788
FXUS66 KPDT 221727
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1027 AM PDT TUE SEP 22 2026
KEY MESSAGES
- BREEZY GAP WINDS TODAY BECOMING LIGHT THROUGH THURSDAY WITH
NEAR TO ABOVE NORMAL TEMPERATURES EACH DAY
- WIDESPREAD LIGHT RAIN AND CASCADE PEAK LIGHT SNOW RETURN
FRIDAY WITH BREEZY TO LOCALLY GUSTY WINDS IN THE LOWER
ELEVATIONS
- TROUGH ENTERING SUNDAY TO CONTINUE BRINGING COOLER
TEMPERATURES THROUGHOUT THE REGION
DISCUSSION
MOSTLY QUIET CONDITIONS ACROSS THE REGION TONIGHT
AS AN UPPER LOW PASSES WELL TO THE SOUTH OF THE PACNW.
NIGHTTIME SATELLITE IMAGERY DOES SHOW DECKS OF CIRRUS DRAPED
ACROSS THE FORECAST AREA, WITH A STRATUS DECKS WEST OF THE
CASCADES. AT THE SURFACE, BREEZY WINDS HAVE DEVELOPED THROUGH
THE CASCADE GAPS POST A WEAK FRONTAL PASSAGE YESTERDAY.
TODAY THROUGH FRIDAY: THROUGH EARLY THURSDAY, THE FORECAST AREA
WILL REMAIN UNDER A WEST TO SOUTHWEST FLOW ALOFT, PROMOTING
MOSTLY QUITE CONDITIONS AND NEAR TO ABOVE NORMAL TEMPERATURES.
HOWEVER, A STRONG, DEEP LOW IN THE GULF OF ALASKA WILL SWING A
COLD FRONT INTO THE AREA TODAY, WHICH WILL REINFORCE BREEZY
WINDS (15-25MPH WITH GUSTS UP TO 35MPH) THROUGH THE CASCADE
GAPS. OTHERWISE, A WEAK SHORTWAVE IMPULSE AND DIFLUENT FLOW
ALOFT WILL PROMOTE A LOW CHANCE (10-20%) OF SHOWER OVER ELEVATED
TERRAIN FROM THE ELKHORN CREST TO THE WALLOWAS THIS AFTERNOON.
THERE IS GREAT AGREEMENT AMONGST ENSEMBLE AND DETERMINISTIC
GUIDANCE THAT AN UPPER TROUGH IN THE NORTHEAST PACIFIC WILL
SWING INTO THE PACNW WITH WIDESPREAD SHOWERS LATE THURSDAY
THROUGH FRIDAY. IN THE LOWER ELEVATIONS, SURFACE PRESSURE
GRADIENTS WILL TIGHTEN FRIDAY IN RESPONSE TO A SURFACE LOW
MOVING INLAND WITH THE TROUGH AXIS. THIS WILL RESULT IN BREEZY
TO LOCALLY GUSTY WESTERLY WINDS (15-30MPH WITH GUSTS 35-50 MPH)
DEVELOPING THROUGH THE CASCADE GAPS AND INTO THE LOWER
ELEVATIONS (CONFIDENCE 65-70%). TEMPERATURES WILL BE ON A
COOLING TREND WITH THE TROUGH PASSAGE, WITH AFTERNOON HIGH
TEMPERATURES IN THE 60S TO LOW 70S, AND 50S IN THE MOUNTAINS.
LAWHORN/82
SATURDAY THROUGH MONDAY: AS THE SHORTWAVE BEGINS TO MOVE
NORTHEAST INTO THE CANADIAN PROVINCES, THERE WILL BE A SHORTWAVE
TROUGH ENTERING FROM THE PACIFIC INTO SOUTHERN OREGON TO
MID/SOUTHERN CALIFORNIA. MODELS ARE IN AGREEMENT WITH OFFSHORE
TROUGHING SATURDAY MORNING INTO MIDDAY, BUT ARE IN DISAGREEMENT
WITH THE POSITION AND STRENGTH OF THE EXITING TROUGH FROM
EARLIER IN THE WEEK. THE GFS MEMBERS SHOW THE EXITING TROUGH
MORE STRONGER AND MORE NORTHWARD. THE CANADIAN AND THE EUROPEAN
MEMBERS DISPLAY A STALLING AND MORE SOUTHWARD POSITION, WITH THE
EUROPEAN BEING THE STRONGEST BRINGING BREEZY CONDITIONS TO THE
CASCADE GAPS SATURDAY MORNING(15% CONFIDENCE). THERE IS MODERATE
CONFIDENCE (40% - 50% CONFIDENCE) THAT THE OFFSHORE TROUGH
MAKES LANDFALL THROUGH SUNDAY, BRINGING LIGHT PRECIPITATION
ALONG THE CASCADES. NEAR NORMAL/ SLIGHTLY BELOW NORMAL
TEMPERATURES WITH MODERATE CONFIDENCE (40% - 50% CONFIDENCE),
WITH MINS IN THE HIGH 40'S AND HIGHS IN THE HIGH 60'S COOLING
FROM SATURDAY INTO MONDAY.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
BROAD WESTERLY SURFACE WINDS AND NO RISK OF CEILINGS OR
VISIBILITY RESTRICTION FOR LOCAL TERMINALS OVER THE TAF PERIOD.
A FEW LOCATIONS LIKE RDM/BDN/DLS CAN HAVE STRONGER WINDS AND
GUSTS IN THE LATER AFTERNOON DUE TO GAP WINDS. A RAMP UP IN
NORTH WIND SPEED AT BND BETWEEN ABOUT 21Z AND 00Z AS DOWNSLOPE
INFLUENCES WINDS, KEEPING CONDITIONS GUSTY THROUGH AROUND 3 OR
4Z. ANY GUSTS AT ALW SHOULD BE OCCASIONAL AND SHORT LIVED EARLY
THIS AFTERNOON, WHILE YKM AND PSC REMAIN LIGHT (UNDER 12 KTS).
PRELIMINARY POINT TEMPS/POPS
PDT 77 45 74 46 / 0 0 0 0
ALW 78 51 75 52 / 0 0 0 0
PSC 82 49 77 48 / 0 0 0 0
YKM 81 48 74 49 / 0 0 0 0
HRI 80 49 77 48 / 0 0 0 0
ELN 72 44 69 44 / 0 0 0 0
RDM 74 38 74 40 / 0 0 0 0
LGD 77 44 77 47 / 0 0 0 0
GCD 80 44 80 48 / 0 0 0 0
DLS 75 50 77 52 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...07/82
AVIATION...71
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