NWS-La Crosse Forecast Discussion

						FXUS63 KARX 240946
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
346 AM CST TUE NOV 24 2009

.SHORT TERM...TODAY INTO THANKSGIVING

AT 3 AM...A NEARLY STATIONARY INVERTED TROUGH WAS LOCATED ACROSS
WESTERN IOWA AND WESTERN MINNESOTA. FURTHER SOUTH...A LOW PRESSURE
SYSTEM WAS DEVELOPING NEAR KANSAS CITY. SCATTERED SHOWERS CONTINUE
TO MOVE NORTHWARD ACROSS PARTS OF MINNESOTA AND IOWA ALONG THE TROUGH.

THE 24.00Z MODELS ARE IN FAIRLY GOOD AGREEMENT THAT THE DEEP
FRONTOGENESIS ALONG THE INVERTED TROUGH WILL GRADUALLY WEAKEN
ACROSS MINNESOTA EARLY THIS MORNING. HOWEVER THERE LINGERS TO BE
SOME FRONTOGENESIS BELOW 700 MB. THIS WILL BE LIKELY ENOUGH TO
KEEP THESE SHOWERS GOING THROUGHOUT THE REMAINDER DAY...BUT THEY
SHOULD BE A BIT MORE SCATTERED ACROSS MINNESOTA.

WHILE THE INVERTED TROUGH WILL BECOME LESS OF A RAIN PRODUCER...
THE DEVELOPING LOW PRESSURE SYSTEM NEAR KANSAS CITY WILL BECOME
THE PRIMARY WEATHER MAKER FOR OUR AREA LATE THIS MORNING AND
AFTERNOON AS IT MOVES EAST NORTHEAST ACROSS SOUTHERN IOWA. THIS
LOW WILL BRING MODERATE TO STRONG 925 MB TO 700 MB MOISTURE
TRANSPORT INTO THE AREA STARTING LATE THIS AFTERNOON AND
CONTINUING INTO TONIGHT. THIS PRECIPITATION WILL INITIALLY MOVE
INTO NORTHEAST IOWA AND SOUTHWEST WISCONSIN BY MID TO LATE MORNING...
AND THEN SPREAD NORTHWARD ACROSS THE REMAINDER OF THE FORECAST
AREA THIS AFTERNOON AND EVENING. WITH AT LEAST 5K FEET OF WARM
AIR...THIS PRECIPITATION WILL BE ALL RAIN.

FROM WEDNESDAY INTO THANKSGIVING MORNING...A WRAP AROUND
PRECIPITATION AND EVENTUALLY A DEFORMATION BAND OF PRECIPITATION
WILL MOVE EAST ACROSS THE FORECAST AREA. AS A SECOND SHORT WAVE
TROUGH MOVES INTO THE REGION ON WEDNESDAY MORNING...THE
TEMPERATURES ALOFT SHOULD COOL ENOUGH THAT THE RAIN WILL GRADUALLY
CHANGE OVER TO SNOW. THIS SHOULD START TO OCCUR WEST OF THE
MISSISSIPPI RIVER MAINLY ON WEDNESDAY AFTERNOON...AND ACROSS THE
REMAINDER OF THE AREA ON WEDNESDAY EVENING. SOME WARM AIR ALOFT
MAY WRAP INTO WISCONSIN ON WEDNESDAY NIGHT...AND THIS MAY DELAY
THE PRECIPITATION CHANGE OVER A BIT MORE. DUE TO THE WARM
GROUND...SOME QUESTION ON WHEN THE PRECIPITATION CHANGES OVER TO
ALL SNOW...AND TRYING TO FIGURE OUT WHERE THE GREATEST SNOW RATES
MAY OCCUR...MAKES PREDICTING THE TOTAL SNOW ACCUMULATIONS RATHER
TRICKY. LOOKING AT THE GFS PRECIPITATION TYPE PLUMES...IT LOOKS
LIKE THE AREA MAY SEE UP TO 2 INCHES OF SNOW BY THANKSGIVING MORNING.

.LONG TERM...THURSDAY NIGHT INTO MONDAY

THE NEXT CHANCE OF PRECIPITATION LOOKS TO BE SOME TIME THIS
WEEKEND AS YET ANOTHER LONG WAVE TROUGH MOVES INTO THE REGION.
HOWEVER THE MODELS CONTINUE TO STRUGGLE WITH THE TIMING OF THIS
SYSTEM. CURRENT GRIDS HAVE THIS PRECIPITATION ON SUNDAY NIGHT AND
MONDAY. HOWEVER IF THE 24.00Z MODELS ARE CORRECT...THIS MAY BE 18
TO 24 HOURS TOO LATE.

&&

.AVIATION...TODAY INTO FRIDAY

BANDS OF -RA/SHRA EXTEND FROM EASTERN MN INTO NORTHWEST IA EARLY
THIS MORNING...ASSOCIATED WITH FRONTOGENETIC FORCING IN THE 900-700
MB LAYER AND A SFC TROUGH RUNNING NORTH OF AN AREA OF LOW PRESSURE
OVER THE MO RIVER VALLEY. THIS PCPN SHOULD CONTINUE TODAY...BUT
LIKELY JUST WEST/NORTH OF KRST. MEANWHILE...MVFR/IFR CEILINGS HAVE
SPREAD ACROSS THE AREA...AND TIME/HEIGHT X-SECTIONS AND BUFKIT
SOUNDINGS KEEP THIS LOW SATURATION OVER KRST/KLSE THROUGH WED.
ALSO...BR HAS ACCOMPANIED THE LOW STRATUS...AND SOME VSBY
RESTRICTIONS ALSO LOOK LIKELY FOR THE NEXT COUPLE DAYS.

AS THE AREA OF LOW PRESSURE MOVES NORTHEAST INTO THE GREAT LAKE
STATES THIS EVENING...THE RAIN THREAT WILL INCREASE FOR THE TAF
SITES. AN UPPER LEVEL SHORTWAVE WILL DROP SOUTHEAST AND SPIN ACROSS
THE REGION ON WED/THU...MOVING IN BEHIND THE DEPARTING LOW. WITH
COLDER AIR FLOWING INTO THE REGION...THE -RA WILL MIX WITH AND
CHANGE OVER TO -SN WED. SOME ACCUMULATIONS ON GRASSY SFCS WILL BE
POSSIBLE...BUT GENERALLY...THE PAVEMENT WILL BE WARM ENOUGH TO
ENCOURAGE MELTING.

OVERALL...A FEW DAYS OF MVFR/IFR CONDITIONS SHOULD IMPACT
KRST/KLSE...WITH SOME IMPROVEMENT AS A RIDGE OF HIGH PRESSURE BUILDS
IN THU NIGHT/FRI.

&&

.ARX WATCHES/WARNINGS/ADVISORIES...
WI...NONE.
MN...NONE.
IA...NONE.
&&

$$

SHORT/LONG TERM...BOYNE
AVIATION...RIECK