132
FXUS66 KPQR 152115
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
215 PM PDT WED APR 15 2026
SYNOPSIS
POST-FRONTAL RAIN AND MOUNTAIN SNOW SHOWERS CONTINUE
BUT WILL DECREASE COVERAGE THROUGH THURSDAY NIGHT. ANY HEAVIER
SHOWER MAY PRODUCE SMALL HAIL, WHILE THERE IS ALSO A 15-30%
CHANCE OF ISOLATED THUNDERSTORMS THIS AFTERNOON AND EVENING.
ACCUMULATING SNOW CONTINUES ABOVE 2500 FEET AND WINTER STORM
WARNINGS REMAIN IN EFFECT IN THE CASCADES THROUGH TONIGHT. THE
COOLER AIRMASS WILL ALSO FAVOR FROST/FREEZE CONDITIONS TONIGHT
AND POSSIBLY THURSDAY NIGHT.
SHORT TERM...NOW THROUGH FRIDAY NIGHT
THE POTENT COLD FRONT
WHICH CROSSED THE REGION LAST NIGHT THROUGH THIS MORNING HAS
EXITED THE REGION TO THE SOUTH AND EAST. BEHIND THE FRONT,
SCATTERED TO NUMEROUS RAIN AND MOUNTAIN SNOW SHOWERS WILL LINGER
INTO THURSDAY AS A CLOSED UPPER-LEVEL LOW PASSES OVERHEAD. WITH
THE COLD CORE LOW ALOFT, ANY SURFACE HEATING DURING SUN BREAKS
BETWEEN SHOWERS WILL EASILY DESTABILIZE THE COLUMN, GENERATING
PERHAPS 200-500 J/KG OF SBCAPE. WHEN COMBINED WITH LOW FREEZING
LEVELS AROUND 2500 FT, EVEN A HEAVY SHOWER COULD RESULT IN SMALL
HAIL REACHING THE SURFACE. THERE IS ADDITIONALLY A 15-30%
CHANCE OF ISOLATED THUNDERSTORMS THIS AFTERNOON AND EVENING,
ALTHOUGH LIMITED INSTABILITY WILL CAP OVERALL THUNDERSTORM
INTENSITY. THESE CHANCES WILL DECREASE AFTER SUNSET, BUT MAY
LINGER LATER INTO THE EVENING AS THE COLDEST AIR WITHIN THE
UPPER LOW SHIFTS OVERHEAD. MEANWHILE IN THE CASCADES ABOVE 2500
FT, SNOW SHOWERS WILL CONTINUE TO PRODUCE ACCUMULATING SNOWFALL.
WINTER STORM WARNINGS REMAIN IN EFFECT UNTIL 5 AM THURSDAY AS
ANOTHER 9-12 INCHES OF SNOW MAY FALL, RESULTING IN STORM TOTAL
ACCUMULATIONS OF 1-2 FEET AT AND ABOVE PASS LEVEL.
AS THE UPPER LOW EXITS EASTWARD AND HEIGHTS BEGIN TO RISE ALOFT,
RAIN SHOWERS WILL TEND TO DWINDLE IN COVERAGE TONIGHT THROUGH
THURSDAY AND THE COOLER AIR MASS WILL SEE TEMPERATURES FALL TO
NEAR-FREEZING ACROSS PORTIONS OF THE REGION. DESPITE MORNING
LOW TEMPERATURES OF 32-36 DEGREES ACROSS THE LOWER ELEVATIONS OF
NW OREGON AND SW WASHINGTON, THE COMBINATION OF PARTLY CLOUDY
SKIES AND PERSISTENT LIGHT WINDS TONIGHT MAY INHIBIT WIDESPREAD
FROST FORMATION. FROST ADVISORIES NONETHELESS REMAIN IN EFFECT
FROM 1-9 AM THURSDAY WEST OF THE CASCADES WITH THE EXCEPTION OF
THE IMMEDIATE COAST, PORTLAND/VANCOUVER METRO, AND COLUMBIA
GORGE WHERE TEMPERATURES WILL REMAIN RELATIVELY WARMER. EAST OF
THE CASCADE CREST IN THE UPPER HOOD RIVER VALLEY, TEMPERATURES
WILL MORE LIKELY FALL INTO THE UPPER 20S TO LOW 30S, AND A
FREEZE WARNING HAS THEREFORE BEEN ISSUED FOR 1-9 AM THURSDAY.
AGRICULTURAL INTERESTS AND THOSE WITH SENSITIVE OUTDOOR PLANTS
SHOULD PLAN TO TAKE PROTECTIVE ACTION TO PREVENT PLANT DAMAGE.
CONDITIONS WILL BE EVEN MORE SUPPORTIVE OF RADIATIONAL COOLING
ON THURSDAY NIGHT, HOWEVER THE SLOWLY MODERATING AIR MASS MAY
COUNTERACT THAT TENDENCY. A FREEZE WATCH HAS BEEN ISSUED FROM
1-9 AM FRIDAY FOR THE AREAS MOST LIKELY TO SEE TEMPERATURES FALL
BELOW FREEZING, NAMELY THE UPPER HOOD RIVER VALLEY AND THE
CASCADE FOOTHILLS OF MARION, LINN, AND LANE COUNTIES.
AS UPPER-LEVEL RIDGING BUILDS ON FRIDAY, DRIER AND WARMER
WEATHER IS EXPECTED ACROSS THE REGION, ALTHOUGH THERE REMAINS
SOME UNCERTAINTY IN THE PROGRESSION OF YET ANOTHER UPPER LOW
OVER THE NORTHEAST PACIFIC. THIS LOW OR OPEN TROUGH MAY MOVE
NEARER TO THE REGION AND BRING CLOUDS AND RAIN, ALTHOUGH
CONFIDENCE IS RELATIVELY LOW AND RAINFALL CHANCES ONLY REACH
5-10% BY LATE FRIDAY NIGHT. -36
LONG TERM...SATURDAY THROUGH WEDNESDAY
AN UPPER-LEVEL LOW OR
OPEN TROUGH TRACKING FROM THE GULF OF ALASKA OVER THE NORTHEAST
PACIFIC WILL BE THE DRIVER OF SENSIBLE WEATHER THIS WEEKEND AND
INTO EARLY NEXT WEEK, AND THE FORECAST REMAINS SENSITIVE TO ITS
LOW-CONFIDENCE EVOLUTION. AN UPPER LOW LOCATED NEARBY WILL
FAVOR CLOUDY SKIES AND RAINFALL CHANCES, WHILE A POSITION WELL
TO THE WEST WOULD SEE CONTINUED WARM AND DRY WEATHER. IF IT IS
LOCATED OFF THE NORTHERN CA OR SOUTHERN OR COAST, THE PATTERN
COULD ALLOW SUFFICIENT MOISTURE TO MOVE NORTHWARD ON ITS
EASTERN FLANK TO SUPPORT CONVECTION ALONG THE CASCADES. -36
AVIATION
POST FRONTAL SHOWERS ARE EXPECTED TO PERSIST THROUGH
THE DAY WITH INCREASING CHANCES FOR CONVECTION IN THE AFTERNOON
THROUGH AT LEAS 01Z THU. HIGHEST PROBABILITIES LIE ALONG THE
CASCADE FOOTHILLS AND TO THE NORTH WITH AROUND A 25-35% CHANCE
INLAND WITHIN THE WILLAMETTE VALLEY. HAVE ALREADY OBSERVED
THUNDER WITHIN THE VICINITY OF SOME WILLAMETTE VALLEY TERMINALS,
BUT HAS YET TO BE WIDESPREAD. THUNDER IS CHALLENGING HERE AS
OFTEN IT MAY BE ONE STORM THAT POPS UP, WHILE OTHER TIMES IT CAN
BE A WIDE SWATH. IN THIS CASE, BECAUSE THE FLOW IS
NORTHWESTERLY (NOT AS FAVORABLE) BEHIND THE PREVIOUS SYSTEM,
WOULD TREND TOWARDS A MORE ISOLATED THUNDERSTORM SCENARIO.
OVERNIGHT, SHOWERS WILL SLOWLY DISSIPATE AND CLEAR. DROPPING
TEMPERATURES MEAN THAT THERE IS A SLIGHT CHANCE FOR FROST
FORMATION OVER EXPOSED SURFACES. IF SKIES REMAIN CLOUDY THOUGH,
THOSE CHANCES DECREASE SIGNIFICANTLY. ANOTHER LIMITING FACTOR
WILL BE THAT WINDS ARE JUST SLIGHTLY ABOVE WHAT WE WOULD LIKE TO
SEE FOR MORE WIDESPREAD FROST FORMATION.
KPDX AND APPROACHES...COMBINATION OF MVFR AND VFR CONDITIONS
WITH SHOWERS. AROUND A 30% CHANCE OF THUNDERSTORMS THROUGH 06Z
THU. THUNDERSTORMS WILL TREND TOWARDS AN ISOLATED SCENARIO.
WITH PASSING STORMS, EXPECT GUSTY OUTFLOW WINDS LEADING TO LLWS
TYPE CONDITIONS. NOTE THAT ATMOSPHERIC LLWS IS NOT EXPECTED, BUT
RATHER ENVIRONMENT INDUCED CONDITIONS. -27
MARINE
POST FRONTAL SHOWERS WILL INCREASE PROBABILITY FOR
LIGHTNING OVER THE WATERS THROUGH AROUND 1700 TODAY. SMALL CRAFT
SEAS PERSIST DUE TO A WESTERLY SWELL COMBINED WITH A WESTERLY
WIND WAVE. THESE SMALL CRAFT SEAS ARE HOVERING RIGHT AROUND 9-10
FT AT 8 SECONDS. HAVE EXTENDED THE ADVISORY THROUGH THURSDAY
MORNING, THOUGH WILL SEE A STEADY DECLINE IN SEAS SHIFTING FROM
WEST TO EAST. IN ADDITION, THERE WILL BE A STRONG EBB EARLY
THURSDAY MORNING FOR THE COLUMBIA RIVER BAR. THE INNER WATERS
WILL SEE LOWERING SEAS AS EARLY AS EARLY THURSDAY MORNING. WINDS
WILL REMAIN WESTERLY THROUGH FRIDAY MORNING, THEN SHIFT TO THE
NORTH AS A HIGH PRESSURE RIDGE SETS UP OVER THE WATERS. THIS
SUMMER TIME PATTERN WILL BRING INCREASED WINDS TO PZZ253 IN THE
AFTERNOON. WHILE NOT QUITE A LOW- LEVEL JET, WE COULD SEE A
SHORT BURST OF GUSTS UP TO 25 KT.
HIGH PRESSURE OVER THE AREA WILL MAINTAIN MORE SETTLED
CONDITIONS THROUGH EARLY NEXT WEEK. -27
PQR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY FROM 1 AM TO 9 AM PDT THURSDAY FOR ORZ104>110-
114>118-123>125.
FREEZE WARNING FROM 1 AM TO 9 AM PDT THURSDAY FOR ORZ121.
FREEZE WATCH FROM LATE THURSDAY NIGHT THROUGH FRIDAY MORNING
FOR ORZ121-124-125.
WINTER STORM WARNING UNTIL 5 AM PDT THURSDAY FOR ORZ126>128.
WA...FROST ADVISORY FROM 1 AM TO 9 AM PDT THURSDAY FOR WAZ203>205-
208.
WINTER STORM WARNING UNTIL 5 AM PDT THURSDAY FOR WAZ211.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT THURSDAY FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL 5 PM PDT THURSDAY FOR PZZ251>253-
271>273.
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