006 FXUS63 KMPX 180556 AFDMPX AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN 1156 PM CST SUN FEB 17 2013 .UPDATE... 06Z AVIATION DISCUSSION ADDED BELOW. && .PREV DISCUSSION... /ISSUED 545 PM CST SUN FEB 17 2013/ TWO SIGNIFICANT WEATHER IMPACTS EXPECTED THIS WEEK ACROSS THE REGION. THE FIRST WILL BE ASSOCIATED WITH A POWERFUL COLD FRONT THAT IS EXPECTED TO MOVE DOWN FROM THE DAKOTAS TOMORROW AND USHER IN ANOTHER BLAST OF ARCTIC AIR. THE SECOND WILL BE A SIGNIFICANT WINTER STORM THAT IS FORECAST TO EMERGE ACROSS THE SOUTHWESTERN US...AND SPREAD HEAVY SNOW ACROSS THE CENTRAL PLAINS UP THROUGH THE GREAT LAKES REGION THURSDAY AND FRIDAY. TODAY THROUGH WEDNESDAY...EARLY AFTERNOON NORTHERN HEMISPHERIC WATER VAPOR TOGETHER WITH GFS 500MB HEIGHTS AND WINDS SHOWED AN ACTIVE PATTERN WITH 3 DISTINGUISHED LONGWAVE TROUGHS. FROM EAST TO WEST...THE FIRST WAS ASSOCIATED WITH THE NOREASTER OFF THE NEW ENGLAND COAST...THE SECOND LOCATED WAS OVER MONTANA...AND THE THIRD WAS FURTHER UPSTREAM IN THE GULF OF ALASKA. A CLOSER LOOK AT THE MIDDLE WAVE REVEALS AN EMBEDDED VORT MAX UPSTREAM OF THE TROUGH AXIS IN WESTERN ALBERTA ALONG THE POLEWARD SIDE OR THE SOUTHWARD MOVING JET DRIVEN BY THE SPEED SHEAR. A SECOND VORT MAX WAS CENTERED OVER MONTANA NEAR THE BASE OF THE TROUGH EXISTING MAINLY DUE TO THE CURVATURE OF THE FLOW. AT THE SURFACE A 998MB SURFACE LOW WAS CENTERED ACROSS THE NORTH DAKOTA/CANADA BORDER. AS TIME PROGRESSES...NUMERICAL MODELS AGREE THAT THE MONTANA SHORTWAVE WILL GAIN STRENGTH AS THE AFOREMENTIONED UPSTREAM UPPER LEVEL JET ROUNDS THE BASE OF THE TROUGH. TONIGHT THE SURFACE LOW WILL PROPAGATE EASTWARD IN CONCERT WITH THE UPPER LEVEL FORCING AND SHOULD BE LOCATED IN NORTHERN MINNESOTA BY MONDAY MORNING. AHEAD OF THIS SURFACE LOW WARM AIR ADVECTION WILL LIFT ACROSS SOUTHEAST MINNESOTA AND WESTERN WISCONSIN CAUSING CLOUDS TO FORM AND POSSIBLY SOME LIGHT FREEZING DRIZZLE...BUT DID NOT HAVE THE CONFIDENCE TO ISSUE ANY HEADLINES. MEANWHILE FURTHER WEST...STRONG COLD AIR ADVECTION WILL FOLLOW IN THE WAKE OF THE TRAILING COLD FRONT ACROSS WESTERN MINNESOTA MONDAY MORNING. AS IT DOES...FORECAST SOUNDINGS SHOW THE BOUNDARY LAYER QUICKLY DESTABILIZING WITH FALLING TEMPERATURES IN TO THE TEENS ACROSS WESTERN MINNESOTA BY NOON...AND SINGLE DIGITS BY EARLY EVENING. BOTH THE NAM AND GFS 17.12 BUFR SOUNDINGS SHOW SEVERAL HOURS OF 35-40KTS ATOP THE MIXED LAYER...WITH A SOLID 30KTS SUSTAINED. THE DENDRITIC ZONE ALSO BECOMES SATURATED IN THE LOWEST 10000FT. BOTH OF THESE WOULD SUPPORT BLOWING SNOW AND REDUCED VISIBILITIES MONDAY AFTERNOON AND EVENING. HOWEVER...THE BEST FORCING WILL BE ALONG THE MN/CANADA BORDER...WITH LITTLE OMEGA SOUTH OF THIS. THEREFORE HAVE RULED OUT BLIZZARD CONDITIONS. THE QUESTION THEN BECOMES WIND ADVISORY OR WINTER WEATHER ADVISORY. STRONG WIND AND FALLING TEMPERATURES ARE A LOCK TO OCCUR WITH THE FRONTAL PASSAGE...BUT THE WILD CARD IS THE SNOW AMOUNTS. SINCE THE POTENTIAL IS THERE...HAVE DECIDED TO GO WITH WINTER WEATHER ADVISORY WITH STRONG WIND WORDING SINCE THIS IMMEDIATELY GIVES THE PUBLIC THE PERCEPTION THAT TRAVEL WILL BE IMPACTED MONDAY EVENING. CONFIDENCE IS HIGH THAT SNOW AMOUNTS WILL REMAIN LESS THAN 3 INCHES...BUT HOLISTIC REASONING SUPPORTS A HEADLINE...AND FEEL THE WINTER WEATHER ADVISORY IS THE BEST APPROACH AT THIS TIME ENDING AT MIDNIGHT. WIND CHILL ADVISORIES WILL LIKELY BE NEEDED FOLLOWING THE WINTER WEATHER ADVISORY...BUT THIS SHOULD BE A SMOOTH TRANSITION MONDAY NIGHT. ON TUESDAY AND WEDNESDAY A HIGHLY AMPLIFIED UPPER LEVEL RIDGE WILL CAUSE SURFACE HIGH TO DEVELOP ACROSS CENTRAL NORTH AMERICA WITH TEMPERATURES STRUGGLING TO GET OUT OF THE SINGLE DIGITS FOR HIGHS ON TUESDAY...AND LOWER TEENS ON WEDNESDAY. THURSDAY THROUGH SUNDAY...NEXT SYSTEM THAT COULD BRING SIGNIFICANT SNOWFALL ACROSS THE REGION FOR THURSDAY AND FRIDAY IS THE TROUGH CURRENTLY OVER THE GULF OF ALASKA. FORECAST MODELS SHOW TWO EMBEDDED SHORTWAVES WITHIN THIS TROUGH PHASING TOGETHER AND MOVING SOUTH PARALLELING THE WEST COAST. AS THE SYSTEM EMERGES OUT OF THE DESERT SOUTHWEST BY MIDWEEK A POWERFUL CYCLONE IS FORECAST TO DEVELOP ON THE FRONT RANGE OF EASTERN COLORADO...WITH SIGNIFICANT SNOW POSSIBLE IN NORTHEAST COLORADO WEDNESDAY NIGHT. AS THE STORM DEVELOPS ON THURSDAY IT WILL TAKE BECOME VERTICALLY STACKED...CAUSING THE SURFACE CYCLONE TO GRADUALLY FILL THROUGHOUT THE THE DAY AS THE UPPER LEVEL FORCING OUTRUNS ITS SURFACE COUNTERPART. BY THURSDAY EVENING THIS MATURE CYCLONE WILL HAVE A WELL DEFINED TROWEL ON THE NORTHEASTERN SIDE OF THE 500MB LOW...WITH A BROAD AREA OF MODERATE SNOW EXPECTED TO BE ONGOING ACROSS THE MN/WI REGION...WHICH SHOULD PUSH NORTHWARD THURSDAY NIGHT. UNLIKE THE LAST STORM...THE THERMAL PROFILES CLEARLY INDICATE ALL SNOW...SO FORTUNATELY THAT IS ONE LESS VARIABLE TO WORRY ABOUT. ALSO...WINDS/BLOWING SNOW SHOULD NOT BE MUCH OF AN ISSUE EITHER. FOR NOW HAVE INCREASES POPS TO THE HIGH CATEGORICAL WELL ABOVE MODEL GUIDANCE...AND WILL WAIT WITH ANY HEADLINE DECISION UNTIL CLOSER TO THE EVENT. && .AVIATION.../06Z TAF ISSUANCE/ COLD FRONT JUST MOVING INTO WRN MN AT 530Z AND WILL BE MOVING THROUGH RWF/AXN BY 9Z...MSP AROUND 12Z...AND EAU AROUND 17Z. VERY DRY AIR AHEAD OF THE FRONT MEANS ANY MVFR CONDS OR LOWER WILL HAVE TO WAIT UNTIL AFTER THE COLD FRONT PASSES. AS A RESULT DELAYED MVFR CIGS A COUPLE OF MORE HOURS FROM WHAT 00Z TAFS HAD AND REMOVED FZDZ MENTION FROM WRN WI. AS FOR SNOW POTENTIAL...STRONG CAA DURING THE MORNING WILL PRIME THE ATMO FOR -SHSN BY THE AFTERNOON...BUT 00Z NAM/GFS ALONG WITH THE RAP SHOW A BAND OF SNOW DEVELOPING IN THE MORNING IMMEDIATELY BEHIND THE FRONT. THIS LOOKS TO FORM RIGHT OVER MSP AND MOVE IN TO WRN WI. SHOULD PROVIDE A QUICK BURST OF HEAVIER SNOW WITH VIS GETTING DOWN TO OR A LITTLE LESS THAN A MILE FROM MSP EAST. OTHER THAN THAT THE COMBO OF STRONG NW WINDS AND OCCASIONAL -SHSN SHOULD PROMOTE A PROLONGED PERIOD OF 2-6SM VSBYS AT MOST TERMINALS FROM THE AFTERNOON INTO THE EVENING. AS FOR THOSE WINDS...TIMED THE DIRECTION CHANGE ON A HRRR/LAMP BLEND. MIX POTENTIAL FROM THE NAM/GFS HAS NOT CHANGED AT ALL WITH 00Z RUNS...WITH TOP OF THE CHANNEL WINDS STILL AROUND 35 KTS ACROSS MN FROM ABOUT 21Z RIGHT THROUGH THE REST OF THE NIGHT. KMSP...FIRST ISSUE WILL BE WIND SHIFT DURING THE MORNING. SPEEDS MAY BE UNDER 7 KTS BY 10Z...ALLOWING FOR SOME LEE WAY ON RUNWAY CONFIGURATION...WITH NW WINDS EXPECTED TO DOMINATE FROM ABOUT 15Z ON. FOR SNOW...NAM/GFS/RAP SHOWING A POST FRONTAL BAND OF SNOW DEVELOPING IN THE LATE MORNING AND WILL BE A CLOSE CALL FOR MSP...WITH HIGHER PROBABILITIES OF IT OCCURRING BEING EAST OF THE FIELD. IF MSP SEES IT...WOULD BE A QUICK 1/2 TO 1 INCH OF SNOW IN A COUPLE OF HOURS. AFTER THAT...MUCH OF THE AFTERNOON THROUGH THE NIGHT WILL BE DOMINATED BY PERIODS OF SNOW SHOWERS AND BLSN...WITH VIS FLUCTUATING BETWEEN IFR AND VFR LEVELS FOR MUCH OF THE TIME. FOR CIGS...EXPECT MVFR CIGS TO MOVE IN BETWEEN 13Z AND 15Z. MAY INITIALLY BE ABOVE 1700...BUT SHOULD SETTLE BELOW THAT LEVEL BY THE AFTERNOON...PERSISTING THERE THROUGH MUCH OF THE NIGHT. /OUTLOOK FOR KMSP/ TUE...MVFR CIGS POSSIBLE. WINDS NW AT 15 TO 25 KTS DECREASING TO 10 TO 20 KTS. WED...VFR. WINDS NW TO E AOB 5 KTS. THU...VFR MORNING. IFR OR LOWER WITH MOD/HEAVY SNOW AFTERNOON/NIGHT. WINDS E AT 15 KTS. && .MPX WATCHES/WARNINGS/ADVISORIES... MN...WINTER WEATHER ADVISORY FROM NOON MONDAY TO MIDNIGHT CST MONDAY NIGHT FOR BROWN-CARVER-CHIPPEWA-DOUGLAS-KANDIYOHI-LAC QUI PARLE-MCLEOD-MEEKER-NICOLLET-POPE-REDWOOD-RENVILLE-SIBLEY- STEARNS-STEVENS-SWIFT-TODD-WRIGHT-YELLOW MEDICINE. WI...NONE. && $$ JRB/MPG