274 
FXUS63 KMPX 220615 AAA
AFDMPX

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1215 AM CST FRI FEB 22 2013

.UPDATE...

UPDATED FOR THE 06Z AVIATION DISCUSSION BELOW.

.DISCUSSION...

THE FORECAST REMAINS ON TRACK FOR ACCUMULATING SNOW TO OVERSPREAD
THE FA FROM SW TO NE EARLY TONIGHT AND THEN CONTINUE THROUGH THE
DAY ON FRIDAY...THEN SLOWLY DIMINISHING FROM WEST TO EAST FRIDAY
NIGHT AND SATURDAY. MOST SOLUTIONS TODAY HAVE ABOUT THE SAME
AMOUNT OF QPF FOR OUR FA AS THOSE FROM 12 TO 24 HOURS AGO.
EXCEPTIONS INCLUDE THE HIRES ARW WRF WITH .50 TO .75 INCHES OF QPF
FOR THE ADVISORY AREA THROUGH FRIDAY WHILE OUR OWN MPXWRF IS NOT
FAR BEHIND. THIS COUPLE WITH SNOW RATIOS BETWEEN 15 AND 20 TO 1
WOULD PUT US WELL ABOVE ADVISORY CRITERIA.

HOWEVER...CHECKING ON FORCING SHOWED LITTLE IN THE WAY OF EXTENDED
MID LEVEL FRONTOGENESIS OVER THE ADVISORY AREA. ELEVATED
INSTABILITY IS ALSO PROJECTED TO WANE AS IT COMES NE FROM WESTERN
IA AFTER MIDNIGHT WITH THE AGEOSTROPHIC VERTICAL CIRCULATION FLAT
ACROSS THE AREA FRIDAY MORNING. THE LOW LEVEL MOISTURE TRANSPORT
IS WELL SE OF HERE OVERNIGHT AND FRIDAY MORNING WITH THE NAM/GFS
290K THETA SURFACES SHOWING A PERIOD OF MIXING RATIOS FROM 1.5 TO
2 G/KG... FROM WEST TO EAST... ON FRIDAY. IN ADDITION... BOTH MODELS
ONLY HAVE PW VALUES RISING TO .35 TO .40 INCHES. THE THALER QG RUN
ACCUMULATED PRECIPITATION FROM THE NAM INDICATED QPF RANGING FROM
A TENTH OF AN INCH NEAR KAXN...AROUND A QUARTER OF AN INCH FROM
KRWF THROUGH THE TWIN CITIES TO KUBE WITH THE HALF INCH AREA NEAR
KDSM BY LATE IN THE DAY ON FRIDAY. THIS IS VERY CLOSE TO THE
GFS/ECMWF SOLUTIONS. THEREFORE...CONFIDENCE REMAINS HIGH WE WILL
HOLD SNOW TOTALS FROM 3 INCHES ON THE NORTHWEST SIDE OF THE
ADVISORY AREA WITH 5 TO 6 INCHES FROM KFRM TO KEAU. FOR THE TWIN
CITIES...A SOLID 4 TO 4.5 INCHES IS INDICATED WITH PERHAPS 3
INCHES OF THAT SNOW FALLING BETWEEN 3 AM AND 9 AM. HENCE...THE
MORNING COMMUTE FOR MANY LOCATIONS IN OUR CWA WILL BE IMPACTED.

THIS SYSTEM WILL BE SLOW TO MOVE OFF FRIDAY NIGHT AND SATURDAY
WITH LIGHT SNOW LINGERING OVER EASTERN MN AND WI. ACCUMULATION
AMOUNTS WILL BE LIGHT AND UP TO AN INCH. A BRIEF RESPITE FROM THE
SNOW SATURDAY NIGHT AND EARLY SUNDAY BEFORE ANOTHER WEATHER SYSTEM
ARRIVES FROM THE WEST. THE UPPER AIR PATTERN WITH THIS SYSTEM IS
NOT BEING HANDLED WELL BETWEEN THE GFS AND ECMWF. THE GFS WOULD
PREFER TO HAVE ONE LARGE UPPER LOW MOVE INTO THE NORTHERN PLAINS
AND UPPER MISSISSIPPI VALLEY REGION SUNDAY NIGHT AND MONDAY AND
THEN MOVE SLOWLY EAST TO THE GREAT LAKES BY TUESDAY. THE ECWMF
BREAKS THIS SYSTEM INTO TWO PIECES AS IT MOVES EAST OF THE
ROCKIES. WE WOULD STILL EXPERIENCE SNOW FROM THE ECMWF MONDAY AND
TUESDAY BUT NOT OF THE INTENSITY SHOWN BY THE GFS. THE GEFS WAS OF
LITTLE HELP WITH A SOLUTION MUCH LIKE THE DETERMINISTIC RUN. THE
REAL CULPRIT IN ALL OF THIS SEEMS TO BE THE BLOCKING PATTERN THAT
STRENGTHENS OVER THE NORWEGIAN SEA AND WESTERN EUROPE EARLY NEXT
WEEK. IN THE END...CHANCE POPS CONTINUE FROM SUNDAY NIGHT THROUGH
WEDNESDAY.

&&

.AVIATION.../06Z TAF ISSUANCE/ 

SNOW IS INCOMING EARLY THIS MORNING...EXPECT DETERIORATING
CONDITIONS OVER THE NEXT 6 HOURS. WIDESPREAD IFR IS EXPECTED WITH
OCCASIONAL LIFR WHERE THE HEAVIEST SNOW IS FALLING IS EXPECTED
THROUGH ABOUT 14-15Z...WITH SLOW IMPROVEMENT THROUGH THE
AFTERNOON. HOWEVER...LIGHT SNOW COULD HANG AROUND FOR QUITE SOME
TIME TODAY.

KMSP...

SNOWY MORNING EXPECTED. TRIED TO GIVE A LOT OF DETAIL IN THE
FIRST 6 HOURS OF THE TAF WITH THE HEAVIEST SNOW FROM ROUGHLY 09Z
TO 11Z. THE MORNING COMMUTE WILL CERTAINLY BE IMPACTED WITH IFR
THROUGH THE MORNING RUSH. WE THINK THE AIRPORT WILL BE IN THE
3-3.5" RANGE FOR SNOWFALL...SO THERE WILL NEED TO BE AT LEAST A
PERIOD OF 1/2SM SNOW AND SNOW RATES IN THE 3/4 INCH PER HOUR
RANGE. THE BEST WINDOW FOR THIS IS EARLY THIS MORNING...CONDITIONS
MAY ALREADY BE IMPROVING SLOWLY JUST AFTER SUNRISE.

/OUTLOOK FOR KMSP/

SAT...MVFR CIGS WITH -SN IN THE MORNING. W WIND 5 KT. 
SUN...VFR CIGS EARLY...MVFR CIGS LATE. CHANCE -SN LATE. SE WINDS
BECOMING NE 5 KT. 
MON...MVFR CIGS WITH CHANCE -SN. NE WINDS 5 TO 10 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER WEATHER ADVISORY UNTIL 6 PM CST FRIDAY FOR BLUE EARTH-
     BROWN-CARVER-CHIPPEWA-DAKOTA-FARIBAULT-FREEBORN-GOODHUE-
     HENNEPIN-KANDIYOHI-LE SUEUR-MARTIN-MCLEOD-MEEKER-NICOLLET-
     REDWOOD-RENVILLE-RICE-SCOTT-SIBLEY-STEELE-WASECA-WATONWAN-
     WRIGHT-YELLOW MEDICINE.

     WINTER WEATHER ADVISORY UNTIL 6 PM CST FRIDAY FOR ANOKA-CHISAGO-
     ISANTI-RAMSEY-SHERBURNE-WASHINGTON.

WI...WINTER WEATHER ADVISORY UNTIL 6 PM CST FRIDAY FOR BARRON-
     CHIPPEWA-DUNN-EAU CLAIRE-PEPIN-PIERCE-POLK-RUSK-ST. CROIX.

&&

$$

RAH/CLF