FXUS63 KGRB 301002
AFDGRB

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREEN BAY WI
402 AM CST MON NOV 30 2009

.SHORT TERM...TODAY THROUGH TUESDAY. ALBERTA CLIPPER LIKE SYSTEM
WILL MOVE FROM LAKE WINNIPEG TO LAKE SUPERIOR TODAY...WHILE
ANOTHER ONE FOLLOWS ON IT'S HEELS FOR TUESDAY NIGHT. 

LEFT OVER STRATOCUMULUS CLOUDS SHOULD MIX OUT TO SOME DEGREE TODAY
BEFORE MIDDLE AND HIGH CLOUDS INCREASE AHEAD OF CLIPPER SYSTEM.
LEFT EXIT REGION OF 100KT 500MB JET WILL MOVE ACROSS NORTHERN
WISCONSIN AND THE UPPER PENINSULA THIS AFTERNOON AND EVENING. PRECIPITABLE
WATER VALUES FROM 00Z SOUNDINGS WERE ONLY ABOUT A QUARTER INCH AT
GRB/MSP/INL BUT THE STRENGTH OF UPPER DYNAMICS SHOULD BE ENOUGH TO
PRODUCE A QUICK INCH OR SO OF SNOW IN THE NORTH WITH LESS IN THE
SOUTH.

THERE MIGHT BE A FEW HOURS OF LAKE EFFECT SNOW SHOWERS IN THE FAR
NORTHCENTRAL PORTION OF THE FORECAST AREA TONIGHT BEFORE WINDS
BECOME TOO WESTERLY. AN INCH OR LESS EXPECTED FROM THAT. SOME
CLEARING POSSIBLE LATE TONIGHT AND EARLY TUESDAY BEFORE CLOUDS
INCREASE AGAIN AHEAD OF THE NEXT CLIPPER SYSTEM.

.LONG TERM...TUESDAY NIGHT THROUGH SUNDAY. MAIN FORECAST CONCERNS
ARE LAKE EFFECT SNOW CHANCES...ESPECIALLY IN THE SNOWBELT REGION
OF LAKE SUPERIOR...AND COLDER TEMPERATURES.

00Z MODELS SHOWED A COLD FRONT PASSING THROUGH THE AREA TUESDAY
NIGHT...BUT DID NOT PRODUCE QPF WITH THAT FEATURE. THEY DID
PRODUCE QPF NEAR THE UPPER MICHIGAN BORDER ASSOCIATED WITH AN UPPER
LEVEL SHORT WAVE. WINDS WERE FORECAST TO VEER A BIT DURING
THE NIGHT AND SHOULD BECOME FAVORABLE FOR LAKE EFFECT ON WEDNESDAY
SO POPS WERE NEED IN THE NORTH.

MODELS STARTED TO SHOW SIGNIFICANT DIFFERENCES LATER IN THE WEEK
BUT GENERALLY INDICATED CONDITIONS THAT SUPPORTED LAKE EFFECT SNOW
IN THE NORTHERN PART OF THE FORECAST AREA...BRINGING MUCH COLDER
AIR OVER THE WARMER WATERS OF LAKE SUPERIOR. ALTHOUGH THE AIR
WILL BE MUCH COLDER THAT THE AIR MASS IN PLACE OVER THE CWA...IT
IS LIKELY THAT SOME MODIFICATION WILL TAKE PLACE AND CLOUDS FROM
THE LAKE WILL RESULT IN LESS RADIATIONAL COOLING DURING THE
NIGHTS. AS A RESULT...ENDED UP WARMING MOST TEMPERATURES A
LITTLE FROM THE PREVIOUS FORECAST...ESPECIALLY THE LOWS.
&&

.AVIATION...CLOUD DECK BETWEEN 2500 AND 4000' AT 09Z SHOULD
GRADUALLY BREAK UP AND WE SHOULD HAVE VFR CONDITIONS BY AFTERNOON.
BE AWARE THAT CIGS WILL LOWER QUICKLY IN THE NORTH THIS EVENING AS
AN ALBERTA CLIPPER SYSTEM APPROACHES FROM THE NORTHWEST. THE
SYSTEM COULD BRING A QUICK INCH OF SNOW NORTH OF A RRL TO IMT LINE
THIS EVENING WITH IFR CIGS AND VSBYS. MVF CIGS AND LIGHTER SNOW
SHOWERS EXPECTED FURTHER SOUTH.
&&

.MARINE...SOUTHWEST WINDS WILL INCREASE TO 15 TO 25 KNOTS WITH
GUSTS TO 30 KNOTS BY LATE AFTERNOON. THEY WILL SHIFT TO THE WEST
THIS EVENING AND THEN DIMINISH LATE TONIGHT. A SMALL CRAFT
ADVISORY WILL BE IN EFFECT BEGINNING AT 21Z.
&&

.GRB WATCHES/WARNINGS/ADVISORIES...
NONE.
&&

$$
RDM/MG