861
FXUS66 KPDT 280913
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
213 AM PDT FRI MAR 28 2025
SHORT TERM...TODAY THROUGH SUNDAY
1. RAIN SHOWERS WITH EMBEDDED ISOLATED THUNDERSTORM THIS EVENING
2. LINGERING SHOWERS THROUGH SATURDAY
3. SEASONABLE TEMPERATURES
CURRENT RADAR SHOWS MUCH OF THE PRECIPITATION TO BE LINGERING ALONG
THE WEST SIDE OF THE CASCADES AS WELL AS ALONG THE CASCADE CRESTS.
GROUND OBSERVATIONS SHOW THAT MUCH OF THE PRECIPITATION IN THE LAST
HOUR HAS REMAIN ALONG THE CRESTS WITH VERY LITTLE ALONG THE EASTERN
SLOPES. THERE IS A SMALL CELL MOVING OVER THE SIMCOE HIGHLANDS OF
KLICKITAT COUNTY, BUT NO GROUND OBSERVATIONS ARE PICKING UP ON ANY
MEASURABLE RAINFALL AT THIS TIME.
MODELS SHOW THE UPPER LEVEL LOW TO STILL BE OFF THE BC COAST. THE
LEADING EDGE OF THE LOW HAS BEEN USHERING IN MOISTURE FROM THE
SOUTHWEST AND BRINGING IT INTO THE REGION. MODELS THEN SHOW THE LOW
TO DEEPEN AND SHIFT A BIT CLOSER TO THE REGION BRINGING WITH IT A
BIT MORE MOISTURE THIS MORNING AND INTO THE AFTERNOON. NBM SHOWS
SNOW LEVELS TO BE ABOVE 3800 FEET AND 80-100% OF THE RAW ENSEMBLES
SHOW THE CASCADE CRESTS WILL SEE 1-3 INCHES. BELOW 3800 FEET, RAIN
WILL DOMINATE WITH 80-100% OF THE ENSEMBLES SHOWING 0.1-0.25 INCHES
OF RAIN AND AS THE PRECIPITATION SPREADS ACROSS THE REGION, 50-70%
OF THE RAW ENSEMBLES SHOW THE LOWLANDS WILL SEE LIGHT RAIN LESS THAN
0.1 INCHES WITH THE BASIN, ADJACENT VALLEYS AND PORTIONS OF CENTRAL
OR SEEING LITTLE TO NO RAIN TODAY. NOT ONLY WILL THERE BE LINGERING
SHOWERS, SHORT TERM HI-RES MODELS ARE SHOWING THE POTENTIAL FOR SOME
EMBEDDED THUNDERSTORMS ACROSS THE CASCADE CRESTS AS WELL AS ALONG
THE EASTERN MOUNTAINS (OCHOCO-JOHN DAY HIGHLANDS) THROUGH WALLOWA
COUNTY. HRRR/NAM/RAP MODELS ARE ALL SHOWING CAPE VALUES BETWEEN 150-
300 J/KG, LIS OF -2 TO -3 AND LAPSE RATES WELL ABOVE 7.5C/KM. THESE
INGREDIENTS MAKE FOR AN UNSTABLE ATMOSPHERE ALLOWING FOR THE
POTENTIAL OF THUNDERSTORMS AND ENSEMBLES SHOW 15-20% PROBABILITIES
OF ISOLATED THUNDERSTORM ALONG THE AFOREMENTIONED AREAS AT OR NEAR
5 PM.
BY SATURDAY THE MODELS SHOW THE LOW TO KICK NORTHWARD LEAVING ONLY
SOME LINGERING SHOWERS OVER THE CRESTS OF THE MOUNTAINS WITH LITTLE
ACCUMULATION. SUNDAY MODELS SHOW A WEAK RIDGE MOVES OVER THE REGION
ALLOWING FOR CONDITIONS TO DRY OUT THROUGH LATE SUNDAY AFTERNOON
AHEAD OF THE NEXT SYSTEM. LINGERING SHOWERS WILL BEGIN TO WORK THEIR
WAY NORTHEASTWARD ACROSS THE REGION LATE SUNDAY AFTERNOON BRINING
LIGHT SNOW TO THE MOUNTAINS AS WELL AS 60-80% PROBABILITIES OF 0.01-
0.05 INCHES OF RAIN ACROSS THE MAJORITY OF THE LOWER ELEVATIONS WITH
ONLY 20-30% FOR ANY MEASURABLE RAIN THROUGH THE BASIN AND ADJACENT
VALLEYS.
TEMPERATURES WILL REMAIN SEASONABLE WITH TEMPERATURES IN THE LOW 60S
THROUGH THE BASIN WITH 70% PROBABILITIES THROUGH SATURDAY AND
INCREASING TO NEAR 90% BY SUNDAY. AS FOR THE LOWER ELEVATIONS AND
VALLEYS, 60-80% SHOW TEMPERATURES TO BE IN THE 50S INCREASING TO 80%
BY SUNDAY WHILE THE HIGHER ELEVATIONS WILL SEE THE 40S. EFI SHOWS
THESE TEMPERATURES TO BE AT OR NEAR SEASON AVERAGES WITH OFFICE DATA
SHOWING TEMPERATURES TO BE 1-3 DEGREES BELOW SEASONAL AVERAGES.
BENNESE/90
LONG TERM...MONDAY THROUGH FRIDAY
CLUSTER ANALYSIS SHOWS MODELS
ARE IN GENERAL AGREEMENT MONDAY, BUT BEGIN TO RAPIDLY DIVERGE
THEREAFTER. FOR TUESDAY, CLUSTERS THAT ARE STRONGLY MORE ECMWF
DOMINANT SHOW A LITTLE MORE CONSISTENCY AS THEY INDICATE A BROAD
TROUGH OVER THE REGION WHILE THOSE STRONGLY MORE GFS DOMINANT HAVE
EITHER A DEEP TROUGH OFF THE COAST OR AN UPPER LEVEL RIDGE. FOR
WEDNESDAY, CLUSTERS FAVORING THE ECMWF CONTINUE TO BE MORE
CONSISTENT WITH AN UPPER TROUGH TO OUR EAST WITH NORTHWESTERLY FLOW
OVER THE AREA WHILE THE CLUSTERS FAVORING THE GFS CONTINUE TO SHOW
EITHER AN UPPER LEVEL RIDGE OR TROUGH OFF THE COAST BUT INCHING
CLOSER. BY THURSDAY, CLUSTER 1 WHICH IS ECMWF DOMINATED (68%
MEMBERS) SHOWS A HIGH AMPLITUDE RIDGE OVER THE EASTERN PACIFIC WHILE
THE GFS DOMINATED CLUSTERS CONVERGE ON A TROUGH OFF THE COAST.
FRIDAY CONTINUES THE DIVERGENCE WITH THE ECMWF ORIENTED CLUSTERS
SHOWING A RIDGE OFF THE COAST WITH GENERAL NORTHERLY FLOW OVER THE
AREA WHILE THE GFS ORIENTED CLUSTERS CONTINUE TO STRUGGLE WITH THE
PATTERN SHOWING EITHER ZONAL FLOW OR A RIDGE OVER THE AREA. THE
DETERMINISTIC MODELS AND ENSEMBLES SHOW A GENERAL TROUGHY PATTERN
THROUGH MUCH OF THE PERIOD. GIVEN UNCERTAINTY, WILL LEAN TOWARDS
MORE "CONSISTENT" ECMWF. AS A RESULT, THE AREA WILL BE DOMINATED BY
A BROAD UPPER LEVEL LOW WITH ALMOST DAILY PRECIPITATION, ESPECIALLY
OVER THE MOUNTAINS.
THE BEST CHANCE OF SEEING WIDESPREAD PRECIPITATION WILL BE MONDAY.
THERE'S A HIGH CHANCE (90%+) OF SEEING 0.10 OF AN INCH OR MORE OVER
THE MOUNTAINS WHILE A MODERATE CHANCE (40-60%) OVER THE REMAINDER OF
THE AREA.
DAYTIME HIGHS WILL GENERALLY BE NEAR NORMAL THROUGHOUT THE PERIOD.
EARLE/81
AVIATION...PREVIOUS DISCUSSION...06Z TAFS
VFR CONDITIONS TO
PREVAIL THROUGH THE PERIOD. LAST OF THE RAIN SHOWERS ARE BEGINNING
TO EXIT THE LOWER COLUMBIA BASIN, WITH DRY CONDITIONS DEVELOPING AT
MOST SITES. ANOTHER ROUND OF SHOWERS ARE EXPECTED TO IMPACT SITE DLS
BETWEEN 12-17Z, AND SITE ALW 17-23Z, WITH VICINITY SHOWERS AT SITE
PDT AFTER 21Z. WINDS HAVE BECOME LIGHT AT MOST SITES THIS EVENING,
AND ARE EXPECTED TO REMAIN LIGHT THROUGH THE OVERNIGHT PERIOD. WINDS
ARE EXPECTED TO INCREASE TO 12-17KTS WITH GUSTS TO AROUND 25KTS
STARTING AROUND 16Z-18Z, AND CONTINUE INTO THE AFTERNOON HOURS AT
ALL SITES.
PRELIMINARY POINT TEMPS/POPS
PDT 60 37 56 34 / 60 20 10 0
ALW 58 40 56 36 / 80 20 20 0
PSC 63 39 61 34 / 30 0 0 0
YKM 58 33 58 33 / 20 0 0 0
HRI 63 37 60 33 / 40 10 10 0
ELN 56 34 56 33 / 20 10 10 0
RDM 55 29 53 29 / 20 10 0 0
LGD 53 34 50 28 / 90 70 30 0
GCD 54 32 49 28 / 90 50 30 0
DLS 60 39 59 36 / 70 10 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...90
LONG TERM....81
AVIATION...82
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