984
FXUS66 KPQR 121111
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
411 AM PDT SUN APR 12 2026
SYNOPSIS
A PATTERN CHANGE IS IN STORE TODAY INTO EARLY NEXT
WEEK AS THE FLOW ALOFT TURNS MORE WEST TO NORTHWEST ALLOWING FOR
CONDITIONS TO TREND A LITTLE COOLER ALTHOUGH SHOWERS PERSIST AT
TIMES. CONFIDENCE IN HIGH IN THE ARRIVAL OF A MORE POTENT
FRONTAL SYSTEM LATER TUESDAY INTO WEDNESDAY USHERING IN
WIDESPREAD PRECIPITATION AND A SHIFT TOWARD CASCADE SNOWFALL
IMPACTS. COOLER OVERNIGHT TEMPERATURES FOLLOW TO END THE WEEK -
WE MAY NOT BE OUT OF THE WOODS WHEN IT COMES TO MORNING FROST
JUST YET.
SHORT TERM...NOW THROUGH TUESDAY
TODAY MARKS THE TRANSITION
BACK TO A MORE PROGRESSIVE WEATHER PATTERN AS AN UPPER-LEVEL LOW
PRESSURE SYSTEM WHICH SAT OFF THE NORTHERN CALIFORNIA COASTLINE
YESTERDAY WHILE FACILITATING A FAIRLY CONVECTIVE ENVIRONMENT
NOW PUSHES INLAND. STILL, MODELS ARE IN GOOD AGREEMENT DEPICTING
WRAP AROUND MOISTURE AND ADDITIONAL BANDS OF SHOWER ACTIVITY
PIVOTING INTO THE REGION AS THE DAY PROGRESSES. BUT UNLIKE THE
PAST COUPLE OF DAYS, THE RETURN OF ONSHORE WNW FLOW NEAR THE
SURFACE SHOULD EFFECTIVELY END ANY ADDITIONAL THUNDERSTORM
CHANCES WEST OF THE CASCADE CRESTS THANKS IN PART TO THE COOLER
TEMPERATURES WITH HIGHS IN THE 50S TO LOW 60S INLAND - A 4 TO 8
DEGREE DROP FROM YESTERDAY. ANTICIPATE PRECIPITATION
PROBABILITIES OF 60-95% OVER MOST OF NORTHWEST OREGON AND
ELEVATED AREAS OF SOUTHWEST WASHINGTON. NORTH OF TILLAMOOK INTO
THE SOUTH WASHINGTON COAST IS THE MAIN EXCEPTION, WITH JUST A
20-40% CHANCE OF PRECIPITATION AS IT REMAINS FURTHER AWAY FROM
THE CORE OF THE UPPER-LEVEL LOW SPINNING MOISTURE OUR WAY.
HEADED THROUGH MONDAY A WEAK EMBEDDED SHORTWAVE FEATURE IS
EXPECTED QUICKLY SWING INTO THE REGION FROM THE NORTHWEST,
MAINTAINING PERSISTENT CHANCES (60-90%) FOR SHOWERS, HIGHEST
ACROSS THE CASCADES, COAST RANGE, AND FOOTHILLS WHERE TERRAIN
FEATURES WILL HELP TO INITIATE AND MAINTAIN MORE FREQUENT
ACTIVITY. AT LEAST AMONG ENSEMBLE AND DETERMINISTIC GUIDANCE
THERE IS GOOD AGREEMENT IN A WEAK HIGH PRESSURE RIDGE FEATURE
BUILDING OVERHEAD LATE MONDAY INTO TUESDAY MORNING, AND WHILE IT
WON'T COMPLETELY END OUR SHOWER CHANCES, IT'LL HELP ENSURE MOST
OF THE LINGERING ACTIVITY REMAINS PINNED TO TERRAIN FEATURES
WHILE THE INLAND VALLEYS TREND MOSTLY DRY. CONFIDENCE IS HIGH
COME TUESDAY AFTERNOON A DECENTLY STRONG COLD FRONTAL BOUNDARY
BEGINS PUSHING INTO THE REGION. BEYOND SOME LOCALLY BREEZY
CONDITIONS DURING THE AFTERNOON, GUSTS 20-35 MPH OUT OF THE
SOUTH (HIGHEST AT THE COAST), THE BULK OF THE IMPACTS
ACCOMPANYING THIS SYSTEM HOLD OFF UNTIL TUESDAY NIGHT AND
WEDNESDAY. SPOILERS: MUCH NEEDED MODERATE TO HEAVY SNOW LIKELY
RETURNS TO THE CASCADES FOR A PERIOD OF TIME. -99
LONG TERM...TUESDAY NIGHT THROUGH SATURDAY
ENSEMBLE AND
DETERMINISTIC GUIDANCE IS IN EXCELLENT AGREEMENT SHOWING A COLD
FRONT SWEEPING THROUGH THE REGION TUESDAY NIGHT INTO WEDNESDAY
MORNING WITH WIDESPREAD PRECIPITATION ACROSS THE REGION. THE
LATEST GUIDANCE HAS BEGUN TO SHOW LESS UNCERTAINTY REGARDING 24
HOUR RAINFALL TOTALS WHEN THE MEAT OF THE FRONT PASSES OVERHEAD
TUESDAY EVENING THROUGH WEDNESDAY MORNING WITH QPF VALUES AROUND
0.6-1.10 INCHES IN THE WILLAMETTE VALLEY THROUGH THE PORTLAND
METRO, 0.8-1.5 ALONG THE COAST/COAST RANGE, AND 0.90-2.0 INCHES
IN THE MOUNTAINS. COOL TEMPERATURES ALONG THE BEHIND THE FRONTAL
BOUNDARY HELP TO RAPIDLY PUNCH SNOW LEVELS BELOW CASCADE PASS
ELEVATIONS, RAISING THE POTENTIAL FOR WINTER-LIKE TRAVEL
IMPACTS. CURRENT PROBABILISTIC GUIDANCE INDICATES A 85-95%
CHANCE OF 6+ INCHES OF SNOWFALL AT THE CASCADE PASSES BETWEEN
TUESDAY AND THURSDAY EVENING (48 HOURS), WITH A 50-70% CHANCE OF
12 INCHES OR MORE. IF THESE TRENDS CONTINUE, WINTER WEATHER
HIGHLIGHTS MAY BECOME NECESSARY FOR PORTIONS OF THE CASCADES.
IN ADDITION TO THE CASCADE SNOWFALL, COOLER AND POTENTIALLY
CLEARER CONDITIONS BEHIND THE SYSTEM MAY INTRODUCE RENEWED FROST
CONCERNS ACROSS PORTIONS OF THE INTERIOR VALLEYS BY MID TO LATE
WEEK. THE FIRST OPPORTUNITY APPEARS WEDNESDAY NIGHT INTO
THURSDAY, WITH A 30-70% CHANCE OF FROST ACROSS MUCH OF THE
INTERIOR LOWLANDS (LOWEST AROUND THE PORTLAND-VANCOUVER METRO)
AND A 50-90% CHANCE OF FREEZING TEMPERATURES IN THE UPPER HOOD
RIVER VALLEY (CHANCES FROM ODELL TO PARKDALE). SIMILAR
CONDITIONS MAY DEVELOP AGAIN THURSDAY NIGHT INTO FRIDAY MORNING,
BUT WITH SLIGHTLY LOWER CHANCES. TEMPERATURES BEGIN TO TREND
WARMER INTO THE WEEKEND EVENTUALLY LESSENING THESE FROST/FREEZE
RELATED CONCERNS. -99/12
AVIATION
SHOWERS HAVE GENERALLY DISSIPATED EARLY THIS MORNING
AS A LOW PRESSURE SYSTEM CONTINUES TO CHURN TO OUR SOUTH.
CONDITIONS ARE A MIX MVFR TO IFR ACROSS THE REGION WITH PATCHY
FOG SIGNIFICANTLY DEGRADING CIGS/VIS IN THE CENTRAL WILLAMETTE
VALLEY (LIFR KSLE AND KUAO AS OF 05-06Z). FLIGHT CONDITIONS OF
IFR TO MVFR ARE LIKELY TO PERSIST THROUGH SUNDAY MORNING. HEADED
THROUGH THE DAY, ANOTHER ROUND OF SHOWERS IS EXPECTED TO PIVOT
ACROSS THE AREA ALTHOUGH KAST MAY REMAIN JUST FAR ENOUGH TO THE
NORTHWEST OF THE MAIN SHOWER BANDS TO AVOID MOST OF THE ACTIVITY.
AS A RESULT OF THE SHOWERS, WE'LL LIKELY SEE PERIODS OF MVFR
CONDITIONS PERSIST AT TIMES DURING THE AFTERNOON INTO THE EVENING
AS WELL - PROBABILITIES FOR MVFR CIG SIT AROUND 30-50% FOR MUCH OF
THE DAY. WINDS REMAIN FAIRLY LIGHT, GENERALLY LESS THAN 5-10
KNOTS AT ALL SITES.
KPDX AND APPROACHES...A MIX OF VFR TO MVFR CONDITIONS ARE ALREADY
IN PLACE EARLY THIS MORNING LIKELY FLIPPING BACK AND FOURTH AT
TIMES THROUGH 18-19Z, ALTHOUGH MVFR IS FAVORED MOST HOURS (50-60%).
STARTING AROUND MIDDAY, ANOTHER ROUND OF WIDESPREAD SHOWERS
LIKELY SWINGS INTO THE PORTLAND METRO AREA STAYING OVERHEAD INTO
THE EVENING. WINDS GENERALLY STAY LIGHT OUT OF THE WNW. -99
MARINE
NORTHERLY WINDS ARE EXPECTED TO CONTINUE INTO EARLY NEXT
WEEK ALBEIT NOT PARTICULARLY STRONG WITH GUSTS STAYING BELOW 20
KNOTS THROUGH MONDAY. SIGNIFICANT WAVE HEIGHTS HOLD IN THE IN THE
4 TO 7 FOOT RANGE THROUGH THIS TIME PERIOD AS WELL. OUR FOCUS THEN
TURNS TO OUR NEXT WEATHER SYSTEM IN THE FORM OF A ROBUST FRONTAL
BOUNDARY ARRIVING LATER TUESDAY INTO WEDNESDAY MORNING WHICH
LIKELY (85-95% CHANCE) RESULTS IN SMALL CRAFT ADVISORY WIND GUSTS
OVER 21 KTS AND SEAS BUILDING TO AROUND 7 TO 10 FEET. HOWEVER,
THERE IS A 10-25% FOR A BRIEF PERIOD GALE FORCE WIND GUSTS
TUESDAY EVENING. WAVE HEIGHTS AND WINDS THEN SLOWLY DECREASE
THURSDAY INTO THE END OF THE WEEK. -99/03
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
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