Lake-Effect Snow in Indiana, February 3 to 4, 2009

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
622 AM CST TUE FEB 3 2009

.DISCUSSION...
317 AM CST

MAIN FORECAST CONCERN THIS PERIOD IS ON THE POTENTIAL HEAVY LAKE
EFFECT SNOW FOR NORTHWEST INDIANA...PARTICULARLY PORTER COUNTY
WHERE UP TO 18 INCHES OF SNOW MAY FALL.

BEFORE THAT THOUGH...WE HAVE AN UPPER LEVEL SHORTWAVE TROF DIGGING
DOWN ACROSS EASTERN IOWA/NORTHWEST ILLINOIS THAT HAS LED TO THE
DEVELOPMENT OF A SFC LOW OVER CENTRAL ILLINOIS. THE FORCING FROM
THESE FEATURES HAS LED TO AN AREA OF LIGHT SNOW ACROSS THE
SOUTHERN PORTION OF THE FORECAST AREA AND HAS BROUGHT A DUSTING
TO AN INCH OF ACCUMULATION. THIS SFC/UPPER LEVEL SYSTEM WILL MOVE
OUT OF THE REGION SHORTLY AFTER DAYBREAK.

ON THE HEELS OF THIS SYSTEM IS ANOTHER CLOSED UPPER LOW OVER THE
UPPER PENINSULA AND RESULTANT SFC LOW OVER CENTRAL MICHIGAN.
EXTENDING WEST OUT OF THIS SFC LOW IS AN INVERTED TROF THAT WILL
RUN DOWN LAKE MICHIGAN THIS MORNING. AS THIS TROF PASSES
BY...WINDS WILL COME AROUND TO THE NORTH AND START UP THE LAKE
EFFECT SNOW MACHINE. A BRIEF PERIOD OF SNOW SHOWERS...CURRENTLY IN
SOUTHERN WISCONSIN...ARE EXPECTED TO COME THROUGH WITH THIS TROF
BUT ARE NOT EXPECTED TO CAUSE MUCH MORE THAN A DUSTING.

THE OVERALL SETUP FOR THIS LAKE EFFECT EVENT LOOKS PRETTY GOOD IN
TERMS OF BEING ABLE TO PRODUCE A HEAVY SNOWFALL FOR NORTHWEST
INDIANA. GOOD LOW TO MID LEVEL LAPSE RATES AS COLD AIR PROPAGATES
IN FROM SOUTHERN CANADA ON THE WESTERN PERIPHERY OF THE DEEPENING
UPPER TROF OVER THE GREAT LAKES. INVERSION HEIGHTS ARE UP AROUND
8KFT IN NW INDIANA WITH FAIRLY UNIDIRECTIONAL WINDS ALOFT. SOME
LIMITATIONS FOR NE ILLINOIS IS THAT RESIDENCE TIME OF ANY LAKE
EFFECT SNOW APPEARS TO BE SMALL...TRAJECTORY OF WINDS APPEARS TO
BE MORE NORTH TO NORTHWEST AT THE SFC ON UP TO 850MB...AND
FORECAST SOUNDINGS ARE SHOWING AN INVERSION SETTING UP AT ABOUT
3KFT SHORTLY AFTER THE BEST VERTICAL FORCING ROLLS BY.

IN COMPARING THE GFS TO THE NAM...THE HIGHER RESOLUTION NAM SEEMS
TO HAVE A BETTER GRIP ON THE FORECAST THERMAL PROFILES WHILE THE
LOWER RES GFS SEEMS TO BE BLEEDING/SMOOTHING THE LAKE ENVIRONMENT
INTO NORTHEAST ILLINOIS. AT THIS POINT...AM NOT OVERLY OPTIMISTIC
WITH SNOWFALL TOTALS REACHING ADVISORY CRITERIA FOR LAKE AND COOK
COUNTIES IN ILLINOIS...BUT WILL KEEP THE ADVISORY GOING AS SOME OF
THE SHORTER TERM GUIDANCE LIKE THE RUC AND LOCALLY RUN WRF ARE
HINTING AT A MESO-LOW DEVELOPMENT...WHICH COULD WOBBLE THE HEAVIEST
SNOW BAND WEST INTO THESE COUNTIES. ALSO...SOUTHEASTERN COOK
COUNTY HAS A BETTER SHOT AT THE SNOW LINGERING AND GETTING TOWARD
THE 4 INCH MARK.

AS FOR NORTHWEST INDIANA...IT IS A DIFFERENT STORY OVER THERE.
RESIDENCE TIME AND TRAJECTORY ALL LOOK GOOD HERE INCLUDING THE
AFOREMENTIONED INVERSION HEIGHTS UP TO 8KFT AND GOOD LOW LEVEL
INSTABILITY. THE ONLY REAL WILD CARD IS WITH THE WINDS AND
POSSIBLE MESO-LOW DEVELOPMENT. THE WINDS ACTUALLY VEER A BIT WITH
HEIGHT...GOING NORTHWEST IN THE LOWEST 3KFT THEN NORTH ON UP
THROUGH THE REST OF THE UNSTABLE LAYER. THIS MAY DISRUPT THE
BANDING A BIT WHERE IF IT WAS COMPLETELY UNIDIRECTIONAL AND
A CONVERGENT WIND FIELD ACROSS THE LAKE YOU WOULD PROBABLY SEE ONE
DISTINCT BAND. THE POSSIBLE MESO-LOW DEVELOPMENT COULD EITHER HURT
OR VERIFY THE FORECAST SNOW TOTALS OF UP TO 18 INCHES IN PORTER
COUNTY. THE HEAVIEST SNOW PERIOD IS EXPECTED TO BE FROM THE LATE
AFTERNOON INTO EVENING WHEN SNOWFALL RATES COULD BE UP TO 2 INCHES
PER HOUR AT TIMES. WITH AN 18 HOUR PERIOD OF ACCUMULATING SNOWFALL
POTENTIAL...WILL BE UPGRADING THE LAKE EFFECT SNOW WATCH TO A
WARNING FOR LAKE/PORTER COUNTIES IN INDIANA AND ADDING TO IT A
LAKE EFFECT SNOW ADVISORY FOR JASPER COUNTY...PRIMARILY THE
NORTHEAST PORTION OF THAT COUNTY.

OVERALL...WILL BE GOING WITH ABOUT 1 TO 4 INCHES FOR LAKE/COOK
COUNTIES IN ILLINOIS...3 TO 6 INCHES ACROSS NORTHEAST JASPER
COUNTY...4 TO 8 INCHES FOR LAKE COUNTY INDIANA WITH LOCALLY UP TO
12 INCHES...6 TO 12 INCHES ACROSS PORTER COUNTY WITH LOCALLY UP
TO 18 INCHES ACROSS NORTHERN PORTER COUNTY.

FOR THE REST OF THE FORECAST PERIOD...NOT MANY CHANGES MADE TO THE
GOING FORECAST WITH LOW WIND CHILLS ON WEDNESDAY MORNING AS THE
RIDGE OF HIGH PRESSURE MOVES IN ACROSS THE REGION. A WIND CHILL
ADVISORY MAY BE NEEDED...BUT WILL LET THE DAY SHIFT TAKE ANOTHER
LOOK BEFORE DOING ANYTHING. THE PATTERN SHIFT WILL BE ON AFTER
THIS WITH HIGHS CLIMBING INTO THE 40S TOWARD THE END OF THE WEEK.

HALBACH

&&

.AVIATION...

1200 UTC TAFS...FORECAST PERIOD ACROSS THE CHICAGO TERMINALS WILL
BEGIN TO DETERIORATE THIS MORNING AS SNOW MOVES SOUTHEAST. SURFACE
TROUGH MOVING SOUTH ALONG THE LAKE HAS ALREADY BEGUN TO BRING SNOW
SHOWERS ACROSS ROCKFORD THIS MORNING. MVFR CEILINGS AND SNOW WILL
MOVE SOUTHEAST INTO THE REST OF THE TERMINALS OVER THE NEXT COUPLE
OF HOURS. AS AREA OF LOW PRESSURE ACROSS THE NORTHERN LAKES MOVES
SOUTHEAST...AND AREA OF HIGH PRESSURE ACROSS THE NORTHERN PLAINS
BUILDS INTO THE UPPER MIDWEST...WINDS ACROSS LAKE MICHIGAN WILL
PROVIDE ADDITIONAL CHANCES FOR LAKE EFFECT SNOW...MAINLY FOR
OHARE...MIDWAY...AND GARY THROUGH THE AFTERNOON. IFR CONDITIONS
ARE FORECAST FOR OHARE AND MIDWAY BY LATE MORNING WITH LIFR
CONDTIONS FORECAST FOR GARY.

PRESSURE GRADIENT WILL CONTINUE TO TIGHTEN WITH DEPARTING LOW AND
HIGH PRESSURE BUILDING IN FROM THE NORTHWEST. THIS WILL INCREASE
WINDS THROUGHOUT THE DAY WITH GUSTS AS HIGH AS 25 KNOTS WELL INTO
THE EVENING. AS HIGH PRESSURE CONTINUES TO BUILD SOUTHEAST INTO
CWA...SKIES WILL BEGIN TO CLEAR WITH GUSTS DIMINISHING FROM WEST
TO EAST.

RODRIGUEZ

&&

.MARINE...

441 PM CST

BRIEF UPDATE TO MARINE DISCUSSION FOR SHORT TERM.

WINDS STRONGER THAN EXPECTED ON FAR SOUTHERN LAKE MICHIGAN LATE
THIS AFTERNOON WITH GUSTS AROUND 30 KNOTS. SHIP OBSERVATION FROM A
COUPLE OF MILES OFF GARY INDICATED FAIRLY ROUGH CONDITIONS WITH 3
TO 5 FOOT WAVES. SURFACE OBS INDICATE A PRESSURE FALL MAXIMA
ACROSS CENTRAL/NORTHEAST IL...AND EXPECT ISALLOBARIC GRADIENT
HELPING TO INCREASE WIND SPEEDS. EXPECT THIS WILL BE A RELATIVELY
SHORT LIVED PROBLEM...WITH PRESSURE FALLS ALREADY DECREASING..BUT
BASED ON REPORTED CONDITIONS HAVE BUMPED UP WINDS/WAVES AND HAVE
ISSUED A SMALL CRAFT ADVISORY FOR IL/IN NEARSHORE WATERS THIS
EVENING. NO MODIS 250 METER RESOLUTION IMAGERY AVAILABLE FOR
SOUTHERN LAKE MICHIGAN THIS AFTERNOON...THOUGH 1 KM GOES VIS
SUGGESTS THERE MAY BE A GOOD AMOUNT OF OPEN WATER IN WFO LOT
NEARSHORE ZONES. WILL LIKELY SEE WINDS DIMINISH SOMEWHAT BEFORE
FRONTAL PASSAGE AND DEVELOPMENT OF GALE FORCE NORTH WINDS TUESDAY.

RATZER

PREVIOUS DISCUSSION...

253 PM CST

LOW PRESSURE CURRENTLY OVER NORTHERN LAKE MI MOVES SOUTHEAST
DURING THE NIGHT WHILE HIGH PRESSURE BUILDS SOUTHWARD FROM CENTRAL
CANADA ACROSS THE NORTHERN AND CENTRAL PLAINS. A COLD FRONT
TRAILING SOUTHWEST ACROSS WI AND IA MOVES ACROSS SOUTHERN LK MI
TONIGHT AS THE LOW CROSSES LOWER MI. A MID LEVEL LOW CURRENTLY
OVER FAR NORTHWEST WI WILL GRADUALLY DROP SOUTHEAST ACROSS THE
LAKE OVERNIGHT AND THEN CONTINUE ON TO NORTHERN IN AND NORTHWEST
OH BY MIDDAY TUESDAY. THIS ALLOWS A TROUGH/SECONDARY COLD FRONT TO
DROP SOUTH THROUGH THE SOUTHERN TIP OF THE LAKE RESULTING IN A
FAIRLY STRONG...DEEP NEAR UNIDIRECTIONAL NORTH FLOW DOWN THE
LAKE. DUE TO THE COLD AIR MASS...SIGNIFICANT TEMPERATURE
DIFFERENTIAL WILL DEVELOP OVER THE OPEN WATERS ALLOWING MOMENTUM
OF 30-35 KT WINDS AT 2-2.5KM TO BE MIXED DOWN IN VIGOROUS LAKE
EFFECT CONVECTIVE CELLS. WILL ALSO BE AN ISALLOBARIC CONTRIBUTION
TO THE WINDS WITH THE STRONG RIDGE BUILDING ACROSS THE PLAINS.
THUS...GALE WATCH HAS BEEN UPGRADED TO GALE WARNING FROM MID
MORNING TUESDAY THROUGH TUESDAY EVENING.

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...LAKE EFFECT SNOW ADVISORY...ILZ006-ILZ014...9 AM TUESDAY TO 3 PM
     TUESDAY.

IN...LAKE EFFECT SNOW WARNING...INZ001-INZ002...9 AM TUESDAY TO 4 AM
     WEDNESDAY.

     LAKE EFFECT SNOW ADVISORY...INZ011...9 AM TUESDAY TO 4 AM
     WEDNESDAY.

LM...GALE WARNING...LMZ080-LMZ669-LMZ671-LMZ673-LMZ675-LMZ740-LMZ741-
     LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-LMZ779-LMZ870-LMZ872-
     LMZ874-LMZ876-LMZ878...9 AM TUESDAY TO MIDNIGHT WEDNESDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ080-LMZ669-LMZ671-LMZ673-
     LMZ675-LMZ740-LMZ741-LMZ742-LMZ743-LMZ744-LMZ745-LMZ777-
     LMZ779-LMZ870-LMZ872-LMZ874-LMZ876-LMZ878...9 AM TUESDAY TO
     MIDNIGHT WEDNESDAY.

     GALE WARNING...LMZ261-LMZ362-LMZ364-LMZ366-LMZ563-LMZ565-LMZ567-
     LMZ868...9 AM TUESDAY TO 6 PM TUESDAY.

     HEAVY FREEZING SPRAY WARNING...LMZ261-LMZ362-LMZ364-LMZ366-
     LMZ563-LMZ565-LMZ567-LMZ868...9 AM TUESDAY TO 6 PM TUESDAY.

&&

HAZARDOUS WEATHER OUTLOOK...CORRECTED
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
631 AM CST TUE FEB 3 2009

ILZ003>006-008-010>014-019>023-032-033-039-INZ001-002-010-011-019-
041245-
WINNEBAGO-BOONE-MCHENRY-LAKE ILLINOIS-OGLE-LEE-DE KALB-KANE-
DUPAGE-COOK-LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-
IROQUOIS-FORD-LAKE INDIANA-PORTER-NEWTON-JASPER-BENTON-
631 AM CST TUE FEB 3 2009 /731 AM EST TUE FEB 3 2009/

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF NORTH CENTRAL
ILLINOIS...NORTHEAST ILLINOIS AND NORTHWEST INDIANA.

.DAY ONE...TODAY AND TONIGHT.

LAKE EFFECT SNOW IS EXPECTED TO DEVELOP THIS MORNING ACROSS FAR
NORTHEAST ILLINOIS AND NORTHWEST INDIANA. THE SNOW WILL END BY
LATE AFTERNOON ACROSS LAKE AND COOK COUNTIES IN ILLINOIS WITH 4
INCHES POSSIBLE CLOSER TO THE LAKE. THE HEAVIEST SNOW IS EXPECTED
TO FALL ACROSS NORTHWEST INDIANA WHERE 6 TO 12 INCHES WITH LOCALLY
HIGHER AMOUNTS TO 18 INCHES ARE POSSIBLE IN NORTHERN PORTER COUNTY.
SNOWFALL RATES OF UP TO 2 INCHES PER HOUR ARE ALSO POSSIBLE AT
TIMES THIS AFTERNOON AND EVENING.

LOCALIZED ICE JAM FLOODING IS POSSIBLE ON AREA RIVERS.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

LAKE EFFECT SNOW WILL COME TO AN END ACROSS NORTHWEST INDIANA
EARLY WEDNESDAY MORNING.

WIND CHILL INDICES ARE EXPECTED TO DROP TO 20 BELOW ZERO ON
WEDNESDAY MORNING AND A WIND CHILL ADVISORY MAY BE NEEDED.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION WILL NOT BE NECESSARY THROUGH TONIGHT...
HOWEVER SPOTTERS ARE ENCOURAGED TO REPORT SNOWFALL TOTALS TO THE
NATIONAL WEATHER SERVICE CHICAGO.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ740>745-041245-
WINTHROP HARBOR TO WILMETTE HARBOR-
WILMETTE HARBOR TO NORTHERLY ISLAND-
NORTHERLY ISLAND TO CALUMET HARBOR-CALUMET HARBOR TO GARY-
GARY TO BURNS HARBOR-BURNS HARBOR TO MICHIGAN CITY-
631 AM CST TUE FEB 3 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE ILLINOIS
NEARSHORE WATERS OF LAKE MICHIGAN AND THE INDIANA NEARSHORE
WATERS OF LAKE MICHIGAN.

.DAY ONE...TODAY AND TONIGHT.

HEAVY FREEZING SPRAY AND GALE FORCE WINDS TO 35 KNOTS ARE LIKELY
INTO THIS EVENING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

HIGH WAVES WILL LEAD TO HAZARDOUS CONDITIONS FOR SMALL CRAFT
WEDNESDAY INTO WEDNESDAY EVENING.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

LMZ080-261-362-364-366-563-565-567-669-671-673-675-777-779-868-
870-872-874-876-878-041245-
LAKE MICHIGAN FROM MICHIGAN CITY IN TO ST. JOSEPH MI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM SEUL CHOIX POINT TO ROCK ISLAND PASSAGE 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN SOUTH OF A LINE FROM SEUL CHOIX POINT TO THE
MACKINAC BRIDGE AND NORTH OF A LINE FROM CHARLEVOIX MI TO SOUTH
FOX ISLAND 5 NM OFFSHORE-
LAKE MICHIGAN FROM CHARLEVOIX TO POINT BETSIE MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM POINT BETSIE TO MANISTEE MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM ROCK ISLAND PASSAGE TO STURGEON BAY WI-
LAKE MICHIGAN FROM STURGEON BAY TO TWO RIVERS WI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM TOW RIVERS TO SHEBOYGAN WI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM SHEBOYGAN TO PORT WASHINGTON WI 5 NM OFFSHORE
TO MID LAKE-
LAKE MICHIGAN FROM PORT WASHINGTON TO NORTH POINT LIGHT WI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM NORTH POINT LIGHT TO WIND POINT WI 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WIND POINT WI TO WINTHROP HARBOR IL 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WINTHROP HARBOR TO WILMETTE HARBOR IL 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM WILMETTE HARBOR IL TO MICHIGAN CITY IN 5 NM
OFFSHORE TO MID LAKE-
LAKE MICHIGAN FROM PENTWATER TO MANISTEE MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM WHITEHALL TO PENTWATER MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM GRAND HAVEN TO WHITEHALL MI 5 NM OFFSHORE TO
MID LAKE-
LAKE MICHIGAN FROM HOLLAND TO GRAND HAVEN MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM SOUTH HAVEN TO HOLLAND MI 5 NM OFFSHORE TO MID
LAKE-
LAKE MICHIGAN FROM ST. JOSEPH TO SOUTH HAVEN MI 5 NM OFFSHORE TO
MID LAKE-
631 AM CST TUE FEB 3 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PORTIONS OF THE OPEN WATERS
OF LAKE MICHIGAN.

.DAY ONE...TODAY AND TONIGHT.

HEAVY FREEZING SPRAY AND GALE FORCE WINDS TO 35 KNOTS ARE LIKELY
THROUGH THIS EVENING.

.DAYS TWO THROUGH SEVEN...WEDNESDAY THROUGH MONDAY.

GALE FORCE WINDS ARE POSSIBLE AGAIN THURSDAY...ESPECIALLY ACROSS
NORTHERN PORTIONS OF THE LAKE.

&&

COMPLETE FORECAST INFORMATION IS AVAILABLE ON THE NWS CHICAGO
WEBPAGE: WEATHER.GOV/CHICAGO

HALBACH/IZZI