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000 FXUS63 KMPX 241122 AAA AFDMPX AREA FORECAST DISCUSSION...UPDATED NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 522 AM CST TUE NOV 24 2009 UPDATED TO ADD THE 12Z AVIATION DISCUSSION BELOW... .DISCUSSION... SEVERAL ACTIVE WEATHER DAYS LIE AHEAD WITH GOOD CONFIDENCE IN THE OVERALL WEATHER PATTERN WITH SOME DETAILS YET TO BE WORKED OUT...MAINLY WITH REGARD TO PRECIP TYPE AND TIMING OF PRECIP TYPE CHANGE WEDNESDAY. EARLY MORNING WATER VAPOR IMAGERY SHOWS A LONGWAVE TROUGH OVER CENTRAL NOAM EXTENDING FROM MANITOBA INTO EASTERN KANSAS AND OKLAHOMA. A QUICK MOVING LOWER AMPLITUDE TROUGH HAS SURGED INTO THE CANADIAN ROCKIES AND WILL DIVE SOUTHEASTWARD INTO WEDNESDAY. A STRONG UPPER LOW IS ALSO SEEN WELL OFF THE BRITISH COLUMBIA COAST AND IS ALREADY STARTING TO FORCE UPPER RIDGING BEHIND THE CANADIAN ROCKIES TROUGH. AT THE SFC...PESKY FRONTAL BOUNDARY/INVERTED TROUGH CONTINUES TO EXTEND FROM CENTRAL MINNESOTA INTO NORTHEASTERN KANSAS...AND WILL CONTINUE TO INTERACT WITH THE UPPER TROUGH AND ASSOCIATED UPPER JET ROUNDING THE EASTERN SIDE OF THE TROUGH RESULTING IN CONTINUED LIGHT RAIN AND LOW CLOUDS FOR MUCH OF THE CWA TODAY. TODAY THROUGH THIS EVENING... THE SFC INVERTED TROUGH WILL BEGIN TO SLOWLY MOVE EASTWARD THIS MORNING AS THE UPPER TROUGH AXIS INCHES EAST AS WELL. THESE FEATURES WILL SPEED UP THIS EVENING AS THE CANADIAN ROCKIES TROUGH APPROACHES FROM THE NORTHWEST. BANDS OF RAIN WILL CONTINUE ALONG THE SFC TROUGH AXIS OVER THE CENTRAL CWA THIS MORNING. THE TROUGH WILL LOSE FOCUS INTO THE AFTERNOON WITH UPPER FORCING SHIFTING SOUTH CLOSER TO THE THE CENTER OF THE UPPER CIRCULATION. THEREFORE BEST COVERAGE AND INTENSITY OF RAIN WILL BE THIS MORNING BEFORE DECREASING THIS AFTERNOON. TEMPERATURES WILL NOT INCREASE MUCH GIVEN THE CLOUD COVER AND RAIN...BUT SHOULD SEE A MODEST INCREASE NORTHWEST THIS AFTERNOON AS VISIBILITY IMPROVES AND CLOUDS BEGIN TO SCATTER. DRIZZLE AND SOME LIGHT RAIL WILL LINGER ACROSS WEST CENT WI AND PERHAPS FAR EAST CENT MN THIS EVENING. TONIGHT AND WEDNESDAY...THE TROUGH OVER THE CANADIAN ROCKIES THIS MORNING WILL BE WORKING INTO WESTERN MN EARLY WEDNESDAY MORNING. THIS TROUGH WILL BE FAIRLY STRONG AND BRING A SURGE OF COLD AIR WITH IT WEDNESDAY WHICH WILL RAISE PRECIP TYPE ISSUES. LEFT EXIT OF APPROACHING UPPER JET ON THE WEST SIDE OF THE INTENSIFYING UPPER TROUGH...SHARP Q-VECTOR CONVERGENCE...AND 160 M H5 HEIGHT FALLS ALL INDICATE STRONG ASCENT. THE LOW WILL WRAP UP LEADING TO A WELL PRONOUNCED DRY SLOT WHICH WILL NOSE NORTHWARD TOWARDS THE MN RIVER VALLEY AND TRANSLATE SOUTHEASTWARD ACROSS FAR SOUTHEAST MN THROUGH THE DAY WEDNESDAY. STRONG PV ANOMALY WILL ALSO TREK SOUTHEASTWARD ACROSS SOUTHERN MN AND BECOME BETTER ORIENTED BY WEDNESDAY EVENING AS THE UPPER LOW CIRCULATION PIVOTS EASTWARD AND MOVES INTO EASTERN IOWA/NW ILLINOIS. BASED ON THE ABOVE FACTORS MAIN PRECIPITATION CORRIDOR LOOKS TO BE BETWEEN THE MN RIVER VALLEY /FROM THE WESTERN MN BORDER TO MANKATO THEN SOUTHEAST TOWARDS OWATONNA/ NORTHWARD TO AND INCLUDING THE INTERSTATE 94 CORRIDOR FROM ALEXANDRIA TO EAU CLAIRE. HIGHEST PRECIP AMOUNTS WILL LIKELY BE ACROSS THE EASTERN HALF OF THIS AREA. WITH THE INCOMING COLD AIR PRECIP TYPE WILL TRANSITION FROM RAIN TO SNOW. PRECIP MAY BEGIN AS RAIN FOR A SHORT TIME ACROSS THE WESTERN CWA BEFORE TURNING TO SNOW BY 12Z WEDNESDAY. THE COLD AIR WILL EXPAND EASTWARD ACROSS THE REST OF THE MN CWA BRINGING A CHANGE TO SNOW BY 18Z OR SO. THE WI CWA WILL BE MORE COMPLICATED. THE LOW WILL WRAP UP MORE TIGHTLY AS IT MOVES INTO EASTERN IOWA WEDNESDAY AFTERNOON. THIS WILL BRING WARM ADVECTION FROM THE EAST OVER WESTERN WI. THIS WILL ACT TO MAXIMIZE ASCENT OVER FAR EAST CENT MN AND WEST CENT WI...ESPECIALLY ALONG AND SOUTH OF INTERSTATE 94...AS WELL AS IMPACT PRECIP TYPE. AT THIS TIME IT LOOKS AS THOUGH THE MN PORTION OF THE AREA WILL BE ABLE TO REMAIN MOSTLY IF NOT ALL SNOW DURING THE AFTERNOON/EVENING GIVEN LOW/MID LEVEL TEMPS AND THICKNESSES. WEST CENT WI LOOKS TO BE A RAIN/SNOW/SLEET MIX DURING THE AFTERNOON AND POSSIBLY LEAN MORE TOWARDS A SLEET/SNOW MIX BY LATE AFTERNOON/EARLY EVENING. LOWEST PRECIP AMOUNTS WILL BE ACROSS THE WESTERN THIRD OR SO OF THE AREA AND INCREASE TO THE EAST AS THE SYSTEM STRENGTHENS. HIGHEST AMOUNTS ARE EXPECTED ALONG AND EAST OF INTERSTATE 35. SNOW ACCUMULATION FORECAST WILL BE TOUGH GIVEN WARM GROUND TEMPS AND UNCERTAINTY IN TIMING/LOCATION OF CHANGEOVER. SFC TEMPS DURING DAYLIGHT HOURS MAY BE ENOUGH TO KEEP ANY SNOW ACCUMULATION DOWN TO A SLUSH WEST BUT AS INTENSITY INCREASES ACCUMULATION CHANCES WILL INCREASE FROM AFTERNOON INTO EARLY EVENING EAST. RIGHT NOW 1 TO 2 INCHES LOOKS POSSIBLE...MAINLY EAST OF I-35 WITH SOME ISOLATED 3 TO 4 INCH AMOUNTS POSSIBLE IF SNOW CAN STICK EARLY ON EAST OF I-35 AND ALONG/SOUTH OF I-94. GUSTY NORTHWEST WINDS ON THE ORDER OF 20 TO 30 MPH /WITH THE UPPER END OF THAT RANGE WEST AND LOWER END EAST/ WILL BUILD IN THROUGH THE DAY AND MAY CAUSE SOME BLOWING SNOW ISSUES DURING THE AFTERNOON AND EVENING IF ACCUMULATION PANS OUT. WEDNESDAY NIGHT THROUGH SATURDAY NIGHT...PRECIP INTENSITY WILL WANE WEDNESDAY EVENING AS THE LOW PULLS OFF TO THE EAST. SHARP NORTHERLY FLOW ALOFT WILL BE IN PLACE AHEAD OF AN ADVANCING UPPER RIDGE WITH SFC RIDGING BUILDING IN AS WELL. THE UPPER LOW WILL SLOW ACROSS THE LOWER GREAT LAKES AS THE PATTERN AMPLIFIES WHICH MAY LEAD TO LINGERING SNOW SHOWERS EAST THURSDAY MORNING. THURSDAY WILL BE ONE OF THE COOLER DAYS THIS MONTH WITH H85 TEMPS OF -4 TO -8 C LEADING TO HIGHS IN THE MID 30S. THE RIDGE WILL PUSH INTO WESTERN MINNESOTA FRIDAY BRINGING WARM ADVECTION WITH IT. THIS WILL KEEP FRIDAY DRY AND A BIT MILDER. SATURDAY ALSO LOOKS DRY AS THE RIDGE SHIFTS EAST. MODELS DISAGREE BY SATURDAY EVENING WITH FALLING HEIGHTS AHEAD OF ANOTHER TROUGH...WITH AT LEAST SMALL CHANCES FOR PRECIPITATION APPEARING LATE IN THE WEEKEND AND EARLY NEXT WEEK. ..MDB.. && .AVIATION... /12Z TAF ISSUANCE/ INVERTED SURFACE TROUGH...STRETCHED FROM NORTH TO SOUTH OVER MN...WILL SLOWLY ADVANCE EAST DURING THE PERIOD. A MORE VIGOURS WEATHER SYSTEM WILL DIVE SOUTHEAST OUT OF CANADA TONIGHT AND WEDNESDAY. LIFR TO IFR FLYING CONDITIONS WILL PERSIST IN THE VINICNITY AND EAST AND WEST OF THE SURFACE TROUGH AXIS. SOME IMPROVEMENT IS EXPECTED THIS AFTERNOON OVER PARTS OF WEST CENTRAL MN THEN OVER CENTRAL SECTIONS OF MN THIS EVENING. PORTION OF WEST CENTRAL WISCONSIN WILL REMAIN IN THE SOUP WITH IFR TO MVFR FLYING CONDITIONS THRU THE PERIOD. LIGHT RAIN/DRIZZLE LINGERING MAINLY EAST OF THE TROUGH AXIS TODAY WITH MORE RAIN/SNOW OR ALL SNOW BY WEDNESDAY MORNING. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...NONE. WI...NONE. && $$ MDB/JM
