400
FXUS66 KPQR 292146
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
246 PM PDT SAT MAR 29 2025
SYNOPSIS
WEAKENING SHOWERS TODAY AS RIDGING BUILDS INTO THE AREA.
SATURDAY NIGHT INTO SUNDAY A BRIEF BREAK IN THE PRECIPITATION AS WELL
AS A SLIGHT WARMING TREND IS EXPECTED. BY THE START OF THE UPCOMING
WEEK, A BROAD AREA OF LOW PRESSURE WILL BRING A RETURN OF COOLER
TEMPERATURES, RAIN AND CASCADE SNOW BY LATE SUNDAY NIGHT/MONDAY AND
THESE CONDITIONS LOOK TO PERSIST THROUGH THE UPCOMING WEEK.
DISCUSSION...TODAY THROUGH FRIDAY
THERE ARE STILL A FEW VERY WEAK
SHOWERS THROUGHOUT THE REGION, MOSTLY VIRGA, BUT ALL PRECIPITATION
TAPERS OFF THROUGHOUT THE REST OF THIS AFTERNOON. SHORTWAVE RIDGING
BUILDS IN THIS EVENING, AND THE MAJORITY OF TONIGHT AND SUNDAY WILL
BE DRY. SUNDAY'S HIGH TEMP WILL BE SLIGHTLY WARMER THAN PREVIOUS
DAYS, WITH A HIGH AROUND THE LOW 60S IN THE NORTHERN WILLAMETTE
VALLEY/SW WASHINGTON LOWLANDS, CLOSER TO THE MID/UPPER 50S AT THE
SOUTHERN WILLAMETTE VALLEY AND COAST.
THE NEXT SYSTEM ARRIVES ON SUNDAY NIGHT/MONDAY IS A RATHER BROAD,
VERTICALLY STACKED LOW, WITH THE SURFACE LOW EXPECTED TO BE AROUND
988 MB AND CENTERED AROUND 45.75N/136.40W ON MONDAY. THIS LOW WILL
SLOWLY WEAKEN AND TRAVEL SOUTHEASTWARD THROUGH THE UPCOMING
WEEK, WITH MODELS SHOWING LANDFALL IN-BETWEEN FLORENCE, OR AND
THE OR/CA BORDER. AS THIS LOW MOVES SOUTHEASTWARD, IT WILL SEND
MULTIPLE FRONTS ACROSS THE REGION. THIS WILL RESULT IN
SOUTH/SOUTHEASTERLY FLOW, THAT ALONG WITH MODERATE WARMING AND A
MOISTURE LATENT ATMOSPHERE WILL RESULT IN AROUND A 10-20% PROBABILITY
FOR THUNDERSTORMS COME MONDAY AFTERNOON AND CONTINUE THROUGH THE LATE
MONDAY EVENING. COOL AND MOIST CONDITIONS WILL CONTINUE AS THE LOW
CONTINUES TO TRUDGE SOUTHEASTWARD AND WILL BRING WIDESPREAD
PRECIPITATION ALONG WITH 850 MB TEMPERATURES DIPPING DOWN TOWARDS -0C
TO -4C. THIS WILL RESULT IN A LOWERING OF SNOW LEVELS TO 2500-3000
FEET. HAVE DECIDED NOT TO ISSUE A WINTER WEATHER ADVISORY FOR THE
INITIAL WAVE OF MOUNTAIN SNOW. NBM GUIDANCE SHOWS ONLY AROUND A
40-60% CHANCE FOR 6 INCHES OR GREATER OF SNOWFALL ACCUMULATION AT
CASCADES ELEVATIONS BETWEEN 3000-5500 FT, WITH CLOSER TO 70% CHANCE
ABOVE 5500 FT. COMBINED WITH THE FACT THAT SNOW LEVELS WILL BE CLOSER
TO 4000-5000 SHORTLY BEFORE THE PRECIPITATION AND ONLY SLOWLY FALLING
ONCE THE INITIAL FRONT PUSHES IN, SNOWFALL ACCUMULATIONS AT ANY
IMPACTFUL AREAS HAS POTENTIAL TO UNDERPERFORM MODEL GUIDANCE.
ULTIMATELY, WITH SHOWERY PRECIPITATION CONTINUING THROUGHOUT THE
MAJORITY OF THE UPCOMING WEEK, SNOW ACCUMULATIONS WILL AT SOME POINT
EXCEED 6 INCHES IN THE SOUTHERN CASCADES, BUT AT LEAST FOR THE
INITIAL WAVE OF PRECIPITATION, ADVISORY-LEVEL SNOWFALL RATES ARE NOT
EXPECTED. CLUSTER ANALYSIS SHOWS AROUND A 60% CHANCE OF RETURNING TO
RIDGING NEXT FRIDAY, POSSIBLY INDICATING DRIER CONDITIONS RETURNING
AT THAT POINT. /JLIU
AVIATION
PRIMARILY VFR CONDITIONS ARE EXPECTED THROUGH THE TAF
PERIOD. A WEAK SHORTWAVE RIDGE HAS BUILT OVERHEAD THIS AFTERNOON
HELPING TO KEEP SHOWER ACTIVITY CONFINED TO THE COAST RANGE AND
CASCADES, OTHERWISE DRY WEATHER PREVAILS. HEADED THROUGH THE
EVENING THESE SHOWERS LIKELY END WITH THE OVERALL UPPER-LEVEL FLOW
BECOMES MORE EASTERLY BY SUNDAY MORNING. WE'LL NEED TO WATCH THE
EVENING AND OVERNIGHT PERIOD BEFORE BOTH EASTERLY WINDS AND HIGH
CLOUDS INCREASE DURING WHICH PARTIAL CLEARING AND AMPLE SURFACE
MOISTURE MAY POTENTIALLY LEAD TO ISOLATED POCKETS OF VALLEY FOG -
20-30% CHANCE AT KEUG, KSLE, KUAO AND KHIO. IT APPEARS THE
DEVELOPMENT OF EASTERLY WINDS AT KTTD, KAST, KONP, AND TO SOME
EXTENT KPDX SHOULD MITIGATE THIS ISOLATED FOG POTENTIAL AT THESE
SITES. ON THAT NOTE WINDS LIKELY BECOME BREEZY THROUGH THE
COLUMBIA GORGE ON SUNDAY WITH GUSTS AROUND 20-30 KNOTS EXPECTED AT
KTTD. LATE IN THE PERIOD THE ARRIVAL OF A FRONTAL BOUNDARY SOUTH
TO NORTH WILL SPREAD LIGHT RAINFALL ACROSS THE REGION, MAINLY
BETWEEN 21-23Z SUNDAY AT MOST TERMINALS.
PDX AND APPROACHES...VFR CONDITIONS PERSIST WITH DRY CONDITIONS
EXPECTED THROUGH MOST OF THE PERIOD. EXPECT A SWITCH TO NORTHERLY
WINDS THIS EVENING BEFORE TURNING EASTERLY SUNDAY MORNING. A
FRONTAL BOUNDARY LIKELY BRINGS LIGHT RAIN TO THE TERMINAL LATE
SUNDAY AFTERNOON ~22-00Z BUT CIGS SHOULD HOLD AOA 5-10KFT. -SCHULDT
MARINE
TODAY A WEAK RIDGE OF HIGH PRESSURE HAS MOVED OVER THE
WATERS LEADING TO SOMEWHAT CALMER CONDITIONS WITH WAVE HEIGHTS OF
6-8FT AT 10 SECONDS. GOING THROUGH TONIGHT INTO SUNDAY MORNING
WINDS LIKELY TURN OFFSHORE BECOMING LOCALLY BREEZY THROUGH
COASTAL GAPS. WINDS THEN TURN SOUTHERLY BY SUNDAY AFTERNOON AND
INCREASE THROUGH SUNDAY NIGHT AS ANOTHER FRONTAL SYSTEM
APPROACHES FROM THE SOUTHWEST. HIGH RESOLUTION GUIDANCE INDICATES
A 75-90% CHANCE FOR LOW END GALE FORCE WINDS LATER SUNDAY
AFTERNOON INTO SUNDAY NIGHT ACROSS THE INNER AND OUTER WATERS
SOUTH OF CAPE FALCON WHICH HAS PROMPTED THE ISSUANCE OF A GALE
WARNING. HOWEVER, CONFIDENCE IS A BIT LOWER FOR FREQUENT GUSTS
ABOVE 34 KT NORTH OF CAPE FALCON SO HAVE DECIDED TO ISSUE A SMALL
CRAFT ADVISORY HERE - WE'LL ALMOST CERTAINLY SEE GUSTS BETWEEN
25-30 KNOTS LATE SUNDAY THROUGH MONDAY MORNING. IT'S WORTH NOTING
THERE IS AT LEAST SOME MINOR UNCERTAINTY AS TO THE
LOCATION/STRENGTH OF A SURFACE LOW ASSOCIATED WITH THE FRONTAL
BOUNDARY AND SHOULD MODELS TREND STRONGER WITH THIS FEATURE THE
SMALL CRAFT MAY NEED TO BE UPGRADED - SOMETHING TO WATCH.
SEAS WILL BUILD AGAIN INTO THE LOW TEENS LATE SUNDAY NIGHT (WIND
WAVE DRIVEN) DUE TO THE AFOREMENTIONED WEATHER SYSTEM. AFTER A
RATHER BRIEF LULL WE'LL SEE THE ARRIVAL OF A FRESH SOUTHWESTERLY
SWELL LATE MONDAY INTO TUESDAY PUSHES SEAS UP INTO THE LOW TO MID
TEEN YET AGAIN BEFORE DECREASING TUESDAY NIGHT INTO WEDNESDAY.
SEAS LEVEL OUT AROUND 5-7 FT AT 9-10 SECONDS FOR THE MIDDLE TO END
OF THE WEEK AS NORTH-NORTHWESTERLY FLOW RESIDES ALOFT. -SCHULDT
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 11 AM PDT THIS MORNING FOR
PZZ251>253-
271>273.
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