808
FXUS66 KPDT 220539
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
ISSUED BY NATIONAL WEATHER SERVICE SPOKANE WA
1039 PM PDT MON APR 21 2025
UPDATED AVIATION DISCUSSION
SHORT TERM...TODAY THROUGH WEDNESDAY NIGHT
KEY MESSAGES:
1. FREEZING TEMPERATURES TONIGHT INTO TUESDAY MORNING.
2. WARMING TEMPERATURES AND DRY CONDITIONS THROUGH MIDWEEK.
CURRENT RADAR AND VISIBLE SATELLITE IMAGERY SHOWS DRY CONDITIONS
AS HIGH LEVEL CLOUDS PASS ACROSS THE LOWER COLUMBIA BASIN FROM
THE NORTHWEST. THIS IS IN RESPONSE TO SIGNIFICANT SURFACE HIGH
PRESSURE, WHICH WILL ALLOW FOR CLEAR SKIES AND COOL CONDITIONS
AFTER SUNSET AS WINDS BEGIN TO SUBSIDE. PRESENT HIGH PRESSURE
OVERNIGHT INTO TUESDAY WILL PROVIDE EFFICIENT RADIATIONAL COOLING,
DROPPING TUESDAY MORNING TEMPERATURES INTO THE UPPER 20S TO LOW
30S ACROSS LOWER ELEVATIONS OF THE NORTHERN BLUE MOUNTAIN
FOOTHILLS AND THE YAKIMA/KITTITAS VALLEYS. CONFIDENCE IN TUESDAY
MORNING TEMPERATURES REACHING 32 OR BELOW IS 80% AND DROPPING TO
28 OR BELOW IS 60%. NORTHWEST FLOW EXPERIENCED TONIGHT WILL TURN
TO MORE OUT OF THE WEST TUESDAY AND WEDNESDAY AS AN UPPER LEVEL
TROUGH DIGS INTO NORTHERN CALIFORNIA AND UPPER LEVEL RIDGING
OCCURS ACROSS THE PACIFIC NORTHWEST.
FLOW ALOFT FROM THE WEST IS ANTICIPATED ON TUESDAY BEFORE TURNING
MORE FROM THE SOUTHWEST INTO WEDNESDAY. HIGH TEMPERATURES TODAY
STAYED JUST SHY OF NORMAL FOR THIS TIME OF YEAR, BUT WILL TREND
ABOVE NORMAL TUESDAY AND AGAIN ON WEDNESDAY AS HIGHS BUMP UP 2 TO
5 DEGREES EACH DAY. EXCELLENT OVERNIGHT HUMIDITY RECOVERIES ARE
EXPECTED THROUGH THE MIDWEEK, BUT AFTERNOON HUMIDITIES WILL STAY
CONSISTENT IN THE MID-20S TO MID-30S TUESDAY BEFORE DROPPING INTO
THE LOW TO UPPER 20S ACROSS LOWER ELEVATIONS OF CENTRAL OREGON,
BLUE MOUNTAIN FOOTHILLS, LOWER COLUMBIA BASIN, AND THE
YAKIMA/KITTITAS VALLEYS. 75
LONG TERM...THURSDAY THROUGH MONDAY
DRY CONDITIONS WILL
CONTINUE THURSDAY AS THE UPPER RIDGE MOVES EASTWARD BEFORE THE
SHORTWAVE TROUGH ARRIVES INLAND OF THE PACNW FRIDAY. LIGHT SHOWERS
MAY DEVELOP OVER THE WA/OR CASCADES FOR THURSDAY EVENING AND
GRADUALLY BECOME WIDESPREAD INTO SATURDAY ACROSS THE FORECAST
AREA. HOWEVER, THIS TROUGH COULD ALSO BRING SOME ISOLATED
THUNDERSTORMS OVER DESCHUTES AND CROOK COUNTY (20-30% CHANCE),
GIVEN THE INFLUENCE OF THE SOUTHWEST FLOW AND RIDGE BREAKDOWN.
SUNDAY ONWARDS, THE TROUGH WILL THEN BEGIN MOVING OUT OF THE PACNW
WITH THE APPROACHING RIDGE THUS LEAVING BEHIND LINGERING SHOWERS
OVER THE BLUES AND CASCADES (<30% CONFIDENCE). THE LOWLANDS WILL
BE MOSTLY DRY. FORECASTING PRECIP ACTIVITY FOR FRIDAY AND SATURDAY
WILL BE TOUGH BECAUSE OF THE TROUGH’S AMPLITUDE. MOST CLUSTER
MEMBERS FAVOR A BROAD TROUGHING PATTERN WHEREAS 40% OF GEFS
MEMBERS AGREE WITH A CLOSED LOW MOVING ONSHORE. MORE ACTIVE
SHOWERS, THUNDERSTORMS AND WINDY CONDITIONS MAY DEVELOP IF THE LOW
DOES CONTINUE. BUT IF NOT, THEN WE COULD HAVE DRY LITTLE TO NO
RAIN.
THURSDAY AFTERNOON INTO EARLY EVENING WILL BE LOCALLY BREEZY
(15-25 MPH) ALONG THE WA CASCADES AND KITTITAS VALLEY. AS THE
SURFACE PRESSURE GRADIENTS INCREASINGLY TIGHTEN, WINDS MIGHT
BECOME SLIGHTLY GUSTY UP TO 25-35 MPH OVER THE AFOREMENTIONED
AREAS INCLUDING NORTH CENTRAL OR AND SIMCOE HIGHLANDS FRIDAY AND
SATURDAY DURING AFTERNOON AND EARLY EVENING HOURS. SUNDAY WILL
REMAIN BREEZY AS WELL. KITTITAS VALLEY COULD HAVE WIND GUSTS UP TO
40 MPH SUNDAY EVENING BUT, CONFIDENCE IS LOW (<20%). WIND
CONDITIONS SHOULD IMPROVE MONDAY ONCE THE RIDGE BUILDS OVER.
FEASTER/97
AVIATION...06Z TAFS
VFR CONDITIONS ARE FORECAST THROUGH THE
VALID PERIOD FOR ALL SITES. WHILE SATELLITE IMAGERY CURRENTLY
SHOWS MOSTLY CLEAR SKIES WITH JUST FEW CIRRUS, THERE IS SOME
UNCERTAINTY IN COVERAGE OF MID-LEVEL CLOUDS OVERNIGHT INTO
TUESDAY AS A WEAK WEATHER SYSTEM MOVES OVERHEAD. WINDS WILL BECOME
MOSTLY LIGHT AND TERRAIN-DRIVEN OVERNIGHT, WITH SOME GUSTS TO 15
KTS TUESDAY AFTERNOON AT BDN/RDM. PLUNKETT/86
PRELIMINARY POINT TEMPS/POPS
PDT 32 61 35 66 / 0 0 0 0
ALW 33 60 37 66 / 0 0 0 0
PSC 33 65 34 71 / 0 0 0 0
YKM 31 63 35 69 / 0 0 0 0
HRI 33 64 34 71 / 0 0 0 0
ELN 31 60 35 68 / 0 0 0 0
RDM 26 59 27 65 / 0 0 0 0
LGD 28 56 30 62 / 0 0 0 0
GCD 28 58 29 63 / 0 0 0 0
DLS 34 65 39 72 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...FREEZE WARNING UNTIL 9 AM PDT TUESDAY FOR ORZ507.
WA...FREEZE WARNING UNTIL 9 AM PDT TUESDAY FOR WAZ026-027-029.
SHORT TERM...75
LONG TERM....97
AVIATION...86
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