986
FXUS63 KFSD 251816
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
1216 PM CST THU DEC 25 2025
KEY MESSAGES
- DENSE FOG ADVISORY EXTENDED THROUGH 15Z FRIDAY MORNING. NOT
MUCH IMPROVEMENT EXPECTED THROUGH THEN, EXCEPT A BIT THIS
AFTERNOON.
- WITH TEMPERATURES NEAR TO JUST BELOW FREEZING, FREEZING FOG
AND PATCHY FREEZING DRIZZLE COULD RESULT IN SLICK SPOTS ON
UNTREATED AND ELEVATED SURFACES THIS MORNING. USE EXTRA
CAUTION ON THE ROADS AND CHECK CONDITIONS BEFORE TRAVELING.
- ABOVE NORMAL TEMPERATURES THROUGH SATURDAY TURN SHARPLY COLDER
SUNDAY ACCOMPANIED BY NORTHWEST WINDS GUSTING 30 TO 45 MPH.
SUB-ZERO WIND CHILLS ARE EXPECTED SUNDAY NIGHT-EARLY MONDAY.
- AREAS OF LIGHT SNOW OR FLURRIES COULD ACCOMPANY THE COLDER
AIR ON SUNDAY. LIGHT SNOW ACCUMULATIONS ARE POSSIBLE, WITH
AREAS OF BLOWING SNOW IF ACCUMULATIONS APPROACH AN INCH OR
MORE.
UPDATE
ISSUED AT 1212 PM CST THU DEC 25 2025
GIVEN THE LATEST MODEL SOUNDINGS WENT AHEAD AND EXTENDED THE
DENSE FOG ADVISORY FOR MOST AREAS EAST OF THE JAMES RIVER
THROUGH FRIDAY MORNING. WHILE WE WILL LIKELY SEE SOME
IMPROVEMENT IN THE VISIBILITY THIS AFTERNOON, THE VISIBILITY
WILL LIKELY DROP QUICKLY AFTER SUNSET AGAIN THIS EVENING AND NOT
SEE MUCH IMPROVEMENT UNTIL TOMORROW MORNING.
DISCUSSION
ISSUED AT 310 AM CST THU DEC 25 2025
DENSE FOG AND POTENTIAL DRIZZLE ARE THE MAIN CONCERNS OVER THE
NEXT 24-30 HOURS. AWOS/ASOS VISIBILITY HAS BEEN VARYING FROM 1/4
MILE TO OVER 1 MILE THROUGHOUT THE NIGHT, AND AREA WEB CAMS SHOW
SIMILAR VARIABILITY. ALTHOUGH VARIABLE, COVERAGE OF 1/2 MILE OR
LOWER VISIBILITY IS SUFFICIENT TO MAINTAIN A DENSE FOG ADVISORY
ACROSS THE AREA THIS MORNING. PREVIOUSLY EXTENDED THE EXPIRATION
THROUGH NOON CST, THOUGH THERE ARE INDICATIONS THAT AREAS NEAR
TO WEST OF THE JAMES RIVER VALLEY MAY BE CANCELLED EARLY AS A
MORE WESTERLY COMPONENT TO WINDS ABOVE THE BOUNDARY LAYER MAY
HELP TO MIX SOME DRIER AIR THROUGH THE SHALLOWER FOG/STRATUS.
UNFORTUNATELY, THIS MIXING DOES NOT APPEAR TO REACH AREAS EAST
OF I-29, ESPECIALLY THOSE AREAS IN NORTHWEST IOWA WHERE MELTING
SNOW WILL CONTINUE TO ADD MOISTURE TO THE BOUNDARY LAYER THROUGH
THE DAY AS DEW POINTS IN THE MID 30S TO NEAR 40 EXPAND NORTH.
ALTHOUGH SLIGHT IMPROVEMENT IN VISIBILITY IS EXPECTED ACROSS THE
FORECAST AREA THIS AFTERNOON, SOME AREAS MAINLY EAST OF I-29
COULD QUICKLY SEE DENSE FOG REDEVELOP AFTER SUNSET. LATER SHIFTS
MAY HAVE TO CONSIDER AN ADDITIONAL DENSE FOG ADVISORY.
WHILE CONFIDENCE IN FOG IS FAIRLY HIGH, CONFIDENCE IN DRIZZLE IS
LESS SO. DID CUT BACK ON COVERAGE OF DRIZZLE CHANCES, HOWEVER
WHETHER MOISTURE DEPOSITING ON SURFACES IS FROM DRIZZLE OR JUST
DENSE FOG, THE NET EFFECT WOULD BE THE SAME. THAT IS, UNTREATED
OR ELEVATED SURFACES BELOW FREEZING (MORE LIKELY NEAR/NORTH OF
I-90 THROUGH MID-MORNING) COULD STILL SEE SLICK SPOTS DEVELOP,
SO THOSE WITH EARLY MORNING TRAVEL PLANS WILL WANT TO MONITOR
ROAD CONDITIONS AND PLAN ACCORDINGLY. THAT SAID, AS LOW LEVEL
WINDS TURN MORE TO THE SOUTHEAST THIS MORNING, WE SHOULD SEE
INCREASING DEW POINTS PUSH NORTHWARD. WHILE THIS MOISTURE COULD
INITIALLY LEAD TO PAVEMENT FROST AS IT MOVES OVER SUB-FREEZING
ROADWAYS, IT WILL ALSO HELP PUSH TEMPERATURES ABOVE FREEZING BY
LATE THIS MORNING, EVEN AS FAR NORTH AS THE HIGHWAY 14 CORRIDOR.
OVERALL, WHILE THIS MOISTURE WILL REINFORCE THE FOG/LOW STRATUS
POTENTIAL IN OUR EAST, IT SHOULD LESSEN THE POTENTIAL FOR LIGHT
ICING AS WE PROGRESS THROUGH THE MORNING.
A WEAK WAVE AND ASSOCIATED SURFACE BOUNDARY MOVE EAST ACROSS THE
FORECAST AREA TONIGHT. MOISTURE ABOVE THE STRATUS IS SPARSE, BUT
SHOULD SEE A BAND OF MID-LEVEL CLOUDS ACCOMPANY THE WAVE. WHILE
CHANCES ARE LOW (<20%), WE COULD SEE A FEW SPRINKLES/LIGHT RAIN
SHOWERS NORTH OF I-90 TONIGHT. TEMPERATURES/DEW POINTS WILL BE
ABOVE FREEZING WHILE ANY LIGHT RAIN IS FALLING, BUT MAY HAVE TO
WATCH FOR REFREEZE OF ANY WET SURFACES AS TEMPERATURES FALL BACK
BELOW FREEZING FRIDAY MORNING. A DRIER WESTERLY FLOW BEHIND THIS
WAVE SHOULD HELP ERODE ANY LINGERING FOG BY LATE MORNING-MIDDAY
FRIDAY, WITH HIGH TEMPERATURES EXPECTED TO RETURN TO THE 40S AND
50S AS WE CLOSE OUT THE HOLIDAY WEEK.
A STRONGER WAVE AND SHARP COLD FRONT PUSH SOUTHEAST ACROSS THE
REGION SATURDAY NIGHT INTO SUNDAY, WHICH WILL LIKELY RESULT IN
MIDNIGHT HIGH TEMPERATURES IN THE 30S, WITH READINGS QUICKLY
FALLING INTO THE 20S AND EVEN TEENS BY MID-MORNING SUNDAY.
MODELS ARE SHOWING DECENT AGREEMENT IN THE TIMING OF THE COLD
FRONT, ALONG WITH A LOW-MODERATE (30-50%) CHANCE OF MEASURABLE
PRECIPITATION (SNOW) IN THE POST-FRONTAL COLD AIR LATE SATURDAY
NIGHT AND SUNDAY. STILL SOME UNCERTAINTY ON HOW MUCH SNOW MAY
FALL, BUT CHANCES ARE CURRENTLY LOW (20% OR LESS) THAT WE'LL SEE
AN INCH OF ACCUMULATION. HOWEVER, IT SHOULD BE NOTED THAT IF
THIS LOWER PROBABILITY SCENARIO MATERIALIZES, NORTHWEST WINDS
GUSTING 30 TO 45 MPH COULD CAUSE AREAS OF BLOWING SNOW WHICH
COULD FURTHER SLOW TRAVEL ON SUNDAY.
THE COLDEST AIR BRIEFLY SETTLES INTO THE AREA BY MONDAY MORNING
WHEN WIND CHILLS IN THE SINGLE DIGITS TO TEENS BELOW ZERO ARE
MOST LIKELY. HIGHS MONDAY REMAIN IN THE TEENS AND 20S, BUT THIS
COOLDOWN WILL BE SHORT-LIVED WITH TEMPERATURES NEAR TO ABOVE
NORMAL RETURNING MID-WEEK AS WE TRANSITION TOWARD 2026.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 1057 AM CST THU DEC 25 2025
THE CHALLENGE FOR THIS TAF PERIOD WILL BE THE FIRST HALF AND
JUST HOW MUCH IMPROVEMENT WE SEE BEFORE THE WEAK FRONTAL PASSAGE
OVERNIGHT. THE LATEST MODEL SOUNDINGS FROM THE RAP/HRRR/NAM ALL
SUGGEST MAINTAINING IFR OR LOWER CONDITIONS UNTIL THIS FRONTAL
PASSAGE MOVES THROUGH, WHICH WOULD KEEP THESE LOWER CONDITIONS
IN THROUGH LATE TONIGHT NEAR AND EAST OF I-29. WHILE THERE COULD
BE SOME IMPROVEMENT TODAY, IT WILL LIKELY NOT LAST LONG. THE
EXCEPTION COULD BE NEAR AND WEST OF THE JAMES RIVER WHERE SOME
IMPROVEMENT ABOVE IFR IS LIKELY LATE AFTERNOON INTO THE EVENING,
BUT THEN AS THE WINDS GO LIGHT LATE TONIGHT BEHIND THIS WEAK
FRONT IFR CONDITIONS WILL AGAIN BE POSSIBLE. ALL IN ALL THE MAIN
MESSAGE WILL BE A CHALLENGE TO IMPROVE THROUGH THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...DENSE FOG ADVISORY UNTIL 9 AM CST FRIDAY FOR SDZ039-040-055-
056-061-062-066-067-069>071.
MN...DENSE FOG ADVISORY UNTIL 9 AM CST FRIDAY FOR MNZ071-072-080-
081-089-090-097-098.
IA...DENSE FOG ADVISORY UNTIL 9 AM CST FRIDAY FOR IAZ001>003-
012>014-020>022-031-032.
NE...DENSE FOG ADVISORY UNTIL 9 AM CST FRIDAY FOR NEZ013-014.
UPDATE...08
DISCUSSION...JH
AVIATION...08
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