458
FNUS76 KPDT 212300
FWSPDT
SPOT FORECAST FOR HWY 20 IFR UNITS 93/81...USFS
NATIONAL WEATHER SERVICE PENDLETON OR
400 PM PDT WED MAY 21 2025
FORECAST IS BASED ON IGNITION TIME OF 0600 PDT ON MAY 22.
***THUNDERSTORMS IMPLY GUSTY AND ERRATIC WINDS***
***WINDS ARE 20 FOOT 10-MINUTE AVERAGES***
***CWR-CHANCE OF WETTING RAIN 0.10 OR GREATER***
***VENTILATION INDEX IS DERIVED FROM THE
TRANSPORT WIND MULTIPLIED BY THE MIXING
HEIGHT IN 100'S OF FEET. INDEX CATEGORIES
ARE A GENERALIZED INDICATOR ONLY.***
IF YOU HAVE QUESTIONS OR CONCERNS WITH THIS FORECAST, PLEASE
CONTACT OUR OFFICE AT (541) 276-8134.
DISCUSSION
A WEAK WEATHER SYSTEM WILL PASS OVERHEAD TONIGHT
THROUGH THURSDAY, FACILITATING A CHANCE OF RAIN SHOWERS. CHANCE
OF WETTING RAIN IS VERY LOW (6%) AND CHANCE OF LIGHTNING IS ALSO
VERY LOW (6%). ANOTHER WEAK SYSTEM IS FORECAST THURSDAY NIGHT
THROUGH FRIDAY, BUT LITTLE TO NO PRECIPITATION IS ANTICIPATED
FOR THE BURN SITE WITH THE BEST CHANCE OF SHOWERS ALONG THE CASCADE
CREST AND EAST OVER THE BLUE MOUNTAINS. WINDS WILL BE PREDOMINANTLY
DIURNALLY DRIVEN, STRONGEST IN THE AFTERNOON AND EVENING BOTH DAYS.
THURSDAY
SKY/WEATHER.........PARTLY TO MOSTLY CLOUDY (40-70 PERCENT). CHANCE
OF RAIN SHOWERS IN THE MORNING.
CWR.................6 PERCENT IN THE MORNING.
CHANCE OF LIGHTNING.6 PERCENT.
MAX TEMPERATURE.....58-61.
MIN HUMIDITY........45-50 PERCENT.
WIND (20 FT)........LIGHT WINDS EARLY MORNING, BECOMING NORTHWEST
6-10 MPH WITH GUSTS OF 15-20 MPH LATE MORNING
THROUGH AFTERNOON.
RIDGETOP WIND.......LIGHT WINDS EARLY MORNING, BECOMING NORTHWEST
6-10 MPH WITH GUSTS OF 15-20 MPH LATE MORNING
THROUGH AFTERNOON.
MIXING HEIGHT.......INCREASING TO 3500-4000 FT AGL BY AFTERNOON.
TRANSPORT WINDS.....WEST 10-15 MPH.
VENTILATION INDEX...POOR (170) INCREASING TO FAIR (480) IN THE
AFTERNOON.
TIME (PDT) 6 AM 8 AM 10 AM NOON 2 PM 4 PM
CHC OF LTNG (%).0 0 0 10 10 10
TEMP............38 44 53 56 58 60
RH..............91 81 59 51 47 45
20 FT WIND......W 3 NW 4 NW 6 NW 8 NW 8 NW 8
20 FT WIND GUST.4 6 12 15 15 15
THURSDAY NIGHT
SKY/WEATHER.........PARTLY CLOUDY (30-40 PERCENT).
CWR.................0 PERCENT.
CHANCE OF LIGHTNING.1 PERCENT.
MIN TEMPERATURE.....33-36.
MAX HUMIDITY........93-98 PERCENT.
WIND (20 FT)........NORTHWEST WINDS 5-9 MPH WITH GUSTS OF 10-15 MPH
IN THE EVENING, BECOMING DRAINAGE WINDS 1-4 MPH
OVERNIGHT.
RIDGETOP WIND.......NORTHWEST WINDS 5-9 MPH WITH GUSTS OF 10-15 MPH
IN THE EVENING, BECOMING DRAINAGE WINDS 1-4 MPH
OVERNIGHT.
MIXING HEIGHT.......DECREASING TO NEAR SURFACE OVERNIGHT.
TRANSPORT WINDS.....WEST 10-15 MPH IN THE EVENING, DECREASING TO 4-8
MPH OVERNIGHT.
VENTILATION INDEX...FAIR (270) DECREASING TO POOR (60) OVERNIGHT.
FRIDAY
SKY/WEATHER.........MOSTLY SUNNY (15-25 PERCENT).
CWR.................0 PERCENT.
CHANCE OF LIGHTNING.1 PERCENT.
MAX TEMPERATURE.....68-71.
MIN HUMIDITY........30-35 PERCENT.
WIND (20 FT)........NORTHWEST WINDS 2-5 MPH IN THE MORNING, INCREASING
TO 6-10 MPH WITH GUSTS OF 10-15 MPH BY AFTERNOON.
RIDGETOP WIND.......NORTHWEST WINDS 2-5 MPH IN THE MORNING, INCREASING
TO 6-10 MPH WITH GUSTS OF 10-15 MPH BY AFTERNOON.
MIXING HEIGHT.......INCREASING TO 6000-6500 FT AGL BY AFTERNOON.
TRANSPORT WINDS.....WEST 4-8 MPH IN THE MORNING, INCREASING TO 8-12
MPH BY AFTERNOON.
VENTILATION INDEX...POOR (70) INCREASING TO FAIR (420) IN THE
AFTERNOON.
FORECASTER...PLUNKETT
REQUESTED BY...TJ WHITEHALL
TYPE OF REQUEST...PRESCRIBED
.TAG 2514475.0/PDT
.DELDT 05/21/25
.FORMATTERVERSION 2.0.0
.EMAIL TJ.WHITEHALL@USDA.GOV
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page