905
FNUS73 KFSD 081444
FWSFSD
SPOT FORECAST FOR PIPE UNIT 1 AND 3...NPS
NATIONAL WEATHER SERVICE SIOUX FALLS SD
944 AM CDT FRI MAY 8 2026
IF CONDITIONS BECOME UNREPRESENTATIVE, CONTACT THE NATIONAL WEATHER
SERVICE.
DISCUSSION
CONFIDENCE IN WIND DIRECTION AND SPEED IS HIGHER THAN NORMAL FOR
MONDAY, SUGGESTING SOUTH SOUTHEAST DIRECTIONS THROUGH THE DAY,
WITH AN INCREASE IN AFTERNOON GUSTS TOWARDS 20 TO 25 MPH.
MIXING HEIGHTS WILL BE FAVORABLE IN THE AFTERNOON AT OR AROUND
6000 FT AGL, WITH TRANSPORT WINDS THROUGH THE LAYER OUT OF THE
SOUTH TO SOUTHWEST AT OR AROUND 20-25 MPH AT PEAK AFTERNOON
HEATING. DISPERSION INDEX IS TYPICALLY NOT CALCULATED BEYOND 36
HOURS FROM OUR OFFICE. HOWEVER I HAVE ADJUSTED SOME OF OUR
PARAMETERS TO ADD IN VALUES FOR MONDAY. FOR FUTURE REFERENCE, M IN
THE PLANNING FORECAST REPRESENTS "MISSING".
RELATIVE HUMIDITY FORECAST REMAIN MORE UNCERTAIN. MODEL GUIDANCE
IS HINTING THAT SOUTHEASTERLY WINDS WILL TRY TO MIX DOWN LOWER
DEWPOINTS WHICH COULD KEEP RH VALUES IN THE 25% RANGE. HOWEVER,
THERE IS CONSIDERABLE SPREAD IN OUR GUIDANCE WHICH HINTS AT A
FASTER NORTHWARD RETURN OF HIGHER DEW POINTS AND POTENTIAL FOR RH
VALUES TO RISE INTO THE LOWER 30% RANGE.
ANY PRECIPITATION CHANCES WILL HOLD OFF UNTIL LATE MONDAY
EVENING.
MONDAY
MAX TEMPERATURE.....AROUND 73.
MIN HUMIDITY........25 PERCENT.
TIME (CDT) 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
SKY COVER.......MCR PC PC PC PC PC PC PC MC
SKY (%).........25 27 31 35 39 41 44 46 52
WEATHER COV.....
WEATHER TYPE....
TSTM COV........
CHC OF PCPN (%).0 0 0 0 0 0 0 0 0
CHC OF THDR (%).0 0 0 0 10 10 10 10 10
TEMP............47 54 59 62 65 68 70 71 73
DEWPOINT........29 30 31 31 32 33 33 34 35
RH..............49 40 34 31 29 27 25 26 25
20 FT WIND DIR..SSE SSE SSE SSE SSE SSE SSE SSE SSE
20 FT WIND SPD..9 10 12 12 13 14 15 16 16
20 FT WIND GUST.14 15 16 18 20 21 22 23 23
MIX HGT (KFT)...1.6 2.2 2.9 3.7 4.4 4.6 4.9 5.1 4.6
TRANSP WIND DIR.SSE SSE SSE SSE SSE SSE S S S
TRANSP WIND SPD.15 16 16 17 17 18 20 21 22
SMOKE DISPERSAL.FR FR GD GD GD EX EX EX EX
MONDAY NIGHT
MIN TEMPERATURE.....AROUND 48.
MAX HUMIDITY........77 PERCENT.
TIME (CDT) 6PM 7PM 8PM 9PM 10P 11P MID 1AM 2AM 3AM 4AM 5AM
SKY COVER.......MC MC MC MC MC MC MC MC MC MC MC MC
SKY (%).........59 65 65 65 65 65 65 65 65 65 65 65
WEATHER COV..... CHC CHC CHC CHC CHC CHC CHC CHC CHC CHC CHC
WEATHER TYPE.... RW RW RW RW RW RW RW RW RW RW RW
TSTM COV........ SCH SCH SCH SCH SCH SCH SCH SCH SCH SCH SCH
CHC OF PCPN (%).0 50 50 50 50 50 50 30 30 30 30 30
CHC OF THDR (%).10 20 20 20 20 20 20 20 20 20 20 20
TEMP............73 71 66 62 59 57 57 56 54 53 51 49
DEWPOINT........35 36 37 37 38 39 39 40 40 41 41 41
RH..............25 28 34 39 45 51 51 55 59 64 68 74
20 FT WIND DIR..SSE SSE SSE SE SE SSE SSE SSE S S S SW
20 FT WIND SPD..16 16 16 16 16 16 15 15 15 14 14 14
20 FT WIND GUST.24 24 24 25 25 25 25 25 25 24 24 23
MIX HGT (KFT)...4.2 3.7 2.8 1.9 1.1 M M M M M M M
TRANSP WIND DIR.SSE SSE SSE SSE SE M M M M M M M
TRANSP WIND SPD.22 22 22 21 20 M M M M M M M
SMOKE DISPERSAL.EX EX GD GD FR M M M M M M M
TUESDAY
MAX TEMPERATURE.....AROUND 72.
MIN HUMIDITY........27 PERCENT.
TIME (CDT) 6AM 7AM 8AM 9AM 10A 11A 12P 1PM 2PM 3PM 4PM 5PM
SKY COVER.......MC PC PC PC PC PC PC MCR MCR MCR MCR MCR
SKY (%).........65 30 30 30 30 30 30 11 11 11 11 11
WEATHER COV.....CHC
WEATHER TYPE....RW
TSTM COV........SCH
CHC OF PCPN (%).30 0 0 0 0 0 0 0 0 0 0 0
CHC OF THDR (%).20 0 0 0 0 0 0 0 0 0 0 0
TEMP............48 48 51 56 61 65 68 70 71 72 72 72
DEWPOINT........41 41 41 42 42 41 40 39 38 37 36 36
RH..............77 77 68 59 50 41 36 32 30 28 27 27
20 FT WIND DIR..W NW NW NW NW NW NW NW NW NW NW NNW
20 FT WIND SPD..14 15 17 20 22 24 26 28 28 26 25 24
20 FT WIND GUST.23 23 24 26 29 31 33 36 37 37 36 35
MIX HGT (KFT)...M M M M M M M M M M M M
TRANSP WIND DIR.M M M M M M M M M M M M
TRANSP WIND SPD.M M M M M M M M M M M M
SMOKE DISPERSAL.M M M M M M M M M M M M
FORECASTER...DUX
REQUESTED BY...KENN PERREAULT
TYPE OF REQUEST...PRESCRIBED
.TAG 2613069.1/FSD
.DELDT 05/08/26
.FORMATTERVERSION 2.0.0
.EMAIL KENN_PERREAULT@NPS.GOV,DAN_SWANSON@NPS.GOV
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