300
FXUS66 KPQR 311812
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1112 AM PDT MON MAR 31 2025
UPDATED AVIATION DISCUSSION
SYNOPSIS
UPPER LEVEL TROUGHING SUPPORTS SEASONABLY COOL AND
SHOWERY CONDITIONS THROUGH WEDNESDAY. THE PATTERN TURNS WARMER
AND DRIER DURING THE LATTER HALF OF THE WEEK.
SHORT TERM...NOW THROUGH WEDNESDAY NIGHT
SCATTERED SHOWERS
CONTINUE ACROSS THE REGION THIS MORNING IN DEEP LAYER SOUTHWEST
FLOW AHEAD OF A DEEP UPPER LEVEL TROUGH CENTERED OFFSHORE OF THE
OREGON COAST. THIS FEATURE WILL MAINTAIN A COOL AND SHOWERY
PATTERN TODAY AND THROUGH MUCH OF THE FIRST HALF OF THE WEEK AS
UPPER LEVEL TROUGHING PERSISTS OVER THE PACIFIC NORTHWEST.
SHOWER ACTIVITY WILL BE ENHANCED THIS AFTERNOON AS THE TROUGH
BEGINS TO MOVE OVERHEAD AND COLD AIR ADVECTION ALOFT HELPS TO
STEEPEN MID LEVEL LAPSE RATES, BRINGING A CHANCE OF
THUNDERSTORMS TO MAINLY COASTAL AREAS. CAN'T RULE OUT A FEW
RUMBLES OF THUNDER INLAND AS WELL, BUT MODEL SOUNDINGS DEPICT
GENERALLY WEAKER AND SHALLOWER INSTABILITY WHICH WILL SERVE TO
LIMIT CHARGE SEPARATION AND CAP THUNDERSTORM PROBABILITIES
AROUND 10% THIS AFTERNOON EAST OF THE COAST RANGE. THAT SAID,
ANY HEAVIER SHOWERS OR THUNDERSTORMS WILL BE CAPABLE OF
PRODUCING SMALL HAIL GIVEN THE AMPLE COLD AIR ALOFT. MODEL QPF
AMOUNTS ARE AROUND A QUARTER INCH ALONG THE COAST THROUGH THIS
EVENING, WITH LIGHTER AMOUNTS EXPECTED INLAND AS THE NBM
PROBABILITY OF A QUARTER INCH OF RAIN SITTING AT 10-15% ACROSS
THE WILLAMETTE VALLEY TODAY. WILL SEE MODEST SNOW ACCUMULATIONS
IN THE CASCADES AS SNOW LEVELS RESIDE AROUND 3000 FEET THIS
AFTERNOON, WITH ANOTHER 2-4 INCHES OF SNOW POSSIBLE IN THE
CASCADE PASSES THROUGH THIS EVENING.
EXPECT A RELATIVE LULL IN SHOWER ACTIVITY ACROSS THE AREA TONIGHT
INTO TUESDAY AS THE CORE OF THE UPPER LOW SLIDES SOUTH TOWARDS
THE OR/CA BORDER AND TRANSIENT SHORTWAVE RIDGING DEVELOPS
OVERHEAD, KEEPING THE GREATER SHOWER POTENTIAL CONFINED TO THE
SOUTHERN EXTENT OF THE AREA ACROSS LANE COUNTY THROUGH TUESDAY
EVENING. MORE WIDESPREAD SHOWERS RETURN ON WEDNESDAY AS ANOTHER
SHORTWAVE CROSSES THE REGION IN NORTHWEST FLOW, BUT QPF VALUES
REMAIN MEAGER. TEMPERATURES WILL REMAIN NEAR OR SLIGHTLY BELOW
SEASONAL NORMS WITH HIGHS IN THE MID 50S THROUGH WEDNESDAY. WILL
CONTINUE TO SEE MINOR SNOW ACCUMULATIONS IN THE CASCADES THROUGH
MID WEEK, LIKELY REMAINING WELL SHY OF ADVISORY CRITERIA IN ANY
ONE PERIOD. /CB
LONG TERM...THURSDAY THROUGH SUNDAY
THE PATTERN WILL BEGIN TO
TRANSITION ON THURSDAY AS THE TROUGH DEPARTS THE REGION AND
SETS THE STAGE FOR UPPER LEVEL RIDGING THROUGH THE WEEKEND.
THURSDAY WILL BE CHARACTERIZED BY DRIER NORTHERLY FLOW BETWEEN
THESE TWO FEATURES, WITH HIGHS AGAIN IN THE 50S AND POTENTIALLY
SOME LIGHT SHOWER ACTIVITY LINGERING ALONG THE HIGHER TERRAIN.
THE WARMING AND DRYING TREND BEGINS IN EARNEST ON FRIDAY AS
ENSEMBLE CLUSTERS SHOW GOOD AGREEMENT ON THE RIDGE BUILDING
OVER THE REGION, WITH TEMPERATURES CLIMBING INTO THE 60S IN THE
INLAND VALLEYS. THE WARMEST TEMPERATURES ARE EXPECTED OVER THE
WEEKEND, WITH NBM PROBABILITIES FOR SURPASSING 70 DEGREES
RANGING FROM 50-70% ACROSS THE WILLAMETTE VALLEY ON SATURDAY
AND 60-80% ON SUNDAY. THE NBM BEGINS TO INCREASE PRECIPITATION
CHANCES AS EARLY AS SUNDAY, BUT ENSEMBLES SHOW GOOD AGREEMENT
ON KEEPING THE AREA DRY THROUGH SUNDAY AND HOLDING OFF THE
ARRIVAL OF THE NEXT TROUGH UNTIL EARLY NEXT WEEK. /CB
AVIATION
CONDITIONS REMAIN A MIX OF VFR TO MVFR THIS MORNING AS
SHOWERY CONDITIONS PERSIST ACROSS THE REGION THANKS TO A SECONDARY
SHORTWAVE TROUGH MOVING OVERHEAD. WITH ANY PASSING SHOWER
ACTIVITY TERMINALS COULD CAN SEE CONTINUED MVFR CIGS AND
SLIGHTLY REDUCED VIS. FOR COASTAL TERMINALS, CANNOT RULE OUT
THUNDERSTORMS AFTER 21-22Z TODAY THOUGH THEY ARE MORE LIKELY TO
STAY OVER THE PACIFIC. KONP WOULD BE THE MOST LIKELY AIRPORT TO
SEE THUNDERSTORMS IN THE VICINITY. AFTER 00-6Z TUESDAY,
CONDITIONS WILL EASE CONSIDERABLY AS THE WEAK LOW PRESSURE
SYSTEM MOVES INLAND TO OUR SOUTH LEADING TO A SIGNIFICANT
DECREASING IN SHOWER ACTIVITY AND GENERALLY DRIER WEATHER
PREVAILING OVERNIGHT.
PDX AND APPROACHES...SHOWER ACTIVITY CONTINUES WITH GENERALLY VFR
CIGS THROUGH THE TAF PERIOD. WILL SEE PERIODS OF MVFR CIGS/VIS
AND GUSTY WINDS WITH PASSING SHOWERS AND HEAVIER RAIN. EXPECT
SHOWERS TO DECREASE AND TAPER OFF THIS EVENING AROUND 04-05Z
FOLLOWED BY DRY WEATHER AND LIGHTER WINDS OVERNIGHT INTO TUESDAY
MORNING. -SCHULDT/MUESSLE
MARINE
MARINE CONDITIONS HAVE BEEN MORE SETTLED THAN EXPECTED
WITH GUSTS UP TO 25 KT, AND SEAS AROUND 5-7 FT AT 8 SECONDS. HAVE
CONTINUED THE SMALL CRAFT ADVISORY THOUGH THE CONDITIONS ARE LESS
WIDESPREAD AS EXPECTED. A SECOND DISTURBANCE MOVES INLAND TODAY
WHICH WILL CAUSE WINDS TO RESURGES WITH GUSTS UP TO 25 KT. LATER
TONIGHT THOSE WINDS WILL SLOWLY EASE FROM NORTH TO SOUTH. WILL
CONTINUE TO MONITOR TO SEE IF THOSE CONDITIONS PERSIST LONGER BUT
GIVEN THE LATEST TREND, THAT PORTION OF THE FORECAST HAS LESS
CERTAINTY.
SEAS WILL STEADILY RISE BEHIND THE SECOND SHORTWAVE WITH A
SOUTHERLY FRESH SWELL AND NORTHWEST BACKGROUND SWELL. SEAS WILL BE
SOUTHERLY SWELL DOMINATED AND THE WIND WAVE WILL BE LESS THAN
PREVIOUS DAYS. SEAS UP TO 10 FT WILL OCCUR LATE TONIGHT BEFORE
DISSIPATING TUESDAY. ONCE WINDS AND SEAS FALL, THEY WILL STAY
CONSISTENT THROUGH MUCH OF THE WEEK. -MUESSLE
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 10 PM PDT THIS EVENING FOR PZZ210.
SMALL CRAFT ADVISORY FROM 5 AM TO 11 AM PDT TUESDAY FOR PZZ210.
SMALL CRAFT ADVISORY UNTIL 5 AM PDT TUESDAY FOR PZZ251>253-
271>273.
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