000 
FXUS63 KARX 170654
AFDLSE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
154 AM CDT FRI MAY 17 2002

FORECAST CONCERNS PRIMARILY FOCUS ON TEMPERATURES...CLOUD TRENDS
AND RAINFALL CHANCES.

EARLY MORNING SURFACE ANALYSIS SHOWED FRONT EXTENDING FROM THE OHIO
VALLEY INTO THE SOUTHERN PLAINS. MID AND HIGH LEVEL CLOUDS OVER
NORTHEAST IOWA AND SOUTHWEST WI SINKING FURTHER SOUTH WITH TIME
AS UPPER LEVEL FLOW BEGINNING TO TURN MORE TO THE NORTHWEST. 11-3.9
MICRON SATELLITE IMAGERY INDICATED LOW CLOUDS OVER LAKE SUPERIOR...AS
WELL AS FURTHER NORTH INTO CANADA. WATER VAPOR IMAGERY SHOWED
LARGE CIRCULATION OVER SOUTHEAST CANADA...WITH MID LEVEL TROUGH
EXTENDING ALONG THE U.S. CANADIAN BORDER AND ROTATING SOUTHWARD.

00Z MODELS WERE VERY SIMILAR WITH SCENARIO OF CLOSED CIRCULATION
REMAINING OVER SOUTHEAST CANADA DURING THE WEEKEND. AVN AND ETA 850
MB TEMPERATURES REMARKABLY CLOSE THROUGH 84HRS...WITH VALUES OF MINUS
2 TO MINUS 5. OF NOTE...850 MB FORECAST READINGS IN THE MODELS WERE
TOO COLD ON THURSDAY...WHICH WILL HAVE TO BE MONITORED WITH THIS
FORECAST PACKAGE. OVERALL THOUGH...NO SIGNIFICANT MODEL DIFFERENCES
TO IMPACT THE DETAILS OF THE FORECAST.

CURRENT ZONES APPEAR TO BE IN GOOD SHAPE WITH COOLER THAN AVERAGE
TEMPERATURES...ALONG WITH SMALL RAIN CHANCES FOR THE AFTERNOON AND
EARLY EVENING HOURS TODAY AND SATURDAY. THIS SUPPORTED BY TQ INDEX
VALUES...STEEP LOW LEVEL LAPSE RATES REACHING 9 C/KM...AND SPOKES OF
SHORT WAVE ENERGY ROTATING AROUND CLOSED LOW. DUE TO THIS
INSTABILITY...DIURNAL CUMULUS SHOULD BE AT A MAXIMUM IN THE
AFTERNOON AND EARLY EVENING...WHICH CURRENT FORECAST HANDLES WELL.

FWC...AVN AND ETA MOS TEMPERATURE GUIDANCE SUGGESTS PERSISTENCE AND
CONTINUITY PROBABLY BE A GOOD WAY TO GO. AS A RESULT...HIGHS SHOULD
BE MAINLY IN THE 50S TO AROUND 60...WITH LOWS IN THE 30S. WITH LIGHT
WINDS AND DEWPOINTS IN THE UPPER 20S TO LOWER 30S...HEADLINES FOR
FROST ADVISORY TONIGHT WILL CERTAINLY NEED TO BE CONTEMPLATED BY DAY
SHIFT. THE WILD CARD IN THIS WILL BE EXTENT OF NIGHTTIME CLOUD COVER
THAT LINGERS IN NORTHERLY FLOW...WHICH TIME/HEIGHT CROSS SECTIONS
INDICATED THERE COULD BE MORE CLOUDS THAN MOS GUIDANCE SUGGESTS.

IN THE LONGER TERM...UPWARD TREND IN TEMPERATURES APPEARS ON TRACK
FOR THE COMING WEEK AS 500 MB RIDGE BUILDS INTO THE NATIONS
MIDSECTION.

.LSE...NONE.

THOMPSON