850
FXUS66 KPDT 271722
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1022 AM PDT THU MAR 27 2025
UPDATED FOR AVIATION
AVIATION
18Z TAFS...VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD.
PERIODS OF RAIN WILL IMPACT ALL TAF SITES, BUT SHOULD NOT BE HARD
ENOUGH TO BRING LOWERED CIGS OR VSBYS. GUSTY WINDS ARE EXPECTED
TO DEVELOP AT BDN AND RDM LATER THIS AFTERNOON AND CONTINUE
THROUGH THE NIGHT AT BDN AND RDM. WINDS AT THESE LOCATIONS SHOULD
GUST IN THE 25 TO 20 KT RANGE. ELSEWHERE, WINDS WILL MAINLY BE 10
KTS OR LESS, THOUGH THERE COULD BE SOME WINDS AROUND 10 TO 15 KTS.
PREV DISCUSSION
/ISSUED 315 AM PDT THU MAR 27 2025/
SHORT TERM...TODAY THROUGH SATURDAY...OVERNIGHT SATELLITE IMAGERY
REVEALS AN IMPRESSIVE LOW PRESSURE SYSTEM CENTERED OFF THE PACIFIC
COAST. WHILE THIS LOW DIDN'T QUITE DELIVER THE CONVECTIVE THREAT WE
WERE EXPECTING WEDNESDAY EVENING, SOME CELLS DID MANAGE TO FORM
ALONG THE CASCADE CRESTS, WITH A FEW SPILLING OVER INTO THE EAST
SLOPES AROUND CLE ELUM AND ELLENSBURG. MOST OF THE REST OF THE
FORECAST AREA, HOWEVER, HAS BEEN DRY, SPARED OF ANY THUNDERSTORM
ACTIVITY.
SO LONG AS THIS LOW PERSISTS, HOWEVER, SO WILL CHANCES FOR RAIN. A
COLD FRONT WILL SWEEP THROUGH THE AREA EARLY THIS MORNING, MAKING
FOR SOME WINDY CONDITIONS TODAY, BEFORE THIS LOW CIRCULATES ANOTHER
BAND OF MOISTURE INTO THE FORECAST AREA. WINDS WILL ORIENT
THEMSELVES A BIT MORE SW THIS TIME, MAKING FOR BETTER PRECIP CHANCES
FOR OUR NECK OF THE WOODS, HOWEVER THE LOW-LEVEL MOISTURE PROFILE IS
STILL LESS THAN IDEAL, SO EXPECT SCATTERED SHOWERS WITH SOME AREAS
DODGING MOISTURE ONCE AGAIN. MODELS DO TAP INTO SOME RESIDUAL
INSTABILITY, SO SOME OF THESE SHOWERS MAY PRODUCE A RUMBLE OF
THUNDER AND SOME LIGHTNING, BUT CERTAINLY AM NOT EXPECTING ANYTHING
STRONG OR SEVERE.
THE LOW FINALLY STARTS TO LIFT UP AND OUT OF THE FORECAST AREA BY
FRIDAY. A SHORTWAVE RIDING ITS SOUTHERN FLANK WILL CIRCULATE THROUGH
THE FORECAST AREA, BRINGING WITH IT YET ANOTHER ROUND OF PRECIP,
ALTHOUGH THIS TIME MAINLY FOR THE MOUNTAINS, AS MOISTURE ADVECTION
WILL BE MUCH WEAKER AND PRECIP WILL PRIMARILY BE TOPOGRAPHICALLY
DRIVEN. SNOW LEVELS WILL REMAIN ELEVATED - LARGELY ABOVE 4000-4500
FT THANKS TO SW FLOW ALOFT - SO NO REAL MOUNTAIN SNOW THREAT, BEFORE
DRY CONDITIONS PREVAIL ON SATURDAY AS WEAK TRANSITORY RIDGING SLIDES
IN OVER THE FORECAST AREA.
AS FAR AS HYDRO CONCERNS GO, RIVER FORECASTS HAVE TRENDED DOWN A TAD
THANKS TO THE LACK OF RAIN THE FORECAST AREA SAW WEDNESDAY. THE WARM
TEMPERATURES HAVE STILL LED TO INCREASED SNOWMELT AND RUNOFF, WITH
RIVERS/STREAMS PEAKING IN LEVELS ON FRIDAY INTO SATURDAY, BEFORE
TRENDING BACK DOWN BY EARLY NEXT WEEK. JOHN DAY RIVER AT SERVICE
CREEK IS STILL EXPECTED TO REACH MINOR FLOOD STAGE FRIDAY AFTERNOON,
HOWEVER ALL OTHER GAUGES CURRENTLY UNDER THE ONGOING RVS ARE
EXPECTED TO PEAK AT JUST BANKFULL. EVANS/74
LONG TERM...SUNDAY THROUGH THURSDAY...
1. ACTIVE PATTERN TO SET UP THROUGH THE PERIOD
2. MOUNTAIN SNOW AND LOW ELEVATION RAIN
3. SEASONABLE TEMPERATURES
A RATHER PICTURESQUE SPRING STRING COMING TO THE PACNW. THE LONG
TERM WILL BE CHARACTERIZED BY AN ACTIVE WEATHER PATTERN. ENSEMBLES
ARE IN DECENT AGREEMENT WITH THE WEATHER SYSTEMS EXPECTED TO COME
THROUGH. MULTIPLE SYSTEMS ARE EXPECTED TO TRAVERSE THE REGION THROUGH
MIDWEEK. HOWEVER, ENSEMBLES DO BEGIN TO SPREAD WITH THE SYSTEMS COME
MONDAY. WITH THE VARIANCES, THE OVERALL PATTERN WILL REMAIN
RELATIVELY ACTIVE WITH ENSEMBLES SHOWING PERSISTENT MOUNTAIN SNOW
AND LOW ELEVATION RAIN. ENSEMBLES SHOW SUNDAY TO BE THE WARMEST AND
DRIEST DAY OF THE LONG TERM AS TEMPERATURES DROP DUE TO THE UPPER
LEVEL LOW AND SURFACE COLD FRONT.
SUNDAY WILL BEGIN WITH THE EXITING OF THE UPPER LEVEL RIDGE AS THE
NEXT UPPER LEVEL LOW BREAKS IT DOWN AND BEGINS TO PUSH INLAND.
SUNDAY WILL BE THE DRIEST DAY OF THE PERIOD UNTIL THE BREAKDOWN OF
THE RIDGE SUNDAY EVENING. MODELS SHOW THE UPPER LEVEL LOW TO BRING
WITH IT PRECIPITATION ALONG THE CASCADE RIDGES AS WELL AS ALONG THE
EASTERN MOUNTAINS. SNOW LEVELS WILL REMAIN ABOVE 3800 FT SUNDAY
BEFORE STEADILY DROPPING TO BETWEEN 2500 FEET AND 3500 FEET. ROUGHLY
70% OF THE RAW ENSEMBLES SHOW 1-3 INCHES OF SNOW TO ACCUMULATE ABOVE
3500 FEET ON SUNDAY. AS THE LOW CONTINUES TO DEEPEN AND PUSH FARTHER
ONSHORE, MODELS SHOW A BIT OF A MOISTURE PUSH LEADING TO 60% OF THE
RAW ENSEMBLES HAVING 3-5 INCHES ALONG THE OR CASCADE CRESTS ABOVE
3500 FEET, 0.5-1.5 INCHES ALONG THE WA CASCADES ABOVE 3500 FEET WITH
40% PROBABILITIES THAT SNOQUALMIE WILL SEE NEAR 0.5 INCHES. 70-80%
SHOW THE NORTHERN BLUES (TOLLGATE/SKI BLUEWOOD) WILL SEE 2-4 INCHES
MONDAY. A LULL IN THE PATTERN MONDAY NIGHT THROUGH TUESDAY NIGHT WILL
ALLOW FOR SOME DRYING, HOWEVER, MODELS SHOW YET ANOTHER LOW FORMING
AND PUSHING INLAND TUESDAY NIGHT BRINGING MORE PRECIPITATION TO THE
AREA. CLUSTERS SHOW THE MAIN VARIANCE TO BE THAT OF POSITIONING AND
TIMING. MODELS ARE ALSO SHOWING THE AMOUNT AND LOCATION OF
PRECIPITATION TO DIFFER AS WELL. WITH THAT SAID, PRECIPITATION WILL
BE PRIMARILY ALONG THE MOUNTAINS AS THE SYSTEM MOVES ONSHORE BEFORE
BECOMING WIDESPREAD WEDNESDAY. ENSEMBLES SHOW LOW ELEVATION RAIN TO
OCCUR DAILY WITH 40-50% PROBABILITIES THAT OVER 90% OF THE CWA,
MINUS YAKIMA ISOLATED PORTIONS OF CENTRAL OR WILL SEE 0.10 INCHES OF
PRECIPITATION MONDAY BEFORE RAINSHADOWING KICKS IN TUESDAY KEEPING
MUCH OF THE PRECIPITATION LOCKED ALONG THE EASTERN SLOPES OF THE
CASCADES AND ALONG THE EASTERN MOUNTAINS AND FOOTHILLS OF THE BLUES.
EACH DAY ENSEMBLES SHOW 50-70% PROBABILITIES OF RAIN ALONG THE
EASTERN MOUNTAINS, FOOTHILLS OF THE NORTHERN BLUES AND THE EAST
SLOPES OF THE CASCADES.
TEMPERATURES WILL BE WARMEST ON SUNDAY AHEAD OF THE SURFACE FRONT
WITH TEMPERATURES AT OR NEAR SEASONABLE. AS THE PERIOD LINGERS ON,
EFI CONTINUES TO SHOW AT SEASONABLE TEMPERATURES. 60-80% OF THE RAW
ENSEMBLES SHOW THE COLUMBIA BASIN IN THE LOW 60S AS WELL AS ISOLATED
PORTIONS OF THE NORTHERN BLUE FOOTHILLS (PENDLETON AND HERMISTON). 60-
80% THEN SHOW THE REMAINDER OF THE REGION BELOW 3500 FEET TO BE IN
THE MID TO UPPER 50S. THE REMAINDER OF THE LONG TERM PERIOD SHOWS
ISOLATED 60S IN THE BASIN WITH 30-50% PROBABILITIES WHILE 50-70%
SHOW THE REST OF THE REGION TO BE IN THE LOW TO MID 50S WITH AREAS
ALONG THE FOOTHILLS SEEING MID TO HIGH 50S. BENNESE/90
AVIATION...12Z TAFS...VFR CONDITIONS EXPECTED THROUGH THE FORECAST
PERIOD. MAIN HIGHLIGHT THROUGH THE PERIOD IS THE WINDS THAT WILL
PERSIST AT RDM AND INCREASE AT BDN. WINDS AT RDM WILL REMAIN 12-18K
KTS WITH GUSTS AS HIGH AS 35 KTS AND BDN WILL SEE AN INCREASE IN
WINDS AROUND 17Z RANGING BETWEEN 15-25 KTS WITH GUSTS AS HIGH AS 35
KTS. DLS/RDM/BDN/YKM WILL ALSO SEE PROB 30 FOR -RA NEAR 21Z AS THE
NEXT SYSTEM MOVES ACROSS. CIGS WILL VARY BETWEEN BKN/OVC AT 5-10KFT.
BENNESE/90
PRELIMINARY POINT TEMPS/POPS
PDT 63 48 59 39 / 40 60 70 30
ALW 62 49 59 41 / 40 60 80 40
PSC 61 48 63 39 / 70 50 30 0
YKM 56 43 58 33 / 60 70 20 0
HRI 62 48 62 39 / 70 50 50 10
ELN 56 40 56 34 / 50 70 30 10
RDM 57 40 55 29 / 40 50 30 10
LGD 63 43 53 35 / 30 30 90 70
GCD 60 41 54 33 / 30 30 90 70
DLS 59 46 59 39 / 70 60 60 10
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...74
LONG TERM....90
AVIATION...77
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