830
FXUS66 KPQR 042121
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
221 PM PDT FRI JUL 4 2025
SYNOPSIS
ONSHORE FLOW CONTINUES AS A SERIES OF SHORT WAVE,
UPPER LEVEL TROUGHS MOVE OVER THE AREA TONIGHT. THIS WILL
INCREASE MIXING AND BRING SOME MOIST AIR INTO THE REGION. AS A
RESULT OF THIS PATTERN THERE IS A SLIGHT CHANCE (15-20%) OF RAIN
SHOWERS THROUGH THIS EVENING ALONG THE CASCADES. COULD SEE
ISOLATED THUNDERSTORMS OVER THE RIDGES THROUGH THE SAME TIME
PERIOD. WARMING AND DRYING TRENDS RETURNS BY THE WEEKEND AND IS
EXPECTED TO PERSIST THROUGH AT LEAST THE MIDDLE OF THE UPCOMING
WEEK.
SHORT TERM...TONIGHT THROUGH MONDAY NIGHT
WHAT REMAINS OF A
BROAD SHORTWAVE THAT RESULTED IN A VERY ACTIVE PERIOD EAST OF
THE CASCADES, WILL HAVE THE POTENTIAL TO BRING SOME VERY LIGHT
SHOWERS AND MAYBE SOME THUNDERSTORMS ALONG THE CASCADES THROUGH
THIS EVENING. CAMS VIA SIMULATED REFLECTIVITY ARE PUTTING AROUND
A 15-20% PROBABILITY OF SHOWERS AND THUNDERSTORMS THROUGH THIS
EVENING. ANY THUNDER STORMS WOULD BE FAR AND FEW BETWEEN.
AS SATURDAY AND SUNDAY APPROACH, EXPECT A GRADUAL WARM UP AS
VERY BROAD HIGH PRESSURE BUILDS OVER THE PACIFIC NW. AT THE
SAME TIME, MODELS SHOW AN UPPER LEVEL LOW DEVELOPING OVER
NORTHERN CALIFORNIA. OVER THE PAST 24 HOURS, THE TRAJECTORY OF
THIS LOW HAVE CHANGED SIGNIFICANTLY. PREVIOUS MODEL RUNS HAD
THIS LOW FURTHER NORTH AS WELL AS STARTING TO MAKE A MORE
NORTH/NORTHEASTERLY TRACK. THIS DRASTIC CHANGE IN THE MODELS IS
RESULTING IN A FAIR AMOUNT OF UNCERTAINTY IN THE FORECAST FOR
THE MIDDLE AND LATTER PARTS OF THE UPCOMING WEEK. WHICH WILL BE
GIVEN MORE DETAIL IN THE LONG TERM DISCUSSION BELOW.
OVERALL, EXPECT A GRADUAL WARMUP THROUGH THE WEEKEND AND INTO
THE START OF THE WEEK. SKIES WILL CONTINUE TO CLEAR FOR INLAND
LOCATIONS, BUT CONSISTENT ONSHORE FLOW WILL HELP THE COAST TO
STAY CLOUDY AND COOLER UNTIL TUESDAY. /42
LONG TERM...TUESDAY THROUGH THURSDAY
GIVEN THAT DETERMINISTIC
MODELS HAVE CHANGED SIGNIFICANTLY OVER THE PAST 24 HOURS, THERE
REMAINS A LOT OF UNCERTAINTY IN THE FORECAST FOR THE MAJORITY OF
NEXT WEEK. HOWEVER, IF THE CURRENT FORECAST HOLDS, THE UPPER
LEVEL LOW MENTIONED ABOVE IS EXPECTED TO MOVE INLAND NEAR THE
OR/CA BORDER. IF THIS HAPPENS, THE WARMEST DAY OF NEXT WEEK
LOOKS TO BE ON TUESDAY. THE CAUSE OF THESE SLIGHTLY COOLER
TEMPERATURES IS THE FACT THAT THE CALIFORNIA LOW WILL HELP TO
TAMP DOWN SOME OF THE HOTTER 850 MB TEMPERATURES ORIGINATING IN
THE GREAT BASIN. MODELS ARE SHOWING 850 MB TEMPERATURES IN THE
13-15 C RANGE WHICH IS ABOUT 5 DEGREES C COOLER THAN YESTERDAY.
SO, WITH THAT IN MIND, LET'S TAKE A LOOK AT THE POSSIBLE DAYTIME
HIGH SPREADS ACROSS OUR CWA ON TUESDAY. WILL LOOK AT THE MOST
LIKELY 25TH-75TH PERCENTILE.
NOTE: TEMPERATURES IN DEGREES FAHRENHEIT
PORTLAND/VANCOUVER: 89-95
SALEM: 94-98
EUGENE: 91-97
HOOD RIVER: 89-96
ASTORIA: 68-70
BATTLE GROUND: 86-92
RAYMOND: 71-78
KELSO/LONGVIEW: 85-93
NEWPORT: 68-70
TRANSITIONING INTO WEDNESDAY, THE LOW WILL CONTINUE TO TREK
EASTWARD INTO IDAHO. THIS WILL RESULT IN INCREASING
NORTHWESTERLY FLOW AND BRINGING IN COOLER, MOISTER AIR. GIVEN
THE SIGNIFICANT CHANGE IN THE MODELS OVER THE PAST 24 HOURS,
HAVE CHOSEN TO HOLD WITH THE NBM. THE NBM HAS LEANED INTO A
SLIGHT COOLER SOLUTION INTO THE LATTER PART OF THE WEEK. WILL
CONTINUE TO MONITOR AND UPDATE AS NEEDED. /42
AVIATION
AN AREA OF LOW PRESSURE ALOFT MOVES OVER NW OREGON
THROUGH THIS EVENING BEFORE SHIFTING EAST OF THE CASCADES BY
SATURDAY MORNING. SOUTHEASTERLY FLOW ALOFT WILL MAINTAIN HIGH
CIRRUS THROUGH THIS AFTERNOON FROM CONVECTION EAST OF THE CASCADES
TODAY. PREDOMINATELY VFR CONDITIONS EXPECTED INLAND THROUGH AT
LEAST 12Z SAT. MARINE STRATUS ALONG THE NORTHERN COAST THIS
MORNING WILL LIKELY (60% CHANCE) PERSIST THROUGH MUCH OF TODAY,
WITH POTENTIAL BREAKS IN THE CLOUDS AND POSSIBLE (40% CHANCE)
IMPROVEMENT TO VFR BETWEEN 20-02Z. THEN, MARINE STRATUS EXPECTED
TO SURGE BACK ONSHORE TONIGHT WITH MVFR CIGS AFTER 02Z SAT.
PDX AND APPROACHES...VFR WITH BROKEN HIGH CLOUDS EXPECTED THROUGH
MUCH OF TONIGHT. THERE IS A 20-30% CHANCE OF MVFR STRATUS PUSHING
UP THE COLUMBIA RIVER AFTER 12Z SATURDAY MORNING. NORTHWEST WINDS
EXPECTED TO INCREASE THIS AFTERNOON TO AROUND 10 KT. /DH
MARINE
SURFACE HIGH PRESSURE OFFSHORE WILL MAINTAIN NORTH TO
NORTHWEST WINDS ACROSS THE COASTAL WATERS THROUGH THE WEEKEND, AND
CONTINUING INTO EARLY NEXT WEEK. PRESSURE GRADIENTS OVER THE
WATERS INCREASE SATURDAY AND SUNDAY AS THE THERMAL TROUGH
STRENGTHENS OVER THE SOUTH OREGON COAST. THIS WILL BRING STRONGER
NORTHERLY WINDS WITH DIURNALLY DRIVEN GUSTS UP TO 20-25 KT EACH
AFTERNOON AND EVENING. A SIMILAR PATTERN IS LIKELY ON MONDAY AS
WELL. SEAS ARE ALSO EXPECTED TO REMAIN FAIRLY CONSISTENT AT AROUND
3 TO 6 FT THROUGH EARLY NEXT WEEK. /DH
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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