791
FXUS63 KFSD 071139
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
539 AM CST FRI MAR 7 2025
KEY MESSAGES
- HEAVIER PRECIPITATION HAS SHIFTED TO ALONG/SOUTH OF US HIGHWAY
20, WITH LINGERING LIGHT SNOW ENDING FROM NORTH TO SOUTH THROUGH
EARLY AFTERNOON.
- WITH SOUTHWARD SHIFT OF HEAVIER SNOW, WINTER WEATHER ADVISORY
WILL END BY NOON FOR MOST AREAS, HOLDING UNTIL 3 PM FROM THE US
HIGHWAY 20 CORRIDOR TO STORM LAKE.
- MILD AND PLEASANT CONDITIONS RETURN THIS WEEKEND INTO EARLY
NEXT WEEK.
- WATCHING A POTENTIALLY IMPACTFUL SYSTEM POISED TO MOVE INTO THE
PLAINS LATE NEXT WEEK, BUT CONFIDENCE IS LOW IN DETAILS.
DISCUSSION
ISSUED AT 355 AM CST FRI MAR 7 2025
WHAT HAPPENED OVERNIGHT: LATE EVENING SAW 2 RELATIVELY DISTINCT
PRECIPITATION BANDS DEVELOP. THE FIRST BAND FOCUSED NEAR A WEAKER
MID LEVEL (~700MB) FRONT LIFTED A BIT FARTHER NORTH TOWARD THE
I-90 CORRIDOR BEFORE WEAKENING IN THE LAST HOUR OR TWO. A SECOND
BAND WHICH APPEARS WELL-TIED TO A STRONGER 700-600MB FRONTOGENETIC
ZONE HAS LARGELY REMAINED SOUTH OF THE SOUTH DAKOTA-NEBRASKA STATE
LINE AND EASTWARD ALONG US HIGHWAY 20 AS THE MAIN UPPER LOW SLIDES
EAST THROUGH NEBRASKA. ALONG WITH THE SOUTHWARD SHIFT OF THE BAND
OVERALL, SHALLOW WARM AIR, ESPECIALLY IN VALLEY LOCATIONS SUCH AS
KSUX/SIOUX CITY, HAS EVEN KEPT PORTIONS OF THIS BAND PRIMARILY
RAIN OVERNIGHT.
ALL OF THE ABOVE HAS LED TO LOWER SNOWFALL TOTALS TO THIS POINT
FOR MUCH OF THE AREA THAN WAS PREVIOUSLY EXPECTED. THE EXCEPTION,
OF COURSE, IS LOCATIONS TOWARD PORTIONS OF THE I-90 CORRIDOR WHERE
THE LEADING BAND PRODUCED A FEW HOURS OF HEAVIER SNOWFALL DURING
THE LATE EVENING AND EARLY OVERNIGHT HOURS. SNOWFALL HERE AT KFSD
THROUGH 3 AM WAS RIGHT AROUND 2 INCHES WITH REPORTS CLOSER TO 3"
ON THE SOUTH END OF SIOUX FALLS/HARRISBURG AREAS.
TODAY: AS THE AFOREMENTIONED UPPER LOW CONTINUES TO SLIDE EAST
INTO SOUTHERN IOWA, THE ASSOCIATED MID-LEVEL FRONT WHICH HAS BEEN
DRIVING THE PRECIPITATION ALONG HIGHWAY 20 WILL LIKEWISE SHIFT
EAST AND WEAKEN EARLIER THAN PREVIOUSLY THOUGHT. THIS SHOULD
ALLOW OUR LINGERING LIGHT SNOW TO END FROM NORTH-NORTHWEST TO
SOUTH-SOUTHEAST THROUGH MIDDAY, PERHAPS PERSISTING IN OUR FAR
SOUTHEAST (HIGHWAY 20 TO STORM LAKE) INTO THE EARLY AFTERNOON.
WITH SNOWFALL TOTALS LIMITED DURING THE OVERNIGHT AS DISCUSSED
ABOVE AND SNOWFALL TAPERING OFF A LITTLE EARLIER, OVERALL SNOW
TOTALS LOOK TO FALL BROADLY IN THE 2-4" RANGE IN AREAS SOUTH OF
I-90, WITH PORTIONS OF THE MISSOURI VALLEY HOLDING IN THE 1-2"
RANGE AT BEST GIVEN THE MUCH LATER CHANGEOVER FROM RAIN TO SNOW.
AS SUCH, HAVE SCALED THE WINTER STORM WARNING BACK TO A WINTER
WEATHER ADVISORY, AND ADJUSTED THE END TIMES EARLIER SO THE
FARTHER WEST/NORTH SECTION ENDS BY 9 AM, LOCATIONS FROM TYNDALL
AND YANKTON INTO MOST OF NORTHWEST IOWA END AT NOON, AND THE
HIGHWAY 20 CORRIDOR/BUENA VISTA COUNTY NOW END AT 3 PM.
CLEARING AFTERNOON SKIES AND A PUSH OF MORE MILD AIR ALOFT FROM
THE WEST WILL HELP TEMPERATURES CLIMB INTO THE LOWER-MID 40S ALONG
AND NORTH OF I-90 IN SD THIS AFTERNOON WITH MID-UPPER 30S EXPECTED
FOR HIGHS ELSEWHERE.
SATURDAY-MONDAY: WEAK TROUGHINESS/NORTHWEST FLOW ALOFT ON SATURDAY
WILL TRANSITION TO A WARM WESTERLY FLOW THROUGH THE WEEKEND AND
INTO EARLY NEXT WEEK. LOW LEVEL TEMPERATURES WARM SUBSTANTIALLY,
WITH 925MB TEMPERATURES PUSHING ABOVE 10C BY LATE SUNDAY INTO
MONDAY. WHILE OUR CURRENT SNOW COVER MAY INITIALLY LIMIT WARMING
IN SOME AREAS, THE PROBABILITY FOR HIGHS IN THE 60S GROWS TO OVER
70% INTO OUR SD COUNTIES ON SUNDAY, AND OVER MOST OF THE FORECAST
AREA BY MONDAY. LOCATIONS ALONG/WEST OF THE JAMES RIVER VALLEY
WILL SEE A MODERATE (>50%) CHANCE OF TOPPING 70F ON MONDAY.
THESE WARMING TEMPERATURES WILL ALSO BE WITHIN A RELATIVELY DRY
AIR MASS WITH BREEZY WEST-SOUTHWEST WINDS RESULTING IN WIDESPREAD
HIGH AND AREAS OF VERY HIGH GRASSLAND FIRE DANGER BY MONDAY.
TUESDAY ONWARD: A WEAK TROUGH AND ASSOCIATED COLD FRONT PUSH
THROUGH THE REGION MONDAY NIGHT, THOUGH LIMITED MOISTURE WILL
PRECLUDE ANY PRECIPITATION CHANCES. TEMPERATURES WILL MOVE CLOSER
TO SEASONAL NORMALS, THOUGH STILL SEVERAL DEGREES ABOVE NORMAL
WITH HIGHS IN THE 40S-LOWER 50S MIDWEEK.
A MUCH STRONGER TROUGH MOVES ACROSS THE ROCKIES NEXT THURSDAY,
WITH SOUTHERLY FLOW AHEAD OF THE TROUGH HELPING TEMPERATURES
REBOUND AGAIN LATE NEXT WEEK. FOR NOW, TIMING/LOCATION OF THE
TROUGH AND ITS LEAD WAVE LOOK SLOW ENOUGH TO KEEP THE FORECAST
DRY THROUGH THURSDAY. HOWEVER, PRECIPITATION CHANCES WILL BE ON
THE INCREASE JUST BEYOND THIS FORECAST PERIOD (THURSDAY NIGHT INTO
FRIDAY) AS THE TROUGH LIFTS OUT OF THE ROCKIES INTO THE PLAINS.
SIGNALS POINT TO A STRONGER SYSTEM, BUT THE FINER DETAILS OF
TIMING/STRENGTH/THERMAL PROFILE STILL VARY WIDELY AMONG THE BROAD
MODEL SPECTRUM, SO IT'S DIFFICULT TO PINPOINT ANY SPECIFICS ABOUT
PRECIPITATION TYPE OR AMOUNTS JUST YET.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 538 AM CST FRI MAR 7 2025
MVFR-IFR CEILINGS AND AREA OF MAINLY MVFR VISIBILITY IN LIGHT SNOW
ARE EXPECTED TO IMPROVE FROM NORTH TO SOUTH THROUGH THE DAY. AREAS
NEAR/SOUTH OF I-90 MAY SEE NORTHEAST TO NORTH WINDS OCCASIONALLY
GUST NEAR 20KT.
VFR CONDITIONS WILL PREVAIL FROM SUNSET THROUGH THE END OF THE
TAF PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR SDZ067>071.
WINTER WEATHER ADVISORY UNTIL 9 AM CST THIS MORNING FOR SDZ066.
MN...NONE.
IA...WINTER WEATHER ADVISORY UNTIL NOON CST TODAY FOR IAZ012>014-
020-021.
WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR
IAZ022-031-032.
NE...WINTER WEATHER ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR
NEZ013-014.
DISCUSSION...JH
AVIATION...JH
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