412
FXUS66 KPDT 180500
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
910 PM PST FRI JAN 17 2025
UPDATED AVIATION DISCUSSION
SHORT TERM...TODAY THROUGH SUNDAY
A COLD AIR OUTBREAK IS IN STORE
FOR THE FORECAST AREA THIS WEEKEND AS AMPLIFIED N/NW FLOW TAKES HOLD
OVER THE PACNW AS A RESULT OF A POLAR VORTEX DIPPING DOWN INTO THE
UPPER MIDWEST. FORECAST CONFIDENCE IS HIGH (80-90%) IN WIDESPREAD
SUB-20 DEGREE OVERNIGHT LOWS FOR THE PERIOD, WITH THE SUNDAY NIGHT
INTO MONDAY MORNING TIMEFRAME EXPECTED TO BE THE COLDEST. ONLY
POTENTIAL LIMITING FACTOR WOULD BE THE DEVELOPMENT OF LOW CLOUDS OR
FOG IN THE COLUMBIA BASIN INSULATING FROM SOME OF THE COLD, AS WE
SAW IN THE LOWER YAKIMA VALLEY THIS MORNING, BUT CONFIDENCE IN LOW
CLOUDS IS NOT GREAT (<30%) AS THIS ONCOMING COLD AND DRY AIRMASS MAY
INHIBIT THE ABILITY FOR THE SURFACE TO BECOME SATURATED. WOULD NOT
BE SURPRISED TO SEE PATCHY FOG AT LEAST FOR TONIGHT'S OVERNIGHT
PERIOD, HOWEVER. OTHERWISE, EXPECT LOWS WELL INTO THE TEENS BY
SUNDAY NIGHT FOR ELEVATIONS ABOVE 2000 FEET, WITH EVEN SINGLE DIGITS
LIKELY (60-70%) FOR OUR USUAL COLD SPOTS LIKE THE BEAR VALLEY,
WALLOWA VALLEY, MEACHAM, AND SUNRIVER/LA PINE.
NOT MUCH ELSE TO SPEAK OF IN THE FORECAST OTHERWISE. THE N/NW FLOW
ALOFT HAS INITIATED SOME UPSLOPE SNOW ALONG THE FOOTHILLS OF THE
BLUES AND INTO THE NORTHERN BLUES, HOWEVER WEBCAMS SHOW THAT SNOW IS
VERY LIGHT WITH LITTLE ACCUMULATIONS ON ROADWAYS. EXPECT PRECIP
CHANCES TO TAPER OFF AS THE AIRMASS BECOMES COLDER AND DRIER OVER
THE COMING DAYS, EVEN IN LIGHT OF A FAVORABLE UPSLOPE PATTERN.
EVANS/74
LONG TERM
MONDAY THROUGH FRIDAY...OVERALL, A QUIET WEATHER PATTERN IS IN STORE
THROUGH THE EXTENDED PERIOD. ON MONDAY, NORTHERLY FLOW WILL REMAIN
IN PLACE AS THE PACIFIC NORTHWEST REMAINS ON THE BACK SIDE OF A
LARGE TROUGH CENTERED OVER THE EASTERN PORTION OF THE NATION. THIS
TROUGH, COUPLED WITH HIGH PRESSURE MOVING IN FROM THE WEST WILL
BRING MAINLY CLEAR SKIES AND LIGHT WINDS. AS A RESULT, VERY COLD
OVERNIGHT TEMPERATURES ARE EXPECTED.
THE RIDGE WILL BUILD IN MONDAY NIGHT, THEN BEGIN TO FLATTEN AS THE
FLOW BECOMES MORE WESTERLY BY TUESDAY, AS A VERY WEAK BUT DRY TROUGH
MOVES ACROSS THE REGION. THE FLOW WILL THEN TURN MORE
NORTHWESTERLY BY LATER TUESDAY AND NORTHERLY BY WEDNESDAY AS MORE
RIDGING BUILDS IN FROM THE WEST. BY FRIDAY THIS LATEST RIDGE IS
EXPECTED TO BREAK DOWN AGAIN AS A STRONGER TROUGH AND COLD FRONT
WILL MOVE IN FROM THE WEST, BRING THE FIRST CHANCE OF PRECIPITATION
TO THE REGION, WITH THE HIGHEST CHANCES IN THE MOUNTAINS.
THE MODEL GUIDANCE IS ACTUALLY IN VERY GOOD AGREEMENT THROUGH THE
PERIOD. THERE ARE MINOR DIFFERENCES WITH THE WEAK SYSTEM MOVING
THROUGH ON TUESDAY. EVEN WITH THE STRONGER SYSTEM ON FRIDAY, WHILE
THE ECMWF IS DEEPER, THE TIMING IS CLOSE, AND THERE IS ALWAYS
NATURAL VARIABILITY IN A SYSTEM AT 7 DAYS OUT. THE ENSEMBLE CLUSTERS
ARE FAIRLY EVEN SPLIT AROUND 25% BY 00Z SATURDAY AS WELL, SO NONE
ARE GIVING A STRONG SIGNAL OF SUPPORT TOWARD ANY PARTICULAR
SOLUTION.
THE EARLY PART OF NEXT WEEK LOOKS TO CONTINUE THE BELOW NORMAL
TEMPERATURES, WITH OVERNIGHT LOWS IN THE TEENS TO AROUND 20 DEGREES
MONDAY NIGHT, MODERATING A BIT INTO THE LOWER 20S TUESDAY NIGHT AND
FOR THE BALANCE OF THE WEEK. HIGH TEMPERATURES WILL BE GENERALLY IN
THE 30S, EXCEPT IN CENTRAL OREGON, WHICH WILL BE NEAR 40 ON MONDAY
AND IN THE LOW TO MID 40S THE REST OF THE WEEK. THESE TEMPERATURES
ARE ABOUT 5 TO 10 DEGREES COLDER THAN NORMAL ON LOWS, AND EXCEPT FOR
CENTRAL OREGON ABOUT 5 DEGREES COOLER THAN NORMAL ON HIGHS.
AVIATION
06Z TAFS...HIGH CIRRUS CLOUDS (BASES 18-25 KFT) AND LIGHT WINDS WILL
CONTINUE THROUGH 06Z/19TH. WISTER/85
PRELIMINARY POINT TEMPS/POPS
PDT 23 36 21 31 / 0 0 0 0
ALW 25 35 23 32 / 20 0 0 0
PSC 27 36 24 36 / 0 0 0 0
YKM 22 36 19 35 / 0 0 0 0
HRI 27 37 24 34 / 0 0 0 0
ELN 21 33 20 32 / 0 0 0 0
RDM 19 38 17 35 / 0 0 0 0
LGD 19 32 17 34 / 20 0 0 0
GCD 17 35 17 36 / 0 0 0 0
DLS 29 41 26 37 / 0 0 0 0
PDT WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
SHORT TERM...74
LONG TERM....77
AVIATION...85
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