FXUS63 KLOT 071210
AFDLOT

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE IL
610 AM CST MON DEC 7 2009

.DISCUSSION...
334 AM CST

TODAY...THE LIGHT SNOW WILL CONTINUE THROUGH THE MORNING. 
THE RADAR AND SURFACE DATA SHOWS LIGHT SNOW ACROSS MOST OF NORTH
CENTRAL ILLINOIS...NORTHEAST ILLINOIS AND NORTHWEST INDIANA. THE
IR SATELLITE IMAGERY SHOWS COLD CLOUD TOPS OVER MICHIGAN. THIS IS
WHERE THE MOISTURE HAS BEEN LIFTED TO 27000 FEET. THERE IS A LOT
OF UPWARD VELOCITY WITH THIS SYSTEM. THE SURFACE LOW HAS MOVED INTO
EASTERN MISSOURI. THE TROUGH WAS FROM THE SURFACE LOW TO CENTRAL
LAKE MICHIGAN. THE SNOW WILL CONTINUE AS THIS TROUGH WILL BE AROUND
THIS MORNING AND THE 700 MB TROUGH OVER WESTERN MINNESOTA WILL
MOVE THROUGH THIS MORNING. WE EXPECT LESS THAN AN INCH IN MOST
PLACES. BY THE AFTERNOON. THE SURFACE TROUGH WILL MOVE EAST WITH 
700 MB TROUGH AND THE SNOW WILL END IN OUR AREA. 

TUESDAY THROUGH WEDNESDAY... WE WILL KEEP THE WINTER STORM WATCH I
N EFFECT. THE GFS...NAM AND THE ECMWF HAVE THE STRONG SURFACE LOW
OVER SOUTHERN LAKE MICHIGAN BY WEDNESDAY MORNING. THE SNOW AMOUNTS
WILL BE LARGER NORTHWEST OF A LINE FROM CHICAGO TO MENDOTA. SOUTH
AND EAST OF THE LINE WE EXPECT RAIN AND SNOW MIXTURE CHANGING TO
SNOW BY WEDNESDAY AFTERNOON. WE WILL ADJUST THE SNOW LINE SOUTH
THIS MORNING. THE WARM AIR ADVECTION ON THE SOUTHEAST SIDE OF THIS
STRONG SURFACE LOW MAY BE FARTHER EAST.

WEDNESDAY NIGHT THROUGH THURSDAY...THE WIND WILL INCREASE TO 
25 TO 30 MPH WITH GUSTS TO 40 MPH. THERE WILL BE SOME BLOWING
SNOW ESPECIALLY IN OUR NORTHWEST COUNTIES. VERY COLD AIR WILL MOVE
INTO NORTH CENTRAL ILLINOIS...NORTHEAST ILLINOIS AND NORTHWEST
INDIANA THURSDAY.

&&

.AVIATION...
609 AM CST

1200 UTC TAFS...BACK EDGE OF WAA SN HAS PUSHED E TO ERN IN AS OF
1130Z WHILE AREA OF SN WITH IFR VSBYS CONTINUES OVR NE IL AND SE
WI. SOME LIGHT SN STILL LINGERS BACK INTO ERN IA WHERE MID LIL TROF
IS. MVFR CIGS AND VSBYS TO PREVAIL TIL MID LEVEL TROF PASSES TO E OF
LOCAL TERMINALS BY LATE MORNING. SUBSIDENCE AND DRYING ALOFT
BEHIND MID LEVEL TROF BUT LOWER LEVELS REMAIN MOIST SO EXPECT AREAS
OF MVFR CIGS INTO LATE AFTERNOON. 

MAJOR STORM SYSTEM TO BE MOVING ACROSS THE PLAINS OVERNIGHT WITH
STRONG WAA AND RESULTING UVV TO SPREAD SN E ACROSS THE MS RIVER
AROUND 09Z AND REACHING NE IL BETWEEN 12Z AND 14Z WITH VSBY DROPPING
TO IFR. 

TRS

&&

.MARINE...
345 AM CST

GALE WATCH EXPANDED TO ENTIRE LAKE WITH START TIME MOVED UP TO TUE
NIGHT AS WELL AS LENGTHENED INTO LATE THU NIGHT. 

WEAK LOW IN NORTHEAST MO TO MOVE NORTHEAST AND ACROSS SOUTHERN
LAKE MI AND CENTRAL LOWER MI DURING THE MORNING.

POTENT LOW TO TRACK NORTHEAST ACROSS THE MID MS VALLEY TUE NIGHT
AND BE NEAR OR OVER SOUTHERN LAKE MI BY WED MORNING. GALES ON THE
LAKE A GIVEN BUT WITH SOME DIFFERENCES IN TRACK OF THE LOW BETWEEN
VARIOUS MODELS TIMING IS A QUESTION. SFC LOW POSITIONS AT 12Z WED
BASED ON SFC WIND STREAMLINES VARY FROM BETWEEN VPZ AND SBN PER
FURTHEST SOUTH GFS ENSEMBLE CLUSTER AND MEAN...TO JUST SOUTH OF
SBM PER FURTHEST NORTH NAM. BEST GUESS AT THIS TIME IS FOR LOW TO
REACH WESTERN SHORE OF THE LAKE AT OR A BIT NORTH OF THE WI STATE
LINE. 

HIGH POTENTIAL FOR GALES ON VARYING PORTIONS OF THE LAKE AHEAD OF
THE APPROACHING DEEPENING LOW TUE NIGHT AS WELL AS WHILE IT
CONTINUES TO DEEPEN AS IT LIFTS NORTHEASTWARD THROUGH THE CENTRAL
GREAT LAKES WED AND INTO SOUTHERN QUEBEC WED NIGHT. 

TRS

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...WINTER STORM WATCH...ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
     ILZ011-ILZ012-ILZ019...6 PM TUESDAY TO 7 PM WEDNESDAY.

IN...NONE.
LM...GALE WATCH...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...9 PM TUESDAY TO 2 AM FRIDAY.

&&

$$