073
FXUS66 KPDT 200154
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
600 PM PST SUN JAN 19 2025
CORRECTED LONG TERM DISCUSSION
SHORT TERM...TONIGHT THROUGH TUESDAY
CURRENT WATER VAPOR
IMAGERY SHOWS A WEAK SHORTWAVE TROUGH DIVING SOUTH OF THE FORECAST
AREA WITH A DEEP NORTHERLY FLOW DEVELOPING THIS AFTERNOON. MEANWHILE
VISIBLE SATELLITE IMAGERY SHOWS MID LEVEL CLOUD COVER OVER THE
FAR NORTHERN BLUES AND WALLOWA COUNTY, WITH MOSTLY CLEAR SKIES
ELSEWHERE.
TONIGHT, A DEEP NORTHERLY FLOW BEHIND THE SHORTWAVE EXIT WILL
ALLOW AN ARCTIC AIRMASS TO FILTER INTO THE INTERMOUNTAIN PACNW,
BRINGING WELL BELOW NORMAL TEMPERATURES TONIGHT AND MONDAY. THERE
IS HIGH CONFIDENCE (80-90%) THAT PERSISTENT CLEAR SKIES AND A
CONTINUED ARCTIC AIR ADVECTION WILL LEAD TO WIDESPREAD MORNING
LOWS FROM -10 TO 10 DEGREES OUTSIDE OF THE COLUMBIA BASIN, WITH
COLDEST TEMPERATURES EXPECTED IN THE BEAR VALLEY (SENECA AREA) AND
LA PINE AREA. IN THE COLUMBIA BASIN AND ADJACENT YAKIMA VALLEY,
TEMPERATURES WILL DROP INTO THE TEENS, WITH A FEW FOOTHILL AREAS
FLIRTING WITH SINGLE DIGIT TEMPERATURES TONIGHT. THE COLD SPELL
WILL CONTINUE THROUGH MONDAY, AS HIGH TEMPERATURES WILL STRUGGLE
TO WARM INTO THE 30S ACROSS THE FORECAST AREA, WITH SOME HIGH
MOUNTAIN VALLEY LOCATIONS AS LOW AS THE MID TEENS IN THE BLUES AND
WA CASCADE EAST SLOPES.
BY MONDAY NIGHT, A SHORTWAVE TROUGH SLIDING ACROSS SOUTHERN BC
WILL HAVE FLATTEN THE RIDGE, EFFECTIVELY TURNING OFF THE ARCTIC
AIRMASS ADVECTION INTO THE REGION. THE SHORTWAVE TROUGH WILL HAVE
VERY LITTLE MOISTURE ASSOCIATED WITH IT, ONLY RESULTING IN A MID
TO UPPER LEVEL CLOUD LAYER DEVELOPING MONDAY NIGHT INTO TUESDAY.
WHILE THE COLD AIR TAP WILL HAVE BEEN TURNED OFF, WIDESPREAD
MORNING LOW TEMPERATURES IN THE TEENS...SINGLE DIGITS HIGH
MOUNTAIN LOCATIONS...WILL DEVELOP ACROSS THE FORECAST AREA
TUESDAY MORNING. OTHERWISE, A TIGHTENING PRESSURE GRADIENT BETWEEN
THE COLUMBIA BASIN AND BAKER VALLEY WILL RESULT IN SOUTHERLY WINDS
INCREASING TO 15-25MPH AND GUSTS UP TO 40MPH IN THE GRANDE RONDE
VALLEY MONDAY NIGHT THROUGH TUESDAY MORNING.
TUESDAY, FLOW ALOFT WILL TURN TO THE NORTHWEST AS UPPER LEVEL
RIDGING AMPLIFIES OVER THE NORTHEAST PACIFIC. AFTERNOON
TEMPERATURES WILL WARM BACK ABOVE FREEZING IN THE LOWER ELEVATIONS
TUESDAY AFTERNOON, WITH DRY CONDITIONS AND LIGHT WINDS PERSISTING
INTO TUESDAY NIGHT. LAWHORN/82
LONG TERM...WEDNESDAY THROUGH SUNDAY
KEY POINTS:
1. TROUGH DIGGING THROUGH THE PACNW GOING INTO THE WEEKEND.
2. MOUNTAIN SNOW/COLUMBIA BASIN. SNOW CHANCES GREATEST ON
FRIDAY/SATURDAY.
3. WEATHER PATTERN WILL DRY OUT BY SUNDAY.
THE LONG TERM WILL BEGIN WITH A RIDGE BUILT JUST OFFSHORE OF THE
PACNW, HINDERING ANY POP CHANCES AREA WIDE THROUGH MID-WEEK. WINDS
WILL GENERALLY BE LIGHT AND VARIABLE WITH THE EXCEPTION OF THE
WALLOWA AND THE GRANDE RONDE VALLEY EXPECTING SOUTHERLY WINDS AT 10-
15 KNOTS. MODELS ARE IN GOOD AGREEMENT THAT BY THURSDAY, THE RIDGE
WILL FLATTEN AND A TROUGH SCENARIO WILL LAY OUT LIGHT PRECIPITATION
ACROSS HIGHER ELEVATION LOCATIONS. WINDS WILL SHIFT FROM SOUTH TO A
MORE NORTH-WESTERLY DIRECTION, PAVING THE WAY FOR SNOW AND RAIN/SNOW
CHANCES TO INCREASE. THIS WILL BE FOLLOWED BY A MORE DRIER/MORE
RIDGING SOLUTION WITH LESS WIDESPREAD PRECIP CHANCES BY THURSDAY
AFTERNOON.
THE GREATEST PRECIP CHANCES WILL OCCUR ON FRIDAY, AS ALL MODELS
SUGGEST TROUGHING TO SOME DEGREE OVER THE CWA. A GOOD MAJORITY OF
ENSEMBLES (62%) HAVE SNOW OF AT LEAST 0.1 INCH IMPACTING THE LOWER
COLUMBIA BASIN & KITTITAS VALLEYS AND ALL MEMBERS SHOWING AT LEAST
0.1 INCH IN THE MOUNTAINS. ANY PRECIP FALLEN FROM THIS SYSTEM IS
EXPECTED TO BE LIGHT WITH LOW QPF AMOUNTS. THE NBM IS GIVING THE
LOWER COLUMBIA BASIN A SLIGHT CHANCE (20-40%) OF SEEING AT LEAST 0.1
INCH OF SNOW, WHILE CHANCES IN THE MOUNTAINS WILL BE GREATER (50-
70%). CHANCES IN THE MOUNTAIN GO DOWN TO 20-30% FOR AT LEAST 1 INCH
OF SNOW.
UNCERTAINTY BRIEFLY BUILDS BACK ON SATURDAY AS ENSEMBLE MEMBERS ARE
ALMOST SPLIT IF THEY WANT TO PUSH THE TROUGH TOWARDS THE SOUTH (55%
OF MEMBERS) WITH A WETTER PATTERN OR PROGRADE TO THE EAST (45% OF
MEMBERS) WITH A DRIER PATTERN. REGARDLESS OF OUTCOME, QPF AMOUNTS
WILL REMAIN VERY LOW AND WELL BELOW ADVISORY LEVELS.
THE PATTERN CHANGES AGAIN WITH INCREASING CONFIDENCE AS WE HEAD INTO
SUNDAY WITH MODELS STARTING TO CONVERGE ON A RIDGE SETTLING CLOSE TO
OR/WA. CHANCES ARE HIGH (80-90%) THAT OUR PATTERN WILL DRY OUT ANY
REMAINING PRECIP FROM THE PREVIOUS SYSTEM, KEEPING US COOL AND DRY
AS WE END THE WEEKEND. /95
AVIATION...00Z TAFS
VFR CONDITIONS WILL PERSIST THROUGH THE
FORECAST PERIOD WITH HIGH CONFIDENCE (80%). CIGS WILL REMAIN HIGH
FEW/SCT 25KFT WITH WINDS LIGHT AND VARIABLE BELOW 6 KTS. OVERNIGHT
AND INTO THE MORNING CIGS WILL DROP TO NEAR 10KFT DUE TO THE MID-
LEVEL MOISTURE (60%). BENNESE/90
PRELIMINARY POINT TEMPS/POPS
PDT 13 26 19 36 / 10 0 0 0
ALW 18 28 22 36 / 10 0 0 0
PSC 19 30 23 35 / 0 0 0 0
YKM 11 27 17 35 / 0 0 0 0
HRI 18 30 22 36 / 0 0 0 0
ELN 9 27 16 36 / 0 0 0 0
RDM 4 32 17 47 / 0 0 0 0
LGD 7 29 16 37 / 10 0 0 0
GCD 7 33 14 43 / 0 0 0 0
DLS 21 32 24 42 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...82
LONG TERM....95
AVIATION...90
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