133
FXUS66 KPQR 142106
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
206 PM PDT TUE APR 14 2026
SYNOPSIS
A STRONG FRONTAL BOUNDARY WILL MOVE ACROSS THE CWA
THROUGH TONIGHT, BRINGING WIDESPREAD RAINFALL TO THE COAST
AND THE INLAND VALLEYS. THIS FRONT WILL ALSO PUSH SNOW LEVELS
DOWN TOWARDS 2000-3500 FT AND BRING HEAVY SNOWFALL TO THE
CASCADES AND PORTIONS OF THE CASCADE FOOTHILLS. DUE TO THE
EXPECTED SNOWFALL IMPACTS FOR THE CASCADES, HAVE ISSUED SOME
WINTER WEATHER HAZARD PRODUCTS, WHICH START EARLY THIS EVENING.
BEHIND THE FRONT SHOWERS RETURN ALONG WITH A 15-30% CHANCE FOR
THUNDERSTORMS STARTING LATE WEDNESDAY MORNING THROUGH WEDNESDAY
NIGHT. AFTERWARDS, CONCERNS SHIFT TO COOLER OVERNIGHT TEMPERATURES
AND POSSIBLE FROST/FREEZE CONDITIONS TO ROUND OUT THE WEEK.
AFTER A BRIEF STINT OF DRY AND WARMER WEATHER SATURDAY,
PRECIPITATION CHANCES RETURN BY EARLY NEXT WEEK.
SHORT TERM...NOW THROUGH WEDNESDAY NIGHT
CURRENT RADAR AND
SATELLITE OBSERVATIONS THIS AFTERNOON SHOW WIDESPREAD CLOUD
COVER WITH RAIN MOVING EAST AND SOUTH ACROSS OUR CWA. THE SOURCE
OF THE RAIN AND CLOUDS IS A LOW PRESSURE SYSTEM, THAT IS SLOWLY
MOVING SOUTHEASTWARD FROM THE GULF OF ALASKA AND TOWARDS THE PAC
NW. AS THIS SYSTEM CONTINUES TO TREK TOWARDS THE REGION,
PRECIPITATION AS WELL AS COOLER CONDITIONS WILL SLOWLY START TO
TAKE HOLD. THIS WILL RESULT IN WIDESPREAD RAIN FOR THE LOWER
ELEVATIONS AND THE COAST, ALONG WITH WET SNOW FOR THE CASCADES.
QPF VALUES HAVE CHANGED VERY LITTLE OVER THE PAST 24 HOURS AND
GENERALLY SHOW A 36 HOUR QPF TOTALS THROUGH WEDNESDAY NIGHT OF
0.75 TO 1.25 INCHES ACROSS THE WILLAMETTE VALLEY AND PORTLAND
METRO, 1.00 TO 2.75 INCHES ALONG THE COAST AND COAST RANGE, AND
1.20 TO 3.00 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.
SO, LETS TALK ABOUT SNOW. THE INCOMING SYSTEM LOOKS TO PUSH SNOW
LEVELS DOWN TOWARDS 2000-2500 FT BY VERY EARLY THURSDAY MORNING
AND GIVEN THAT A ROBUST SLUG OF MOISTURE WILL ACCOMPANY THE COLD
AIR, THAT MEANS THAT SNOW IS IN THE FORECAST FOR THE CASCADES
AND PARTS OF THE CASCADE FOOTHILLS. FOCUSING ON THE CASCADES
ABOVE 3500 FT, ROUGHLY 12 TO 22 INCHES OF SNOW ACCUMULATION IS
EXPECTED. THIS LOOKS TO START AROUND 5PM THIS AFTERNOON THROUGH
EARLY THURSDAY MORNING. HIGHEST SNOWFALL TOTALS ARE EXPECTED
MAINLY ABOVE 3500-4000 FT. AS FOR THE CASCADE FOOTHILLS, THE
PRIMARY AREA IN QUESTION IS THE CLACKAMAS COUNTY CASCADE
FOOTHILLS. 1 TO 4 INCHES OF SNOW ACCUMULATION IS EXPECTED, WITH
THE HIGHEST ACCUMULATIONS ABOVE 1500 FT, THIS INCLUDES MT. HOOD
VILLAGE AND ZIGZAG, OR. 1 INCH OR LESS FOR LOCATIONS AROUND
1000 FT, WHICH INCLUDES SANDY, OR. THE TIME OF CONCERN FOR THE
CLACKAMAS COUNTY CASCADE FOOTHILLS IS FROM 3AM TO 11AM
WEDNESDAY.
THE LATEST NBM PROBABILITIES SHOW A 75-90% PROBABILITY OF 12
INCHES OR GREATER SNOWFALL OVER A 48 HOUR PERIOD FROM THIS
AFTERNOON THROUGH THURSDAY AFTERNOON AT SANTIAM LEVEL AND
WILLAMETTE PASS, SLIGHTLY LOWER (35-45%) 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 3AM TO 11AM 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 AS THE CORE OF THE UPPER LEVEL
LOW MOVES OVER THE REGION. MOST MODELS SHOW CONVECTIVE
AVAILABLE POTENTIAL ENERGY (CAPE) VALUES PEAKING AROUND 200 TO 500
J/KG, WITH VERY LITTLE CONVECTIVE INHIBITION (CIN) AROUND -5 TO
10 J/KG. THESE CONDITIONS ARE RESULTING IN A 15-30% CHANCE FOR
THUNDERSTORM DEVELOPMENT WITHIN THE POST-FRONTAL ENVIRONMENT
ACROSS THE CWA. THE MAIN TIME PERIOD OF FOCUS IS 11AM TO 7PM ON
WEDNESDAY WHEN HEATING BETWEEN SHOWER BANDS MAY BE MAXIMIZED.
CONVECTIVE ALLOWING MODEL (CAM) SOUNDINGS ARE SHOWING A SKINNY
CAPE PROFILE AND ALONG WITH COOLER TEMPERATURES ALOFT, THIS
DOES SUPPORT TINY HAIL/GRAUPEL DEVELOPMENT WITH ANY
THUNDERSTORMS THAT DEVELOP AND GIVEN THAT WHEN SPRING TIME
THUNDERSTORMS DEVELOP WITHIN OUR CWA, THEY HAVE A TENDENCY TO
PRODUCE A LOT OF TINY 0.10-0.25" DIAMETER (PEA SIZE) HAIL. ALSO,
WHILE HAIL/GRAUPEL MIGHT BLANKET SURFACES, IT WILL TYPICALLY
NOT LINGER, ONCE THE CELL THAT PRODUCED IT MOVES OUT OF THE
AREA.
TO SUMMARIZE, ANY OF THESE POP-UP THUNDERSTORMS MAY PRODUCE
MODERATE TO HEAVY RAIN, INFREQUENT LIGHTNING, SMALL
HAIL/GRAUPEL, ALONG WITH 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. /42-99
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. THE LATEST NBM PROBABILITIES FOR TEMPERATURES
BELOW 36 DEGREES F WEDNESDAY NIGHT INTO THURSDAY MORNING FOR
THE PORTLAND/VANCOUVER METRO IS 10-30% CHANCE. FROM THE
PORTLAND/VANCOUVER METRO AREAS SOUTHWARD TOWARDS SALEM AND
EUGENE, OR, EXPECT A 15-75% CHANCE. FOR LOCATIONS NORTH OF
VANCOUVER, EXPECT A 15-60%. 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 SIMILAR PROBABILITIES.
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. /42-99
AVIATION
WESTERLY FLOW ALOFT AHEAD OF AN UPPER LEVEL TROUGH TODAY
AS A COLD FRONT PUSHES ACROSS THE AREA WITH RAINFALL INCREASING
LATER THIS AFTERNOON THROUGH TONIGHT. AS OF 20Z, CONDITIONS REMAIN
A MIX OF MVFR AND VFR WITH CIGS AROUND FL025-FL035, ALONG WITH
RAIN REDUCING VISIBILITY AT THE COAST TO AROUND 3-5 SM. CHANCES
FOR WIDESPREAD MVFR INLAND QUICKLY INCREASE TO 50-70% LATER THIS
AFTERNOON/EVENING, AFTER 00Z WED; WHILE CHANCES FOR IFR AT THE
COAST INCREASE TO AROUND 30-40% AROUND THE SAME TIME. SOUTHERLY
WINDS ARE ALSO EXPECTED TO REMAIN BREEZY THROUGH THIS EVENING,
WITH GUSTS UP TO 30 KT LIKELY. THE COLD FRONT IS EXPECTED TO SLIDE
SOUTHWARD ACROSS THE AREA OVERNIGHT, WITH WINDS BEHIND THE FRONT
SHIFTING TO THE WNW AND STEADY RAIN QUICKLY DECREASING, WITH THE
FRONT EXITING THE AREA BY 18Z WED. CONDITIONS ARE LIKELY (70-80%
CHANCE) TO RETURN TO VFR BY AROUND 15Z WED, FOLLOWED BY INCREASING
SHOWERS LATER WED MORNING.
KPDX AND APPROACHES...AS OF 20Z, LOWER VFR CIGS WITH LIGHT RAIN.
CONDITIONS ARE EXPECTED TO DETERIORATE AS A COLD FRONT PUSHES
INCREASING RAIN ACROSS THE AREA. PROBS FOR MVFR INCREASE TO AROUND
60-80% BY 00Z WED, AND CONTINUE THROUGH AT LEAST 10-12Z WED.
SOUTHERLY WINDS ARE EXPECTED TO REMAIN BREEZY WITH GUSTS UP TO
25-30 KT THROUGH AT LEAST 08Z TONIGHT. AROUND 10-12Z WED, EXPECT
THE FRONT TO PUSH THROUGH WITH WEST TO NORTHWEST WINDS AND A
RETURN TO VFR CONDITIONS LIKELY. /DH
MARINE
GUSTY SOUTHWEST WINDS CONTINUE TO INCREASE THIS
AFTERNOON AS A STRONG COLD FRONT APPROACHES THE COASTAL WATERS.
LATEST GUIDANCE INCREASED WINDS ENOUGH TO WARRANT A GALE WARNING
FOR THE NORTHERN COASTAL WATERS, AS WELL AS THE INNER CENTRAL
WATERS AND THE COLUMBIA RIVER BAR. EXPECT SOUTHWEST WIND GUSTS UP
TO 35 KT THERE, WHILE ELSEWHERE, WIDESPREAD GUSTS TO 30 KT IS
EXPECTED, WITH ISOLATED GUSTS UP TO 35 KT POSSIBLE, ESPECIALLY
OVER THE INNER WATERS AS THE FRONT IMPINGES ALONG THE COAST. THE
INCREASED WIND WAVES ARE EXPECTED TO BUILD SEAS TO AROUND 8 TO 10
FT WITH A PERIOD OF AROUND 8-10 SECONDS. SEAS REMAIN STEEP AND
CHOPPY THROUGH TONIGHT.
BEHIND THE FRONTAL BOUNDARY, EXPECT AN ABRUPT SHIFT TO THE
NORTHWEST AS THE FRONT DROPS SOUTH OVERNIGHT. BREEZY NORTHWEST
WINDS WITH GUSTS UP TO 20-25 KT CONTINUE THROUGH WEDNESDAY 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 10 TO 12 FT WED NIGHT AS A NORTHWEST
SWELL MOVES THROUGH THE WATERS. THE SMALL CRAFT ADVISORY REMAINS
IN PLACE 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 LATER
THIS WEEKEND, POSSIBLY INCREASING WINDS AND SEAS. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY FROM 3 AM TO 11 AM PDT WEDNESDAY FOR
ORZ123.
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...GALE WARNING UNTIL 8 PM PDT THIS EVENING FOR PZZ210-251-252-271.
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 5 AM PDT
WEDNESDAY FOR PZZ210.
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 5 AM PDT
THURSDAY FOR PZZ251-252-271.
SMALL CRAFT ADVISORY UNTIL 5 AM PDT THURSDAY FOR
PZZ253-272-273.
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