700
FXUS66 KPDT 242231 AAA
AFDPDT
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PENDLETON OR
1051 AM PDT THU APR 24 2025
SHORT TERM...TODAY THROUGH SATURDAY NIGHT
KEY MESSAGES:
1. WARMING CONTINUES FRIDAY.
2. ISOLATED AFTERNOON THUNDERSTORMS POSSIBLE FRIDAY AND SATURDAY.
3. BREEZY TO WINDY CONDITIONS SATURDAY.
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWING DRY CONDITIONS
AS SOME HIGH LEVEL CLOUDS ARE BEGINNING TO PUSH INTO DESCHUTES,
JEFFERSON, AND CROOK COUNTIES FROM THE SOUTH. THESE CLOUDS ARE
ASSOCIATED WITH THE UPPER LEVEL RIDGE OVERHEAD SHIFTING TO THE
NORTHEAST AS AN UPPER LEVEL TROUGH APPROACHES THE COAST, ALLOWING
FOR FLOW ALOFT TO TURN OUT OF THE SOUTH THIS EVENING INTO FRIDAY.
THE ADDITIONAL CLOUD COVER WILL KEEP OVERNIGHT TEMPERATURES TONIGHT
WARMER THAN THE LAST SEVERAL DAYS AS FRIDAY MORNING TEMPERATURES
SHOULD ONLY DROP INTO THE UPPER 30S TO LOW 40S ACROSS THE LOWER
COLUMBIA BASIN, BLUE MOUNTAIN FOOTHILLS, AND CENTRAL OREGON. THIS
ENHANCED SOUTHERLY FLOW WILL ALSO ATTRIBUTE TO A WARM FRIDAY
AFTERNOON WITH HIGHS BREAKING INTO THE LOW 80S ACROSS PORTIONS OF
THE LOWER COLUMBIA BASIN, AND IN THE MID-TO UPPER 70S ALONG THE BLUE
MOUNTAIN FOOTHILLS AND GORGE.
THE APPROACHING UPPER LEVEL TROUGH WILL CLOSE INTO AN UPPER LOW
PRESSURE EARLY FRIDAY MORNING AND MOVE SOUTH ALONG THE NORTHERN
CALIFORNIA COAST BEFORE MOVING ONSHORE BY THE EVENING. WRAP-AROUND
MOISTURE ASSOCIATED WITH THIS LOW PRESSURE SYSTEM WILL BRING RAIN
CHANCES (30-50%) TO OUR SOUTHERN COUNTIES (DESCHUTES, JEFFERSON,
CROOK, WHEELER, GRANT) IN THE AFTERNOON BEFORE INCREASING CHANCES
(40-70%) AND EXPANDING INTO THE BLUE MOUNTAINS, GRANDE RONDE VALLEY,
AND WALLOWA COUNTY THROUGH THE EVENING. THERE WILL ALSO BE A CHANCE
(10-20%) FOR ISOLATED THUNDERSTORMS AFTER 1 PM FOR DESCHUTES, CROOK,
WHEELER, GRANT, AND UNION COUNTIES THROUGH THE EVENING. THE STORM
PREDICTION CENTER (SPC) HAS INCLUDED THESE AREAS IN THEIR GENERAL
THUNDERSTORMS (0 OF 5) CATEGORY AS THE HREF AND NBM ADVERTISE
SURFACE CAPE OF BETWEEN 200-300 J/KG WITH LOW LEVEL SHEAR OF AROUND
25 KTS. A SIMILAR SETUP WILL OCCUR ON SATURDAY AFTERNOON/EVENING AS
ISOLATED THUNDERSTORMS WILL ALSO BE POSSIBLE ACROSS CROOK, GRANT,
UNION, AND WALLOWA COUNTIES WITH MEAN CAPE OF 200-300 J/KG. THE
STORM CONCERNS WILL BE ASSOCIATED WITH GUSTY AND ERRATIC WINDS AND
LIGHTNING. RAIN AMOUNTS OF 0.10-0.20" WILL BE POSSIBLE ACROSS
DESCHUTES AND CROOK COUNTIES AND 0.01-0.05" ACROSS GRANT AND
JEFFERSON COUNTIES FRIDAY AND 0.15-0.25" OVER GRANT, CROOK, AND
SOUTHERN WALLOWA COUNTIES ON SATURDAY.
A PRESSURE GRADIENT IS ANTICIPATED TO SET UP ALONG THE CASCADES TO
PROVIDE ELEVATED WEST-NORTHWEST WINDS THROUGH THE GORGE, SIMCOE
HIGHLANDS, SOUTHERN BLUE MOUNTAIN FOOTHILLS, AND KITTITAS COUNTY AS
SUSTAINED WINDS OF 15-25 MPH AND GUSTS OF UP TO 40 MPH WILL BE
POSSIBLE ON SATURDAY. CONFIDENCE IN THESE WIND VALUES IS MODERATE TO
HIGH (60-70%) AS THE NBM SUGGESTS A 60-80% CHANCE OF GUSTS REACHING
35 MPH OR GREATER AND A 50-70% CHANCE OF 40 MPH OR GREATER. THESE
WINDS WILL BE INCREASING THROUGH THE AFTERNOON AND PEAK THROUGH THE
EVENING HOURS AS EVEN WINDIER CONDITIONS ARE EXPECTED ON SUNDAY. 75
LONG TERM...SUNDAY THROUGH THURSDAY
MAIN WEATHER CONCERNS WILL BE
A DEPARTING LOW PRESSURE SYSTEM ON SUNDAY AND A SHORTWAVE CROSSING
THE AREA TUESDAY AND TUESDAY NIGHT. THIS WILL GENERATE BREEZY TO
WINDY CONDITIONS EACH AFTERNOON SUNDAY THROUGH TUESDAY. MODELS ARE
IN EXCELLENT AGREEMENT IN HAVING A LARGE RIDGE OF HIGH PRESSURE
BUILDING IN THE EASTERN PACIFIC AS THE UPPER LOW AND TROUGH DEPARTS
ON SUNDAY. THE RIDGE THEN BUILDS FURTHER MONDAY WHILE THE TROUGH
MOVES INTO THE ROCKIES. THE RIDGE FLATTENS ON TUESDAY AS A SHORTWAVE
RIDES OVER THE TOP OF THE RIDGE. MODELS BEGIN HAVING SOME
DIFFERENCES WEDNESDAY AS THE RIDGE RESTRENGTHENS AND IS CENTERED
ALONG THE WASHINGTON/BRITISH COLUMBIA COAST. THE RIDGE STRENGTHENS
FURTHER ON THURSDAY THOUGH 58 PERCENT OF THE MODEL CLUSTERS HAVE THE
RIDGE CENTERED OVER OUR AREA AND THE REST HAVE IT OVER IDAHO. THE
EXTREME FORECAST INDEX MAINLY HIGHLIGHTS WIND SPEEDS AND WIND GUSTS
SUNDAY AND MONDAY WITH VALUES OF 0.80 TO 0.90. IT ALSO HIGHLIGHTS
WARM TEMPERATURES NEXT THURSDAY WITH A VALUE OF 0.73.
SUNDAY WILL SEE A TROUGH CENTERED NEAR THE NEVADA/UTAH BORDER AND A
RIDGE BUILDING OFFSHORE. THIS WILL GIVE MOST OF THE AREA A DRY
NORTHERLY FLOW THOUGH CIRCULATION AROUND THE LOW WILL KEEP A SLIGHT
CHANCE OF SHOWERS IN WALLOWA COUNTY. ANY RAIN AMOUNTS WILL BE LIGHT.
TIGHT PRESSURE GRADIENTS WILL LEAD TO STRONG WEST TO NORTHWEST WINDS
OF 20 TO 30 MPH IN THE KITTITAS VALLEY, COLUMBIA GORGE AND SOUTHERN
BLUE MOUNTAIN FOOTHILLS WHILE THE REST OF THE LOWER ELEVATIONS WILL
REACH 15 TO 25 MPH. NBM PROBABILITIES GIVE THE KITTITAS VALLEY AND
COLUMBIA GORGE AN 80 PERCENT CHANCE OF HAVING 30 MPH SUSTAINED WINDS
WHILE THE CHANCES ARE 40 PERCENT IN THE SOUTHERN BLUE MOUNTAIN
FOOTHILLS. WIND HIGHLIGHTS MAY BE NECESSARY, ESPECIALLY IN THE
KITTITAS VALLEY. TEMPERATURES WILL BE IN THE UPPER 60S TO MID 70S IN
THE COLUMBIA BASIN WHILE THE REST OF THE AREA WILL BE IN THE UPPER
50S TO MID 60S.
ON MONDAY, MODELS AGREE IN HAVING THE TROUGH OVER THE ROCKIES AND
OUR AREA ON THE EASTERN PORTION OF THE RIDGE. THIS SHOULD BE A DRY
DAY THOUGH A SHORTWAVE RIDING OVER THE RIDGE ARRIVES ALONG THE
CASCADES LATE MONDAY NIGHT. WINDS WILL REMAIN BREEZY (15 TO 25 MPH)
THOUGH LESS STRONG THAN SUNDAY. TEMPERATURES WILL BE A FEW DEGREES
WARMER AND WILL RISE TO THE MID 60S TO MID 70S.
THE SHORTWAVE WILL MOVE THROUGH THE AREA TUESDAY GIVING THE
MOUNTAINS AND THE BLUE MOUNTAIN FOOTHILLS A CHANCE OF RAIN WHILE THE
REST OF THE AREA HAS A SLIGHT CHANCE OF RAIN. RAIN AMOUNTS WILL BE
UP TO A TENTH OF AN INCH IN THE MOUNTAINS AND JUST A FEW HUNDREDTHS
ELSEWHERE. WIND WILL BE BREEZY AGAIN TUESDAY AFTERNOON WITH THE
COLUMBIA BASIN AT 10 TO 20 MPH WHILE THE KITTITAS VALLEY AND THE
COLUMBIA GORGE REACH 15 TO 25 MPH. THE GENERALLY CLOUDY SKIES AND
RAIN WILL LOWER TEMPERATURES A DEGREE OR TWO.
WEDNESDAY AND THURSDAY WILL BE QUIET AS THE RIDGE BUILDS OVERHEAD.
NO RAIN IS EXPECTED AND WINDS WILL BE FAIRLY LIGHT. TEMPERATURES
WILL BE THE MAIN STORY AS TEMPERATURES WEDNESDAY WARM TO THE LOWER
TO MID 70S IN THE LOWER ELEVATIONS WITH MID TO UPPER 60S IN THE
MOUNTAINS. THURSDAY WILL WARM ANOTHER 5 TO 8 DEGREES TO THE UPPER
70S TO LOWER 80S IN THE LOWER ELEVATIONS AND IN THE MID 60S TO MID
70S IN THE MOUNTAINS. THIS WILL BE THE FIRST 80 DEGREE DAY FOR A
NUMBER OF PLACES INCLUDING THE DALLES, THE TRI-COITIES AND
HERMISTON. PERRY/83
AVIATION...18Z TAFS
VFR CONDITIONS TO PREVAIL THROUGH THE PERIOD.
HIGHER CIRRUS WILL BE MOVING INTO THE AREA FROM THE SOUTHWEST LATE
THIS AFTERNOON AND EVENING AND INCREASING FROM FEW TO SCT ABOVE 20K
FEET AGL OVERNIGHT. KRDM AND KBDN WILL BECOME BKN AT 12K-15K FEET
AGL AFTER 10Z-12Z. WINDS WILL GENERALLY BE LIGHT, LESS THAN 12 KTS,
THROUGH THE PERIOD WITH WIND DIRECTIONS DIURNALLY DRIVEN. THE
EXCEPTIONS ARE KRDM AND KBDN ARE EXPECTED TO HAVE NORTHERLY WINDS OF
10-12 KTS GUSTING TO 20 KTS FROM 21Z-05Z. PERRY/83
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...75
LONG TERM....83
AVIATION...83
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