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295
FXUS63 KMPX 230425
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
1025 PM CST MON DEC 22 2014

.UPDATE...
ISSUED AT 650 PM CST MON DEC 22 2014

THE CHANGE OVER TO SNOW IS OBVIOUSLY TAKING ITS TIME THIS EVENING.
THERE SEEM TO BE A FEW REASONS WHY. OUR BALLOON LAUNCHED A COUPLE
HOURS AGO SHOWED A FREEZING LEVEL AT ABOUT 1000FT ABOVE THE
GROUND. THAT`S TYPICALLY THE ROUGH THRESHOLD FOR A RAIN-TO-SNOW
CHANGE. SURFACE TEMPS ARE GENERALLY IN THE MID 30S...WHICH WOULD
CERTAINLY YIELD SNOW IF WE HAD SATURATION OVER A DEEP LAYER (AND
THROUGH THE DENDRITE GROWTH ZONE). AS OF RIGHT NOW...WE ARE
SOMEWHAT LACKING SATURATION IN THAT LAYER...WHICH IS ABOVE
10-12KFT. WE ARE ALSO LACKING IN FORCING. WE HAVE WEAK OMEGA WITH
THE APPROACHING TROUGH. IF THE LIFT WERE STRONGER WE WOULD
UNDOUBTEDLY HAVE DEEPER SATURATION AND IT WOULD BE SNOWING ALMOST
EVERYWHERE. SO...RIGHT NOW...WE ARE KIND OF WAITING FOR THE FLOW
TO BECOME MORE E-NE SO WE GET SOME COLD ADVECTION - ALONG WITH
SOME MINOR COOLING DUE TO NIGHTFALL. VARIOUS LOCATIONS AROUND THE
FORECAST AREA THAT HAVE A LITTLE HIGHER ELEVATION HAVE BEEN
REPORTING LIGHT SNOW OR "UP" AT TIMES THIS EVENING. THE MAIN
PRECIP BAND ARRIVES BY ABOUT MID MORNING AND MOST OF THAT WILL BE
SNOW GIVEN THE GOOD FORCING. THAT WILL BE FAIRLY FAR TO THE
EAST...IN FAR EASTERN MN AND WESTERN WI. SO WITH THAT...WESTERN
AND EVEN MUCH OF CENTRAL MN COULD BE ON THE OUTSIDE OF THE MAIN
SNOW BAND AND THUS RECEIVE LITTLE SNOW. THIS INCLUDES PLACES LIKE
ST. CLOUD, LITCHFIELD AND REDWOOD FALLS. THE TC METRO STILL LOOKS
OK FOR MINOR SNOW ACCUMS...BUT THE BEST LOCATIONS SHOULD BE FROM
ALBERT LEA TO EAU CLAIRE.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 322 PM CST MON DEC 22 2014

LIGHT SNOW IS BEGINNING TO MIX IN WITH THE RAIN AT MID AFTERNOON
ACROSS THE TWIN CITIES AND POINTS SOUTH TO IOWA AS THE THERMAL
PROFILE IS BEGINNING TO COOL BELOW 0C IN THE 875-925MB LAYER. EVEN
SURFACE TEMPERATURES HAVE COOLED A COUPLE OF DEGREES THIS
AFTERNOON ACROSS MUCH OF OUR FA. CONTINUED COOLING HEADING INTO THE
EVENING HOURS WILL LIKELY LEAD TO MUCH OF THE PRECIPITATION ACROSS
CENTRAL MN THROUGH THE TWIN CITIES AND WEST CENTRAL WI BECOMING
SNOW. SHORT TERM MODEL SOLUTIONS INDICATE A DIMINISHING TREND TO
THE PRECIPITATION IN THESE AREAS WHICH SHOULD KEEP SNOW
ACCUMULATIONS MINIMAL. IT REMAINS WARMER OVER WEST CENTRAL THROUGH
SOUTH CENTRAL MN THIS EVENING WITH JUST LIGHT RAIN EXPECTED.
HOWEVER...VISIBILITIES HAVE LOWERED NEAR THE BUFFALO RIDGE...ALONG
THE SURFACE TROUGH AXIS...AND SOME DENSE FOG CAN BE EXPECTED EARLY
TONIGHT SOUTHWEST OF THE MN RIVER VALLEY UNTIL WINDS BECOME MORE
NORTHEAST LATER TONIGHT.

TUESDAY REMAINS A REAL PROBLEM WEATHER WISE. A CLOSED MID LEVEL
LOW WILL EJECT NORTHEAST FROM IA INTO WI DURING THE DAY. THIS
PLACES A DEFORMATION ZONE FROM SOUTH CENTRAL MN THROUGH WEST
CENTRAL WI. THE THERMAL PROFILE INDICATES THIS WILL BE MAINLY AN ALL
SNOW EVENT. HOWEVER...SOME WARMER AIR ARRIVES INTO WEST CENTRAL WI
DURING THE MORNING IN THE 850-900MB LAYER WITH TEMPERATURES RISING
ABOVE 0C ALLOWING FOR A MIX OF RAIN AND SNOW. MODEL SPREAD REMAINED
TODAY WITH TIMING AND DEPTH WITH THIS SYSTEM BUT MORE IMPORTANTLY
WITH THE EXPECTED PRECIPITATION AMOUNTS. FOR THIS REASON THE SREF
WAS USED FOR QPF AMOUNTS AS IT WAS HIGHER THAN MOST SOLUTIONS.
THIS PLACED BETWEEN 0.15 AND 0.25 INCHES OF QPF IN THE
AFOREMENTIONED AREAS. THE PROBLEM THAT ARISES IS WITH THE SNOW
RATIOS. THE AF SNOW RATIO METHOD RESULTS IN VALUES IN THE RANGE OF
3:1 TO 5:1. THE COBB TECHNIQUE WOULD BE MORE IN THE 8:1 TO 9:1
RANGE. THE COBB VALUES WERE USED BUT WITH RATIOS LESS THAN 10:1
SNOW AMOUNTS ONLY CAME UP IN THE 1 TO 2 INCHES RANGE IN THE
MORNING WITH ANOTHER HALF INCH TO 1 INCH IN THE AFTERNOON. STILL
THINK THESE MAY BE TOO LOW WITH A POTENTIAL 4 INCH BAND POSSIBLE
BEGINNING SOMEWHERE BETWEEN FAIRMONT AND ALBERT LEA AND EXTENDING
NORTHEAST THROUGH DAKOTA COUNTY AND THEN THROUGH NEW RICHMOND AND
RICE LAKE IN WEST CENTRAL WI. AREAS TO THE WEST AND NORTH WILL SEE
MUCH LESS SNOW. ALL OFFICES HELD ON TO THE WINTER WEATHER ADVISORY
FOR PORTIONS OF WI DUE TO THE UNCERTAINTY OVERNIGHT AS WELL AS ON
TUESDAY. LITTLE VARIATION IN THE TEMPERATURES TONIGHT AND TUESDAY
WITH LOWS TONIGHT IN THE 31-34 DEGREE RANGE WITH HIGHS ON TUESDAY
FROM 33 TO 36.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 322 PM CST MON DEC 22 2014

TWO CONCERNS OVER THE NEXT SEVERAL DAYS...ONE FOR TUESDAY
EVENING...WITH ANOTHER PROBLEM BY THE END OF THE WEEK.

THE TRANSITION FROM TUESDAY INTO TUESDAY NIGHT WILL BE ASSOCIATED
WITH THE DECAYING UPPER LOW ACROSS THE WESTERN GREAT LAKES...WITH A
STRONGER UPPER LOW/SFC LOW/ DEVELOPING ON THE SOUTHERN JET ACROSS
MO/AR/IL. CONFIDENCE REMAINS HIGH ENOUGH TO CONTINUE HIGH END CHC
POPS FOR TUESDAY EVENING ACROSS MOST OF THE CWA. THE MAIN REASON IS
THE DEFORMATION ZONE CENTERED ACROSS OUR REGION...WILL CONTINUE TO
SHEAR OUT...SQUEEZING OUT A FEW HUNDREDTHS...RESULTING WITH AN
ADDITIONAL HALF INCH OF SNOW. AGAIN...NOT EXPECTING TOO MUCH
ESPECIALLY CONSIDERING THE SOUTHERN STREAM HAVING MORE INFLUENCE ON
THE OVERALL WEATHER PATTERN.

ALTHOUGH THE PATTERN REMAINS PROGRESSIVE ACROSS THE CONUS THIS
WEEK...THE RESULTING SLOWER MOVEMENT OF TODAY/S TUESDAY SYSTEM WILL
LEAD TO A SLOWER SOLUTION FOR THE SYSTEM BY THE END OF THE WEEK. THE
EC AND THE LOCAL HOPWRF /24KM/ SOLUTIONS HAVE SHOWN FRIDAY SYSTEM
WARMER AND FURTHER NORTHWARD ACROSS THE UPPER MIDWEST. IN
ADDITION...THERE WILL LIKELY BE A STRONG THERMAL GRADIENT ALONG WITH
A SHARP CONTRAST BETWEEN THE DRIER AIR TO THE SOUTH...AND THE
STRONGER FRONTAL BANDING TO THE NORTH. BASICALLY...IT IS QUITE
POSSIBLE WE CAN SEE A LOCALIZED BAND OF 6+ INCHES OF SNOW WHERE THE
STRONGEST BANDING OF THE 85H/70H/60H FRONT LIES FRIDAY/FRIDAY NIGHT.
THE BEST SCENARIO IS TO CONTINUE CHC POPS...LEAN MORE TOWARD HIGHER
QPF AMTS ACROSS OUR NW CWA AS THIS SYSTEM EVOLVES THRU THE NEXT FEW
DAYS.

TEMPS WILL LIKELY REMAIN ABV NORMAL THRU AT LEAST FRIDAY...OR UNTIL
FRIDAY/S SYSTEM BRINGS DOWN COLDER AIR FOR THE END OF THE YEAR.
LONGER RANGE MODELS HAVE DEPICTED THE COOLER TEMPS FOR THE FIRST
WEEK OF 2015...BUT NOTHING TOO ABNORMAL...MAINLY CLIMATOLOGY
WHICH IS LOWS AROUND 5 TO 10...WITH HIGHS IN THE TEENS AND 20S.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1021 PM CST MON DEC 22 2014

LIGHT MIXED PRECIPITATION WILL CONTINUE OVERNIGHT ACROSS MOST
TERMINALS...WITH THE CHANGEOVER TO SNOW TAKING LONGER THAN INITIALLY
EXPECTED DUE TO WEAK FORCING AND WARM TEMPS NEAR THE SURFACE.  IFR
CIGS SHOULD PERSIST AT ALL TERMINALS THROUGH TUESDAY MORNING...WITH
PRECIP POSSIBLY WEAKENING TO DRIZZLE/FLURRIES AT MN TERMINALS BY
EARLY MORNING.  CHANGEOVER TO ALL SNOW SHOULD OCCUR BY TUESDAY
MORNING...WITH A BAND OF SNOW MOVING INTO THE AREA FROM THE SE.
FROM THE MID-MORNING THROUGH THE AFTERNOON...SNOW COULD BE HEAVY AT
TIMES IN EASTERN TERMINALS.  LIFR VIS AND CIGS ARE LIKELY AT
EAU...AND POSSIBLE AT RNH AND MSP.  SNOW INTENSITY WILL DECREASE
FROM THE LATE AFTERNOON THROUGH THE REMAINDER OF THE PERIOD...BUT
OVERCAST CONDITIONS WITH IFR CIGS WILL PERSIST AT ALL TERMINALS.

KMSP...

IFR CIGS REMAIN LIKELY OVERNIGHT...WITH PRECIPITATION REMAINING
LIGHT AND POSSIBLY DECREASING IN INTENSITY TO DRIZZLE BY 09Z.  MAIN
BAND OF SNOW SHOULD MOVE IN BETWEEN 13Z-15Z...WITH MOST ACCUMULATING
SNOW AND POSSIBLE LIFR CONDITIONS OCCURRING THROUGH LATE AFTERNOON.
SNOW WILL DECREASE IN INTENSITY AFTER THIS TIME...BUT IFR CIGS COULD
REMAIN THROUGH THE END OF THE PERIOD.

/OUTLOOK FOR KMSP/
WED...MVFR. WINDS NW 10-15 KTS.
THU...VFR.  WINDS W 5-10 KTS.
FRI...MVFR WITH CHC -SN.  WINDS NW 10 KTS.

&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...NONE.
WI...WINTER WEATHER ADVISORY UNTIL 6 PM CST TUESDAY FOR WIZ016-027.

&&

$$

UPDATE...CLF
SHORT TERM...RAH
LONG TERM...JLT
AVIATION...ADL








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