Area Forecast Discussion
Issued by NWS Sioux Falls, SD

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000
FXUS63 KFSD 201737
AFDFSD

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1137 AM CST THU NOV 20 2014

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 300 AM CST THU NOV 20 2014

BAND OF STRATUS IS CURRENTLY FILLING IN...EXTENDING RIGHT ALONG THE
MISSOURI RIVER VALLEY. THE QUESTION IS HOW LONG THESE CLOUDS WILL
REMAIN OVER THAT AREA...AND WILL THEY EXPAND FURTHER OR DISSIPATE.
THEY APPEAR TO BE ALONG A WEAK VORT FILAMENT...AND THERE IS A WEAK
SHORT WAVE PASSING ACROSS LOCATIONS TO THE NORTHEAST OF OUR AREA.
FURTHERMORE...A BAROCLINIC ZONE MARKING A WARM FRONT ALOFT NEAR 900-
850MB IS EVIDENT...AND THAT IS WHERE THE CLOUDS ARE BASED. EXCEPT
FOR THE RAP13...ALL INDICATIONS ARE FROM OTHER MODELS IS THAT THE
STRATUS WILL GRADUALLY ERODE THROUGH THE MORNING HOURS. OVER SNOW
COVER THAT SCENARIO CAN BE PROBLEMATIC...ESPECIALLY WITH LIGHT WINDS
AS WE WILL HAVE TODAY. BUT THE STRATUS IS ALSO NOT VERY THICK. SO IT
IS A TOUGH CALL. FOR NOW...LINGERED STRATUS CLOSE TO OUR MO RIVER
COUNTY ZONES FOR MUCH OF THE MORNING...BUT THEN CLEARED IT OUT FOR
THE AFTERNOON HOURS AFTER RETURN FLOW BEGINS FOR THOSE AREAS.

WITH SURFACE HIGH PRESSURE FIRMLY MOVING ACROSS OUR AREA TODAY...
WINDS WILL BE LIGHT...NOT AIDING THE MIXING PROCESS MUCH OVER THE
SNOW COVER. THEREFORE HIGHS CHANGED VERY LITTLE FOR TODAY GIVEN THE
LATEST DATA...RANGING FROM THE UPPER 20S CLOSEST TO THE WARM FRONT
IN GREGORY COUNTY...TO THE MID TEENS NEAR BROOKINGS AND MUCH OF
SOUTHWEST MN. TONIGHT IS A DIFFERENT STORY AS THE ENTIRE FORECAST
AREA WILL RECEIVE A SOUTH TO SOUTHEAST FLOW OF AIR. THE QUESTION
REMAINS IS HOW FAR OUR EASTERN ZONES TEMPERATURES WILL FALL DURING
THE EVENING BEFORE STEADYING OUT. WENT WITH THE COLDEST GUIDANCE
READINGS GENERALLY ALONG AND EAST OF THE I 29 CORRIDOR DUE TO VERY
LIGHT WINDS IN THE EVENING. WEST OF I 29...CONSENSUS BIAS CORRECTED
RAW VALUES LOOKED ON TARGET. AT ANY RATE...IT IS LIKELY THAT ALL
LOCATIONS IN OUR FORECAST AREA WILL HAVE SLOWLY RISING TEMPERATURES
FROM AROUND MIDNIGHT ONWARD.

.LONG TERM...(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 300 AM CST THU NOV 20 2014

WHILE THE GFS IN PARTICULAR SEEMS TO OVERDO THE LOW LEVEL MOISTURE
FIELDS WITH THE WAA FRIDAY...MODELS INDICATE AN AREA OF HIGH LEVEL
MOISTURE SIGNIFICANT ENOUGH TO PRODUCE DENSE HIGH CLOUDS SPREADING
AND MOVING OVER THE AREA. THUS...WHILE THE LEVEL OF THE CLOUD COVER
IS IN DOUBT...WILL KEEP A LOT OF CLOUDS FOR FRIDAY. FRIDAY NIGHT
SHOULD SEE MOST OF THIS HIGH LEVEL MOISTURE PASS ON...BUT LOW CLOUDS
SHOULD INCREASE OVER THE SOUTHEAST AND LINGER SATURDAY. THERE ARE A
LOT OF QUESTIONS STILL ABOUT THE NORTHWEST EXTENT OF THIS MOISTURE
AND FEEL AT THIS TIME OF YEAR THE MODELS COULD EVEN BE UNDERDOING IT
ALONG WITH A LITTLE TOO MUCH LOW LEVEL WARMING. HOWEVER FOR NOW WILL
KEEP MOST OF THE CLOUDS FOR FRIDAY NIGHT AND SATURDAY IN THE
SOUTHEAST.

WINDS FRIDAY WILL INCREASE ESPECIALLY EAST. AT THIS TIME DO NOT
THINK IT WILL GET WINDY ENOUGH FOR BLOWING SNOW...GIVEN THE
INCREASING AGE OF THE SNOW COVER AND NO NEW SNOW. THESE WINDS SHOULD
BE SOMEWHAT LESS BY SATURDAY.

TEMPERATURES WILL BE WARMING REGARDLESS OF THE EXTENT OF THE CLOUD
COVER. GIVEN THE SOUTHERLY BREEZE...WARMING WITH IT...AND THE SNOW
COVER...WE ARE POINTING TO A LOW DIURNAL RANGE WITH HIGHS GETTING
INTO THE 30S TO LOW 40S...AND LOWS WARMING TO THE 20S TO LOW 30S.
SOME AREAS OF FOG WOULD NOT BE OUT OF THE QUESTION SATURDAY NIGHT
WITH THE CONTINUING LOW LEVEL MOISTURE INCREASE AND WINDS SLACKING
OFF SOME...BUT WILL NOT PUT IN AT THIS TIME.

THE EXTENDED PERIOD SUNDAY THROUGH WEDNESDAY WILL BRING COOLER
WEATHER AGAIN...THOUGH NOT AS COLD AS SOME RECENT DAYS. TIMING
STRENGTH AND PATH OF DIGGING WAVES BY LATE IN THE WEEKEND ARE NOT
TOGETHER ENOUGH TO BRING A THREAT OF MUCH SNOW TO THIS AREA SUNDAY
NIGHT AND MONDAY...BUT SOME LIGHT SNOW ON THE BACK SIDE OF THE
SYSTEM IS QUITE POSSIBLE. AM KEEPING A LESSER MENTION OF BLOWING
SNOW WITH THESE CHANCE POPS AS IT IS BECOMING EVIDENT THAT THERE WILL
NOT BE QUITE ENOUGH WIND TO BLOW THE CURRENT SNOW AROUND AS IT
CONTINUES TO AGE AND ENDURE SOME LIKELY TEMPERATURES ABOVE FREEZING.
YES IT WILL GET WINDY DURING THIS TIME...JUST NOT ENOUGH. TUESDAY
AND WEDNESDAY ARE FORECAST TO BE MODESTLY COLD. THE WEDNESDAY/
THURSDAY SNOW THREAT FROM A NORTHERN ROCKIES WAVE IS STILL VERY
UNCERTAIN ON TIMING AND STRENGTH...WILL KEEP POPS OUT FOR WEDNESDAY
DAYTIME WITH THE MODEL TREND SHIFTING TO A LITTLE LATER TIMING...
THURSDAY IS STILL JUST BEYOND THE FORECAST PERIOD.

&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1135 AM CST THU NOV 20 2014

BAND OF STRATUS EXPECTED TO HANG TOUGH THROUGHOUT THE AFTERNOON
HOURS ALONG THE MISSOURI VALLEY...EXPANDING THROUGH THE OVERNIGHT
HOURS. MVFR TO HIGH END IFR CEILINGS ARE EXPECTED TO DEVELOP
OVERNIGHT TONIGHT...AND PERSIST THROUGH THE DAY ON FRIDAY.

&&

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

$$

SHORT TERM...MJ
LONG TERM...
AVIATION...



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