087
FXUS66 KPQR 041019
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
319 AM PDT THU JUN 4 2026
SYNOPSIS
A TRANSIENT RIDGE TODAY WILL KEEP CONDITIONS
SEASONABLE AND GENERALLY DRY. A DEEPER TROUGH AND ASSOCIATED LOW
PRESSURE SYSTEM SHIFTS SOUTHWARD INTO THE REGION FRIDAY TO
SATURDAY INCREASING ONSHORE FLOW AND RETURNING MORE WIDESPREAD
CHANCES FOR PRECIPITATION. SLIGHT CHANCES FOR THUNDERSTORMS
FRIDAY AND SATURDAY AFTERNOON. DRIER WEATHER RETURNS SUNDAY
BEFORE ANOTHER TROUGH RETURNS CHANCES FOR PRECIPITATION EARLY
NEXT WEEK.
SHORT TERM...NOW THROUGH SATURDAY NIGHT
SATELLITE IMAGERY
SHOWS WIDESPREAD CLOUD COVER OVER THE REGION WITH MOST AREAS
SITTING UNDER OVERCAST SKIES. THESE CLOUDS HAVE KEPT OVERNIGHT
TEMPERATURES ON THE WARM SIDE WITH LOWS IN THE UPPER 40S TO MID
50S FOR MANY LOCATIONS AS OF 3 AM. THROUGH THE DAY TODAY THOUGH
THOSE CLOUDS WILL THIN AS A TRANSIENT RIDGE MOVES OVER THE
REGION. WILL SEE LITTLE IN THE WAY OF SENSIBLE WEATHER AS
TEMPERATURES REMAIN SEASONABLE AND FLOW IS ZONAL. ESPECIALLY IN
THE AFTERNOON AND EARLY EVENING, THERE WILL BE A CONTRAST
BETWEEN A SURFACE HIGH OVER THE NORTHERN ROCKIES AND AN INCOMING
TROUGH OVER THE PACIFIC. BASED ON MODELS, COULD SEE BREEZY
WESTERLY WINDS NEAR SUNSET BUT WILL GENERALLY BE WITHIN EAST-
WEST ALIGNED TERRAIN LIKE THE LOWER I-5 CORRIDOR, COAST RANGE
GAPS, AND THE COLUMBIA RIVER GORGE. GUSTS AS HIGH AS 20 MPH ARE
POSSIBLE WITH A 10% CHANCE OF GUSTS UP TO 25 MPH.
THE OVERALL FORECAST ON FRIDAY AND THROUGH THE WEEKEND HAS
REMAINED UNCHANGED AND MODELS ARE IN GOOD AGREEMENT IN THE
SYNOPTIC PATTERN. A LOW ALOFT CONTINUES TO BE THE DOMINATE
FEATURE AS IT DROPS DOWN NEAR VANCOUVER ISLAND BY FRIDAY
AFTERNOON. AS THIS UPPER TROUGH MOVES IN, IT WILL PUSH A WEAK
FRONT INTO NORTHWEST OREGON AND SOUTHWEST WASHINGTON. THIS WILL
RETURN MORE WIDESPREAD CHANCES FOR PRECIPITATION, WITH THE
HIGHEST CHANCES OVER SOUTHWEST WASHINGTON AND THE NORTH OREGON
COAST, COAST RANGE, AND CASCADES. GIVEN THE SHOWERY NATURE OF
THIS SYSTEM, RAINFALL AMOUNTS WILL VARY ACROSS THE AREA AND THE
HIGHEST AMOUNTS WILL ULTIMATELY DEPEND ON WHERE SHOWERS SET-UP.
OVERALL, SHOWERS WILL BE NON-IMPACTFUL. GIVEN THE NORTHERN
TRACK OF THIS TROUGH, CHANCES FOR PRECIPITATION ARE HIGHEST AS
YOU GO FURTHER NORTH. IN ADDITION, THERE IS A 10-15% CHANCE FOR
THUNDERSTORMS ACROSS THESE AREAS AS INSTABILITY INCREASES DUE TO
COLD AIR ALOFT, A SLIGHT SOUTHWESTERLY FLOW, ALONG WITH
SUFFICIENT LIFT FROM THE TROUGH. ANY PASSING THUNDERSTORMS COULD
PRODUCE LIGHTNING, BRIEF HEAVY RAIN, ERRATIC WINDS, AND/OR
SMALL HAIL.
ONSHORE FLOW WILL ALSO INCREASE AS THIS UPPER TROUGH MOVES IN.
WEST-SOUTHWESTERLY WINDS WON'T BE TOO IMPACTFUL ACROSS MOST
AREAS WITH GUSTS UP TO 20 MPH ALONG THE I-5 CORRIDOR, HOWEVER,
TYPICAL BREEZY SPOTS DURING ONSHORE FLOW LIKE THE CENTRAL GORGE
AND UPPER HOOD RIVER VALLEY COULD GUST UP TO 35-40 MPH. THE 90TH
PERCENTILE WINDS ON FRIDAY EVENING ARE AROUND 20-25 MPH WITHIN
THE EAST-WEST ALIGNED TERRAIN, AND AROUND 30 MPH ALONG THE
HIGHER ELEVATIONS OF THE CASCADES. IF THE LOW SHIFTS ANY FURTHER
NORTH THOUGH THESE WINDS WILL BE LESS IMPACTFUL.
TRANSITIONING INTO SATURDAY THE LOW WILL SHIFT SLIGHTLY MORE
SOUTHWARD (THINK OF A REVERSE 'J' SHAPE) WHICH WILL ENHANCE
PRECIPITATION ONCE AGAIN. AT THIS TIME THERE REMAINS AMPLE
CONVECTIVE POTENTIAL FOR THUNDERSTORMS AGAIN IN THE AFTERNOON
AND PERIODS OF RAIN. MOST OF THE RAIN REMAINS CONCENTRATED TO
THE NORTH. -27/10
LONG TERM...SUNDAY THROUGH WEDNESDAY
FOR THOSE WITH SUNDAY
PLANS, THERE WILL BE A BRIEF DRIER PERIOD AS A SHORTWAVE RIDGE
PASSES OVER THE PACIFIC NORTHWEST. 500 MB ENSEMBLES ARE FALLING
INTO BETTER AGREEMENT WITH ANOTHER LONGWAVE TROUGH MOVING OVER
THE AREA. UNCERTAINTY REMAINS IN THE EXACT TRACK AS IT'S QUITE
MESSY WITH DETERMINISTIC SURFACE PLOTS SHOWING A NUMBER OF SMALL
MESOSCALE LOWS EMBEDDED WITHIN THE TROUGH. HOWEVER, THIS SYSTEM
WILL ENCOURAGE OVERALL MORE MOIST AND COOL AIR TO MOVE INTO THE
AREA. THEREFORE WILL MAINTAIN A TREND OF BELOW NORMAL HIGH
TEMPERATURES. WHEN OBSERVING THE 24-HR PRECIPITATION DIFFERENCES
BETWEEN THE ENSEMBLES, AROUND HALF OF THE SOLUTIONS ARE
TRENDING DRIER THAN THE COMPOSITE ENSEMBLE AND THE OTHER HALF
WETTER. THIS ONLY EMPHASIZES THE LEVEL OF UNCERTAINTY.
ULTIMATELY IT WILL ONCE AGAIN COME DOWN TO THE TRACK OF THE
SYSTEM. WHEN LOOKING AT INDIVIDUAL ENSEMBLE MEMBERS, THERE IS
CONSENSUS THOUGH THAT RAIN WILL START AT SOME POINT ON MONDAY
BUT HOW MUCH RAIN IS UNDETERMINED.
TUESDAY INTO WEDNESDAY IS A BIT OF A BLUR AS THE TWO DAYS RUN
SEAMLESSLY INTO ONE ANOTHER. POST FRONTAL RAIN SHOWERS EXPECTED
WITH BREEZY WESTERLY WINDS ONCE AGAIN POSSIBLE. ONE THING TO
CONSIDER IS THAT SOME OF THE MODELS ARE SUGGESTING THAT THE LOW
WILL MOVE ALMOST DIRECTLY OVER THE FORECAST AREA. IF THIS
OCCURS, THE JET STREAM WILL DIP JUST TO THE SOUTH AND WE WILL BE
IN A VERY DYNAMIC PATTERN. IN FACT, THERE ARE A FEW OF THE
MODEL RUNS THAT SUGGEST THAT WE COULD SEE GREATER THAN 1 INCH OF
RAIN ON TUESDAY INTO WEDNESDAY. AGAIN THOUGH, UNCERTAINTY IS
INCREDIBLY HIGH AND THE LARGER TREND IS TOWARDS NON-IMPACTFUL
ACCUMULATIONS. -27
AVIATION
ONSHORE FLOW CONTINUES TO SUPPORT LOW STRATUS ALONG
MUCH OF THE COAST AND OVER THE CASCADES AND CASCADE FOOTHILLS.
SUB-VFR CONDITIONS ALONG THE COAST WITH VFR CONDITIONS ACROSS THE
INTERIOR LOWLANDS CONTINUE. CHANCES FOR IFR TO MVFR CEILINGS
INCREASE TONIGHT INTO EARLY TOMORROW MORNING BOTH INLAND AND AT
THE COAST. BY 12Z THURSDAY, CHANCES FOR CEILINGS BELOW 3000 FT
INCREASE TO 25-50% FOR INLAND TAF SITES, EXCEPT 60-75% AT KSLE AND
KEUG. CHANCES FOR CEILINGS BELOW 3000 FT RANGE BETWEEN 75-95% AT
KAST AND KONP THROUGH 12Z THURSDAY. CONDITIONS EXPECTED TO IMPROVE
BACK TO VFR FOR ALL TERMINALS AFTER 18-20Z THURSDAY. WINDS BECOME
LIGHT AND VARIABLE AFTER 08-10Z THEN INCREASE TO 5-10 KT FROM THE
WEST AFTER 20-22Z THURSDAY.
KPDX AND APPROACHES...VFR CONDITIONS CONTINUE. THERE IS A 30-40%
CHANCE FOR CEILINGS BELOW 3000 FT BETWEEN 08-17Z THURSDAY AS LOWER
CLOUDS FORMING ALONG THE CASCADE FOOTHILLS ATTEMPT BACKBUILDING
WESTWARD TOWARDS THE KPDX TERMINAL. WEST WINDS 5 KT OR LESS
THROUGH THE PERIOD. -19/23
MARINE
LOOKING AT FAIRLY BENIGN CONDITIONS OVER THE NEXT
SEVERAL DAYS DESPITE A SERIES OF FRONTAL SYSTEMS MOVING THROUGH.
GENERALLY WESTERLY FLOW OVER THROUGH SATURDAY. SEAS ARE
EXPECTED TO REMAIN AROUND 5 TO 6 FT AS A WESTERLY SWELL
PERSISTS. SEAS THEN BUILD TO 6-8 FT AT 11 TO 12 SECONDS LATE
TONIGHT NIGHT INTO FRIDAY MORNING AS A WEAK FRONTAL BOUNDARY
APPROACHES THE WATER. THIS FRONT WILL ALSO BRING INCREASING
WESTERLY WINDS WITH GUSTS UP TO 20 KT. THERE IS LESS THAN A 5%
CHANCE OF WIND GUSTS OF 25 KT OR GREATER.
A SECONDARY FRONT ARRIVES ON SATURDAY, BRINGING A SHIFT TO
NORTHWEST WINDS. HOWEVER, WIND SPEEDS ARE NOT EXPECTED TO
INCREASE MUCH WITH THIS FRONTAL PASSAGE. THERE IS LESS THAN A
15% CHANCE OF SMALL CRAFT ADVISORY WINDS. THE TIME PERIOD WITH
HIGHEST WIND SPEEDS WILL LIKELY OCCUR ON MONDAY AS STRONGER
SYSTEM MOVES OVER THE WATERS, BRINGING SOUTH WINDS UP TO 20-25
KT AND SEAS APPROACHING 9-10 FT. -27/23
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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