268
FXUS66 KPDT 201704
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
1004 AM PDT MON APR 20 2026
KEY MESSAGES
- LAST DAY OF DRY CONDITIONS BEFORE A COLD FRONT PASSAGE BRINGS
UNSETTLED WEATHER THROUGH THE REGION.
- THUNDERSTORM DEVELOPMENT POSSIBLE (10-25% CHANCES) TUESDAY
AND, TO A LESSER EXTENT, THROUGH WEDNESDAY MORNING.
- BREEZY TO LOCALLY WINDY CONDITIONS DEVELOPING WITH THE PATTERN
CHANGE.
DISCUSSION
RIGHT NOW THROUGH TUESDAY MORNING: SYNOPTIC WISE, UPPER LEVEL
RIDGING WILL CONTINUE TO DOMINANTLY INFLUENCE THE PATTERN IN
THE SHORT TERM. HIGH CLOUDS ARE CURRENTLY IN THE REGION WITH
NO/VERY LITTLE PRECIPITATION REACHING THE GROUND. MONDAY WILL
SEE THE WARMEST DAY IN THE IMMEDIATE FUTURE BEFORE A COLD FRONT
PASSES ON TUESDAY (MORE ON THAT LATER ON). TODAY, WE'LL SEE HIGH
TEMPERATURES IN THE HIGH 70S TO LOW 80S IN MOST OF THE
POPULATED REGIONS (>90% CHANCE) WITH LIGHT TO VARIABLE WINDS.
TUESDAY MORNING TO WEDNESDAY NIGHT: OVERALL GUIDANCE SHOWS GOOD
CHANCES OF THUNDERSTORM COVERAGE, BUT TO WHAT EXTENT IS A BIT
LESS CLEAR. LREF CLUSTERS AREN'T IN GREAT AGREEMENT WITH THE
AMOUNT OF CAPE THAT WILL DEVELOP, WHICH IN TURN MEANS THE EXTENT
OF THUNDERSTORM DEVELOP ISN'T CLEAR. OUT OF THE CLUSTERS, 78% OF
CLUSTERS LIKES TO DEVELOP 400-700 J/KG OF CAPE WITH A SECOND
MAXIMA SPOT IN THE KITTITAS VALLEY WITH SIMILAR AMOUNTS OF CAPE.
THE OTHER 22% ONLY BRING THE CAPE VALUES UP TO 200 J/KG, WITH
LIMITED CAPE VALUES IN THE KITTITAS VALLEY.
CHANCES OF WETTING RAIN REMAIN HIGH (70-90% CHANCE) LATE TUESDAY
AFTERNOON THROUGH THE OVERNIGHT HOURS INTO WEDNESDAY. A PORTION OF
THE BLUE MOUNTAINS WILL SEE A TOTAL OF UP TO 2.5" THROUGH
WEDNESDAY (60-80% CHANCE) WITH AREAS OF THE COLUMBIA BASIN
REACHING UP TO 1" (50-70%). BREEZY TO LOCALLY WINDY CONDITIONS
WILL DEVELOP AS TIGHT PRESSURE GRADIENTS DEVELOP FROM THE LOW
PRESSURE SYSTEM BRINGING AT LEAST 30-40 MPH GUSTS ACROSS THE
REGION (50-70%). WIND ADVISORY HIGHLIGHTS ARE POSSIBLE WITH THE NBM
HINTING THAT PROBABILITIES OF 45 MPH+ GUSTS TO THE FOOTHILLS OF
THE BLUES AT 60-80% WITH PARTS OF THE BASIN REACHING 40-60%.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
VFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. WINDS WILL
GENERALLY BE 10 KTS OR LESS, EXCEPT AT BDN AND RDM, WHICH WILL
SEE GUSTS TO AROUND 20 KTS THIS AFTERNOON AND EARLY EVENING
BEFORE DECREASING ONCE AGAIN.
BY THE END OF THE FORECAST PERIOD, RAIN CHANCES WILL BE CREEPING
UP AT DLS, BDN AND RDM, BUT WILL STILL BE TOO LOW TO WARRANT A
MENTION IN THE INDIVIDUAL FORECASTS. IN LATER TAF ISSUANCES RAIN
CHANCES WILL NEED TO BE INTRODUCED, AND POSSIBLY THUNDER AS
WELL.
PRELIMINARY POINT TEMPS/POPS
PDT 75 48 71 44 / 0 0 40 80
ALW 76 52 73 46 / 0 0 20 80
PSC 80 49 78 49 / 0 10 10 70
YKM 79 50 76 50 / 0 10 20 40
HRI 78 49 74 46 / 0 10 20 70
ELN 75 48 69 45 / 0 10 30 40
RDM 75 43 61 36 / 10 20 50 50
LGD 75 44 73 42 / 0 0 40 90
GCD 77 44 69 39 / 0 10 70 90
DLS 78 52 67 48 / 10 20 40 40
PDT WATCHES/WARNINGS/ADVISORIES
WA...NONE.
OR...NONE.
DISCUSSION...95
AVIATION...77
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