Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 281756
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1156 AM CST SUN DEC 28 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 240 AM CST SUN DEC 28 2014

LATEST WATER VAPOR IMAGERY SHOWS A FAIRLY STRONG WAVE DIGGING
INTO THE NORTHWEST UNITED STATES WITH THE LEAD ENERGY WORKING INTO
WESTERN WYOMING. THIS WAVE WILL SPREAD ACROSS THE AREA TONIGHT
INTO MONDAY AND WILL BE RESPONSIBLE FOR ALLOWING FRIGID ARCTIC AIR
TO SETTLE INTO THE REGION. AT 8Z THE ARCTIC AIR WAS ABOUT HALFWAY
THROUGH EASTERN NORTH DAKOTA AND SPREADING SOUTH AND WEST. THIS
COLD AIR WILL REACH THE INTERSTATE 90 CORRIDOR BY EARLY AFTERNOON
AND INTO THE MISSOURI RIVER VALLEY AROUND SUNSET.

ONE ROLE THIS COLDER AIR WILL PLAY IS TO SET UP A THERMAL PROFILE
THAT IS VERY SUPPORTIVE OF LIGHT SNOWFALL...COUPLED WITH THE
INCOMING UPPER LEVEL SUPPORT AND DECENT MID LEVEL FRONTAL FORCING.
WENT AHEAD AND UPPED POPS QUITE A BIT IN THE SOUTHERN CWA AND KEPT
THEM QUITE A BIT LOWER IN THE FAR NORTH AND NORTHEAST CWA. NOT ONLY
WILL THE ARCTIC AIR MASS BE COLDER BUT ALSO MUCH DRIER...SO SNOWFALL
WILL BE MUCH MORE DIFFICULT TO COME BY TO THE NORTH OF INTERSTATE
90. SHOULD SEE THE BEST CHANCES FOR SNOW FROM ABOUT 3Z THROUGH
12Z...ESPECIALLY IN THE SOUTHWEST CWA. NO PLANS FOR ANY HEADLINES AT
THIS TIME AS SNOWFALL TOTALS APPEAR TO BE MAINLY IN THE 1 TO 2 INCH
RANGE.

HIGHS TODAY WILL RANGE FROM THE TEENS IN THE NORTHERN CWA TO THE MID
20S IN THE SOUTHERN CWA. DO EXPECT SOME FALLING TEMPERATURES BY MID
AFTERNOON. LOWS TONIGHT SHOULD MAINLY BE IN THE SINGLE DIGITS WITH
MONDAY MORNING WIND CHILL VALUES PUSHING 15 BELOW ZERO IN THE NORTH
AND AROUND ZERO IN THE FAR SOUTH.

.LONG TERM...(MONDAY THROUGH SATURDAY)
ISSUED AT 240 AM CST SUN DEC 28 2014

LIGHT SNOW IS EXPECTED TO DECREASE STEADILY FROM THE NORTH MONDAY
WITH UP TO ANOTHER INCH EXTREME SOUTHWEST IN GREGORY COUNTY. THERE
IS A QUESTION ON THE SPEED OF THE DECREASE AND THE CLEARING FROM THE
NORTH. HAVE ELECTED TO GO WITH THE FASTER CLEARING SUGGESTED BY THE
NAM AND GFS...GIVEN THE PUSH OF COLDER AIR AT LOW UP TO MID LEVELS.
THE CANADIAN AND EC ARE SLOWER. SKIES WILL PROBABLY GO CLEAR TO
MOSTLY CLEAR MONDAY NIGHT THOUGH THERE IS SOME QUESTION IN THE
SOUTHWEST CORNER OF THE AREA WHERE MORE CLOUDS COULD HANG IN. WITH
THE SNOW COVER...THE COLD AIR FLOW WILL TAKE TEMPERATURES DOWN TO A
DECENT CHUNK BELOW ZERO BY EARLY TUESDAY MORNING...AND WIND CHILLS
WILL DIVE INTO THE ADVISORY ZONE. AFTER COORDINATION HAVE ELECTED TO
HOLD OF ON ADVISORY TO BETTER FIRM UP TIMING AND OTHER DETAILS...
WILL CONTINUE TO ADVERTISE THE EVENT IN THE HAZARDOUS WEATHER
OUTLOOK.

THE COLD AIR WILL BE AROUND FIRMLY AT LEAST THROUGH WEDNESDAY
MORNING...WITH PERHAPS ANOTHER WIND CHILL ADVISORY NEEDED TUESDAY
NIGHT. WITH THE SURFACE RIDGE PASSING QUICKLY AND ALSO PASSING TO
THE SOUTHWEST OF OUR AREA...WINDS WILL NOT GO CALM BUT RETAIN SOME
IDENTITY AS THEY BEGIN TO GO FROM NORTH/NORTHWEST TO MORE
WEST/SOUTHWEST.

WEDNESDAY INTO FRIDAY WILL BRING A WARMING TREND AS THE UPPER FLOW
QUICKLY GOES NORTHWESTERLY AND SOME OF THE WESTERN CANADIAN MILDER
AIR FLOWS IN. FRIDAY AND FRIDAY NIGHT WILL BRING THE APPROACH AND
PASSAGE OF ANOTHER ARCTIC FRONT WITH A THERMAL PATTERN FAVORABLE FOR
LIGHT SNOW...EVEN THOUGH THE CA UPPER LOW WHICH DEVELOPS EARLY THIS
WEEK SEEMS DESTINED TO PASS WELL SOUTH OF OUR AREA. SATURDAY WILL
THEN BE COLDER AGAIN.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1156 AM CST SUN DEC 28 2014

PRIMARY AVIATION CONCERN IS THE IMPACT OF LIGHT SNOWFALL TONIGHT
AND TOMORROW MORNING. CURRENTLY...AN AREA OF STRATUS WITH CIGS
FROM 600 TO 2100 FT JUST NORTH OF KHON. EXPECT THIS TO REACH KHON
BY 21Z BRINGING MVFR CONDITIONS. THIS STRATUS SHOULD REACH KFSD
AROUND 23Z AND KSUX AROUND 04Z. AT THE SAME TIME...SNOW IS
EXPECTED TO DEVELOP THIS EVENING IN SOUTH CENTRAL SOUTH DAKOTA AND
SPREAD EAST AND NORTHEAST. MOST OF THE SNOW WILL STAY SOUTH OF
KHON. DID NOT HAVE ANY RESTRICTIONS AT KHON DUE TO SNOW ALTHOUGH
LATE TONIGHT CIGS WILL BE AROUND 3000 FT. AT KFSD AND KSUX...SNOW
WILL RESTRICT VSBYS FOR A TIME LATER TONIGHT AND MONDAY MORNING.
SNOW IS EXPECTED TO BE LIGHTER AT KFSD SO HAVE A FEW HOURS OF
3-5SM -SN ALTHOUGH THERE COULD BE 1 OR 2 HOURS WITH IFR VSBYS
DURING THAT TIME. AT KSUX...EXPECT IFR VSBYS TO DEVELOP LATE
TONIGHT AND CONTINUE INTO MONDAY MORNING. CIGS MAY ALSO DROP TO
LESS THAN 1000 FT IN HEAVIER SNOWFALL. CONDITIONS SHOULD BEGIN TO
IMPROVE TOWARD 18Z MONDAY.

&&

.FSD WATCHES/WARNINGS/ADVISORIES...
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
&&

$$

SHORT TERM...08
LONG TERM...
AVIATION...SCHUMACHER


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