Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 030454
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1054 PM CST MON MAR 2 2015

.UPDATE...
ISSUED AT 932 PM CST MON MAR 2 2015

BASED OFF OF THE LATEST 00Z NAM AND 00Z GEM REGIONAL...HAVE BACKED
OFF ON THE SNOW AMOUNTS IN OUR NORTHWEST FORECAST AREA. FOR
INSTANCE LOWERED HURON TO AROUND 3.5 INCHES OF SNOWFALL. IT
APPEARS THAT JUST DUE TO THE PURE SPEED OF THE SYSTEM MOVING
THROUGH...THAT SNOW AMOUNTS WILL BE HELD DOWN EVEN IN THAT PART OF
OUR FORECAST AREA. THE 00Z GEM REGIONAL HAS A QUARTER INCH OF QPF
FOR HURON WHILE THE 00Z 12KM NAM AS 0.18...WHILE THE NAMDNG5 HAS
EVEN A BIT LESS. THE WIND AND SNOW WILL HIT LIKE A TON OF BRICKS
IN OUR WESTERN ZONES...THEN EXIT JUST AS QUICKLY AS THE FRONTAL
PASSAGE MOVES EAST. MOST OF THE REST OF THE FORECAST AREA WILL
RECEIVE LESS THAN TWO INCHES OF SNOW...WITH 1.3 NOW PROJECTED AT
SIOUX FALLS AND LESS THAN AN INCH AT SIOUX CITY. STILL HAVE A
THREAT OF SOME PATCHY FREEZING DRIZZLE LATE TONIGHT IN NORTHWEST
IA AND IMMEDIATE ADJACENT AREAS...BUT THE THREAT IS DISORGANIZED
ENOUGH TO NOT PUT OUT ANY SORT OF A WINTER WEATHER ADVISORY FOR
FREEZING DRIZZLE AT THIS TIME. THEREFORE NO CHANGES TO THE
HEADLINES. NEED TO STRESS THAT ALTHOUGH THIS IS NOT A LONG
DURATION EVENT...30 TO 50 MPH WINDS BEHIND THE FRONT IN ABOUT A 6
HOUR WIND...COUPLED WITH ANY FALLING SNOW...WILL DEFINITELY WRECK
HAVOC ON THE VISIBILITIES FOR A TIME.

&&

.SHORT TERM...(THIS EVENING THROUGH TUESDAY)
ISSUED AT 251 PM CST MON MAR 2 2015

THE MODELS HAVE REALLY COME INTO GOOD AGREEMENT ON THE OVERALL
PATTERN FOR TONIGHT. THE FOCUS FOR HEAVIEST SNOW CONTINUES TO BE IN
THE NORTHERN CWA...AS WELL AS THE FAR WESTERN CWA. WARMER AND MORE
MOIST AIR IS BUILDING NORTHWARD THROUGH NEBRASKA WHICH IS PUSHING
THE DENDRITIC LAYER HIGHER AND FARTHER NORTH. THIS IS MUCH OF THE
DRIVING FORCE BEHIND WHY THE BETTER PRECIPITATION IS GOING TO BE IN
THE NORTHERN CWA. AS THE WAVE MOVES ONTO THE WESTERN HIGH PLAINS
LATE TONIGHT THE MID LEVEL BOUNDARY WILL SLOW AND STALL OUT NEAR
HIGHWAY 14 AND WITH MID LEVEL WINDS BACKING A LITTLE CONVERGENCE
ALONG THIS BOUNDARY WILL INCREASE AND ALLOW SNOW TO DEVELOP. AT THIS
TIME BELIEVE THAT SOMEWHERE BETWEEN HE 700MB AND 750MB FRONT WILL
BE THE MAIN FOCUS WITH SOME MARGINAL AMOUNT OF INSTABILITY AVAILABLE
ABOUT THIS. WITH THIS IN MIND THE TIMING OF THE UPPER LEVEL WAVE
SHOULD BRING SNOW INTO CHAMBERLAIN AND HURON BY ABOUT 9Z WITH THE
FRONT RAPIDLY FILLING IN TOWARDS BROOKINGS AND MARSHALL. SLIGHTLY
LOWER CONFIDENCE TOWARDS SOUTHWEST MINNESOTA AS THE MID LEVEL FRONT
COULD SLIP JUST A BIT NORTH OF THIS AREA...BUT TOO CLOSE TO IGNORE
POTENTIAL RIGHT NOW. THIS HEAVIER BAND OF SNOW WILL BE IN PLACE AT
THESE LOCATIONS FROM ABOUT 9Z THROUGH 12-13Z...THEN START SLIDING
RAPIDLY SOUTH AS THE WAVE MOVES THROUGH. BY 18Z VIRTUALLY ALL OF THE
PRECIPITATION SHOULD BE EAST OF THE AREA AS LARGE SCALE SUBSIDENCE
FILLS IN. ALONG WITH THIS SNOWFALL WILL BE A VERY STRONG NORTH
WIND...ALBEIT THE MAJORITY OF THE STRONGEST WINDS SHOULD OCCUR AFTER
THE SNOW FALLS. THE BEST CHANCE FOR A COMBINATION OF FALLING SNOW
WILL BE ALONG THE WESTERN AND NORTHERN FRINGES OF THE CWA. SO WITH
AN EXPECTATION OF 2-4 INCHES IN THESE LOCATIONS AND WINDS GUSTING TO
40 TO 50 MPH A BLIZZARD WARNING WILL BE HOISTED. JUST TO THE SOUTH
AND EAST OF THIS WARNING A WINTER WEATHER ADVISORY WILL BE
ISSUED...MAINLY ALONG INTERSTATE 90 AND JUST SOUTH OF THERE IN SOUTH
DAKOTA INTO SOUTHWEST MINNESOTA. AT THIS TIME SNOWFALL AMOUNTS SOUTH
OF THE HURON TO MARSHALL LINE LOOK LIGHT ENOUGH THAT WIDESPREAD LESS
THAN A QUARTER MILE VISIBILITY SEEMS UNLIKELY. THERE WILL BE SOME
BLOWING AND DRIFTING SNOW HOWEVER SO STILL POTENTIALLY NASTY TRAVEL
CONDITIONS. NORTHWEST IOWA WILL NOT SEE ANY HEADLINES AT THIS TIME
BUT IT WILL BE AN AREA TO WATCH...MAINLY FROM ABOUT MIDNIGHT TO 8 AM
WHERE THE SOUNDINGS ARE HINTING AT THE POTENTIAL FOR SOME LIGHT
FREEZING DRIZZLE. IF IT CAN BECOME WIDESPREAD ENOUGH THEN AN
ADVISORY FOR SOME LIGHT ICING MAY BE NEEDED.

TEMPERATURES WILL FALL A BIT THIS EVENING THEN REMAIN STEADY OR RISE
SLIGHTLY LATE TONIGHT...BEFORE STARTING THE DOWNWARD SPIRAL THROUGH
THE DAY ON TUESDAY. TEMPERATURES AROUND SUNRISE TUESDAY MORNING
LIKELY TO BE IN THE MID 20S TO LOWER 30S WITH SUNSET TEMPERATURES IN
THE SINGLE DIGITS AND LOWER TEENS.

.LONG TERM...(TUESDAY NIGHT THROUGH MONDAY)
ISSUED AT 251 PM CST MON MAR 2 2015

FOCUS IN THE MEDIUM RANGE IS ON THE WARM UP AS STRONG CHINOOK
PATTERN SETS UP.  HAVE CONTINUED TO NUDGE FORECAST HIGHS UPWARDS
LATE IN THE WEEK...AND BOLSTERED HIGHS ON SUNDAY INTO MONDAY AS 925
HPA TEMPS WARM WELL INTO THE SINGLE DIGITS ABOVE ZERO.  AS LONG AS
THE WESTERLY FLOW IS ABLE TO REMAIN AT THE SURFACE...THINK THE
POTENTIAL FOR STRATUS IS REDUCED.  HAVE THEREFORE SIDED WITH
FORECAST HIGHS AT OR ABOVE ENSEMBLE MEMBERS WITH LIMITED SNOW COVER
EXPECTED ACROSS THE AREA. MODELS SUGGEST A WAVE MAY TRY TO DROP
THROUGH THE AREA ON SATURDAY INTO SUNDAY...BUT MOISTURE IS SEVERELY
LIMITED SO KEPT FORECAST DRY FOR NOW.

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)
ISSUED AT 1053 PM CST MON MAR 2 2015

VFR WILL PREVAIL IN THE NEAR TERM...BUT A BAND OF SNOW WILL MOVE
INTO THE HURON AREA DURING THE PRE DAWN HOURS TUESDAY...WITH A
STRONG WIND SHIFT TO THE NORTH AND NORTHWEST FOLLOWING BY DAY
BREAK. THE STRONG WIND ACROSS THE FORECAST AREA WILL HIT VERY
SUDDENLY...WITH FAIRLY LIGHT WINDS IN A PRE FRONTAL TROUGH AHEAD
OF THE COLD FRONT. BUT BEHIND THE FRONT...THE WINDS WILL RAPIDLY
INCREASE TO 30 TO 45 MPH AND LAST THAT WAY FOR AROUND 6 HOURS.
DURING FALLING SNOW...ESPECIALLY AT HURON...VISIBILITIES WILL BE
GREATLY REDUCED TUESDAY MORNING INTO THE LOWER END IFR CATEGORY.
THE SNOW WILL NOT BE AS GREAT AT SIOUX FALLS...AND CERTAINLY NOT
AT SIOUX CITY. THEREFORE VISIBILITY REDUCTIONS WILL LIKELY BE LESS
SEVERE AND MORE BRIEF. ONE THING TO KEEP AN EYE ON HOWEVER IS THE
POTENTIAL FOR LIGHT FREEZING DRIZZLE AT KFSD AND KSUX BETWEEN 09Z
AND 12Z TUESDAY. THIS HINGES ON STRATUS DEVELOPING AHEAD OF THE
COLD FRONT AND THERE IS A QUESTION AS TO HOW LOW ANY STRATUS WILL
FORM. BY TUESDAY AFTERNOON...CONDITIONS SHOULD BE MVFR UNDER
INSTABILITY CUMULUS WITH SLOWLY DECREASING WINDS.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...WINTER WEATHER ADVISORY FROM 10 AM TO 5 PM CST TUESDAY FOR
     SDZ054>056-059>062-065>067.

     BLIZZARD WARNING FROM 11 AM TO 6 PM CST TUESDAY FOR SDZ040.

     WINTER WEATHER ADVISORY FROM 7 AM TO 3 PM CST TUESDAY FOR SDZ050-
     063-064.

     BLIZZARD WARNING FROM 7 AM TO 3 PM CST TUESDAY FOR SDZ038-039-
     052-053-057-058.

MN...BLIZZARD WARNING FROM 11 AM TO 6 PM CST TUESDAY FOR MNZ071-072.

     WINTER WEATHER ADVISORY FROM 11 AM TO 6 PM CST TUESDAY FOR
     MNZ080-081-089-090-097-098.

IA...NONE.
NE...NONE.
&&

$$

UPDATE...MJ
SHORT TERM...08
LONG TERM...
AVIATION...MJ


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