874
FXUS66 KPDT 270945
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
245 AM PDT SUN APR 27 2025
SHORT TERM...TODAY THROUGH TUESDAY
PRECIP CHANCES WILL LARGELY
MOVE OUT OF OUR AREA TODAY AS A CUTOFF LOW TO OUR SOUTH SLOWLY
MEANDERS ITS WAY TOWARD THE ROCKIES. WALLOWA COUNTY MAY GET CLIPPED
BY SOME LINGERING WRAP-AROUND MOISTURE (15-25%) THIS AFTERNOON, BUT
OTHERWISE EXPECT A DRY FORECAST THROUGH MONDAY AS DRY NORTHERLY FLOW
FILTERS INTO THE FORECAST AREA. ON THE BACK END OF THIS DEPARTING
CUTOFF LOW, PRESSURE GRADIENTS WILL TIGHTEN, MAKING FOR ANOTHER
BLUSTERY DAY, ESPECIALLY THROUGH THE CASCADE GAPS AND FOOTHILLS OF
THE BLUE MOUNTAINS. PRESSURE GRADIENTS AREN'T QUITE WHERE WE'D LIKE
TO SEE THEM TO NECESSITATE A WIND ADVISORY, BUT SHOULD NOTE THAT THE
COLUMBIA RIVER GORGE AND KITTITAS VALLEY ARE EXPECTED TO SEE WIND
GUSTS APPROACH AT LEAST 40 MPH AT TIMES THIS AFTERNOON AND EARLY
EVENING (60-70%). CONFIDENCE IS JUST NOT HIGH ENOUGH FOR WINDS TO
EXCEED MUCH FURTHER BEYOND THAT. EXPECT GUSTS IN THE 15-30 MPH RANGE
ACROSS THE REST OF THE FORECAST AREA.
AFTER A QUIET MONDAY, MODELS CLIP US WITH A WEAK SHORTWAVE TO OUR
NORTHWEST AROUND LATE TUESDAY MORNING. MODELS ARE AGGRESSIVE WITH
POPS (WIDESPREAD 30-50%, HIGHER ACROSS THE EASTERN MOUNTAINS), BUT
LESS SO WITH QPF. MUCH OF THIS SYSTEM'S MOISTURE LIES TO OUR
NORTHWEST, SO NOT ANTICIPATING MUCH WITH THIS SYSTEM OUTSIDE OF SOME
LIGHT RAIN SHOWERS, WITH HEAVIEST AMOUNTS OVER THE EASTERN MOUNTAINS
OF OREGON. RIDGING THEN STARTS TO MOVE IN HEADING INTO WEDNESDAY,
KICKING OFF A WARMING TREND HEADING INTO THE START OF MAY.
EVANS/74
LONG TERM...WEDNESDAY THROUGH SUNDAY
SENSIBLE WEATHER CONCERNS
THROUGH THE EXTENDED FORECAST WILL MAINLY INVOLVE THE PASSAGE OF
AN UPPER TROUGH ACROSS THE PACNW FRIDAY INTO THE WEEKEND, WHICH WILL
BRING PERIODS OF RAIN AND HIGH MOUNTAIN SNOW SHOWERS AND A THREAT
OF ISOLATED TO WIDELY SCATTERED THUNDERSTORMS.
THE MID WEEK WILL START WITH UPPER LEVEL RIDGING BUILDING ACROSS
THE PACNW, WITH THE INFLUENCE OF THE RIDGE PERSISTING INTO EARLY
FRIDAY MORNING. UNDER THE UPPER RIDGE, TEMPERATURES WILL
EXPERIENCE A WARMING TREND INTO THE UPPER 70S TO MID 80S ACROSS
THE LOWER ELEVATIONS OF THE FORECAST AREA THURSDAY AFTERNOON
(CONFIDENCE 70-90%). OTHERWISE, A DRY AIRMASS WILL FILTER INTO
THE REGION AND LIGHT WINDS WITH LOCALLY BREEZY AFTERNOONS WILL
PREVAIL UNDERNEATH THE UPPER RIDGE.
THURSDAY NIGHT, ENSEMBLE CLUSTER GUIDANCE IS IN GREAT AGREEMENT
THAT THE UPPER RIDGE WILL BEGIN TO TRAVERSE THE ROCKIES, WITH AN
UPPER LEVEL TROUGH AND COLD FRONT BOUNDARY SWINGING TOWARDS THE
PACNW. THE UPPER TROUGH WILL DEVELOP A NEGATIVE TILT AS IT
APPROACHES THE PACNW COAST FRIDAY MORNING WITH A LEADING SOUTH-
SOUTHWEST FLOW ALOFT. WIDESPREAD SHOWERS WILL DEVELOP BY THE
AFTERNOON FROM SOUTHWEST TO NORTHEAST ACROSS THE FORECAST AREA AS
THE UPPER TROUGH CONTINUES TO APPROACH THE PACNW(CONFIDENCE
60-75%). THE NEGATIVE TILT AND SOUTHWEST FLOW ALOFT WILL ALSO
LEAD TO INCREASING INSTABILITY ACROSS THE EASTERN MOUNTAINS,
RESULTING IN CHANCES (15-30%) OF ISOLATED TO WIDELY SCATTERED
THUNDERSTORMS DEVELOPING FRIDAY AFTERNOON. BREEZY WINDS (GUSTS
25-40MPH) WILL DEVELOP WITH THE APPROACH AND SUBSEQUENT PASSAGE
OF THE COLD FRONT FRIDAY AFTERNOON INTO THE OVERNIGHT HOURS
(CONFIDENCE 65-80%).
LATE FRIDAY NIGHT INTO SUNDAY, THE UPPER TROUGH WILL SLOWLY PUSH
ACROSS THE PACNW, RESULTING IN PERSISTENT RAIN AND HIGH MOUNTAIN
SNOW SHOWERS ACROSS THE CASCADES AND THE EASTERN MOUNTAINS
(CONFIDENCE 50-70%). HOWEVER, AS THE UPPER TROUGH AXIS APPROACHES
THE CASCADE CREST SATURDAY AFTERNOON, RAIN SHOWERS ACROSS THE
LOWER ELEVATIONS WILL TAPER OFF WITH DRY CONDITIONS PERSISTING
INTO SUNDAY (CONFIDENCE 55-70%). BREEZY WINDS (GUSTS 20-40MPH)
THROUGH THE CASCADE GAPS AND INTO THE COLUMBIA BASIN AND PORTIONS
OF NORTH CENTRAL OR WILL PERSIST INTO SATURDAY AND SUNDAY.
OVERALL, ENSEMBLE CLUSTER GUIDANCE IS IN GOOD AGREEMENT WITH THE
PROGRESSION OF THE UPPER TROUGH THROUGH SATURDAY, THOUGH SOME
DIFFERENCES IN TIMING OF THE TROUGH PASSAGE ARE PRESENT AMONGST
MEMBERS. LOOKING AT SUNDAY, DISAGREEMENT DOES INCREASE AMONGST MEMBERS
ON WHEN/WHERE THE UPPER TROUGH TRANSITIONS INTO A CUT-OFF UPPER
LOW IN THE GREAT BASIN, WITH ABOUT 40% OF MEMBERS DEPICTING
SHOWERS PERSISTING INTO SUNDAY AFTERNOON, AND THE REMAINING 60%
PUSHING SHOWERS OUT OF THE FORECAST AREA BY THE AFTERNOON HOURS.
LAWHORN/82
AVIATION...12Z TAFS
VFR CONDITIONS TO PREVAIL THROUGH THE
PERIOD. CIGS WILL REMAIN FEW-SCT AOA 15KFT AGL THROUGH THE PERIOD.
BREEZY WEST TO NORTHWEST WINDS, 15-25KTS WITH GUSTS TO AROUND
35KTS WILL CONTINUE AT SITE DLS THROUGH THE PERIOD. WINDS WILL
INCREASE TO 12-20KTS WITH GUSTS UP TO 30KTS AT SITES
PDT/RDM/BDN/YKM AROUND OR AFTER 18Z. LIGHT WINDS, LESS THAN 12KTS,
WILL PERSIST AT SITES ALW/PSC THROUGH THE PERIOD. LAWHORN/82
PRELIMINARY POINT TEMPS/POPS
PDT 70 43 71 48 / 0 0 0 10
ALW 70 46 69 50 / 0 10 0 20
PSC 78 45 75 49 / 0 0 0 20
YKM 75 45 76 50 / 0 0 0 20
HRI 74 44 74 49 / 0 0 0 10
ELN 69 45 68 47 / 0 0 0 30
RDM 65 32 69 41 / 0 0 0 10
LGD 65 40 67 43 / 10 0 0 10
GCD 66 37 69 41 / 0 0 0 10
DLS 65 44 68 49 / 0 0 0 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...74
LONG TERM....82
AVIATION...82
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