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