925
FXUS66 KPQR 131227 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
427 AM PST TUE JAN 13 2026
UPDATED SHORT TERM DISCUSSION, AVIATION DISCUSSION AND PQR
WATCHES/WARNINGS/ADVISORIES.
SYNOPSIS
A STRONG AND PERSISTENT AREA OF HIGH PRESSURE WILL REMAIN
LOCKED IN PLACE OVER THE PACIFIC NORTHWEST THROUGH THE WEEK. THIS
PATTERN WILL SUPPORT AN EXTENDED PERIOD OF DRY WEATHER, LIGHT WINDS,
AND TEMPERATURES RUNNING ABOVE SEASONAL NORMS. IN CONTRAST, PORTIONS
OF THE INTERIOR LOWLANDS, PARTICULARLY THE WILLAMETTE VALLEY, WILL
LIKELY EXPERIENCE COOLER DAYTIME TEMPERATURES DUE TO FOG AND LOW
STRATUS DURING THE OVERNIGHT AND MORNING HOURS OVER THE NEXT FEW
DAYS. LATE IN THE WEEK, COLD EASTERLY WINDS WILL FLOW THROUGH THE
COLUMBIA RIVER GORGE, WITH SUB-FREEZING OVERNIGHT TEMPERATURES LIKELY
IN THE UPPER HOOD RIVER VALLEY AND MUCH OF THE WILLAMETTE VALLEY.
UPDATE...TUESDAY MORNING
OBSERVED SURFACE TEMPERATURES OVER THE
SOUTHERN WILLAMETTE VALLEY THIS MORNING ARE A FEW DEGREES COLDER THAN
EXPECTED, FALLING TO 28-30 DEGREES. AT THE SAME TIME, THIS AREA
CONTINUES TO SEE AREAS OF DENSE FOG WITH SURFACE VISIBILITIES AROUND
1/4 MILE OR LESS. GIVEN THE SUB-FREEZING TEMPERATURES IN PLACE AND
THE POTENTIAL FOR LIGHT RIMING OF ICE ON SURFACES, HAVE REPLACED THE
DENSE FOG ADVISORY FOR THIS AREA WITH A FREEZING FOG ADVISORY. AS
SUCH, A FEW SLICK SPOTS WILL BE POSSIBLE THIS MORNING, MAINLY FOR
LOCATIONS WITHIN THE WILLAMETTE VALLEY TO THE SOUTH OF SALEM THAT
CONTINUE TO OBSERVE DENSE FOG. STILL EXPECTING FOG TO LIFT BY NOON,
WITH TEMPERATURES WARMING ABOVE FREEZING. -23
DISCUSSION...NOW THROUGH MONDAY
LITTLE HAS CHANGED IN THE
OVERALL FORECAST SINCE YESTERDAY AFTERNOON. WEATHER CONDITIONS NOW
THROUGH JAN. 20TH WILL BE FAIRLY CONSISTENT EACH DAY DUE TO AN
ANOMALOUSLY STRONG UPPER-LEVEL RIDGE CENTERED OVER THE PACIFIC
NORTHWEST AND NORTHEAST PACIFIC. MODELS STILL SUGGEST 500 MB HEIGHTS
WILL PEAK AROUND 585-590 MB ALONG THE RIDGE AXIS TODAY INTO TONIGHT
IN WESTERN OR/WA, HIGHEST TO THE SOUTH. THESE VALUES ARE AROUND THE
99TH PERCENTILE COMPARED TO CLIMATOLOGY, SIGNIFYING THE UNUSUAL
STRENGTH OF THIS HIGH PRESSURE SYSTEM. ENSEMBLE GUIDANCE REMAINS IN
STRONG AGREEMENT THAT THIS RIDGE WILL PERSIST THROUGH THE UPCOMING
WEEKEND, RESULTING IN CALM, DRY, AND RELATIVELY MILD CONDITIONS FOR
MID-JANUARY, ESPECIALLY FOR ELEVATIONS ABOVE 1000 FEET WHERE FOG AND
LOW STRATUS WILL NOT BE A FACTOR. WHILE SOME GUIDANCE INDICATES WEAK
SHORTWAVE ENERGY MAY ROTATE AROUND THE PERIPHERY OF THE RIDGE THIS
WEEKEND, THESE FEATURES ARE EXPECTED TO REMAIN MOISTURE-STARVED AND
SHOULD NOT DISRUPT THE DRY PATTERN. THE TIMING OF A MORE MEANINGFUL
PATTERN CHANGE REMAINS UNCERTAIN, THROUGH A GROWING SUBSET OF
ENSEMBLE GUIDANCE (AROUND 75%) SUGGESTS A POTENTIAL BREAKDOWN OF THE
RIDGE AND A RETURN OF AT LEAST LIGHT PRECIPITATION SOMETIME BETWEEN
JANUARY 21 TO 23. UNTIL THEN, DRY WEATHER WILL CONTINUE EACH DAY FROM
TUESDAY THROUGH AT LEAST MONDAY.
ONE EXCEPTION TO THE OTHERWISE CALM CONDITIONS WILL BE INCREASING
EASTERLY WINDS IN THE WESTERN COLUMBIA GORGE, CASCADES, AND PORTIONS
OF THE EAST PORTLAND AND VANCOUVER METRO AREA LATE THURSDAY INTO
FRIDAY AS OFFSHORE PRESSURE GRADIENTS STRENGTHEN. WITH THE AIRMASS
ORIGINATING FROM THE COLUMBIA BASIN, EXPECT COOLER TEMPERATURES TO
ADVECT INTO THE UPPER HOOD RIVER VALLEY, COLUMBIA RIVER GORGE AND
WILLAMETTE VALLEY. THE UPPER HOOD RIVER VALLEY COULD SEE OVERNIGHT
MINIMUM TEMPERATURES FALL BELOW FREEZING IN THE MORNINGS THURSDAY
THROUGH AT LEAST SUNDAY (20-40% CHANCE FOR OVERNIGHT TEMPS TO FALL
BELOW 32 F). LOW TEMPERATURES ARE FORECAST TO DROP TO NEAR FREEZING
ACROSS MOST OF THE WILLAMETTE VALLEY AS WELL.
OTHERWISE, DENSE FOG AND LOW STRATUS REMAINS THE MAIN CONCERN FOR THE
INTERIOR LOWLANDS THIS WEEK, ESPECIALLY DURING THE OVERNIGHT AND
MORNING HOURS TODAY THROUGH THURSDAY WHEN REDUCED VISIBILITIES WILL
POSE A TRAVEL HAZARD FOR MANY COMMUTERS. NOTE WEBCAM AND SURFACE
WEATHER OBSERVATIONS FROM 3 AM TUESDAY SHOWED WIDESPREAD FOG OVER
MOST OF THE WILLAMETTE VALLEY WITH VISIBILITIES FALLING BELOW 1/2-1
MILE. FOG WAS ALSO BEING OBSERVED IN THE COAST RANGE LOWLANDS.
THEREFORE, A DENSE FOG ADVISORY REMAINS IN EFFECT FOR THESE AREAS
THROUGH THIS MORNING. IN CONTRAST, AREAS ABOVE THE VALLEY INVERSION,
INCLUDING THE COAST RANGE, CASCADE FOOTHILLS, AND HIGHER TERRAIN IN
THE CASCADES WILL EXPERIENCE SIGNIFICANTLY WARMER AND SUNNIER
CONDITIONS, WITH HIGHS COMMONLY IN THE UPPER 50S TO MID 60S. COASTAL
AREAS WILL ALSO TREND MILD, WITH AFTERNOON TEMPERATURES WELL INTO THE
50S AND NEAR 60 DEGREES.
THE PROLONGED PERIOD OF HIGH PRESSURE WILL ALSO FAVOR STAGNANT
AIR CONDITIONS WITH LIMITED VERTICAL MIXING. THESE CONDITIONS
ARE CONDUCIVE TO THE ACCUMULATION OF AIR POLLUTANTS NEAR THE
SURFACE, PARTICULARLY IN VALLEY LOCATIONS PRONE TO INVERSIONS.
AN AIR STAGNATION ADVISORY REMAINS IN EFFECT FOR THE WILLAMETTE
VALLEY AND MAY BE EXPANDED AS THE WEEK PROGRESSES. STATE AIR
QUALITY AGENCIES CONTINUE TO RECOMMEND AVOIDING OUTDOOR BURNING
AND MINIMIZING THE USE OF RESIDENTIAL WOOD-BURNING DEVICES.
RESIDENTS ARE ENCOURAGES TO MONITOR LOCAL AIR QUALITY INFORMATION AND
COMPLY WITH ANY BURN RESTRICTIONS ISSUED BY THEIR LOCAL AGENCIES.
-23/12
AVIATION
HIGH PRESSURE BUILDS OVER THE REGION THROUGH THE NEXT
SEVERAL DAYS, BRINGING DRY AND CALM CONDITIONS WITH VALLEY FOG AND
LOW STRATUS. FOG AND LOW STRATUS ARE EXPECTED TO LIFT BY 20-23Z
TUESDAY, HOWEVER THERE IS A 20-30% CHANCE LOW STRATUS LINGERS
THROUGH THE DAY TUESDAY DESPITE IMPROVING SURFACE VISIBILITIES.
THE CENTRAL AND SOUTHERN WILLAMETTE VALLEY FROM KSLE TO KEUG HAVE
THE HIGHEST CHANCE OF LOW STRATUS CONTINUING THROUGH THE DAY, OR
WITH CLEARING ONLY LASTING A FEW HOURS IN THE LATE AFTERNOON AND
EARLY EVENING. REGARDLESS OF THE OUTCOME, LOW STRATUS AND FOG WILL
QUICKLY EXPAND AGAIN TUESDAY NIGHT AFTER 03-06Z. FOG MAY BE DENSE
AT TIMES TUESDAY MORNING AND AGAIN TUESDAY NIGHT THROUGH MONDAY
MORNING, WITH SURFACE VISIBILITIES DROPPING TO 1/4-1/2 SM OR
LESS. NOTE DENSE FREEZING FOG IS OCCURRING AT KEUG WITH SURFACE
VISIBILITIES AT 1/4 SM AND TEMPERATURES AROUND 28-29 DEGREES. THIS
IS COLD ENOUGH FOR A THIN LAYER OF RIME ICE TO FORM ON SURFACES,
WHICH CAN RESULT IN SLICK SPOTS.
CONFIDENCE IS INCREASING THAT KTTD AND KONP WILL STAY FOG FREE
THIS MORNING THROUGH THIS AFTERNOON WITH CLEAR SKIES, HOWEVER
THERE IS STILL A 10-20% CHANCE FOG DOES BRIEFLY FORM AT KTTD
TOWARDS 15Z TUESDAY.
KPDX AND APPROACHES...WHILE FOG HAS NOT FORMED AT THE KPDX
TERMINAL YET THIS MORNING, PROBABILITIES INCREASE TO NEAR 60% FOR
FOG AND SURFACE VISIBILITIES AT 1/2 SM OR LOWER BY 15Z TUESDAY.
WHILE NOT GUARANTEED TO HAPPEN, SUSPECT THIS WILL OCCUR AS FOG IS
CURRENTLY BEING OBSERVED AROUND 5-10 MILES NORTHWEST OF THE KPDX
TERMINAL AND WINDS REMAIN CALM. ASSUMING FOG DOES DEVELOP AT THE
TERMINAL BY 15Z TUESDAY, EXPECT CONDITIONS TO IMPROVE TO VFR BY
20-21Z TUESDAY, HOWEVER THERE IS A 20% CHANCE LOW STRATUS WILL
CONTINUE THROUGH THE DAYLIGHT HOURS. REGARDLESS OF ANY CLEARING
THAT DOES OR DOES NOT OCCUR, EXPECT FOG AND LOW STRATUS TO RETURN
BY 06Z TUESDAY WITH LIFR TO IFR FLIGHT CONDITIONS THEREAFTER. -23
MARINE
WINDS HAVE BECOME RELATIVELY LIGHT THIS MORNING AS HIGH
PRESSURE STRENGTHENS OVER THE REGION, WITH SEAS HOVERING BETWEEN
10-12 FT THIS MORNING BEFORE LOWERING TO 8-10 FT THIS AFTERNOON.
NORTHERLY WINDS DEVELOP LATE WEDNESDAY INTO THURSDAY AS A THERMAL
TROUGH BUILDS NORTHWARD UP THE SOUTH OREGON COAST, WITH SEAS
INCREASING BY A FOOT OR TWO. NORTHERLY WINDS WILL LIKELY PEAK IN
STRENGTH ON THURSDAY WITH GUSTS UP TO 25 KT OVER THE CENTRAL AND
SOUTHERN OUTER WATERS.
VERY CALM CONDITIONS ARE EXPECTED FRIDAY THROUGH MONDAY AS STRONG
HIGH PRESSURE STAYS LOCKED IN PLACE OVER THE REGION. WINDS SHOULD
STAY UNDER 10-15 KT THIS WEEKEND WITH SEAS AROUND 4-6 FT. -23
PQR WATCHES/WARNINGS/ADVISORIES
OR...DENSE FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR ORZ104-105-
109>111-114-115.
AIR STAGNATION ADVISORY UNTIL 4 AM PST FRIDAY FOR ORZ109>111-
114>118.
FREEZING FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR
ORZ116>118.
WA...DENSE FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR WAZ205-206.
AIR STAGNATION ADVISORY UNTIL 4 AM PST FRIDAY FOR WAZ205-206.
PZ...SMALL CRAFT ADVISORY UNTIL 10 AM PST THIS MORNING FOR
PZZ210-251-252-271-272.
WWW.WEATHER.GOV/PORTLAND
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