841
FXUS66 KPDT 031754
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
954 AM PST TUE FEB 3 2026
KEY MESSAGES
- HIGH PRESSURE RETURNS TO THE REGION TUESDAY
- PATTERN CHANGE EXPECTED OVER THE WEEKEND
UPDATE
AREAS TO WIDESPREAD DENSE FOG HAS EXPANDED OVER SOME WELL
TRAVELED AREAS THIS MORNING, PARTICULARLY THE KITTITAS AND
YAKIMA VALLEY AS WELL AS THE OREGON WASHINGTON HIGHWAY ALONG THE
FOOTHILLS OF THE BLUES. LATEST LAMP GUIDANCE KEEP THE LOW
VISIBILITY ANCHORED THOUGH AT LEAST NOON, SO WENT AHEAD WITH
ISSUING DENSE FOG ADVISORIES FOR THESE AREAS THIS MORNING. THE
NEXT STEP IS TO DETERMINE HOW QUICK THIS FOG REDEVELOPS TONIGHT
ASSUMING IT ALL LIFTS. RUSSELL/71
DISCUSSION
CURRENT RADAR SHOWS NO RETURNS AS THE SHORTWAVE WARM FRONT HAS
TRAVERSED TO THE EAST. THE NIGHTTIME SATELLITE SHOWS SOME FOG
FORMING THROUGH THE KITTITAS VALLEY WITH GROUND OBSERVATIONS
SHOWING VIS TO BE DECREASING ALONG THE I90 CORRIDOR. PATCH FOG
WILL CONTINUE THROUGH THE MORNING BEFORE CLEARING OUT LATER IN
THE MORNING.
MODELS SHOW THE UPPER LEVEL RIDGE ALREADY BUILDING INTO THE
REGION. THIS WILL BRING INCREASING STRATUS AND POTENTIAL FOG
BACK TO THE AREA OVER THE NEXT FEW DAYS. WHILE THIS PATTERN
DURING WINTER DOES TYPICALLY BRING WITH IT THE POTENTIAL FOR AIR
STAGNATION, THE NBM SHOWS MIXING HEIGHTS TO HOVER ABOVE 1500
FEET AND THE ABUNDANCE OF LOW CLOUDS EXPECTED THROUGH THE
PERIOD. HOWEVER, FOG WILL REMAIN THE DAILY CONCERN THROUGH THE
PERIOD AHEAD OF THE NEXT SYSTEM. 50-60% OF THE RAW ENSEMBLES
SHOW THAT TUESDAY MORNING KITTITAS, YAKIMA AND A LARGE SWATH
THROUGH THE COLUMBIA BASIN WILL SEE VIS DROP AS LOW AS IF NOT
LOWER THAN 3 MILES. BY WEDNESDAY, PROBABILITIES INCREASE TO
60-70% OF 3 MILES OR LESS VIS THROUGH MUCH OF THE COLUMBIA
BASIN AND KLICKITAT COUNTY ALONG THE SIMCOE HIGHLANDS AND ALONG
THE NORTHERN BLUE FOOTHILLS. BY THURSDAY MODELS SHOW THE AXIS OF
THE HIGH TO TILT AND THE BACK EDGE OF THE HIGH WILL BRING IN
SOUTHERLY FLOW. THIS WILL BRING IN AIR WARMER AND HAS THE
POTENTIAL TO DECREASE THE CHANCES OF FOG FORMING OVERNIGHT
THURSDAY AND FRIDAY (60-70% CONFIDENCE).
BY SATURDAY MODELS SHOW THE INITIAL BREAKDOWN OF THE RIDGE AS
AN UPPER LEVEL LOW BEGINS TO BUILD IN OFFSHORE BRING INCREASED
PRECIPITATION CHANCES (70-90%) TO THE CASCADES AND SPREADING TO
THE EASTERN MOUNTAINS SATURDAY NIGHT WITH 40-60% CHANCES.
CLUSTERS AND MODELS ARE IN DECENT AGREEMENT THROUGH THE WEEKEND,
THERE IS A TELLTALE DIFFERENCE IN THE TIMING BETWEEN MODELS.
THE EURO HAS PRECIPITATION COMING IN AHEAD OF THE GFS.
REGARDLESS, PRECIPITATION AND COOLER TEMPERATURES ARE EXPECTED
OVER THE WEEKEND. 90
AVIATION...18Z TAFS
FOG AND LOW STRATUS WILL BRINGS PERIODS
OF MVFR OR LOWER CONDITIONS ACROSS MOST SITES THROUGH THE
PERIOD. SITES DLS/PDT/YKM/ALW/PSC WILL BE STUCK UNDER THE
STRATUS LAYER FOR MOST OF THE PERIOD, WITH HIRES SHORT TERM
GUIDANCE ATTEMPTING TO CLEAR PDT/PSC OUT BY THIS AFTERNOON, BUT
CONFIDENCE IS LOW (<20%) IN THESE SOLUTIONS. CIGS ARE EXPECTED
TO REMAIN MOSTLY AT MVFR OR LOWER HEIGHTS THROUGH THE PERIOD.
CONFIDENCE IS MOD-HIGH (50-80%) THAT THESE SITES WILL ALSO SEE
LOWERED VSBY IMPACTS THROUGHOUT THE PERIOD AS THE ASSOCIATED FOG
LAYER MOVES AROUND THE LOWER ELEVATIONS. THAT SAID, CONFIDENCE
IS LOW (20-30%) ON EXACT TIMING OF THE VSBY IMPACTS. SITE
RDM/BDN ARE EXPECTED TO REMAIN CLEAR AND DRY THROUGH THE PERIOD.
WINDS WILL BE LIGHT, 12KTS OR LESS, THROUGH THE PERIOD.
LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 34 50 32 48 / 0 0 0 0
ALW 37 50 35 48 / 0 0 0 0
PSC 34 48 34 49 / 0 0 0 0
YKM 35 50 32 50 / 0 0 0 0
HRI 35 49 33 48 / 0 0 0 0
ELN 33 45 29 46 / 0 0 0 0
RDM 29 60 27 56 / 0 0 0 0
LGD 36 56 37 56 / 0 0 0 0
GCD 33 59 34 59 / 0 0 0 0
DLS 38 51 36 50 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...DENSE FOG ADVISORY UNTIL NOON PST TODAY FOR WAZ026-027-029.
OR...DENSE FOG ADVISORY UNTIL NOON PST TODAY FOR ORZ507.
UPDATE...71
DISCUSSION...90
AVIATION...82
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