National Weather Service Raw Text Product

102 
FXUS63 KMPX 030558
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1158 PM CST SAT FEB 2 2013

.UPDATE...

UPDATED FOR AVIATION DISCUSSION BELOW.

&&

.DISCUSSION...
/ISSUED 320 PM CST SAT FEB 2 2013/
A PARADE OF WEAK CLIPPER SYSTEMS WILL MOVE ACROSS THE REGION AND
PRODUCE SEVERAL ROUNDS OF LIGHT SNOW OVER THE UPPER MIDWEST.
TEMPERATURES WILL GRADUALLY MODERATE TO NEAR 30 BY THE MIDDLE OF
THE WEEK...AND LAST THROUGH THE WEEKEND. THE LONG RANGE MODELS
HINT AT A POTENTIALLY SIGNIFICANT STORM NEXT WEEKEND...BUT
CONFIDENCE IS LOW IN THE TIMING AND PLACEMENT OF THIS FEATURE.

TODAY AND TONIGHT...EARLY AFTERNOON VISIBLE SATELLITE IMAGERY 
OVERLAID WITH SURFACE OBS SHOWED A TIGHT CIRCULATION/SURFACE LOW 
DROPPING DOWN ACROSS NORTH DAKOTA...WITH LIGHT SNOW SPREADING OUT 
AHEAD OF IT...AND BLISTERING NORTHWEST WINDS BEHIND THE TRAILING 
COLD FRONT. A WEAK BUT COMPACT UPPER LEVEL PV ANOMALY WAS THE 
DRIVING FORCE BEHIND THIS SYSTEM...AND ALTHOUGH IT WILL WEAKEN AS IT 
PROPAGATES SOUTHEASTWARD TOWARDS THE MN/WI AREA...THERE WILL STILL 
BE ENOUGH DYNAMICAL FORCING AND ISENTROPIC ASCENT TO PRODUCE SOME 
LIGHT SNOW. UPSTREAM SNOW-TO-LIQUID REPORTS CONFIRM THE FORECAST
THERMODYNAMIC PROFILES PORTRAYAL OF A LIGHT AND FLUFFY SNOW...SO
HAVE RATIOS NEAR 30:1. DESPITE THE LIGHT QPF AMOUNTS...THIS WILL
YIELD TOTALS SNOWFALL AMOUNTS OF 1...TO PERHAPS 2 INCHES BY LATE
THIS EVENING...WITH THE HEAVIEST AMOUNTS FORECAST TO BE ALONG THE
MINNESOTA RIVER VALLEY. THIS ALONE WOULD NOT BE OF MUCH
SIGNIFICANCE...BUT FORECAST SOUNDINGS ALSO SHOW A DESTABILIZING
BOUNDARY LAYER TONIGHT...INDICATIVE OF THE AFOREMENTIONED STRONG
NORTHWEST WINDS CURRENTLY ONGOING UPSTREAM IN THE DAKOTAS. IN
FACT...BUFR SOUNDINGS OF BOTH THE NAM...RAP...AND A FEW MEMBERS OF
THE SREF SHOW 35 TO 40KTS AT THE TOP OF THE MIXED LAYER ACROSS THE
MINNESOTA RIVER VALLEY...SO HAVE INCREASE SURFACE WINDS
CONSIDERABLY TO ACCOUNT FOR THIS. THE DESTABILIZING FORCE BEHIND
THESE STRONG WINDS CAN BE SEEN IN THE DIFFERENTIAL COLD AIR
ADVECTION BETWEEN THE SURFACE AND H925. THIS SET UP COULD EASILY
CAUSE BLIZZARD CONDITIONS IF IT WERE STRENGTHENING WITH TIME...BUT
SINCE IT IS WEAKENING ONLY ANTICIPATING PERHAPS A FEW AREAS OF
BRIEF VERY POOR VISIBILITIES. NONE THE LESS...DID ISSUE A WINTER
WEATHER ADVISORY SINCE TRAVEL WILL BE IMPACTED THIS EVENING AND
OVERNIGHT.

TOMORROW THROUGH SATURDAY...THERE ARE NOT REALLY ANY SIGNIFICANT 
CHANGES FROM THE PREVIOUS FORECAST. THE MODELS ARE STILL IN VERY 
GOOD AGREEMENT OF ANOTHER ROUND OF SNOW BEGINNING SUNDAY 
EVENING...AND DISRUPTING THE MONDAY MORNING COMMUTE. THIS SYSTEM HAS 
SHIFTED SLIGHTLY SOUTH...SO HAVE EXPANDED THE CATEGORICAL POPS IN 
THAT DIRECTION. HOWEVER...DID NOT TRIM THE NORTHERN EDGE BECAUSE 
FORECAST SOUNDINGS STILL SHOW DEEP SATURATION IN THE DENDRITIC ZONE 
WITH OMEGA...SO EXPECT ANOTHER BROAD AREA OF SNOWFALL...WITH PERHAPS 
SOME 2-4 INCH AMOUNTS POSSIBLE ACROSS SOUTHERN MINNESOTA IF A 
FRONTOGENETIC BAND IS ABLE TO FOCUS THE BROAD LARGE SCALE FORCING
ACROSS A NARROW AREA. ANOTHER SYSTEM REMAINS ON TRACK FOR MONDAY
NIGHT/TUESDAY MORNING...WITH THE HIGHEST SNOWFALL AMOUNTS NORTH OF
I-94. THE SAME IS TRUE FOR A SYSTEM ON WEDNESDAY NIGHT/THURSDAY.
LOOKING AHEAD...A STORM CURRENTLY WEST OF THE ALEUTIAN ISLANDS
WILL MOVE ACROSS THE GULF OF ALASKA DOWN THE CALIFORNIA COAST AND
EMERGE FROM THE DESERT SOUTHWEST FOR THE WEEKEND. CONSIDERING
THE WAVE IS POSITIVELY TILTED AND BECOMES CUTOFF...HAVE LOW
CONFIDENCE IN THE NUMERICAL MODELS DEVELOPMENT OF A SIGNIFICANT
WINTER STORM BY NEXT WEEKEND...SO CHOSE A BLEND OF MODEL CONSENSUS
AND PREVIOUS FORECAST.

&&

.AVIATION.../06Z TAF ISSUANCE/ 
ALBERTA CLIPPER NOW CENTERED SOUTH OF KMKT WITH GUSTY NW WINDS
BEHIND IT OVER SW INTO SC MN. BEST LIFT AND HEAVIEST PRECIP NOW INTO
WEST CENTRAL WISC HOWEVER SOME LIFT PERSISTS ALL THE WAY INTO WEST
CENTRAL AND NORTHERN MN...AND OBSERVATIONS SHOW FLURRIES OR LIGHT
SNOW STILL IN THAT AREA. THEREFORE WILL HANG ON TO LIGHT SNOW AND
MVFR VSBYS THROUGH THE NEXT FEW HOURS IN EASTERN MN AND WESTERN
WISC. A SHORT RESPITE OF 10-12 HOURS BEFORE SNOWFALL WITH NEXT
CLIPPER. APPEARS THIS ONE WILL BE STRONGER WITH BEST PRECIP AXIS
ORIENTED FROM KAXN TO KMSP AND KEAU. WILL INDICATE IFR VSBY SUNDAY
AFTERNOON INTO THE EVENING.

KMSP...CONFIDENCE AVERAGE IN TERMS OF MAINTAINING MVFR VSBY THE
NEXT THREE HOURS UNTIL 09Z. HOWEVER...WOULD NOT BE SHOCKED IF
MVFR VSBY OCCASIONALLY OCCURS UNTIL 11Z OR 12Z. OTHERWISE.. VFR
DURING MOST OF THE DAY SUNDAY BEFORE NEXT SYSTEM MOVES IN. TIMING
VARIES WITH MODELS BUT IN GENERAL IT DOES LOOK LIKE SOMETIME FROM
23Z TO 03Z IS WHEN IFR VSBY WILL BECOME MOST LIKELY IN SNOW.

/OUTLOOK FOR KMSP/
MONDAY...VFR CONDITIONS EXPECTED. NORTHEAST WIND LESS THAN 10 KT.
MONDAY NIGHT...CHANCE OF SNOW WITH MVFR CEILINGS AND VISIBILITIES
EXPECTED WITH IFR CONDITIONS POSSIBLE. SOUTH WIND 5 TO 10 KT
BECOMING SOUTHWEST 10 TO 20 KT.

TUESDAY...CHANCE OF SNOW EARLY WITH MVFR CEILINGS AND VISIBILITIES
EXPECTED WITH IFR CONDITIONS POSSIBLE. THEN VFR. SOUTHWEST WIND 10
TO 20 KT SHIFTING NORTHWEST.
TUESDAY NIGHT...VFR CONDITIONS EXPECTED. WEST WIND 5 TO 15 KT.

WEDNESDAY...CHANCE OF SNOW LATE WITH MVFR CEILINGS AND
VISIBILITIES POSSIBLE. SOUTH WIND 5 TO 15 KT.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER WEATHER ADVISORY UNTIL 3 AM CST SUNDAY FOR BLUE EARTH-
     BROWN-CHIPPEWA-FARIBAULT-FREEBORN-LAC QUI PARLE-MARTIN-
     NICOLLET-REDWOOD-RENVILLE-STEVENS-SWIFT-WATONWAN-YELLOW 
     MEDICINE.

WI...NONE.
&&

$$