Cold in Illinois, January 25, 2004

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO IL
1140 AM CST SUN JAN 25 2004

.AVIATION DISCUSSION FOR 18Z TAFS...

STRONG EASTERLY SURFACE WINDS AND TIMING AND INTENSITY OF SNOW ARE
MAIN CONCERNS FOR THIS TAF CYCLE. VERY STRONG EAST WINDS SUSTAINED
AT AROUND 18KTS ALTHOUGH NOT REAL GUSTY IN STABLE AMS. ONE CONCERN
IS STRATO CU AROUND 2K FT OFF LAKE MICHIGAN. CURRENTLY LOW LEVEL
WINDS ABOUT 100 DEGREES AND CLOUDS ARE FROM UGN NORTHWARD INTO WIS.
BY EVENING WINDS EXPECTED TO BECOME 070-090 WHICH COULD PUSH LAKE
CLOUDS INTO CHICAGO AREA TERMINALS.

MODELS CONTINUE TO LIFT SYSTEM FROM THE OH VALLEY
NORTHWARD...HOWEVER MAIN LIFT AND PRECIP WILL REAMIN WELL SOUTH AND
EAST OF TERMINALS. SOME LIGHT SNOW EXPECTED IN CHICAGO TERMINALS
THIS EVENING. DRY AIR IN LOW LEVELS MAY DELAY ONSET OF SNOW UNTIL
ABOUT 02-03Z. BEST TIME FOR IFR VSBYS WOULD BE 03Z-09Z. SNOW
DIMINISHING TO FLURRIES BY MORNING AND POSSIBLY SOME MORE LIGHT SNOW
MONDAY AFTERNOON BEYOND THIS TAF PERIOD. WINDS DIMINISHING SOME BY
MID DAY MONDAY.

ALLSOPP

&&

.DISCUSSION FOR MORNING GRIDS/ZONE FORECASTS...

PROBLEM FOR THE DAY IS THE UPCOMING SNOW EVENT. FCST SCENARIO NOT
MUCH DRASTICALLY DIFFERENT THAN YESTERDAY WITH RATHER WEAK UPR WAVE
PASSING ACROSS AREA TONIGHT. GFS IS THE PREFERRED MODEL CHOICE AND
THIS TAKES UPR FEATURE FURTHER SOUTH THAN ETA. IN EFFECT...THIS
KEEPS UPR LVL WARMING AT A MINIMUM AND REALLY CUTS BACK ON MOISTURE.
EVEN ETA WARMING ALOFT SHOWING TOO MUCH TRYING AT THE SAME TIME TO
WARRANT WARNING AMOUNTS OF ZR- OR IP-. THUS AM CUTTING BACK ON
AMOUNTS BUT WUD FEEL SAFER TO BLEND SCENARIO WITH ETA A BIT AND UP
SNOW AMOUNTS TO 2 TO 4 INCHES TOTAL FOR THE FAR SOUTH FADING TO 1-3
CHI TO LASALLE...THEN INCH OR LESS NORTH AND WEST OF THERE. THIS IS
ALL FOR TODAY AND TONIGHT.

MONDAY IS A BIT MORE DIFFICULT TO BLEND. THERE SHOULD STILL BE SOME
SNOW AROUND WITH AMOUNTS OF A HALF INCH OR LESS. BUT THE SFC LOW ON
THE GFS IS DOWN IN NRN AR MONDAY WHILE REFORMING OVER NWRN INDY ON
THE ETA.

RAPID DEEPENING OF THE LONGWAVE TROF IN THE ROCKIES TONIGHT WILL
FORM A CLOSED UPR LOW IN OK AND KICK OUT ACROSS NRN AR MONDAY. THE
NEXT BIG SNOW EVENT WILL THUS BE MONDAY NIGHT WITH THE MAJORITY OF
SNOW SOUTH OF CHI AREA. BUT VALUES EVEN IN NRN IL LOOK TO BE MORE
THAN THIS EVENT TODAY AND TONIGHT. THE ETA WILL BRING THE SNOW IN
SOONER TO THE CHI AREA ON MONDAY EVENING BUT LIGHTER ON AMOUNTS.
THUS THE EVENT COMING MONDAY NIGHT WILL NEED TO BE MONITORED. MODEL
DIFFS ARE TOO GREAT TO WARRANT A WATCH RIGHT NOW. THIS WOULD ALSO BE
TOO CONFUSING WITH A WINTER WX ADVISORY IN EFFECT FOR SOME OF THE
SAME AREA.

THE UPR LOW FINALLY PASSES ON TUESDAY WITH SFC RIDGING APPEARING
OVER THE AREA ONCE AGAIN AND LAKE EFFECT SNOWS FOR NWRN INDY
APPEARING TUESDAY NIGHT. THIS IS SHORTLIVED WITH RIDGE PASSAGE WED
MRNG AND ANOTHER CLIPPER SPEEDING DOWN THE UPR NW FLOW. THUS MORE
SNOW WED NGT AND THURSDAY.

RLB

&&

.LOT...WINTER WX ADVISORY THIS AFTERNOON AND TONIGHT
FORD...IROQUOIS...BENTON...NEWTON AND JASPER COUNTIES
IL...NONE.
IN...NONE.
LK MI...NONE.

&&

HAZARDOUS WEATHER OUTLOOK...CORRECTION TO WATCH COUNTIES
NATIONAL WEATHER SERVICE CHICAGO IL
1015 PM CST SAT JAN 24 2004

ILZ003>006-008-010>014-019-020>023-032-033-039-INZ001-002-010-
011-019-251200-
WINNEBAGO-BOONE-MCHENRY-LAKE IL-OGLE-LEE-DE KALB-KANE-DU PAGE-COOK-
LA SALLE-KENDALL-GRUNDY-WILL-KANKAKEE-LIVINGSTON-IROQUOIS-FORD-
LAKE IN-PORTER-NEWTON-JASPER-BENTON-
1015 PM CST (1115 PM EST) SAT JAN 24 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR NORTH CENTRAL AND NORTHEAST
ILLINOIS...NORTHWEST INDIANA...AND THE ADJACENT WATERS OF LAKE
MICHIGAN.

.DAY ONE...OVERNIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A WINTER STORM WATCH HAS BEEN POSTED FOR FORD...AND IROQUOIS
COUNTIES IN ILLINOIS AND FOR NEWTON...JASPER...AND BENTON
COUNTIES IN INDIANA FOR SUNDAY AFTERNOON THROUGH MONDAY MORNING.

A STORM SYSTEM WILL MOVE FROM THE SOUTHERN PLAINS INTO THE OHIO
VALLEY SUNDAY AND SUNDAY NIGHT. SNOW IS EXPECTED TO DEVELOP SUNDAY
AFTERNOON SOUTH OF A STREATOR TO KANKAKEE TO DE MOTTE INDIANA LINE.
THE SNOW WILL CONTINUE INTO SUNDAY NIGHT...AND CHANGE TO FREEZING
RAIN IN THE WATCH AREA.  SNOW IS ALSO EXPECTED TO SPREAD NORTHWARD
ACROSS THE REMAINDER OF THE AREA SUNDAY EVENING.  SNOWFALL AMOUNTS
OF 2 TO 4 INCHES ARE POSSIBLE.

A SECOND DISTURBANCE IS EXPECTED TO LIFT OUT OF THE SOUTHERN PLAINS
ON MONDAY AND SPREAD ANOTHER ROUND OF SNOW ACROSS NORTHERN ILLINOIS
AND NORTHWEST INDIANA MONDAY AFTERNOON AND EVENING.

.SPOTTER INFORMATION STATEMENT...

SPOTTER REPORTS OF SNOW AND ICE ACCUMULATIONS WILL BE APPRECIATED.

LMZ740>746-766-251200-
WINTHROP HARBOR IL TO NEW BUFFALO MI-
LAKE MICHIGAN-
1015 PM CST SAT JAN 24 2004

.DAY ONE...OVERNIGHT

NO HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...SUNDAY THROUGH FRIDAY

A SMALL CRAFT ADVISORY HAS BEEN POSTED FOR SUNDAY AND SUNDAY NIGHT.
EAST TO NORTHEAST WINDS ARE EXPECTED TO INCREASE INTO THE 20 TO 30
KNOT RANGE BY SUNDAY AFTERNOON AND CONTINUE SUNDAY NIGHT.

&&

           NWS CHICAGO WEBPAGE:

    HTTP://WWW.CRH.NOAA.GOV/LOT (LOWER CASE)
OR  HTTP://WEATHER.NOAA.GOV/CHICAGO (LOWER CASE)

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