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000
FXUS63 KMPX 041926
AFDMPX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TWIN CITIES/CHANHASSEN MN
126 PM CST TUE MAR 4 2014

.SHORT TERM...(TONIGHT)
ISSUED AT 112 PM CST TUE MAR 4 2014

SEVERAL FACTORS HAVE SLOWLY COME TOGETHER THIS AFTN FOR A QUICK 2
TO 4 INCH SNOWFALL ACROSS FAR SOUTHERN MN DUE TO THE COMBINATION
OF A STRONG SHRTWV & WAA LAYER /92-70H/ MOVING THRU SOUTHERN MN
THIS EVENING.

ALTHOUGH REGIONAL RADAR WAS DEPICTING A LARGE AREA OF HIGHER
RETURNS ACROSS SD/ND MOVING SE EARLY THIS AFTN...THE CONTINUED DRY
FLOW FROM THE GREAT LAKES WILL KEEP MOST OF THE ACCUMULATING
SNOWFALL SOUTH OF I-94. IT MAY EVEN TAKE A FEW HRS BEFORE THE
ATMOSPHERE SATURATES ENOUGH FOR THE SNOW TO REACH THE GROUND IN EC
MN. OVER THE PAST FEW RUNS OF THE HOPWRF AND RAP...THERE REMAINS A
VERY SHARP BOUNDARY BETWEEN NO SNOWFALL...AND LOCALLY 1 TO 2
INCHES ALONG THE I-94 CORRIDOR. TRENDS HAVE BEEN FOR THE DRIER AIR
TO HOLD THE NE 1/3 OF MPX CWA DRY...WITH THE BULK OF THE QPF SOUTH
OF NEW ULM TO OWATONNA. I DID NOT WANT TO GET TOO SPECIFIC ON
WHERE THE CUTOFF WOULD BE TO THE NE...BUT IT IS LIKELY THAT THE
NORTHERN PART OF THE TWIN CITIES MAY ONLY GET FLURRIES...WITH ONE
TO TWO INCHES IN SCOTT/DAKOTA COUNTIES. AGAIN...THIS IS BASED ON
THE CURRENT RUN OF BOTH THE HOPWRF/RAP. ANY DEVIATION TO THE
STRONGER FORCING ALONG THE 92-70H FRONTOGENETIC ZONE THIS
EVENING...WILL CAUSE MORE OR LESS SNOWFALL ACROSS CENTRAL MN/WC
WI. OTHERWISE...THIS SYSTEM IS FAIRLY FAST AND WILL MOVE OUT OF
THE REGION BY 12Z.

.LONG TERM...(WEDNESDAY THROUGH MONDAY)
ISSUED AT 329 AM CST TUE MAR 4 2014

DESPITE THE NUMBER OF SLIGHT CHANCE AND CHANCE POPS IN THE
FORECAST FOR THE LONG TERM...THIS PERIOD WILL BE MOSTLY DRY WITH
THE MAIN AREAS OF PRECIPITATION STAYING WITH THE NORTHERN STREAM
IN SOUTHERN CANADA...AND THE SOUTHERN STREAM FROM THE SOUTHWEST
THROUGH THE GULF COAST. TWO CHANCES OF PRECIPITATION PRESENT
THEMSELVES WITH THE FIRST ON THURSDAY...AND THE SECOND ON FRIDAY.
BOTH THE NAM AND GFS REALLY BROAD BRUSH THE FA WITH LIGHT QPF
DURING THESE PERIODS...WHILE THE EC SHOWS WHAT APPEARS TO BE A
MORE REALISTIC OUTPUT...KEEPING THE PRECIPITATION IN NORTH CENTRAL
MN AND AREAS NORTHWARD WHERE THE DEEPEST SATURATION OCCURS AND
BEST FORCING /ALBEIT WEAK/ IS PRESENT. BEHIND THESE TWO WAVES...A
MODIFIED ARCTIC HIGH WILL PUSH SOUTHEAST THROUGH ALBERTA AND
SASKATCHEWAN INTO THE UPPER MIDWEST INTO SATURDAY. THE POSITION OF
THE SURFACE HIGH SATURDAY MORNING WILL BE KEY IN THE MIN TEMPS.
DID LOWER MIN TEMPERATURES FOR SATURDAY MORNING SLIGHTLY FOR
NOW...AND WE DO HAVE A SHOT OF SEEING BELOW ZERO TEMPERATURES
SATURDAY MORNING DEPENDING ON THE EFFICIENCY OF RADIATIONAL
COOLING.

THE BRIEF WARM UP AHEAD OF THE ARCTIC HIGH WILL BRING WARM AIR
ALOFT ON THE POSITIVE SIDE OF 0C INITIALLY...SO SUBSEQUENT SHIFTS
WILL NEED TO SORT OUT ANY P TYPE ISSUES IF THE PRECIPITATION STAYS
IN THE FORECAST. FOR NOW...WENT WITH ALL SNOW FOR THIS PERIOD AS
CONFIDENCE IN PLACEMENT OF THE THERMAL RIDGE ALOFT ALONG WITH QPF
IS LOW. DID NOT FEEL ADDING PRECISION WOULD HELP WITH ACCURACY IN
THIS REGARD...AS THE MODEL SPREAD IN DAYS 3-4 IS TOO WIDE TO NAIL
DOWN TRANSITION AREAS BETWEEN RAIN/SNOW/SLEET. WILL HAVE TO WATCH
FOR DRIZZLE AND POTENTIAL FOG ON FRIDAY...BUT DID NOT MENTION IT
IN THE FORECAST PACKAGE YET. ECMWF KEEPS SOUTHERN MN DRY AND WARM
INTO FRIDAY...WHILE NAM/GFS WANT TO SPREAD LIGHT QPF THROUGH THE
AREA. AGAIN...TEMPERATURES CRASH THIS WEEKEND WITH HIGHS ON
SATURDAY EXPECTED TO BE AROUND 15 DEGREES BELOW NORMAL.
THANKFULLY...BOTH THE GFS AND EC SHOW A DECENT THERMAL RIDGE
WORKING EASTWARD MONDAY AS ZONAL FLOW OFF THE ROCKY MOUNTAINS
DESCENDS DOWN THE HIGHER TERRAIN...AND UNDERGOES COMPRESSION WITH
THE PRESSURE CHANGE AND WARMS NICELY. HENCE...TEMPERATURES NEAR 40
ARE FORECAST MONDAY WITH A SLIGHT CHANCE OF RAIN...DURING THE
AFTERNOON.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1127 AM CST TUE MAR 4 2014

MVFR/IFR CIGS/VSBYS WILL DEVELOP THIS AFTN IN WC/SW MN...AND
CONTINUE THRU MOST OF THE TAF PERIOD BASED ON UPSTREAM OBS IN
ND/SD AS A POTENT SHRTWV MOVES SE ACROSS THE UPPER MIDWEST.
CONFIDENCE IS HIGH ON IFR VSBYS IN -SN DEVELOPING FOR KRWF BY
20-21Z...WITH LESS CONFIDENCE KAXN/KSTC/KRNH FOR THE FIRST 6 HRS
BASED ON DRIER AIR FILTERING SW ACROSS NORTHERN/CENTRAL MN THIS
AFTN/EVENING. BETTER LIFT/SATURATION IS NOTED IN WC/SW/SC MN BY
21-00Z...WITH MARGINAL FOR AREAS NORTH OF I-94. WINDS WILL REMAIN
FROM THE E/NE...BECOME MORE E/ESE BY WEDNESDAY MORNING.

KMSP...

BASED ON LATEST OBS/REGIONAL RADAR IN SD/ND...AM LEANING TOWARD
IFR VSBYS DEVELOPING BY 23Z. CONFIDENCE ON SNOWFALL DEVELOPING IS
HIGH...BUT LOW CONFIDENCE ON HOW LOW THE VSBYS WILL GET FROM DRIER
AIR FILTERING IN FROM THE NE DURING THE LATE AFTN/EVENING TIME
FRAME. BEST TIME FRAME OF IFR VSBYS WILL OCCUR BETWEEN 23-03Z OR
DURING THE WORSE TIME PERIOD FOR AIR TRAFFIC. IN ADDITION...THERE
COULD BE SOME MODERATE SNOWFALL ARND 00-02Z. MAY CONSIDER AN AWW
IF UPSTREAM CONDS WARRANT. WINDS WILL REMAIN FROM THE E/ENE THRU
TONIGHT...AND BECOME MORE SE/ESE BY WEDNESDAY MORNING.

/OUTLOOK FOR KMSP/

WED NGT...VFR. WINDS SE 5-10 KTS.
THU...VFR. CHC MVFR/-SN. WINDS S 10-15 KTS.
FRI...VFR. CHC MVFR/-SN EARLY. WINDS N 10 KTS.


&&

.MPX WATCHES/WARNINGS/ADVISORIES...
MN...WINTER WEATHER ADVISORY FROM 6 PM THIS EVENING TO 3 AM CST
     WEDNESDAY FOR MNZ074-082>085-091>093.

WI...NONE.
&&

$$

SHORT TERM...JLT
LONG TERM...SPD
AVIATION...JLT