701
FXUS66 KPDT 222331
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
431 PM PDT WED OCT 22 2025
.UPDATED AVIATION.
AVIATION...00Z TAFS
VFR CONDITIONS PREVAIL FOR THE NEXT
24-HOURS. DRY CONDITIONS WITH LIGHT WINDS OF <12 KNOTS EXPECTED,
EXCEPT FOR DLS THAT HAVE GUSTS UP TO 30-35 KNOTS OVER THE NEXT
COUPLE OF HOURS. NOT EXPECTING CIG OR VIS ISSUES GOING THROUGH THE
TAF PERIOD.
PREV DISCUSSION
/ISSUED 312 PM PDT WED OCT 22 2025/
DISCUSSION...A PREDOMINANTLY QUASI-ZONAL 500-HPA RIDGE IS
FORECAST THROUGH THURSDAY NIGHT. THIS WILL LEAD TO MOSTLY NEAR- TO
ABOVE-NORMAL AFTERNOON HIGH TEMPERATURES ACROSS THE FORECAST
AREA. THE MAIN ITEMS TO NOTE DURING THE PERIOD ARE BREEZY SOUTH
TO SOUTHEAST WINDS THROUGH THE GRANDE RONDE VALLEY THIS AFTERNOON
AND A CHANCE (25-54%) OF LIGHT RAIN SHOWERS ALONG THE WASHINGTON
CASCADE CREST THIS AFTERNOON AND EVENING AS A SHORTWAVE CLIPS THE
PACIFIC NORTHWEST.
A STRONGER 500-HPA TROUGH WILL LIKELY (>95% CHANCE) ARRIVE FRIDAY
NIGHT THROUGH THE WEEKEND, WITH ENSEMBLE AND DETERMINISTIC
GUIDANCE SUGGESTING MULTIPLE SHORTWAVES, AND PERHAPS SURFACE LOWS,
ROTATING AROUND THE BASE OF THE PARENT TROUGH AFTER THE INITIAL
COLD FRONTAL PASSAGE FRIDAY AFTERNOON THROUGH SATURDAY MORNING.
CURRENTLY, HIGHEST CONFIDENCE IN ACTIVE WEATHER IS FRIDAY NIGHT
THROUGH SUNDAY AFTERNOON, DURING WHICH TIME THE MOUNTAINS
(CASCADES AND BLUES) GENERALLY HAVE PERSISTENT 55-95% POPS, WITH
35-80% POPS FOR THE LOWER ELEVATIONS. SNOW LEVELS WILL DROP TO
PASS LEVEL OVER THE WEEKEND, ESPECIALLY SUNDAY AS THE TROUGH MOVES
ONSHORE. ADVISORY-LEVEL MOUNTAIN SNOWFALL LOOKS LIKE A DISTINCT
POSSIBILITY. CURRENT PROBABILITIES OF EXCEEDING 6 INCHES OF SNOW
FOR THE CASCADES RANGE FROM 40-90%, HIGHEST FOR PASSES AT OR ABOVE
4500 FT, WHILE THE NORTHERN BLUE MOUNTAINS HAVE A LOWER 5-30%
PROBABILITY OF 6 INCHES OR MORE OF SNOW FOR THE PASSES. AREAS FROM
SOUTHERN BEND SOUTH THROUGH LA PINE HAVE A LOW (5-25%) CHANCE OF
REACHING OR EXCEEDING 2 INCHES OF SNOW.
ASIDE FROM PRECIPITATION CHANCES, BREEZY TO WINDY SOUTH TO WEST
WINDS ARE ANTICIPATED WITH THE WEEKEND SYSTEM. WILL NOTE THERE IS
SIGNIFICANT SPREAD AMONG ENSEMBLE NWP GUIDANCE WITH RESPECT TO
MAGNITUDE OF SURFACE WINDS. MOREOVER, CURRENT GUIDANCE IS SHOWING
35-55 KT 850-HPA WINDS WITH FRONTAL PASSAGE LATE FRIDAY AND AGAIN
SATURDAY WITH AS AN OFFSHORE SURFACE LOW TRACKS NORTHEASTWARD INTO
THE PACIFIC NORTHWEST. WHILE THERE IS A WHOLE LOT MORE THAT GOES
INTO A WIND FORECAST THAN JUST LOOKING AT ONE PRESSURE LEVEL,
850-HPA WINDS ARE OFTEN USED AS A PROXY FOR WHAT CAN MIX TO THE
SURFACE. THE HIGH END OF THE AFOREMENTIONED RANGE WOULD LEAD TO A
VERY WINDY SCENARIO, WHILE THE WEAKER END OF THE RANGE WOULD BE
NOTHING NOTEWORTHY FOR OUR FORECAST AREA. ADDITIONALLY, THE NBM
CURRENTLY PAINTS WIDESPREAD 20-70% PROBABILITIES OF ADVISORY-
LEVEL WIND GUSTS (45 MPH OR GREATER) DURING THE PERIOD WITH A
10-40% PROBABILITY OF REACHING WARNING-LEVEL WIND GUSTS (58 MPH
OR GREATER) FOR WIND-PRONE PORTIONS OF SOUTH-CENTRAL WASHINGTON,
CENTRAL AND NORTHEAST OREGON FOR THE LATE FRIDAY THROUGH SUNDAY
TIMEFRAME.
NOTABLY, PRIOR TO COLD FRONTAL PASSAGE, CONFIDENCE IS MEDIUM-HIGH
(60-80%) IN A PERIOD OF LOW RH (15-25%) AND BREEZY TO WINDY
SOUTHWEST WINDS (WIDESPREAD 15-25 MPH WITH GUSTS OF 25-35 MPH)
LEADING TO INCREASED POTENTIAL FOR CRITICAL FIRE WEATHER
CONDITIONS ACROSS FIRE WEATHER ZONES OR700, OR704, AND OR705
DURING THE LATE MORNING THROUGH EARLY EVENING HOURS IN CENTRAL
OREGON. LOCALLY STRONGER WINDS OF 25-35 MPH AND GUSTS OF 35-45 MPH
ARE ALSO FORECAST.
AVIATION...18Z TAFS...VFR CONDITIONS EXPECTED. LIGHT, TERRAIN-
DRIVEN WINDS LESS THAN 10 KTS WILL PREVAIL ACROSS ALL SITES, WITH
FEW-SCT MID-LEVEL CIGS ROLLING THROUGH THE REGION AS WELL. SOME
CLEARING WILL TAKE PLACE THIS EVENING, BEFORE MID-LEVEL CIGS
RETURN OVERNIGHT HEADING INTO THURSDAY. 74
PRELIMINARY POINT TEMPS/POPS
PDT 40 65 44 68 / 0 0 0 10
ALW 45 64 47 67 / 0 0 0 10
PSC 39 66 42 63 / 0 0 0 20
YKM 39 63 42 63 / 0 10 0 60
HRI 40 65 42 64 / 0 0 0 20
ELN 37 60 37 56 / 0 10 10 70
RDM 32 66 38 67 / 0 0 0 30
LGD 36 65 41 66 / 0 0 0 10
GCD 35 66 41 69 / 0 0 0 10
DLS 47 66 47 64 / 10 10 0 70
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...86
LONG TERM....86
AVIATION...95
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