Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 142055
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
255 PM CST SUN FEB 14 2016

.SHORT TERM...(THIS EVENING THROUGH MONDAY)
ISSUED AT 255 PM CST SUN FEB 14 2016

A COUPLE OF RELATIVELY MINOR CONCERNS FOR TONIGHTS FORECAST. THE
FIRST DEALS WITH THE STUBBORN LOW LEVEL MOISTURE WHICH PERSISTED
OVER MOST OF THE CWA THROUGHOUT THE DAY. WEAK FLOW EAST OF A STOUT
LOW LEVEL THERMAL BOUNDARY NEAR/JUST EAST OF THE MISSOURI RIVER
VALLEY HAS BEEN UNABLE TO SCOUR THE LOW LEVEL MOISTURE...AND AS A
RESULT NUMEROUS MODELS POINTING TO POTENTIAL FOR FOG DEVELOPMENT AS
WE MOVE THROUGH THE EVENING. MAIN FOCUS LOOKS TO BE WEST OF I-29 IN
THE EVENING...ALONG/JUST AHEAD OF SHIFT TO MORE WESTERLY FLOW...THEN
TRANSITIONING TO AREAS ALONG AND EAST OF I-29 DURING THE LATTER HALF
OF THE NIGHT/EARLY MONDAY. EXCEPTION WILL BE FAR NORTHEAST CWA WHERE
DOWNSLOPE FLOW WILL LIMIT FOG/LOW STRATUS.

OTHER ITEM OF NOTE FOR TONIGHT IS A SUBTLE WAVE DROPPING SOUTHEAST
FROM EASTERN MONTANA...THROUGH WESTERN/SOUTH CENTRAL SD INTO EASTERN
NEBRASKA OVERNIGHT. MOISTURE DEPTH SOMEWHAT LIMITED...BUT FORECAST
SOUNDINGS DO SHOW 2-3 HOUR WINDOW FOR LOCATIONS ALONG THE MISSOURI
RIVER VALLEY WHERE IT MAY BE SUFFICIENT TO ALLOW VERY LIGHT PRECIP
REACH THE SURFACE. UNFORTUNATELY...THOSE SOUNDINGS ALSO SHOW A WARM
LAYER DEVELOP AHEAD OF THE WAVE BELOW 850MB...AND WILL CONTINUE TO
CARRY A MIX OF PRECIP TYPES AS THE WAVE SCOOTS THROUGH TONIGHT. ANY
PRECIP SHOULD BE SOUTH OF THE CWA WELL BEFORE DAYBREAK. TEMPERATURES
TONIGHT WILL MOVE LITTLE UNDER THE STRATUS ACROSS THE EASTERN AREAS
OF THE CWA...WHILE OUR FAR SOUTHWEST CORNER DROPS BACK TO JUST BELOW
FREEZING.

MONDAY EXPECT THE LOW LEVEL BOUNDARY TO MAKE A BETTER PUSH TO THE
EAST...WITH DEEPER WESTERLY FLOW SCOURING OUT ANY STRATUS/FOG FROM
WEST TO EAST THROUGH THE DAY. ATTENTION THEN TURNS TO NEXT WAVE
WHICH WILL LARGELY IMPACT THE FORECAST AREA AFTER SUNSET. WITH THE
WESTERLY FLOW...TEMPERATURES CONTINUE TO LOOK MILD...WITH FORECAST
HIGHS FROM THE MID 30S NORTHEAST TO MID 40S IN SOUTH CENTRAL SD.


.LONG TERM...(MONDAY NIGHT THROUGH SUNDAY)
ISSUED AT 255 PM CST SUN FEB 14 2016

MODELS SEEM FAIRLY CONSISTENT WITH THE NORTHWESTERLY WAVE COMING IN
QUICKLY MONDAY NIGHT. THE DYNAMICS WITH THIS CLIPPER APPEAR STRONGER
BUT THE THERMAL SUPPORT/FRONTOGENESIS LOOKS WEAKER AND PRECIPITATION
POTENTIAL IS MODEST. ONE BIG DIFFERENCE RELATES TO PRECIPITATION
TYPE WITH FAIRLY WARM AIR OVER MUCH OF THE AREA AT THE START BEING
REPLACED BY COLDER AIR AS THE SOUTHEAST MOVING SYSTEM SPEEDS BY. WE
THEREFORE HAVE AN ASSORTMENT OF RAIN AND FREEZING RAIN BECOMING SNOW
AS THE COLD AIR ARRIVES...OR AT LEAST WHERE IT ARRIVES BEFORE THE
PRECIPITATION ENDS FROM THE WEST. SO...WE ARE LOOKING AT AN INCH OR
TWO FROM A DE SMET/FSD/SLB LINE AND NORTHEAST. EXPECT THE
PRECIPITATION TO END BY THE END OF THE NIGHT...THAT IS 12Z/6AM
TUESDAY.

ANOTHER DIFFERENCE FROM YESTERDAYS SYSTEM IS THE WINDS WHICH WILL BE
TAME AT THE START AND BECOME STRONG NORTHWESTERLY FOR A WHILE AS THE
SURFACE LOW PASSES BY. THE STRONGEST WINDS WILL CORRESPOND WITH THE
STRONG PRESSURE RISES AND WILL BE FROM THE LATTER PART OF
ACCUMULATIONS LATE MONDAY NIGHT INTO THE EARLY MORNING DAYLIGHT
HOURS OF TUESDAY...AFTER WHICH THEY SHOULD SLOWLY BUT STEADILY EBB.
HAVE GONE WITH SOME MENTION OF BLOWING SNOW AND KEPT IT IN THE ABOVE
MENTIONED AREA OF ACCUMULATIONS...LINGERING IT INTO LATE MORNING...
EXCEPT TO THE EARLY AFTERNOON IN PART OF NORTHWEST IOWA WHERE THE
DECENT WINDS WILL LAST THE LONGEST. AT THIS TIME THE BLOWING SNOW
THREAT IS NOT GREAT ENOUGH FOR A HIGHLIGHT IN THE FORM OF A WATCH OR
ADVISORY.

TEMPERATURES WILL COOL MODESTLY BEHIND THIS SYSTEM FOR TUESDAY AND
REMAIN MODESTLY COOL WEDNESDAY AS BACK DOOR HIGH PRESSURE SLIDES
SOUTHEAST TO THE NORTHEAST OF OUR AREA. CLOUDS IN THE MID LEVEL
FRONTOGENETICAL BAND OVER THE AREA WILL INCREASE AS THIS HIGH
APPROACHES AND WILL KEEP A LITTLE CHANCE OF LIGHT SNOW TUESDAY NIGHT
NORTH AND EAST...BUT WITH NO REAL DYNAMIC SUPPORT...IT DOES NOT SEEM
MORE THAN A LITTLE CHANCE. THESE CLOUDS SHOULD DECREASE SLOWLY
WEDNESDAY.

THURSDAY WILL BRING DECENT WARMING AND PARTLY TO MOSTLY CLOUDY
SKIES. THE VERY STRONG WARMING WITH THE UPPER RIDGING SHOULD WORK
WITH THE INCREASING FEBRUARY SOLAR ANGLE TO PUSH TEMPERATURES INTO
THE 40S OVER THE SNOW COVER NORTHEAST...WITH 50S SOUTHWEST.

A WAVE PASSING FRIDAY COULD BRING A FEW LIGHT SHOWERS WITH
CONTINUED VERY MILD TEMPERATURES...THEN THE WEEKEND SHOULD BE DRY
WITH A WEAK COOLING TREND...TO LESS ABOVE NORMAL...BEHIND THIS
SYSTEM.


&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z MONDAY AFTERNOON)
ISSUED AT 1134 AM CST SUN FEB 14 2016

MVFR-LOCALLY IFR CONDITIONS WILL PERSIST OVER MUCH OF THE FORECAST
AREA THROUGH TONIGHT...EAST OF A WEAK THERMAL BOUNDARY SEPARATING
SEASONALLY COOL AIR TO THE EAST FROM MUCH MORE MILD AIR TO THE
WEST. GENERAL IMPROVEMENT EXPECTED WEST TO EAST LATE TONIGHT AND
MONDAY MORNING AS BOUNDARY BEGINS TO MAKE A PUSH EASTWARD.


&&

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

$$

SHORT TERM...JH
LONG TERM...
AVIATION...JH


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