562
FXUS66 KPDT 182011
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
111 PM PDT MON MAY 18 2026
KEY MESSAGES
- SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER WALLOWA
COUNTY TODAY
- BREEZY TO LOCALLY WINDY WESTERLY WINDS THROUGH THE CASCADE
GAPS TODAY AND TUESDAY
- WARMING AND MOSTLY DRY TUESDAY THROUGH THE WEEK
DISCUSSION
DAYTIME HEATING HAS LED TO MODEST INSTABILITY (SURFACE-BASED
CAPE OF A COUPLE HUNDRED J/KG OR LESS PER SPC'S RAP-BASED
MESOANALYSIS AND FORECAST SOUNDINGS FROM THE 12Z HREF/REFS)
THIS AFTERNOON ACROSS THE BLUES AND WASHINGTON CASCADES. WHILE
ACTIVITY HAS BEEN ISOLATED ELSEWHERE, SCATTERED RAIN SHOWERS
HAVE DEVELOPED ACROSS WALLOWA COUNTY. THROUGH EVENING, THERE IS
A SLIGHT CHANCE (15 PERCENT) OF THUNDER ACROSS WALLOWA COUNTY,
WITH LOWER (5-10 PERCENT) CHANCES OF RAIN SHOWERS AND THUNDER
FOR OTHER PARTS OF THE BLUES AS WELL AS THE WASHINGTON CASCADES.
TUESDAY THROUGH SATURDAY, WARMING TEMPERATURES AND MOSTLY DRY
CONDITIONS ARE FORECAST REGION-WIDE AS AN UPPER-LEVEL RIDGE OF
HIGH PRESSURE WILL LIKELY (90-95 PERCENT CHANCE) BUILD INTO THE
REGION FROM THE PACIFIC AND DOMINATE THE WEATHER. A COUPLE WEAK
SHORTWAVES PASSING THROUGH NORTHWESTERLY FLOW ALOFT COUPLED WITH
MODEST DIURNALLY INDUCED INSTABILITY (SURFACE-BASED CAPE OF A
UP TO A COUPLE HUNDRED J/KG FROM FORECAST SOUNDINGS) MAY
FACILITATE SOME ISOLATED SHOWERS FOR THE MOUNTAINS THROUGH
THURSDAY, BUT POPS ARE LOW (10 PERCENT OR LESS).
BREEZY TO LOCALLY WINDY WESTERLY WINDS ARE FORECAST THROUGH THE
CASCADE GAPS TODAY AND TUESDAY, BUT NOT ANTICIPATING A NEED FOR
ANY WIND HEADLINES. IN YESTERDAY'S DISCUSSION, MENTIONED THE
POTENTIAL FOR WESTERLY WINDS TO MEET ADVISORY CRITERIA ON
THURSDAY. ENSEMBLE GUIDANCE HAS SINCE TRENDED TOWARDS A SOLUTION
THAT WOULD LEAD TO A WIND REVERSAL TO MOSTLY LIGHT
NORTHEASTERLY (OFFSHORE) WINDS LATE WEDNESDAY AND THURSDAY AS A
SHORTWAVE DIGS SOUTH ACROSS THE NORTHERN PLAINS AND ROCKIES,
JUST CLIPPING THE EDGE OF OUR FORECAST AREA. CONSIDERING THERE
IS STILL SOME ENSEMBLE SPREAD, WILL PLACE CONFIDENCE IN THIS
SOLUTION AT MEDIUM (60 PERCENT).
CONSIDERABLE UNCERTAINTY IN THE 500-HPA PATTERN IS PRESENT IN
ENSEMBLE SOLUTIONS BY THE WEEKEND, WITH ROUGHLY 45-50 PERCENT OF
THE VARIANCE IN SOLUTIONS EXPLAINED BY TIMING DIFFERENCES AMONG
SOLUTIONS REGARDING THE ARRIVAL OF A TROUGH OR CLOSED LOW FROM
THE PACIFIC.
THE NBM HAS WESTERLY WINDS RETURNING TO THE REGION BY LATE
FRIDAY, PERSISTING THROUGH THE WEEKEND. HIGHEST CHANCES (10-40
PERCENT) OF REACHING ADVISORY-LEVEL WINDS HAVE NOW BEEN PUSHED
BACK TO SATURDAY AND SUNDAY THROUGH WIND-PRONE AREAS OF THE
LOWER ELEVATIONS, PRIMARILY THE EASTERN COLUMBIA RIVER GORGE,
NORTH-CENTRAL OREGON, THE FOOTHILLS OF THE BLUE MOUNTAINS, AND
THE KITTITAS VALLEY. OF COURSE, THE MAGNITUDE OF WINDS WILL BE
TIED TO THE SYNOPTIC PATTERN, AND GIVEN THE UNCERTAINTY (SEE
PARAGRAPH ABOVE), CAN'T REALLY TALK ABOUT MUCH CONFIDENCE IN
FORECAST DETAILS YET.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
VFR CONDITIONS ARE FORECAST FOR THE NEXT 24 HOURS AT ALL SITES.
WINDS WILL BE DIURNALLY AND TERRAIN-DRIVEN, BREEZY FROM LATE
MORNING THROUGH EVENING. THERE IS A VERY LOW (10 PERCENT) CHANCE
OF RAIN SHOWERS THIS AFTERNOON AT YKM WITH EVEN LOWER CHANCES
(5 PERCENT OR LESS) ELSEWHERE.
PRELIMINARY POINT TEMPS/POPS
PDT 42 72 46 73 / 0 0 0 0
ALW 46 72 49 73 / 0 0 0 0
PSC 44 77 48 79 / 0 0 0 0
YKM 44 76 47 79 / 0 0 0 0
HRI 44 75 48 77 / 0 0 0 0
ELN 41 68 43 73 / 0 0 0 0
RDM 30 72 37 74 / 0 0 0 0
LGD 36 68 40 70 / 0 0 0 0
GCD 34 71 38 74 / 0 0 0 0
DLS 45 74 49 78 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86
AVIATION...86
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