513
FXUS63 KFSD 040759
AFDFSD
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SIOUX FALLS SD
259 AM CDT SUN MAY 4 2025
KEY MESSAGES
- SEASONABLY MILD TEMPERATURES WILL DOMINATE THE WEEK AHEAD
WITH HIGHS MOSTLY IN THE 70S (A FEW LOCATIONS WILL SEE LOWER
80S BY THE END OF THE WEEK) AND LOWS IN THE 40S TO LOWER 50S.
- ALTHOUGH GRASSES ARE GREENING UP, LOCALIZED ELEVATED FIRE
DANGER IS EXPECTED TODAY AND MONDAY WHERE DRY GRASSES ARE
STILL MORE PREVALENT, MAINLY WEST OF I-29 WHERE AFTERNOON
WINDS WILL BE GUSTING 20-30 MPH.
- MOSTLY DRY CONDITIONS WILL PERSIST THROUGH THE WEEK, WITH
ONLY LOW (<30%) CHANCES OF LIGHT RAIN AROUND MIDWEEK.
DISCUSSION
ISSUED AT 259 AM CDT SUN MAY 4 2025
TODAY-MONDAY: DOMINANT OMEGA BLOCK WILL KEEP ANY SENSIBLE
WEATHER WELL AWAY FROM THE AREA EARLY THIS WEEK, WITH MOSTLY
CLEAR SKIES AND SEASONABLY MILD TEMPERATURES (HIGHS IN THE 70S
AND LOWS IN THE 40S). SURFACE HIGH PRESSURE RIDGE WILL NUDGE
EASTWARD, CENTERED FROM WESTERN IOWA INTO WISCONSIN. THIS WILL
KEEP LIGHT/VARIABLE WINDS OVER THE EASTERN PORTIONS OF THE AREA,
WHILE LOCATIONS WEST OF I-29 SEE BREEZY SOUTHEAST TO SOUTH
WINDS DEVELOP IN THE LATE MORNING/AFTERNOON HOURS. OCCASIONAL
AFTERNOON GUSTS 20-30 MPH IN THESE AREAS, COMBINED WITH LOW
HUMIDITY LEVELS OF 20-30% WILL RESULT IN ELEVATED FIRE DANGER
IN LOCALIZED AREAS WHERE DRIER/DORMANT GRASSES ARE STILL MORE
PREVALENT AND SUSCEPTIBLE TO FIRE STARTS AND SPREAD. OVERALL,
THOUGH, SATELLITE ESTIMATES INDICATE LOCATIONS WEST OF I-29,
AND ESPECIALLY WEST OF US HWY 81 (ARLINGTON TO YANKTON), HAVE
SEEN MORE WIDESPREAD GREEN-UP IN RESPONSE TO POCKETS OF HEAVIER
RAINFALL OVER THE PAST WEEK TO 10 DAYS. THIS SHOULD OFFSET THE
BREEZIER WINDS AND LIMIT FIRE DANGER FOR MUCH OF THE AREA.
TUESDAY-THURSDAY: THE PROMINENT OMEGA BLOCK OVER THE PLAINS
WILL GRADUALLY TRANSITION TO A REX BLOCK THROUGH THE MID-WEEK.
THE EASTERN TROUGH WILL LIFT INTO NEW ENGLAND AND THE EASTERN
CANADIAN PROVINCES, WHILE THE WESTERN UPPER LOW SLIDES INTO THE
CENTRAL PLAINS, UNDERCUTTING THE STRONG UPPER RIDGE WHICH WILL
REMAIN IN PLACE ACROSS THE NORTHERN PLAINS/WESTERN GREAT LAKES.
MUCH OF THE PRECIPITATION ASSOCIATED WITH THIS UPPER LOW WILL
REMAIN WELL SOUTH OF OUR FORECAST AREA. HOWEVER, THERE IS SOME
UNCERTAINTY REGARDING THE NORTHWARD EXTENT OF THE LIGHT RAIN
POTENTIAL OWING TO NORTH-SOUTH DIFFERENCES IN THE TRACK OF THE
LOW PRESSURE. THIS RESULTS IN LOW (<30%) CHANCES FOR LIGHT RAIN
FOR PORTIONS OF OUR AREA THROUGH THE MID-WEEK PERIOD.
THE FIRST LOW CHANCE WILL BE WEST OF THE JAMES RIVER VALLEY ON
TUESDAY, AS A SHORTWAVE ROTATES NORTHWESTWARD AROUND THE UPPER
LOW AS IT BEGINS TO PUSH THROUGH THE SOUTHERN/CENTRAL ROCKIES. A
PREVALENT EASTERLY FLOW WILL KEEP LOW-LEVEL MOISTURE LIMITED IN
OUR FORECAST AREA, THOUGH, SO RAIN PROSPECTS ARE CONFINED TO OUR
FAR WEST WITH A SPOTTY FEW HUNDREDTHS AT BEST. WEAK INSTABILITY
COULD LEAD TO AN ISOLATED THUNDERSTORM IN THE AFTERNOON-EVENING.
THE SECOND LOW CHANCE OF LIGHT RAIN WILL BE NEAR-SOUTH OF I-90
ON WEDNESDAY, AND AGAIN THIS IS LARGELY DEPENDENT ON THE TRACK
OF THE LOW PRESSURE PASSING TO OUR SOUTH. STILL ONLY LOOKING AT
A 20-30% PROBABILITY FOR MEASURABLE RAINFALL DURING THIS PERIOD,
THOUGH AGAIN WEAK INSTABILITY COULD SUPPORT AN ISOLATED THUNDER
THREAT. IN EITHER OF THESE CASES, VERY WEAK DEEP LAYER SHEAR AND
AT BEST A FEW HUNDRED J/KG MUCAPE WILL PRECLUDE ANY POTENTIAL
FOR SEVERE STORMS.
FRIDAY-SATURDAY: THE UPPER LOW TO OUR SOUTH CONTINUES TO SLOWLY
TREK EASTWARD, ALLOWING A BROAD UPPER RIDGE TO BUILD FROM THE
ROCKIES INTO THE WESTERN-NORTHERN PLAINS. THIS WILL PROMOTE A
RETURN TO A DRY FORECAST WITH TEMPERATURES PERHAPS WARMING INTO
THE LOWER 80S IN SOME LOCATIONS.
AVIATION /06Z TAFS THROUGH 06Z MONDAY/
ISSUED AT 1018 PM CDT SAT MAY 3 2025
VFR CONDITIONS ARE EXPECTED THROUGH SUNDAY. WINDS WILL REMAIN
QUITE VARIABLE ESPECIALLY IN AREAS EAST OF THE JAMES RIVER
OVERNIGHT. EAST OF THE JAMES RIVER, A PREVAILING SOUTHEAST WIND
MAY CONTINUE. VALLEY FOG MAY BE POSSIBLE AROUND DAYBREAK.
WINDS THROUGH THE REGION TURN SOUTHEAST THROUGH SUNDAY AS CLEAR
SKIES CONTINUE.
FSD WATCHES/WARNINGS/ADVISORIES
SD...NONE.
MN...NONE.
IA...NONE.
NE...NONE.
DISCUSSION...JH
AVIATION...DUX
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