035
FXUS66 KPDT 231106
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
406 AM PDT SAT MAY 23 2026
KEY MESSAGES
- WARM, DRY CONDITIONS THROUGH THE WEEKEND
- BREEZY TO LOCALLY WINDY THROUGH THE CASCADE GAPS TODAY, THEN
WIDESPREAD BREEZY TO WINDY MONDAY
- A LOW-PRESSURE SYSTEM AND COLD FRONT ARE LIKELY (80 PERCENT
CONFIDENCE) TO ARRIVE BY MONDAY AFTERNOON AND EVENING, BUT
DETAILS ARE STILL UNCERTAIN
DISCUSSION
WATER VAPOR IMAGERY REVEALS A COUPLE FEATURES OF INTEREST
UPSTREAM IN THE PACIFIC OCEAN. THE FIRST FEATURE IS A SHORTWAVE
APPROACHING THE BRITISH COLUMBIA COAST, AND THE SECOND IS A MORE
PRONOUNCED SHORTWAVE LOCATED JUST SOUTH OF THE ALEUTIAN ISLANDS.
OVERHEAD, A WEST-NORTHWEST FLOW ASSOCIATED WITH A FLATTENING
RIDGE IS PRESENT.
ENSEMBLE NWP GUIDANCE IS IN EXCELLENT AGREEMENT THAT THE FIRST
SHORTWAVE WILL TRACK INLAND ACROSS BRITISH COLUMBIA THROUGH THE
DAY, REMAINING WELL NORTH OF THE FORECAST AREA. HOWEVER, IT WILL
KEEP QUASI-ZONAL TO ZONAL FLOW OVER THE PACIFIC NORTHWEST AND
PREVENT THE RIDGE FROM AMPLIFYING. A CROSS-CASCADE TEMPERATURE
GRADIENT DURING THE AFTERNOON (WARMER ON THE EAST SIDE) WILL AID
IN PRODUCING MODEST PRESSURE GRADIENTS (5-9 MB BETWEEN PDX AND
GEG) AND DRIVE BREEZY TO LOCALLY WINDY WESTERLY WINDS THROUGH
THE CASCADE GAPS, ESPECIALLY THE EASTERN COLUMBIA RIVER GORGE,
KITTITAS VALLEY, AND WIND-PRONE PORTIONS OF NORTH-CENTRAL
OREGON. NOT ANTICIPATING WINDS TO REACH ADVISORY CRITERIA -- AT
LEAST NOT OVER A WIDESPREAD AREA -- BASED ON THE LACK OF A
STRONG JET ALOFT (PEAKING AT 25-35 KTS BETWEEN 925 MB AND 850
MB), AND NBM PROBABILITIES OF EXCEEDANCE SUPPORT A LOW-MEDIUM
CHANCE (30-60 PERCENT) FOR THE AFOREMENTIONED AREAS. STILL
EXPECTING PRESSURE GRADIENTS TO SLACKEN BY A FEW MILLIBARS ON
SUNDAY, RESULTING IN BREEZY, BUT NOT WINDY, WESTERLY WINDS
THROUGH THE CASCADE GAPS. OTHERWISE, ZONAL FLOW ALOFT WILL KEEP
DRY CONDITIONS IN PLACE.
THE SHORTWAVE SOUTH OF THE ALEUTIAN ISLANDS IS PASSING OVER A
BAROCLINIC ZONE. ENSEMBLE NWP GUIDANCE IS UNANIMOUS IN
SUGGESTING IT WILL INDUCE SURFACE CYCLOGENESIS THROUGH THE DAY,
AND DEEPEN INTO A CLOSED UPPER-LEVEL LOW THROUGH SUNDAY AS IT
DIGS SOUTHEAST JUST OFF THE COAST OF SOUTHEAST ALASKA AND
BRITISH COLUMBIA.
WHILE THERE ARE SLIGHT DIFFERENCES AMONG ENSEMBLE SYSTEMS, THEY
ARE ALL IN AGREEMENT THAT THE LOW WILL CONTINUE TO DIG
SOUTHEAST THROUGH MONDAY, WITH THE LOW CENTER REMAINING
OFFSHORE. THIS WILL RESULT IN ANOTHER WARM DAY, ESPECIALLY FOR
EASTERN OREGON AND EASTERN WASHINGTON WHICH WILL BE UNDER
SOUTHWESTERLY FLOW ALOFT AND AWAY FROM THE CASCADE GAPS AND
INFLUENCE OF COOLER MARINE AIR.
BREEZY TO LOCALLY WINDY SOUTHWESTERLY WINDS ARE FORECAST PRIOR
TO THE ARRIVAL OF WIDESPREAD BREEZY TO WINDY WESTERLY WINDS BY
MONDAY AFTERNOON AND EVENING AS A COLD FRONT SWEEPS ACROSS THE
REGION. WINDS MAY APPROACH ADVISORY CRITERIA ACROSS THE REGION,
BUT CONFIDENCE IS JUST MEDIUM (50 PERCENT) IN DETAILS OF THE
WIND FORECAST GIVEN ENSEMBLE SPREAD IN THE TIMING/LOCATION OF
THE LOW AS IT TRACKS INTO THE PACIFIC NORTHWEST BY LATE MONDAY.
IN ADDITION TO LIKELY (75 PERCENT OR HIGHER) CHANCES OF
PRECIPITATION ACROSS THE CASCADE CREST, PRECIPITATION CHANCES
(50-80 PERCENT) SPREAD EASTWARD ACROSS THE BLUE MOUNTAINS AND
THEIR FOOTHILLS BY AFTERNOON AND ESPECIALLY EVENING. CHANCES OF
WETTING RAIN (0.10" OR MORE OF PRECIPITATION) THROUGH TUESDAY
MORNING ARE MODEST (10-50 PERCENT) FOR THE SOUTHERN BLUE
MOUNTAINS REGION, BUT MEDIUM-HIGH (40-80 PERCENT) FOR THE
NORTHERN BLUE MOUNTAINS AND WALLOWA COUNTY, AND EVEN HIGHER FOR
THE CASCADE CREST (70-95 PERCENT CHANCE). WILL NOTE SOME CAMS
(NOTABLY THE RRFS) ARE SUGGESTING SOME CONVECTION ACROSS THE
NORTHERN BLUE MOUNTAINS AND FOOTHILLS MONDAY AFTERNOON AHEAD OF
OR ALONG THE COLD FRONTAL BOUNDARY. CONFIDENCE IN THIS SOLUTION
IS CURRENTLY LOW, AND DO NOT HAVE A MENTION OF THUNDER IN THE
FORECAST AT THIS TIME.
BY TUESDAY, AND ESPECIALLY WEDNESDAY, ENSEMBLE SYSTEMS BEGIN TO
DIVERGE IN THEIR REPRESENTATION OF THE 500-MB PATTERN. PER
ENSEMBLE CLUSTER ANALYSIS OF LATEST 00Z RUNS, ROUGHLY 60 PERCENT
OF MEMBERS FAVOR A DEEPER LOW CENTERED OVER NE CALIFORNIA AND
NW NEVADA WHILE THE REMAINING ~40 PERCENT SHOW A SLIGHTLY
SHALLOWER LOW CENTERED OVER THE GREAT BASIN (27 PERCENT OF
MEMBERS) OR SOUTHEAST OREGON (12 PERCENT OF MEMBERS). A SLIGHT
CHANCE TO CHANCE (15-50 PERCENT) OF SHOWERS IS FORECAST BOTH
DAYS, BUT CONFIDENCE IN PRECIPITATION AMOUNTS AND TEMPERATURES
IS LOWER THAN AVERAGE GIVEN THE SENSITIVITY OF THE FORECAST TO
THE LOCATION AND MAGNITUDE OF THE LOW.
ENSEMBLE SOLUTIONS CONTINUE TO DIVERGE THURSDAY AND FRIDAY, BUT
OVER 60 PERCENT OF ENSEMBLE MEMBERS SHOW THE LOW OVER CENTRAL
CALIFORNIA OR THE GREAT BASIN AND FAVOR CONTINUED SHOWERY
WEATHER.
THUNDER CHANCES THROUGH THE WEEK WILL BE TIED TO THE LOCATION
OF THE LOW, AND CURRENTLY HAVE A 10-25 PERCENT CHANCE EACH DAY
MONDAY THROUGH FRIDAY.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
VFR CONDITIONS ARE FORECAST FOR THE NEXT 24 HOURS AT ALL SITES.
SKIES WILL REMAIN CLEAR TO PARTLY CLOUDY, PREDOMINANTLY THIN
CIRRUS. BREEZY WINDS OF 10-20 KTS WITH GUSTS OF 20-30 KTS WILL
PERSIST AT DLS, AND PERIODS OF BREEZY WINDS ARE FORECAST TO
DEVELOP THIS AFTERNOON AND EVENING AT ALL OTHER SITES.
PRELIMINARY POINT TEMPS/POPS
PDT 83 50 82 50 / 0 0 0 0
ALW 84 55 82 56 / 0 0 0 0
PSC 89 54 87 54 / 0 0 0 0
YKM 88 52 85 53 / 0 0 0 0
HRI 86 54 85 53 / 0 0 0 0
ELN 78 49 76 48 / 0 0 0 0
RDM 83 43 84 45 / 0 0 0 0
LGD 82 47 83 48 / 0 0 0 0
GCD 84 45 86 46 / 0 0 0 0
DLS 82 54 83 54 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...86
AVIATION...86
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