Area Forecast Discussion
Issued by NWS Twin Cities, MN

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FXUS63 KMPX 222122
AFDMPX

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

.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 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1132 AM CST MON DEC 22 2014

LESS THAN MVFR CEILINGS ALONG WITH IFR/MVFR VISIBILITIES WILL
PREVAIL AT THE TAF SITES DURING THE FORECAST PERIOD AS AN AREA OF
LOW PRESSURE OVER SD MOVES SOUTHEAST INTO IA. THIS WILL MEAN A
GRADUAL BACKING IN THE SURFACE WINDS FROM SE TO NE. AS THE WINDS
BECOME MORE EASTERLY THIS EVENING...THE LOW LEVEL THERMAL PROFILE
BEGINS TO COOL FROM THE EAST WITH KSTC...KRNH AND KEAU SUSCEPTIBLE
TO A CHANGEOVER TO SNOW QUICKER THAN THE TAF INDICATES.
HENCE...CONFIDENCE IS LOW ON EXACTLY WHEN THE CHANGEOVER OCCURS.
CONFIDENCE DOES INCREASE BY TUESDAY MORNING THAT A BAND OF
LIGHT TO MODERATE SNOW WILL DEVELOP ACROSS SOUTH CENTRAL MN
THROUGH THE SOUTHERN TWIN CITIES AND ON ACROSS WEST CENTRAL WI.
CONFIDENCE IS ALSO INCREASING THAT SNOW ACCUMULATION IN THIS BAND
WILL BE IN THE 2 TO 4 INCH RANGE. THE TAF SITE IN THE BULLS EYE
RIGHT NOW FOR 4 INCHES IN KEAU. HENCE...MODERATE SNOW INDICATED AT
KEAU AFTER 12Z. KRNH AND KMSP WILL BE ON THE WESTERN EDGE...BUT A
QUICK 2 INCHES OF ACCUMULATION IN THE MORNING IS LOOKING LIKELY.

KMSP...SHORT TERM MODEL SOLUTIONS POINT TO ALL RAIN AT THE
AIRFIELD THROUGH 03Z. THIS WAS INCORPORATED INTO THE TAF. A MIX OF
RAIN AND SNOW DEVELOPING THEREAFTER WITH AN ALL SNOW SCENARIO BY
DAYBREAK TUESDAY. SEVERAL INCHES OF ACCUMULATION LIKELY DURING THE DAY.
SE WINDS THIS AFTERNOON BACKING TO THE NORTHEAST THIS EVENING THEN
BECOMING NORTH BY TUESDAY AFTERNOON. SPEEDS 10-15 KNOTS.

/OUTLOOK FOR KMSP/

WED...MVFR. WINDS NW 10-15 KTS.
THU...VFR. WINDS W 5-10 KTS.
FRI...MVFR CHC -SN. WINDS NW 10 KTS.

&&

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

&&

$$

SHORT TERM...RAH
LONG TERM...JLT
AVIATION...RAH







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