Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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FXUS63 KFSD 162308
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
508 PM CST TUE DEC 16 2014

.SHORT TERM...(THIS EVENING THROUGH WEDNESDAY)
ISSUED AT 314 PM CST TUE DEC 16 2014

RIDGE OF HIGH PRESSURE WILL MOVE OVERHEAD TONIGHT BRINGING
DECREASING WINDS. GIVEN THE NEW SNOWPACK...THIS COULD SET THE STAGE
FOR A COLD NIGHT. HOWEVER CLOUD COVER IS PRETTY UNCERTAIN WITH
MODELS NOT HANDLING THE CURRENT SITUATION TOO WELL. AREAS WEST OF
THE JAMES RIVER AND SOUTHWEST MINNESOTA HAVE THE BEST CHANCE OF
STAYING MOSTLY CLOUDY. MORE UNCERTAIN IN BETWEEN...WHERE WE
CURRENTLY HAVE SOME CLEARING. THE RAP...WHICH MAY HAVE THE BEST
HANDLE ON THE CURRENT SITUATION...MOVES STRATUS BACK INTO THIS REGION
AFTER MIDNIGHT. LOW CONFIDENCE FORECAST...BUT WILL CARRY MOSTLY
CLOUDY SKIES FOR NOW OVERNIGHT FOR A MAJORITY OF THE AREA. LOW
TEMPERATURES WILL BE HEAVILY DEPENDENT ON CLOUD COVER. COULD ALSO
SEE A FEW FLURRIES IN THE CLOUD COVER AS WELL. PLACES THAT ARE CLOUD
FREE COULD EASILY DROP TO -5 OR EVEN A BIT COLDER...WHILE LOCATIONS
IN STRATUS WILL PROBABLY BE AROUND +10. SO WILL LIKELY SEE DECENT
TEMPERATURE GRADIENTS TONIGHT...AND GIVEN THE UNCERTAINTY PLAYED
LOWS MORE TOWARDS CONSENSUS...LEANING A BIT TOWARDS THE COLD SIDE
WHERE WE HAVE THE BEST CHANCE OF CLEARING AND BETTER RADIATIONAL
COOLING.

HIGH SLOWLY SHIFTS OFF TO THE EAST ON WEDNESDAY. LOOKS LIKE A DAY OF
WEAK MIXING AND COLD TEMPERATURES. CLOUD COVER REALLY DEPENDS ON WHAT
HAPPENS TONIGHT. IF WE STRATUS OVER...CLOUDS WILL LIKELY BE SLOW TO
CLEAR THROUGH THE DAY KEEPING IT MOSTLY CLOUDY. ON THE OTHER
HAND...IF WE STAY MORE CLEAR TONIGHT...THEN COULD BE QUITE A BIT OF
SUN TOMORROW. EITHER WAY HIGHS SHOULD STAY ON THE COOLER SIDE OF
GUIDANCE WHERE WE HAVE SNOWPACK...ONLY SEEING THE TEENS...WITH MID
20S OVER NORTHWEST IOWA WHERE SNOW COVER IS LESS OR NON EXISTENT.

.LONG TERM...(WEDNESDAY NIGHT THROUGH TUESDAY)
ISSUED AT 314 PM CST TUE DEC 16 2014

A SLOW AND STEADY WARMING TREND ALONG WITH DRY CONDITIONS WILL
PREVAIL INTO THE UPCOMING WEEKEND. OVERALL TEMPERATURES WILL BE NEAR
NORMAL...BUT WILL CREEP UP TO NEAR FREEZING OR SLIGHTLY ABOVE BY
SUNDAY.

MODEST AREA OF ISOTROPIC LIFT WILL ALLOW MID AND HIGH CLOUDS BUILD
INTO THE AREA FROM THE SOUTHWEST WEDNESDAY NIGHT. MIGHT GET ENOUGH
LIFT INTO THE MISSOURI VALLEY LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING TO ALLOW FOR SOME ISOLATED LIGHT SNOWFALL...BUT BETTER LIFT
AND SUPPORT REMAINS WELL SOUTH OF THE FORECAST AREA SO ANY SNOW THAT
DOES MAKE IT INTO OUR SOUTHERN BORDER WOULD BE MINIMAL. TEMPERATURES
WILL FALL OFF SOMEWHAT QUICKLY WEDNESDAY EVENING THEN STABILIZE AS
THE CLOUDS ARRIVE. HIGHS ON THURSDAY WILL BE WARMER THAN WEDNESDAY
EVEN WITH MORE ABUNDANT CLOUDS...BUT STILL SLIGHTLY BELOW AVERAGE IN
THE LOW 20S TO NEAR 30.

SOUTHERLY WINDS AND WARMING MID LEVEL TEMPERATURES WILL POTENTIALLY
TO TRAP LOW LEVEL MOISTURE ACROSS THE BULK OF THE FORECAST AREA AS
AN UPPER TROUGH EMERGES FROM THE NORTHERN ROCKIES AND SWINGS THROUGH
THE NORTHERN PLAINS. THIS SHOULD ALLOW LOW LEVEL CLOUDS TO BLANKET
THE FORECAST AREA INTO AT LEAST FRIDAY NIGHT. A WIND SHIFT MAY HELP
BREAK UP THE CLOUDS IN OUR WEST ON SATURDAY...BUT THE EASTERN HALF
IS LESS CERTAIN. NOT LOOKING LIKE MUCH IN THE WAY OF MEASURABLE
PRECIPITATION CHANCES WITH WEAK SPLIT FLOW SO WILL LEAVE FORECAST
DRY. TEMPERATURES WILL CREEP TO RIGHT AROUND FREEZING IN OUR SOUTH
FRIDAY AND IMPROVE ACROSS THE BOARD A FEW MORE DEGREES ON SATURDAY.

MODEL CONFIDENCE LOWERS AT THE START OF NEXT WEEK WITH THE TIMING
AND TRACK OF A SHORTWAVE TRACKING THROUGH THE PLAINS SUNDAY. THE
ECMWF BRINGS THE WAVE ACROSS THE FORECAST AREA WHILE THE GFS AND GEM
SPLIT IT AROUND THE AREA TO THE NORTH AND SOUTH RESPECTIVELY. A MORE
SUBSTANTIAL WAVE DIGS INTO THE PLAINS ON MONDAY OR MONDAY
NIGHT...WITH THE ECMWF QUITE A BIT FASTER THAN THE GFS. WITH SOME
TIMING CONCERNS WILL KEEP CHANCES LOW. TEMPERATURES LOOK TO BE WARM
ENOUGH MONDAY FOR BOTH RAIN AND SNOW MENTION.

&&

.AVIATION...(FOR THE 00Z TAFS THROUGH 00Z WEDNESDAY EVENING)
ISSUED AT 505 PM CST TUE DEC 16 2014

ALL THREE TERMINALS ARE IN A BIT OF A VOID WHEN IT COMES TO CLOUD
COVER THIS EVENING. WIDESPREAD STRATUS CONTINUES TO LINGER WEST OF
THE MISSOURI RIVER...WITH MORE SCATTERED STRATUS ALONG THE EASTERN
EDGE OF SOUTH DAKOTA. MODELS A BIT UNSURE AS FAR AS WHERE THIS
CLOUD COVER WILL REMAIN OVERNIGHT. PREVAILING LIGHT NORTH TO
NORTHEAST WIND FETCH IN THE CLOUD BEARING LAYER MAY TRY TO ADVECT
A BIT OF THIS STRATUS INTO THE TERMINALS OVERNIGHT...BUT REALLY
UNCERTAIN AS TO HOW FAR WEST THIS CLOUD COVER WILL REACH. FOR
NOW...WILL BE OPTIMISTIC AND WATCH TRENDS.

WINDS WILL REMAIN LIGHT THROUGH MUCH OF WEDNESDAY AS SURFACE
RIDGING SLIDES THROUGH THE REGION.

&&

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

$$

SHORT TERM...CHENARD
LONG TERM...
AVIATION...DUX


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