AREA FORECAST DISCUSSION
NWS CHICAGO IL
AFDCHI 505 AM CST FRI JAN 30 2004
.AVIATION DISCUSSION FOR THE 12 UTC TAF
EXPECT VFR CONDITIONS THROUGH PERIOD. WIND VECTORS WILL STAY FAIRLY
CONSTANT BETWEEN 280 AND 310 DEGREES. A WEAK DISTURBANCE EVIDENT ON
SATELLITE LOCATED SRN MI INTO IA AT 11Z WILL CONTINUE TO DIVE SE
TODAY. CURRENT TRAJECTORY OF SYSTEM WILL TAKE MAIN ENERGY...LOWER
CLOUDS AND SNOW FLURRIES SOUTH OF TERMINALS. HOWEVER...CIRRUS
SHIELD AND POSSIBLY SOME AC WILL AFFECT TERMINALS MAINLY BEFORE 00Z
SAT. EXPECT SKC CONDITIONS FOR SECOND HALF OF FORECAST CYCLE.
STEFKOVICH
.DISCUSSION...
PATTERN STAYS ACTIVE INTO NEXT WEEK. FIRST CONCERN IS ARCTIC HIGH
OVER MIDWEST AND COLD TEMPS/WIND CHILLS TODAY. THEN FORECAST FOCUS
SHIFTS TO LIGHT SNOW SAT NIGHT INTO SUN THEN A MORE SIGNIFICANT
SYSTEM FOR LATE SUNDAY INTO MONDAY. HIGH OVER MIDWEST/PLAINS EARLY
THIS AM SLOWLY WEAKENS AS IT SHIFTS TO THE OH VALLEY BY SAT MORNING.
LOW TEMPS THIS MORNING IN THE 5 TO 10 BELOW RANGE AND WITH WNW FROM
COLD AIR AND THICKER SNOW PACK THINK GUIDANCE TEMPS ARE GENEROUS FOR
HIGHS AND PLAN ON LOW SINGLE DIGITS. WINDS WILL REMAIN AROUND
10 MPH THRU AFTERNOON THEN BEGIN TO DIMINISH OVERNIGHT SO EXPECT
WIND CHILLS TO SLOWLY RISE INTO THE -10 TO -15 RANGE AND WILL KEEP
WIND CHILL ADVISORY GOING UNTIL CURRENT EXPIRATION TIME OF NOON.
NEXT CLIPPER SYSTEM COMES ACROSS UPPER MIDWEST SATURDAY NIGHT. STILL
SOME UNCERTAINTY ON HOW FAR SOUTH SNOW WILL FALL. FOR NOW WILL
LEAVE CHANCE POPS GOING BUT EXPECT MOST SNOW ACROSS FAR NORTHERN
COUNTIES TOWARD WI BORDER WHERE A DUSTING TO AN INCH IS POSSIBLE.
MAIN WX SYSTEM NEXT SEVERAL DAYS HOWEVER WILL BE DEVELOPING LOW OVER
THE SOUTHERN PLAINS SUNDAY AFTERNOON. LOW LIFTS NORTH ACROSS
SOUTHERN IL AND THEN NORTHERN IN ON MONDAY. FA LOOKS TO BE IN PRIME
AREA FOR SNOWFALL. ALTHOUGH ETA...GFS...AND CANADIAN IN REASONABLE
AGREEMENT...TOO FAR OUT FOR AMOUNTS BUT CERTAINLY NEEDS TO BE WATCH.
THAT LOW LIFTS NORTHEAST ACROSS EASTERN GREAT LAKES TUESDAY WITH
HIGH PRESSURE BUILDING ACROSS THE UPPER PLAINS INTO WESTERN LAKES
TUESDAY NIGHT. COLDEST AIR ARRIVES AT THAT TIME AND NEW MEX NUMBERS
HOLD COLD AIR PLUNGE OFF LONGER THAN GOING FORECAST. WITH THE WAY
GUIDANCE FLIP-FLOPPED ON COLD AIR NOW SEVERAL DAYS AGO...ONLY
CHANGES WILL BE TO AGREE WITH SURROUNDING GRIDS.
&&
.AVIATION DISCUSSION FOR THE 00 UTC TAF
COLD AIR WILL MOVE INTO THE REGION AS A CONTINENTAL ARCTIC AIR MASS
MOVES INTO THE REGION. THE -20 500 MB TEMPERATURE WILL BE AS FAR
SOUTH AS ALABAMA...MISSISSIPPI AND ARKANSAS TONIGHT. ACARS SOUNDINGS
SHOW THE TYPE OF INVERSION ASSOCIATED WITH CONTINENTAL ARCTIC AIR
MASS. THE WIND WILL BECOME 5 TO 10 KNOTS AT 300 DEGREES OVERNIGHT
AND WITH VERY COLD TEMPERATURES. HIGH PRESSURE WILL EXTEND FROM
MANITOBA TO IOWA TONIGHT. THE HIGH WILL DRIFT EAST FRIDAY. WE USED
COMBINATION OF THE ETA AND AVN MODELS FOR MOVEMENT OF THE SURFACE
HIGH AND CROSS SECTION FORECASTS FOR FORECASTING THE LOCATION OF THE
ARCTIC JET STREAM. WE WILL FORECAST SOME CIRRUS CLOUDS OVERNIGHT AND
FORECAST A SCATTERED ALTOCUMULUS CLOUDS AT 15000 FT AFTER 1400 UTC
IN THE TAFS FOR NORTHEAST ILLINOIS. WHW
&&
.LOT...WATCHES/WARNINGS/ADVISORIES...
IL...WIND CHILL ADVISORY ALL COUNTIES UNTIL NOON.
IN...WIND CHILL ADVISORY ALL COUNTIES UNTIL NOON CST...1 PM EST.
LK MI...NONE.
&&
$$