555
FXUS63 KFSD 031113
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
613 AM CDT SAT MAY 3 2025
KEY MESSAGES
- PATCHY AND MOSTLY SHALLOW FOG HAS DEVELOPED THIS MORNING,
MAINLY IN RIVER VALLEYS AND OTHER LOW LYING AREAS. VISIBILITY
MAY BRIEFLY DROP BELOW ONE MILE.
- PATCHY AREAS OF FROST THIS MORNING AS TEMPERATURES DROP INTO
THE LOWER TO MID 30S. GREATEST FROST RISK REMAINS ALONG AND
EAST OF I- 29.
- MOSTLY DRY CONDITIONS PERSIST THROUGH NEXT WEEK WITH ONLY LOW
CHANCES (< 30%) FOR RAIN RETURNING MID WEEK. NEAR TO ABOVE
AVERAGE TEMPERATURES PREVAIL.
UPDATE
ISSUED AT 606 AM CDT SAT MAY 3 2025
PATCHY AND MOSTLY SHALLOW FOG HAS DEVELOPED IN RIVER VALLEYS AND
OTHER LOW LYING AREAS OVER THE LAST HOUR OR SO. EXPECT THIS TO
CONTINUE THROUGH THE MID MORNING HOURS. VISIBILITY MAY BRIEFLY
DROP BELOW ONE MILE. IF TRAVELING, BE PREPARED FOR QUICKLY
CHANGING CONDITIONS.
DISCUSSION
ISSUED AT 309 AM CDT SAT MAY 3 2025
NOW-MONDAY: SURFACE HIGH PRESSURE IS KEEPING SKIES CLEAR AND WINDS
CALM TO LIGHT SO FAR THIS MORNING. A FEW LOCATIONS THROUGH 3 AM CDT
HAVE ALREADY DROPPED INTO THE MID 30S WHERE WINDS ARE CALM, AND
EXPECT TEMPERATURES TO DROP A FEW MORE DEGREES BEFORE DAYBREAK. THIS
WILL LIKELY LEAD TO PATCHY FROST DEVELOPMENT WITH DEW POINTS ALSO IN
THE LOWER TO MID 30S. GREATEST RISK IS ALONG AND EAST OF I-29.
OMEGA BLOCK PATTERN BEGINS TO BUILD TODAY, WITH MID/UPPER LEVEL LOW
DEEPENING OVER THE SOUTHWEST AND ANOTHER LOW SPINNING TO OUR
SOUTHWEST AND OUR SOUTHEAST, PLACING US IN THE DEVELOPING RIDGE.
TODAY BRINGS LIGHT AND VARIABLE WINDS AS SURFACE HIGH PRESSURE
SLIDES THROUGH DURING THE DAY. EXPECT PLENTIFUL SUNSHINE WITH HIGHS
IN THE MID 60S EAST OF MN/IA STATE HWY 60 TO THE LOWER 70S IN THE
JAMES RIVER VALLEY. ALTHOUGH SKIES REMAIN CLEAR TONIGHT, SOUTHERLY
WINDS SHOULD KEEP TEMPERATURES A BIT MORE MILD - LOWS IN THE LOWER
TO MID 40S.
RAISED HIGHS A COUPLE OF DEGREES FOR SUNDAY. TEMPERATURES AT 925MB
AND 850MB ARE BOTH PROGGED TO BE WARMER THAN TODAY, AND BETWEEN
MIXING AND SOUTHERLY FLOW, THINK THAT WE'LL WARM INTO THE MID AND
UPPER 70S FOR MOST PLACES. SKIES REMAIN MOSTLY CLEAR AS WE REMAIN
UNDER HIGH PRESSURE. HOWEVER, TIGHTENING SURFACE PRESSURE GRADIENT
WILL LEAD TO BREEZIER SOUTHERLY WINDS - ESPECIALLY WEST OF I-29
WHERE THE GRADIENT IS MOST COMPRESSED. WINDS MAY GUST TO 30 MPH IN
THIS AREA SUNDAY. LOWS REMAIN NEAR AVERAGE, IN THE MID 40S.
MOST OF THE SAME FOR MONDAY, ALTHOUGH WE BEGIN TO SEE A BREAKDOWN OF
THE OMEGA BLOCK PATTERN LATER IN THE DAY AND SURFACE LOW PRESSURE
EJECTS INTO THE WESTERN DAKOTAS. WARMER AND BREEZY CONDITIONS
PREVAIL MONDAY WITH HIGHS IN THE 70S AND WIND GUSTS TO 30 MPH. LOWS
REMAIN WARM - IN THE MID/UPPER 40S.
TUESDAY-NEXT WEEKEND: BY MID WEEK, REX BLOCK PATTERN TAKES HOLD OVER
THE PLAINS STATES, WITH LOW PRESSURE CENTERED OVER THE SOUTHERN
PLAINS AND ACROSS EASTERN MT AND HIGH PRESSURE TO OUR NORTHEAST.
WITH THE MAIN LOW FURTHER SOUTH, PRECIPITATION CHANCES REMAIN LOW
FOR OUR AREA (LESS THAN 30%). CHANCES FOR MORE THAN A TENTH OF AN
INCH OF PRECIPITATION CONTINUE TO TREND DOWNWARD, TO 25% OR LESS
(WITH THE HIGHEST PROBABILITY FOR THE MO RIVER VALLEY INTO THE US
HWY 20 CORRIDOR). TEMPERATURES THROUGH THIS PERIOD REMAIN ABOVE
AVERAGE. WARMEST TEMPERATURES ARE EXPECTED TOWARD THE END OF NEXT
WEEK AND TO START NEXT WEEKEND WHEN MID AND UPPER LEVEL RIDGING
SLIDES EAST.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 606 AM CDT SAT MAY 3 2025
PATCHY AND PREDOMINANTLY SHALLOW FOG HAS DEVELOPED THIS MORNING
IN RIVER VALLEYS AND OTHER LOW LYING AREAS. CONDITIONS HAVE BEEN
RAPIDLY CHANGING, WITH KSUX BOUNCING BETWEEN VFR, IFR, AND LIFR
CONDITIONS OVER THE COURSE OF 25 MINUTES. GIVEN THIS AND THE
PATCHY NATURE, CONFIDENCE IS TOO LOW TO MENTION AT KFSD OR KHON,
BUT COULD SEE BRIEF VISIBILITY RESTRICTIONS HERE IF FOG
DEVELOPS. ANY FOG SHOULD MIX OUT BY 14-15Z.
OTHERWISE, LIGHT WINDS AND MOSTLY CLEAR SKIES (VFR CONDITIONS)
PREVAIL THROUGH THE PERIOD.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
UPDATE...SG
DISCUSSION...SG
AVIATION...SG
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