925
FXUS66 KPQR 141108
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
408 AM PDT TUE APR 14 2026
SYNOPSIS
A STRONG FRONTAL BOUNDARY ARRIVES TODAY AND TONIGHT
USHERING IN WIDESPREAD RAINFALL ACROSS THE COAST THROUGH THE
INLAND VALLEYS, AND HEAVY SNOWFALL TO THE CASCADES. DUE TO THE
EXPECTED SNOWFALL IMPACTS FOR THE LATTER AREA, A WINTER STORM
WARNING IS IN EFFECT. IN THE WAKE OF THE FRONT SHOWERS AND A
SLIGHT CHANCE (15-25%) FOR THUNDERSTORMS FOLLOW ON WEDNESDAY
THEN CONCERNS SHIFT TO COOLER OVERNIGHT TEMPERATURES AND FROST
TO END THE WEEK. AFTER A BRIEF STINT OF DRY AND WARMER WEATHER
ON SATURDAY, PRECIPITATION CHANCES RETURN BY EARLY NEXT WEEK.
SHORT TERM...NOW THROUGH WEDNESDAY NIGHT
THIS MORNING
SATELLITE AND RADAR OBSERVATIONS SHOW MOISTURE ASSOCIATED WITH
OUR NEXT POTENT WEATHER DISTURBANCE STREAMING INTO FAR NORTHERN
WASHINGTON AND VANCOUVER ISLAND, THE FIRST SIGNS OF A RATHER
SIGNIFICANT PATTERN CHANGE ANTICIPATED TO OCCUR LATER TODAY INTO
THE MIDDLE OF THE WEEK. THE ROBUST UPPER-LEVEL LOW HELPING TO
STEER THIS FRONTAL BOUNDARY IS SLATED TO CONTINUE ITS DIVE OUT
OF THE GULF OF ALASKA BRINGING A SWATH OF WIDESPREAD
PRECIPITATION AND EVENTUALLY COOLER CONDITIONS. QPF VALUES HAVE
CHANGED LITTLE WITH THE LATEST FORECAST GUIDANCE AMOUNTS FROM
TODAY THROUGH WEDNESDAY GENERALLY RANGING FROM 0.75 TO 1.25
INCHES ACROSS THE WILLAMETTE VALLEY AND PORTLAND METRO, 1.00 TO
2.25 INCHES ALONG THE COAST AND COAST RANGE, AND 1.10 TO 2.30
INCHES ACROSS THE CASCADES. HOWEVER, FOR THE LATTER REGION,
ESPECIALLY AT PASS LEVEL, THE PRECIPITATION WILL LIKELY BE
FALLING AS SNOW FOR A GOOD CHUNK OF THIS EVENT.
SPEAKING OF SNOW THE INCOMING SYSTEM LOOKS TO BRING ROUGHLY 10
TO 22 INCHES OF SNOWFALL TO THE CASCADES STARTING THIS AFTERNOON
THROUGH EARLY THURSDAY MORNING MAINLY ABOVE 3500-4000 FT
ALTHOUGH, SNOW LEVELS LIKELY BOTTOM OUT AROUND 2000-3000FT ON
WEDNESDAY JUST BEHIND THE FRONT - HIGHER ELEVATION, MORE
IMPACTS. THE LATEST NBM PROBABILITIES SHOW A 60-90% PROBABILITY
OF 12 INCHES OR GREATER SNOWFALL OVER A 48 HOUR PERIOD FROM
TODAY THROUGH THURSDAY AFTERNOON AT SANTIAM LEVEL AND WILLAMETTE
PASS, SLIGHTLY LOWER (30-40%) AT GOVERNMENT CAMP. OVERALL THE
HIGHEST AMOUNTS LIKELY FALL IN THE HIGH CASCADES FROM MARION TO
LANE COUNTY. THE PERIOD TO WATCH AS FAR THE GREATEST TRAVEL
IMPACTS ARE WILL BE FROM 4-10AM ON WEDNESDAY WHEN SNOWFALL RATES
IN THE HEAVIER PRECIPITATION BANDS RIGHT ALONG THE FRONT MAY
EXCEED 1-1.5 IN/HR. SO, IF YOU ARE PLANNING TO TRAVEL OVER THE
CASCADES PASSES, PARTICULARLY WEDNESDAY MORNING, PLEASE PREPARE
FOR WINTER-LIKE TRAVEL CONDITIONS.
ONE OTHER INTERESTING FACET OF THE FORECAST WE'RE WATCHING IS
THE POTENTIAL FOR 1-3 HR PERIOD OF DYNAMIC COOLING TEMPORARILY
PUNCHING SNOW LEVELS INTO THE 500-1500FT RANGE NEAR SUNRISE
WEDNESDAY MORNING. THIS HAS BEEN A FEATURE HINTED AT BY THE LAST
SEVERAL RUNS OF THE HIGHER RESOLUTION GUIDANCE LIKE THE HRRR
AND NAMNEST RIGHT ON THE BACK EDGE OF THE COLD-FRONTAL BOUNDARY
WHERE PERSISTENT HEAVIER PRECIPITATION COMBINED WITH COLD AIR
JUST ABOVE THE SURFACE (-5C AT 850MB) COULD FACILITATE THIS
PROCESS, ASSUMING ALL THE PROPER VARIABLES ALIGN. THE AREAS OF
PARTICULAR INTEREST ARE SOUTHWEST WASHINGTON INTO THE PORTLAND
METRO AND THE HIGHER COAST RANGE/CASCADE VALLEYS. IF THIS WERE
TO OCCUR ELEVATIONS AS LOW AS 500FT COULD SEE A RAIN/SNOW MIX OR
"CHUNKY RAIN" FOR AN HOUR OR TWO WITH NO IMPACTS. THE CHANCES
FOR A LIGHT SLUSH-UP IN THE GRASS GETS HIGHER ONCE YOU REACH
1500FT, PARTICULARLY IN THE CASCADE FOOTHILLS/VALLEYS, BUT DUE
TO THE WARM ANTECEDENT CONDITIONS MOST IMPACTS REMAIN 2000FT+.
PROGRESSING THROUGH WEDNESDAY A SHOWERY POST FRONTAL
ENVIRONMENT QUICKLY OVERTAKES THE REGION COUPLED WITH INCREASING
INSTABILITY DURING THE AFTERNOON THANKS TO THE CORE OF THE
UPPER LEVEL LOW MOVING OVERHEAD. MOST MODELS SHOW CONVECTIVE
AVAILABLE POTENTIAL ENERGY (CAPE) VALUES PEAKING AROUND 200-500
J/KG, WHICH IS DECENT FOR OUR POST-FRONTAL ENVIRONMENT WEAK
THUNDERSTORM SET-UPS. THE MAIN TIME PERIOD OF FOCUS IS 11AM TO
7PM ON WEDNESDAY WHEN HEATING BETWEEN SHOWER BANDS MAY BE
MAXIMIZED. GIVEN THIS INFORMATION, THERE IS A 15-25% CHANCE FOR
THUNDERSTORMS ACROSS THE MAJORITY OF OUR CWA. ANY OF THESE POP-
UP THUNDERSTORMS MAY PRODUCE MODERATE TO HEAVY RAIN, INFREQUENT
LIGHTNING, SMALL HAIL/GRAUPEL, GUSTY AND ERRATIC WINDS. SO,
WHEN THUNDER ROARS, GO INDOORS OR WHEN YOU SEE A FLASH (OF
LIGHTNING), DASH INSIDE. WITH THE LOSS OF DAYTIME HEATING
THUNDERSTORM CHANCES DECREASE WEDNESDAY NIGHT ALTHOUGH SHOWERS
LIKELY PERSIST. -99/42
LONG TERM...THURSDAY THROUGH MONDAY
BY THURSDAY, THE UPPER
LEVEL LOW AND ASSOCIATED FRONT HAVE LEFT THE CWA, BUT WILL LEAVE
THE REGION UNDER COOLER CONDITIONS WITH INCREASING CLEARING.
THURSDAY INTO FRIDAY LOOKS TO HAVE OVERNIGHT LOWS BELOW NORMAL
BOTTOMING OUT IN THE MID 30S ACROSS THE LOWLANDS AND SPELLING A
POTENTIAL FOR FROST. BELOW FREEZING TEMPERATURES ARE EVEN
FORECAST FOR THE HIGHER COAST RANGE/CASCADE VALLEYS, INCLUDING
THE HOOD RIVER VALLEY. CURRENTLY, THE PORTLAND/VANCOUVER METRO
THERE IS A 10-40% CHANCE OF OVERNIGHT LOWS AT OR BELOW 36
DEGREES F. FROM THE PORTLAND/VANCOUVER METRO AREAS SOUTHWARD
TOWARDS SALEM AND EUGENE, OR, EXPECT A 45-85% CHANCE OF
OVERNIGHT LOWS AT OR BELOW 36 DEGREES F. FOR LOCATIONS NORTH OF
VANCOUVER, EXPECT A 50-75% CHANCE OF OVERNIGHT LOWS AT OR BELOW
36 DEGREES F. ADDITIONALLY, THERE IS A 80-95% CHANCE OF AT LEAST
FREEZING TEMPERATURES IN THE UPPER HOOD RIVER VALLEY FOR
WEDNESDAY NIGHT INTO THURSDAY MORNING. SIMILAR CONDITIONS MAY
DEVELOP AGAIN THURSDAY NIGHT INTO FRIDAY MORNING, THOUGH WITH
SLIGHTLY LOWER PROBABILITIES (ONLY 10-30% LOWER).
LOOKING TOWARDS THE WEEKEND, TEMPERATURES GRADUALLY WARM, REDUCING
THESE MORNING FROST CONCERNS. ENSEMBLES SHOW A SHORTWAVE RIDGE
OF HIGH PRESSURE MOVING QUICKLY OVERHEAD ON SATURDAY, BUT BEING
QUICKLY FOLLOWED BY ANOTHER LOW PRESSURE SYSTEM ON SUNDAY
ORIGINATING FROM THE GULF OF ALASKA. NOW, BEYOND SUNDAY AND INTO
THE START OF NEXT WEEK, WPC CLUSTER GUIDANCE IS FAVORING THIS
LOW HOLDING JUST OFF THE OR/WA COAST OR MOVING OVER THE INLAND
PAC NW, WHICH MEANS THAT COOLER AND MOISTER CONDITIONS ARE
FAVORED FOR THE START OF NEXT WEEK. -99/42
AVIATION
CONDITIONS ARE GENERALLY VFR ACROSS THE REGION THIS
MORNING WITH INCREASING SOUTHERLY FLOW AHEAD OF A QUICKLY
APPROACHING COLD-FRONTAL SYSTEM. CHANCES FOR MVFR CIGS ALONG THE
COAST QUICKLY INCREASE TO 70-80% BY 14-16Z THIS MORNING AS RAIN
MOVES OVERHEAD WITH A 40-60% CHANCE FOR IFR CONDITIONS DURING THE
AFTERNOON AND EVENING. INLAND TERMINALS WILL HOLD ON TO VFR
CONDITIONS A BIT LONGER WITH MVFR PROBABILITIES INCREASING AFTER
18Z TO 40-60% AS RAIN INCREASES, BUT CIGS MAY FLUCTUATE UNTIL THE
LATER AFTERNOON AND EVENING WHEN MORE UNIFORM CLOUD COVER IS
EXPECTED TO MOVE IN OVERHEAD AND MVFR CONDITIONS LIKELY SETTLE IN.
ALONG WITH RAIN, WINDS WILL INCREASE ALSO INCREASE TODAY WITH
GUSTS ALONG THE COAST REACHING TO 25-35 KT AFTER 18Z AND 20-25 KT
FOR INLAND LOCATIONS.
KPDX AND APPROACHES...VFR CONDITIONS LIKELY PERSIST THROUGH THE
MORNING HOURS HOWEVER STRATIFORM RAINFALL INCREASES MIDDAY INTO
THE MID AFTERNOON. CIGS ARE EXPECTED TO RESPOND IN-KIND WITH
CHANCES FOR MVFR CONDITIONS RISING AFTER 16-18Z - PROBABILITIES
BETWEEN 70-80% AFTER 20Z. SOUTHERLY WINDS ALSO INCREASE DURING THE
AFTERNOON WITH GUSTS BETWEEN 20-25 KNOTS PERSISTING THROUGH THE
EVENING. -99
MARINE
THE FOCUS TODAY REMAINS ON THE ARRIVAL OF A ROBUST
COLD-FRONTAL BOUNDARY SLOWLY SPREADING ACROSS THE WATERS NORTH TO
SOUTH. AS A RESULT EXPECT SOUTHWEST WINDS TO INCREASE WITH GUSTS
UP TO 30 KT ACROSS ALL COASTAL WATERS. WINDS ARE EXPECTED TO BE
STRONGEST THIS AFTERNOON INTO EARLY TUE EVENING. DURING THIS
TIME, THERE WILL BE AROUND A 3-6 HOUR PERIOD WHEN GUSTS COULD (30-50%
CHANCE) EXCEED 34 KT, PRODUCING MARGINAL GALE FORCE WIND
GUSTS. A SMALL CRAFT ADVISORY IS IN EFFECT ACROSS THE INNER AND
OUTER WATERS INCLUDING THE COLUMBIA RIVER BAR STARTING THIS
MORNING. THE INCREASED WIND WAVES ARE EXPECTED TO BUILD SEAS TO
AROUND 7 TO 10 FT WITH A PERIOD OF AROUND 8-10 SECONDS. SEAS
REMAIN STEEP AND CHOPPY THROUGH TUE NIGHT AS WELL.
BEHIND THE FRONTAL BOUNDARY TUESDAY NIGHT WINDS ABRUPTLY SHIFT
NORTHWEST WITH GUSTS INCREASING BACK UP TO 20-25 KT AS AN AREA
OF LOW PRESSURE DROPS ALONG THE CANADIAN COAST TOWARD THE PUGET
SOUND. THIS WILL ALSO BRING A 15-25% CHANCE OF THUNDERSTORMS OVER
THE WATERS THROUGH WED EVENING. SEAS ARE EXPECTED TO PERSIST AT
AROUND AROUND 8 TO 10 FT ON WEDNESDAY, BUILDING SLIGHTLY TO AROUND
9 TO 11 FT WED NIGHT AS A NORTHWEST SWELL MOVES THROUGH THE
WATERS. GIVEN THESE SEAS THE SMALL CRAFT ADVISORY WAS EXTENDED OUT
INTO THURSDAY MORNING. HIGH PRESSURE THEN BUILDS OVER THE WATERS
LATER THIS WEEK AS NORTHERLY WINDS RETURN AND SEAS GRADUALLY
SUBSIDE TO AROUND 3 TO 6 FT FRIDAY INTO SATURDAY. THERE IS
POTENTIAL FOR ANOTHER WEATHER SYSTEM TO IMPACT THE WATERS THE
SECOND HALF OF THE WEEKEND INTO EARLY NEXT WEEK LIKELY INCREASING
WINDS AND SEAS YET AGAIN. -99/DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 5 AM PDT
THURSDAY FOR ORZ126>128.
WA...WINTER STORM WARNING FROM 5 PM THIS AFTERNOON TO 5 AM PDT
THURSDAY FOR WAZ211.
PZ...SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 5 AM PDT
WEDNESDAY FOR PZZ210.
SMALL CRAFT ADVISORY FROM 5 AM EARLY THIS MORNING TO 5 AM PDT
THURSDAY FOR PZZ251-271.
SMALL CRAFT ADVISORY FROM 8 AM THIS MORNING TO 5 AM PDT
THURSDAY FOR PZZ252-253-272-273.
WWW.WEATHER.GOV/PORTLAND
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