AS GOOD. WITH THIS IN MIND...ANY LINGERING LAKE INDUCED SNOW SHOWERS
SHOULD REMAIN LIGHT...SO ANY ADDITIONAL ACCUMULATIONS ACROSS
NORTHEASTERN ILLINOIS/NORTHWESTERN INDIANA AFTER MIDNIGHT TONIGHT
SHOULD GENERALLY REMAIN UNDER AN INCH. AN ADDITIONAL 3 TO 5 INCHES
IS STILL EXPECTED BEFORE THE SNOW ENDS LATER THIS EVENING. THIS
SHOULD RESULT IN AROUND 12 TO 16 INCHES ACROSS MUCH OF NORTHERN
ILLINOIS...WITH LIGHTER AMOUNTS FAR SOUTH CLOSER TO THE TRACK OF
THIS SYSTEM.

WIND SPEEDS LOOK TO REMAIN ELEVATED OVERNIGHT TONIGHT AND THIS WILL
LIKELY CONTINUE TO RESULT IN BLOWING SNOW OVER THE AREA AFTER THE
CURRENT 06 UTC ENDING TIME OF THE BLIZZARD AND WINTER STORM WARNING.
I THOUGH ABOUT EXTENDING THE HEADLINES SOME...BUT ONCE THE SNOW
STOPS WIDESPREAD WHITEOUT CONDITIONS WILL BE UNLIKELY.
THEREFORE...IF CONDITIONS STILL WARRANT A HEADLINE OVERNIGHT...A
WINTER WX ADVISORY MAY BE THE BETTER ROUTE TO GO.

KJB

&&

.LONG TERM...
118 PM CST

MONDAY THROUGH MONDAY NIGHT...
LOW PRESSURE WILL CONTINUE TO DEPART THE REGION TO THE EAST...WITH
ANTI-CYCLONIC FLOW REPLACING IT OVER THE FORECAST AREA FOR MON.
LONGWAVE FLOW PATTERN CONTINUES TO BE IN A SOMEWHAT NORTHWEST
ORIENTATION. THIS COUPLED WITH THE SFC RIDGE CENTER POSITIONED
JUST SOUTH OF THE CWFA WILL KEEP WINDS GENERALLY FROM THE
WEST/NORTHWEST. ENOUGH DRY AIR SHUD MIX DOWN TO THE SFC AND ERODE
THE BULK OF THE CLOUDS...HOWEVER NOT TOO CONFIDENT THAT CLEAR
SKIES WILL LINGER VERY LONG. THE FLOW WILL REMAIN PROGRESSIVE AND
HELP TO PUSH THE SFC RIDGE EAST/SOUTHEAST OF THE AREA BY LATE MON
NGT.

THIS WILL SETUP A WEAK MID-LVL WAVE SLIDING SOUTHEAST ACROSS THE
NORTHERN PLAINS TO ARRIVE LATE MON NGT IN THE FAR WESTERN CWFA. LLVL
FLOW WILL TURN SOUTHWESTERLY AND COULD KEEP SOME DRY AIR LOCKED IN
LONG ENOUGH TO KEEP ANY PRECIP WEST OF THE FORECAST AREA UNTIL LATE
MON NGT.

HIGHS MON WILL STRUGGLE TO WARM DESPITE THE THINNING SOLAR
SHIELDING...WITH TEMPS GENERALLY IN THE LOW/MID TEENS. THEN MON NGT
TEMPS ALOFT WILL EASILY RADIATE WITH LGT WINDS AND THIN CLOUD COVER.
FRESH SNOW PACK WILL LIKELY HELP TEMPS TO COOL INTO THE SINGLE
DIGITS ABOVE ZERO. WITH CLOUDS RETURNING LATE MON NGT FROM A WEAK
MID-LVL SYSTEM...TEMPS COULD RISE A DEGREE OR TWO AFTER
MIDNIGHT/EARLY TUE.

CURRENT EXPECTATION IS THAT ANY ACCUMULATIONS MON NGT WOULD BE LESS
THAN ONE HALF INCH.

TUESDAY THROUGH WEDNESDAY...
WITH A MID-LVL WAVE PIVOTING EAST OVERHEAD TUE MORNING...LLVL FLOW
WILL REMAIN SOUTHWESTERLY WITH SOME WEAK WARM AIR ADVECTING INTO THE
FORECAST AREA. TEMPS SHUD WARM INTO THE 20S TUE...AND WITH A GOOD
PUSH OF WARM AIR ADVECTION IN THE SOUTHERN TIER OF COUNTIES...TEMPS
COULD TAG 30 DEGREES TUE AFTN.

500MB TROUGH AXIS IS PROGGED TO SEND YET ANOTHER MID-LVL WAVE DIVING
SOUTHEAST ACROSS THE NORTHERN PLAINS TUE MORNING. GUIDANCE HAS
CONTINUED TO PROG THE ARRIVAL OF THIS FEATURE INTO THE CWFA TUE NGT.
FORCING APPEARS TO BE RATHER WEAK...HOWEVER ENOUGH MOISTURE AND LIFT
COULD EASILY PRODUCE SOME LGT SNOW ONCE AGAIN LATE TUE NGT. AT THIS
TIME IT WOULD APPEAR AROUND 1 INCH OF SNOW.

CONSIDERABLE CLOUDINESS TUE NGT WILL HELP TO HOLD TEMPS UP...WITH
OVERNIGHT LOWS IN THE UPR TEENS TO MID 20S.

SOME LINGERING LGT SNOW WED MORNING...WITH FLOW STARTING TO FLATTEN
BY MIDDAY WED. AS THE LOW LIFTS NORTHEAST WED MORNING ACROSS LOWER
MI...A TRAILING BOUNDARY WILL SLOWLY SAG SOUTH ACROSS THE WESTERN
GREAT LAKES AND MID-MISSOURI VALLEY. A WEAK WAVE WILL TRY TO DEVELOP
OVER THE CENTRAL PLAINS EARLY WED...AND COULD BRING ADDTL LGT PRECIP
BACK INTO THE FAR WEST/SOUTHWEST CWFA LATE WED AFTN.

WEDNESDAY NIGHT THROUGH SATURDAY...
ENSEMBLES CONTINUE THE THEME OF AN ACTIVE FLOW...WITH TROUGHING
GENERALLY OVER THE GREAT LAKES REGION AND RIDGING REMAINING OVER
WESTERN CANADA. THERE IS SOME WEAK FLATTENING IN THE LONGWAVE
PATTERN THUR...BUT THIS APPEARS TO BE ONLY FOR ONE PERIOD.

THEN ENSEMBLES ARE BEGINNING TO SUGGEST BROAD RIDGING WILL DEVELOP
ACROSS THE SOUTHWEST CONUS...WHICH COULD SHIFT THE NORTHWEST FLOW
ORIENTATION TO THE NORTHEAST. ROBUST THERMAL TROUGH SWINGS OVER THE
REGION THUR...BRINGING MUCH COOLER AIR BACK WITH HIGHS IN THE SINGLE
DIGITS TO LOW TEENS. THUR NGT TEMPS COULD THEN DROP BELOW ZERO.
THEN FOR THE START OF THE UPCOMING WEEKEND TEMPS COULD WARM BACK
INTO THE LOW 30S.

BEACHLER

&&

.AVIATION...

//ORD AND MDW CONCERNS...UPDATED 18Z...

* SNOW THROUGH TONIGHT. LIGHT LAKE EFFECT SNOW EARLY MONDAY MAINLY
  FOR MDW. PREVAILING VIS AT OR UNDER 1SM THROUGH THIS EVENING.

* NELY WINDS GUSTING TO 30-35 KT LATE THIS AFTERNOON/EARLY
  EVENING.

* BLOWING AND DRIFTING SNOW LIKELY THIS AFTERNOON AND TONIGHT.

* PERIODS OF VIS 1/4SM OR LESS THIS AFTERNOON WHEN GUSTS INCREASE
  TO 30 KT AND HIGHER.

* IFR-LIFR CIGS THROUGH LATE EVENING.

KMD

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

STEADY SNOWFALL CONTINUES THROUGH THE AFTERNOON AND EVENING. THE
SNOW HAS BEEN WET TO THIS POINT...BUT FROM NORTH TO SOUTH IT WILL
SHIFT TO A DRIER SNOW AS THE AFTERNOON AND EVENING GO ON.
VISIBILITIES HAVE BEEN LARGELY STEADY AROUND 1/2 MILE...AND WHILE
FLUCTUATIONS IN THIS WILL OCCUR FROM TIME TO TIME...EXPECT 1/2 TO
3/4 VSBYS TO GENERALLY BE THE RULE. AS THE WINDS RAMP UP LATER THIS
AFTERNOON AND EVENING...FEEL THAT THERE WILL BE OCCASIONAL 1/4 MILE
VISIBILITIES AS THE SNOW GETS A BIT MORE BLOWABLE...BUT STILL NOT
CONFIDENT IN THIS CONDITION PREVAILING. WILL HAVE TO MONITOR AS THE
WINDS RAMP UP. IF THIS WERE TO OCCUR...IT WOULD BE THE LATE
AFTERNOON AND EARLY EVENING PERIOD WHEN THE SURFACE LOW MOVES A BIT
FARTHER NORTH AND EAST. THINK THAT THE 22Z-02Z TIME FRAME WOULD BE
THE BEST BET FOR THIS. WINDS HOLD IN THE 050 DIRECTION THEN BACK
THROUGH THE EVENING TO 020 BY MID EVENING...THEN NNW OVERNIGHT.

SHOULD SEE SOME SLIGHTY IMPROVEMENT IN VSBY AND DECREASE IN SNOWFALL
FROM 4Z-6Z...AND AFTER 6Z SNOWFALL SHOULD DECREASE SIGNIFICANTLY
THOUGH NOT END...AND WINDS SHOULD START A MORE SIGNIFICANT
DOWNWARD TREND.  EXPECT LIGHT LAKE EFFECT SNOW SHOWERS OVERNIGHT.
MOST TERMINALS EXCEPT MDW AND GYY SHOULD BE DRY BY DAYBREAK WITH A
WEAKENING WESTERLY WIND.

KMD

//ORD AND MDW CONFIDENCE...UPDATED 18Z...

* MEDIUM TO HIGH CONFIDENCE IN WX/VIS TRENDS.

* MEDIUM CONFIDENCE IN CIG TRENDS.

* MEDIUM CONFIDENCE IN TIMING OF IMPROVING CIG/VIS.

* MEDIUM TO HIGH CONFIDENCE IN WIND TRENDS.

KMD

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

MONDAY NIGHT...VFR/WX NIL EARLY. CHANCE SNOW WITH MVFR CIGS/VIS
LATE.

TUESDAY...SLIGHT CHANCE SNOW EARLY WITH MVFR CIGS/VIS. VFR/WX NIL
AFTERNOON.  SNOW LIKELY WITH IFR CIG/VIS OVERNIGHT.

WEDNESDAY...SLIGHT CHANCE SNOW WITH MVFR CIG/VIS EARLY. VFR/WX NIL
OVERNIGHT.

THURSDAY...VFR/WX NIL.

FRIDAY...VFR/WX NIL.

SATURDAY...SLIGHT CHANCE SNOW WITH MVFR CIG/VIS POSSIBLE.

KREIN

&&

.MARINE...
135 PM CST

LOW PRESSURE HAS BEEN SLOW TO LIFT NORTHEAST ACROSS THE OHIO
VALLEY...REACHING EAST CENTRAL IL BY EARLY THIS AFTERNOON. THIS
LOW CONTINUES TO DEEPEN AND WILL ALLOW FOR GALES TO INCREASE FROM
35 KT TO LIKELY CLOSER TO 40 KT. THE FAR NORTHERN PORTIONS OF LAKE
MICHIGAN MAY STRUGGLE TO SEE THE STRONGER GRADIENT DEVELOP AND
STRONGER GALES...BUT THE EXPECTATION IS THAT GALES WILL EVENTUALLY
REACH THE NORTHERN PORTIONS LATER THIS EVENING. WITH MUCH COLDER
AIR SLIDING ACROSS THE LAKE WITH GALE CONDITIONS...HEAVY FREEZING
SPRAY WILL BE LIKELY. LOW PRESSURE WILL THEN SLIDE NORTHEAST LATE
TONIGHT...AND THIS WILL ALLOW THE GRADIENT TO STEADILY RELAX
OVERNIGHT. THIS WILL GALES/FREEZING SPRAY TO COME TO AN END LATE
TONIGHT. BROAD HIGH PRESSURE WILL BUILD IN EARLY MONDAY...BRINGING
MUCH LIGHTER WINDS TO LAKE MICHIGAN.

THE FLOW REMAINS RELATIVELY ACTIVE...WITH THE HIGH PRESSURE
QUICKLY SLIDING EAST MONDAY EVENING AND FLOW TURNING
SOUTHWESTERLY. THE GRADIENT BEGINS TO INCREASE LATE MONDAY NIGHT
INTO TUESDAY...BUT AT THIS TIME IT APPEARS WINDS WILL REMAIN
BETWEEN 10-20KT POSSIBLY UP TO 25KT.

A SERIES OF LOW PRESSURE SYSTEMS WILL CONTINUE TO FEED FROM WEST
TO EAST ACROSS LAKE MICHIGAN THROUGH MID-WEEK...BUT AT THIS TIME
THE SYSTEMS ARE NOT EXPECTED TO BE STRONG.

BEACHLER

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKESHORE FLOOD ADVISORY...ILZ006-ILZ014 UNTIL 10 AM MONDAY.

     BLIZZARD WARNING...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ013-ILZ014-ILZ019-ILZ020-ILZ021-ILZ022
     UNTIL MIDNIGHT MONDAY.

     WINTER STORM WARNING...ILZ023-ILZ032-ILZ033-ILZ039 UNTIL
     MIDNIGHT MONDAY.

IN...BLIZZARD WARNING...INZ001-INZ002 UNTIL MIDNIGHT MONDAY.

     WINTER STORM WARNING...INZ010-INZ011-INZ019 UNTIL MIDNIGHT
     MONDAY.

LM...GALE WARNING...LMZ080-LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-
     LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-LMZ742-
     LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ868-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878 UNTIL 3 AM MONDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ261-LMZ362-LMZ364-
     LMZ366-LMZ563-LMZ565-LMZ567-LMZ669-LMZ671-LMZ673-LMZ675-
     LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-
     LMZ868-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878 UNTIL 3 AM MONDAY.

&&

$$

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