Area Forecast Discussion
Issued by NWS La Crosse, WI

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FXUS63 KARX 180911
AFDARX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LA CROSSE WI
311 AM CST THU DEC 18 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 311 AM CST THU DEC 18 2014

PESKY UPPER TROUGH STILL LINGERS OVER THE GREAT LAKES WITH THE
LAST LOBE OF SHORT WAVE ENERGY HANGING BACK ACROSS LAKE SUPERIOR.
LOW CLOUDS ASSOCIATED WITH IT STILL COVER THE BULK OF WI...BUT ARE
STARTING TO SHOW SOME SIGNS OF BREAKING UP. MEANWHILE...SATELLITE
WATER VAPOR IMAGERY SHOWS A NICE CIRCULATION ENTERING THE WESTERN
DAKOTAS. VERY LITTLE MOISTURE WITH IT SO PRIMARILY RESULTING IN
CLOUD GENERATION. FINALLY...ANOTHER WEAK SHORT WAVE TROUGH WAS
TRAVERSING THE LOWER MISSISSIPPI RIVER VALLEY AND HEADING TOWARD
TENNESSEE. SOME PEEKS AT THE SUN ANTICIPATED TODAY WITH THE AREA
BETWEEN SYSTEMS...BUT WITH THE LOW ADVANCING ACROSS THE DAKOTAS
EXPECT MORE CLOUD TO INVADE. WITH ALL THE CLOUDS...KEPT DIURNAL
TEMPERATURE SWING SMALL.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 311 AM CST THU DEC 18 2014

MEDIUM RANGE FORECAST MODELS BEGINNING TO COME INTO BETTER
AGREEMENT WITH THE EXPECTED PATTERN FOR THE UPCOMING HOLIDAY WEEK.
BLOCKED PATTERN WILL EVOLVE BRIEFLY INTO ZONAL FOR THE WEEKEND
BEFORE CONTINUING ON TO FAVOR A DEEP LONG WAVE TROUGH OVER THE
CENTRAL CONUS BY EARLY NEXT WEEK...WITH A LARGE RIDGE SETTING UP
JUST OFF THE CALIFORNIA COAST. ENERGY DROPPING INTO THE BACK SIDE
OF THE TROUGH RESULTS IN THE DEVELOPMENT OF A CLOSED LOW OVER
MN/IA AREA BY MONDAY...WHICH THEN STALLS AND DEEPENS OVER THE
GREAT LAKES THROUGH MID WEEK. THIS WAS HINTED AT IN PREVIOUS
RUNS...BUT IS NOW LOOKING MORE AND MORE LIKELY WITH THE MODELS
GENERALLY SETTLING IN ON A VERY SIMILAR SOLUTION.

AS THE TROUGH BEGINS TO DEVELOP ON SATURDAY...INCREASING ADVECTION
OF WARM AND MOIST AIR BEGINS. FORECAST SOUNDINGS SUGGEST BROAD
WEAK LIFT WITH THE BOUNDARY LAYER BECOMING SATURATED OR NEARLY SO
LATE SATURDAY INTO SUNDAY. MODELS TRENDING TOWARD BETTER CHANCES
FOR PRECIPITATION...AND WITH THE TEMPERATURE REGIME STILL ON THE
COOL SIDE OF THE FREEZING MARK...FREEZING DRIZZLE APPEARS TO BE A
POSSIBILITY. ADDED THIS SATURDAY NIGHT...TRENDING TOWARD A
RAIN/SNOW MIX AS WE MOVE INTO THE DAY SUNDAY. PERSONS WITH TRAVEL
PLANS WILL WANT TO BE COGNIZANT OF THIS. BY MONDAY...SURFACE LOW
DEVELOPS AND MAIN FORCING OF THE DEVELOPING CLOSED LOW BEGINS TO
IMPACT THE FORECAST AREA. BOOSTED RAIN/SNOW CHANCES INTO THE
LIKELY CATEGORY FOR MONDAY AS A RESULT. THE AREA GETS ON THE COLD
SIDE OF THE SYSTEM BY TUESDAY WITH NORTHWEST WINDS USHERING COLD
AIR BACK INTO THE REGION. EXPECT PERIODS OF LIGHT SNOW OFF AND ON
THROUGH WEDNESDAY. WHILE IT DOES NOT APPEAR THAT LARGE QUANTITIES
OF SNOW WILL FALL...IT IS LOOKING MORE AND MORE LIKELY THAT WE
WILL SEE AT LEAST SOME LIGHT SNOW COVER BY CHRISTMAS.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)
ISSUED AT 1120 PM CST WED DEC 17 2014

STRATUS DECK MOVED INTO RST DURING THE EVENING...BUT ITS
EXTREMELY CLOSE TO CLEARING WITH CLEAR SKIES PRESENT OVER EASTERN
OLMSTED COUNTY. FIGURE ANOTHER 1-2 HOURS AND THE STRATUS SHOULD
LEAVE THE TAF SITES. THE CLEARING SHOULD LEAD TO SOME MVFR BR
DEVELOPMENT. MEANWHILE...LSE IS ALSO ON THE EDGE OF STRATUS...BUT
IN THIS CASE STRATUS IS JUST NORTHEAST OF THE TAF SITE OVER
NORTHERN LA CROSSE COUNTY. A NORTH-NORTHEAST FLOW SHOULD PUSH
THIS STRATUS INTO LSE BY 08Z. THAT SAME FLOW IS EXPECTED TO
CONTINUE MARCHING THE STRATUS DECK TOWARDS RST...MOVING IN
SOMEWHERE AROUND 12Z. ONCE THE STRATUS MOVES IN THIS MORNING...THE
COMBINATION OF LIGHT WINDS AND BEING NEAR THE MINIMUM OF DAYLIGHT
LENGTH SUPPORTS THE STRATUS HANGING AROUND INTO THE EVENING HOURS.


&&

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

$$

SHORT TERM...MW
LONG TERM...MW
AVIATION...AJ



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