053
FXUS66 KPDT 172307
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
407 PM PDT WED SEP 17 2025
AVIATION
A DEEP DRY ATMOSPHERIC COLUMN WILL CONTRIBUTE TO EXPECTED
WIDESPREAD VFR CONDITIONS THROUGH THE OVERNIGHT AND THURSDAY. LAMP
GUIDANCE SUGGESTS LIGHT AND VARIABLE WINDS FOR MOST OF THE AREA
ALTHOUGH NORTH WINDS 10-12KT AT BND AND RDM CAN LINGER THROUGH 02Z
AND AND A WESTERLY COMPONENT THROUGH 12Z AT DLS. RUSSELL/71
PREV DISCUSSION
/ISSUED 210 PM PDT WED SEP 17 2025/
DISCUSSION...TODAY THROUGH FRIDAY: QUIET, BENIGN WEATHER PREVAILS
WITH WARM, DRY CONDITIONS AS THE HIGH PRESSURE SYSTEM GRADUALLY
MOVES EASTWARD. HOWEVER, THE THERMAL TROUGH REMAINS PERSISTENT. THE
APPROACHING UPPER TROUGH WILL LAST TOMORROW INTO FRIDAY, BUT WITH
BOTH DAYS REMAINING DRY. THIS WEATHER PATTERN WILL KEEP THE HIGH
TEMPERATURES IN THE 70S AND 80S WITH A 60-90% PROBABILITY OF
REACHING IN THE MID TO HIGH 80S. DAYTIME RHS WILL REMAIN IN THE 30S
TODAY FOR LOWER ELEVATIONS, THOUGH WITH JOHN DAY HIGHLANDS AND BASIN
IN THE MID-TEENS AND LOW 20S BEFORE IMPROVING TOMORROW ONWARDS.
SATURDAY THROUGH WEDNESDAY: THE DETERMINISTIC MODELS AND ENSEMBLES
DO SHOW AN AGREEMENT FOR SATURDAY WITH THE PACNW IN BETWEEN A
CUTOFF LOW EXTENDED ACROSS CA COAST AND AN UPPER RIDGE OVER
BRITISH COLUMBIA. THE ECMWF FAVORS LIGHT MOISTURE OVER THE EASTERN
MOUNTAINS SATURDAY AROUND 5PM FROM AN POTENTIAL UPSLOPE FLOW, BUT
THE GFS HAS THE CASCADES WITH LIGHT PRECIP LATER ON THAT DAY AS
WELL. OVERALL, THIS RAISES A CHALLENGE IN FORECASTING THE PRECIP
DUE TO THE TIMING DIFFERENCE WITH THE FRONTAL SYSTEM.
HOWEVER WITH THIS PATTERN AND THE ASSOCIATED THERMAL TROUGH, GUSTY
WEST WINDS COULD DEVELOP ALONG THE CASCADE GAPS AT 20-30 MPH. THIS
MAY POTENTIALLY PROMOTE ELEVATED FIRE WEATHER CONDITIONS FOR NEARBY
WILDFIRES. CONFIDENCE IS LOW (<30%) AT THIS TIME, BUT WILL BE
MONITORED AS SATURDAY COMES NEAR. AS THE FRONTAL SYSTEM ARRIVES
SUNDAY, SHOWERS WILL DEVELOP OVER THE WA/OR CASCADES AND THE
WALLOWAS (15-30% CHANCE). WE MAY HAVE A BREAK MONDAY THROUGH
TUESDAY EARLY MORNING WITH THE HIGH PRESSURE BUILDING OVER.
TUESDAY LATE MORNING, SHOWERS WILL RETURN ACROSS THE CASCADES
BEFORE BECOMING MORE WIDESPREAD WEDNESDAY. GUSTY WINDS WILL ALSO
DEVELOP OVER THE FOOTHILLS-BLUES MOUNTAINS OF OR AND PORTIONS OF
YAKIMA AND KITTITAS VALLEY SUNDAY AFTERNOON INTO EVENING. REST OF
THIS WEEK WILL LIGHT WINDS WITH OCCASIONAL BREEZES. FEASTER/97
AVIATION...18Z TAFS (PREVIOUS DISCUSSION)...VFR CONDITIONS
PREVAIL THROUGH THE TAF PERIOD WITH WINDS LESS THAN 12KTS.
FEASTER/97
PRELIMINARY POINT TEMPS/POPS
PDT 84 54 82 56 / 0 0 0 0
ALW 86 58 84 59 / 0 0 0 0
PSC 85 53 85 53 / 0 0 0 0
YKM 87 54 85 54 / 0 0 0 0
HRI 85 54 84 54 / 0 0 0 0
ELN 84 51 82 49 / 0 0 0 0
RDM 83 44 80 48 / 0 0 0 0
LGD 85 49 87 53 / 0 0 0 0
GCD 87 51 88 54 / 0 0 0 0
DLS 87 58 84 57 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
DISCUSSION...97
AVIATION...71
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