589
FNUS76 KOTX 210944
FWSOTX
SPOT FORECAST FOR NORTH SIWASH UNIT 30B...USFS
NATIONAL WEATHER SERVICE SPOKANE WA
244 AM PDT MON SEP 21 2026
FORECAST IS BASED ON IGNITION TIME OF 0600 PDT ON SEPTEMBER 21.
DISCUSSION
DRY, MILD CONDITIONS TODAY WITH WINDS LESS THAN 10 MPH. CLOUDS
INCREASE TONIGHT AND TUESDAY. TEMPERATURES COOL A FEW DEGREES
TUESDAY WITH SLIGHTLY HIGHER WINDS. CONTINUED COOLING INTO
WEDNESDAY, THEN MILDER THURSDAY AHEAD OF SYSTEM THAT WILL BRING
SHOWER CHANCES, BREEZY CONDITIONS AND AGAIN COOLER TEMPERATURES
FRIDAY. THE CHANCE OF WETTING RAIN IS LOW AT 20 PERCENT.
IF CONDITIONS BECOME UNREPRESENTATIVE, CONTACT THE NATIONAL WEATHER
SERVICE.
***************************************************************
FORECASTS FOR 20 FOOT WIND SPEEDS (VALLEYS AND RIDGE TOPS) ARE
10 MINUTE AVERAGES REFLECTING RAWS WIND.
***VENTILATION INDEX IS DERIVED FROM TRANSPORT WIND
MULTIPLIED BY THE MIXING HEIGHT DIVIDED BY 100.
CATEGORIES: LOW (< 200), MODERATE (200-500),
HIGH (500-800), AND VERY HIGH (> 800).
***************************************************************
TODAY
SKY/WEATHER.........SUNNY.
CWR.................0 PERCENT.
CHANCE OF LIGHTNING.0 PERCENT.
MAX TEMPERATURE.....71-75.
MIN HUMIDITY........35-40 PERCENT.
WIND (20 FT)........SOUTHEAST WINDS 2 TO 4 MPH IN THE VALLEYS AND
4 TO 8 MPH ON THE RIDGES...TURNING SOUTHWEST
3 TO 6 MPH.
MIXING HEIGHT.......6000 FT AGL IN THE AFTERNOON.
TRANSPORT WINDS.....SOUTH AROUND 7 MPH SHIFTING TO THE SOUTHWEST IN
THE AFTERNOON.
VENTILATION INDEX...MODERATE (255) INCREASING TO MODERATE (438) IN
THE AFTERNOON.
TONIGHT
SKY/WEATHER.........MOSTLY CLEAR THEN BECOMING MOSTLY CLOUDY.
CWR.................0 PERCENT.
CHANCE OF LIGHTNING.0 PERCENT.
MIN TEMPERATURE.....48-50.
MAX HUMIDITY........64-66 PERCENT.
WIND (20 FT)........SOUTH WINDS 3 TO 6 MPH, LOCALLY TO 9 MPH
ON THE RIDGETOPS.
MIXING HEIGHT.......1500 FT AGL.
TRANSPORT WINDS.....SOUTH 5 TO 6 MPH.
VENTILATION INDEX...LOW (62).
TUESDAY
SKY/WEATHER.........PARTLY SUNNY.
CWR.................0 PERCENT.
CHANCE OF LIGHTNING.0 PERCENT.
MAX TEMPERATURE.....67-72.
MIN HUMIDITY........42-45 PERCENT.
WIND (20 FT)........SOUTH WIND 3 TO 6 MPH IN THE MORNING...
BECOMING WEST-NORTHWEST 4 TO 8 MPH WITH
GUSTS TO 12 MPH IN THE AFTERNOON.
MIXING HEIGHT.......5500 FT AGL IN THE AFTERNOON.
TRANSPORT WINDS.....SOUTHWEST 6 TO 11 MPH.
VENTILATION INDEX...MODERATE (248) INCREASING TO HIGH (683) IN THE
AFTERNOON.
FORECASTER...MSC
REQUESTED BY...JUSTIN COLVIN
TYPE OF REQUEST...PRESCRIBED
.TAG 2622210.0/OTX
.DELDT 09/21/26
.FORMATTERVERSION 2.0.0
.EMAIL MEGAN.PRIMMER@USDA.GOV,RACHAEL.MIDDLEKOOP@USDA.GOV,JUSTIN.L.COLVIN@USDA.GOV,MARSHALL.MYHRE@USDA.GOV
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