551
FXUS66 KPQR 300909
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
209 AM PDT SUN MAR 30 2025
SYNOPSIS
RIDGING BUILDS INTO THE AREA BRINGING A BRIEF BREAK
IN PRECIPITATION AS WELL AS A SLIGHT WARMING TREND TODAY. THIS
WILL BE SHORT LIVED AS A BROAD AREA OF LOW PRESSURE WILL BRING
COOL AND WET CONDITIONS BACK TO THE REGION THROUGH THE LATTER
PART OF THE UPCOMING WEEK. ANOTHER SHORTWAVE RIDGE LOOKS TO
DEVELOP WEDNESDAY EVENING/THURSDAY WHICH WILL BRING WARM AND DRY
CONDITIONS ONCE AGAIN.
DISCUSSION...TODAY THROUGH SATURDAY
SHORTWAVE RIDGING
CONTINUES TO BUILD OVER THE REGION TODAY. THIS WILL BRING ABOUT
A BRIEF REPRIEVE IN PRECIPITATION ALONG WITH A SLIGHT WARMING
TREND ACROSS THE CWA. HOWEVER, THIS WILL BE SHORT LIVED AS A
BROAD AREA OF LOW PRESSURE WILL BRING A RETURN TO COOL AND WET
CONDITIONS STARTING THIS EVENING. COOL AND WET CONDITIONS WILL
REMAIN IN THE FORECAST THROUGH THE MAJORITY OF THE UPCOMING WEEK
WITH ANOTHER SHORTWAVE RIDGE BRINGING WARM AND DRIER CONDITIONS
BY THURSDAY.
THE NEXT SYSTEM WHICH ARRIVES TONIGHT LOOKS TO BE A DETACHED LOW
OF WHICH THE PARENT LOW LOOKS TO BE AROUND 43.82N/137.28W ON
MONDAY. LOOKING AT CAMS, THE DETACHED LOW WILL MOVE RATHER
SWIFTLY NORTHWARD AS IT PARALLELS THE OR/WA COAST. THIS LOW
WILL BRING THE FIRST SLUG OF MOISTURE AND COOL AIR TO THE
REGION. WARM MOIST AIR OVER RELATIVELY COOLER OCEAN WATER, WILL
ALSO RESULT IN A 10-15% PROBABILITY FOR THUNDERSTORMS OVER OUR
COASTAL WATERS IN ADDITION TO ISOLATED, GUSTY WINDS (UP TO 35
MPH) FOR INLAND LOCATIONS AS THE PRESSURE GRADIENT OPENS UP.
AS THE DISTENDED LOW MARCHES NORTHWARD, THE LARGER PARENT LOW
WILL CONTINUE TO TRAVERSE SOUTHEASTWARD TOWARDS SOUTHERN OREGON
AS IT SLOWLY WEAKENS. MODELS HAVE NARROWED DOWN THE POTENTIAL
LANDFALL AREA CLOSER TO THE OR/CA BORDER ON TUESDAY. AS THIS LOW
CONTINUES TO MOVE SOUTHEASTWARD, IT WILL SEND MULTIPLE FRONTS
ACROSS THE REGION AND 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 STARTING MONDAY AFTERNOON AND CONTINUING THROUGH
LATE MONDAY EVENING.
COOL AND MOIST CONDITIONS WILL PERSIST ON TUESDAY, BUT BY THIS
TIME THE LOW LOOKS TO BE WELL SOUTH OF OUR FORECAST AREA. NOW,
WHILE COOL TEMPERATURES ALONG WITH SHOWERS WILL CONTINUE, THIS
PATTERN IS NOT FAVORABLE FOR THUNDERSTORM DEVELOPMENT. AS THE
LOW CONTINUES TO MOVE SOUTHEASTWARD. 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.
AT THIS TIME, DO TO THE SHOWERY NATURE OF THE PRECIPITATION 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, WHICH WILL
HINDER SNOWFALL ACCUMULATIONS AROUND PASS-LEVEL. OVERALL, 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. HOWEVER, WE WILL CONTINUE TO MONITOR THE SITUATION AS
IT MORE INFORMATION COMES IN. WEDNESDAY LOOKS TO BE VERY SIMILAR
IN COMPARISON TO TUESDAY.
THURSDAY THROUGH SATURDAY LOOK TO BE VERY SIMILAR TO EACH OTHER
AS A SHORTWAVE RIDGE BUILDS ACROSS THE REGION. DAYTIME HIGHS
WILL STARTING THE 50S ON THURSDAY AND WARMING AROUND 5-7
DEGREES EACH DAY WITH DAYTIME HIGHS IN THE UPPER 60S TO LOW 70S
EXPECTED BY SATURDAY. /42
AVIATION
LARGELY VFR FLYING CONDITIONS ARE EXPECTED AT ALL
TERMINALS THROUGH MUCH OF THE PERIOD. LIGHT NORTH WINDS AT AROUND
5 KT WILL TURN OUT OF THE EAST TO SOUTHEAST BY 18Z SUNDAY. HIGH
CLOUDS AT 15-20 KFT CONTINUE TO SPREAD OVER THE REGION FROM THE
SOUTH, LIMITING THE POTENTIAL FOR RADIATION FOG EARLY SUNDAY
MORNING. THERE REMAINS A SLIGHT CHANCE, 5-15%, THAT
CENTRAL/SOUTHERN WILLAMETTE VALLEY TERMINALS, INCLUDING SLE/EUG,
MAY SEE RESTRICTED VIS FROM FOG OR MIST, MOST LIKELY FROM 12-16Z
SUN. AS WINDS INCREASE OUT OF THE EAST THROUGH SUNDAY MORNING,
TERMINALS WEST OF THE COLUMBIA GORGE, INCLUDING PDX/HIO WILL SEE
GUSTS TO 15-20 KT AFTER 18Z SUNDAY, WHILE STRONGER GUSTS OF 20-30
KT ARE EXPECTED CLOSER TO THE GORGE MOUTH AT TTD AFTER 15Z SUNDAY.
THESE EAST WINDS WILL ALSO ACT TO LIMIT THE FOG/MIST POTENTIAL AT
AFOREMENTIONED TERMINALS, AS WELL AS AT UAO THROUGH THE OVERNIGHT
PERIOD. A FRONTAL BOUNDARY WILL ARRIVE FROM THE SOUTH LATE IN THE
PERIOD, AFTER 18Z SUNDAY, SPREADING LOW-VFR CIGS AND RAIN SHOWERS
FROM SOUTH TO NORTH. HOWEVER, MVFR CIGS/VIS CANNOT BE RULED OUT
AT THIS POINT, ESPECIALLY ALONG THE COAST INCLUDING AST/ONP WHERE
MVFR CIGS BECOME MORE LIKELY AFTER 21-24Z SUN. INLAND, COULD SEE
BRIEF MVFR CIGS AND VIS IN HEAVIER RAIN.
PDX AND APPROACHES...VFR FLYING CONDITIONS WITH SCT-BKN HIGH
CLOUDS 20 KFT AND UNRESTRICTED VIS WILL CONTINUE THROUGH SUNDAY
MORNING. LIGHT NORTH TO NORTH-NORTHWEST WINDS AT AROUND 5 KT WILL
TURN OUT OF THE EAST BY 12-15Z SUNDAY, BEFORE SPEEDS INCREASE TO
10-15 KT GUSTING UP TO 20-25 KT AFTER 15-18Z SUNDAY. A FRONTAL
BOUNDARY WILL APPROACH FROM THE SOUTH, ARRIVING BY 21-23Z SUNDAY,
BRINGING RAIN SHOWERS. HOWEVER, LOW-END VFR CIGS AT 4-6 KFT AND
UNRESTRICTED VIS ARE EXPECTED TO PREVAIL WITHIN LIGHT RAIN SHOWERS
WITH A SMALL CHANCE OF MVFR CIGS IN HEAVIER SHOWERS. BEHIND THE
BOUNDARY, WINDS SHIFT SOUTHERLY BY 21-24Z SUNDAY WITH GUSTS UP TO
20-25 KTS CONTINUING THROUGH AROUND 06Z MONDAY. -PICARD/HEC
MARINE
OFFSHORE WINDS THIS MORNING ARE LOCALLY BREEZY THROUGH
COASTAL GAPS. OCCASIONAL WIND GUSTS UP TO 20-25 KTS ARE POSSIBLE,
THOUGH NOT WIDESPREAD ENOUGH FOR A SMALL CRAFT ADVISORY. WINDS
THEN TURN SOUTHERLY BY THIS AFTERNOON AND INCREASE THROUGH TONIGHT
AS ANOTHER FRONTAL SYSTEM APPROACHES FROM THE SOUTHWEST. HIGH
RESOLUTION GUIDANCE INDICATES A 75-90% CHANCE FOR LOW END GALE
FORCE WINDS LATER THIS AFTERNOON INTO TONIGHT ACROSS THE INNER
AND OUTER WATERS SOUTH OF OCEAN PARK, WA, INCLUDING THE COLUMBIA
RIVER BAR. A GALE WARNING HAS BEEN ISSUED FOR ALL COASTAL WATERS.
WINDS DECREASE SOMEWHAT BY EARLY MONDAY MORNING, THOUGH REMAIN
ELEVATED WITH GUSTS UP TO 30 KTS, OCCASIONALLY UP TO 35 KTS,
THROUGH MONDAY AFTERNOON AS ANOTHER LOW PRESSURE SYSTEM APPROACHES
THE WATERS. A SMALL CRAFT ADVISORY HAS BEEN ISSUED FOR ALL WATERS.
SEAS WILL BUILD AGAIN INTO THE LOW TEENS LATE TONIGHT DRIVEN BY
THE STRONG WINDS. WINDS WILL REMAIN ELEVATED THROUGH MONDAY INTO
TUESDAY AS A FRESH SOUTHWESTERLY SWELL ARRIVES, KEEPING SEAS UP
INTO THE LOW TO MID TEENS. SEAS DECREASE TUESDAY NIGHT INTO
WEDNESDAY, LEVELING OUT AROUND 5 TO 7 FT AT 9 TO 10 SECONDS BY
WEDNESDAY AFTERNOON, REMAINING FOR THE MIDDLE TO END OF THE WEEK
AS NORTH TO NORTHWESTERLY FLOW RESIDES ALOFT, KEEPING WINDS FAIRLY
LOW, AND THE PREVAILING SWELL REMAINS LOW. -SCHULDT/HEC
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 8 AM PDT THIS MORNING FOR PZZ210.
SMALL CRAFT ADVISORY FROM 2 AM TO 11 AM PDT MONDAY FOR PZZ210-
251>253-271>273.
GALE WARNING FROM 4 PM THIS AFTERNOON TO 2 AM PDT MONDAY FOR
PZZ210-251-271.
GALE WARNING FROM 1 PM THIS AFTERNOON TO 2 AM PDT MONDAY FOR
PZZ252-253-272-273.
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