621
FXUS66 KPQR 181756
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
1056 AM PDT FRI JUL 18 2025
SYNOPSIS
EXPECT ONSHORE FLOW TO CONTINUE TO INCREASE IN THE
COMING DAYS FACILITATING A COOLING TREND THROUGH THE WEEKEND
INTO EARLY NEXT - WIDESPREAD NEAR TO BELOW NORMAL TEMPERATURES
RETURN BY SUNDAY/MONDAY. AN UPPER- LEVEL TROUGH MAY PROVIDE THE
BEST RAINFALL CHANCES SO FAR THIS MONTH ON MONDAY, ALTHOUGH ODDS
REMAIN LOW FOR ACCUMULATING PRECIPITATION. FORECAST CONFIDENCE
STILL REMAINS FAIRLY LOW THROUGH THE COMING WORKWEEK BEYOND A
GENERAL WARMING TREND INTO TUESDAY/WEDNESDAY.
SHORT TERM...NOW THROUGH SUNDAY NIGHT
SATELLITE IMAGERY
EARLY THIS MORNING DEPICTS A MARINE STRATUS/FOG LAYER CURRENTLY
IN PLACE ACROSS THE COASTLINE STRETCHING EASTWARD INTO SEVERAL
OF THE ATTENDANT COAST RANGE RIVER VALLEYS INCLUDING THE I-5
CORRIDOR NEAR LONGVIEW/KELSO. THIS STRATUS WILL ATTEMPT TO SURGE
INTO THE WILLAMETTE VALLEY COME SUNRISE BUT THE MAJORITY OF
HIGH RESOLUTION GUIDANCE KEEPS IT PINNED FURTHER WESTWARD.
MOSTLY SUNNY SKIES FAVORED ACROSS THE INLAND VALLEYS THIS
MORNING. COME THE AFTERNOON HOURS, AN UPPER-LEVEL SHORTWAVE
RIDING DOWN THE B.C. COASTLINE WILL PUSHING INTO THE REGION
USHERING IN FURTHER ONSHORE FLOW IN ADDITION TO SLIGHTLY
CLOUDIER AND BREEZIER CONDITIONS THIS AFTERNOON - THE LATTER OF
THE THREE FEATURES MOST EVIDENT THROUGH THE CENTRAL COLUMBIA
GORGE WHERE GUSTS LIKELY REACH 30-35 MPH. ANTICIPATE 850MB
TEMPERATURES TO FALL FROM AROUND 15-16C TODAY TO 9-11C ON
SATURDAY/SUNDAY HELPING TO PUSH SURFACE TEMPERATURES TO BELOW-
NORMAL VALUES. AFTERNOON HIGHS THROUGH THE WEEKEND ARE EXPECTED
IN THE LOW 60S ALONG THE COAST AND MID 70S TO LOW 80S WITHIN
INLAND VALLEYS. INCREASED MARINE STRATUS COVERAGE MAY SEE AREAS
COASTAL FOG AND MIST, MOST LIKELY OVERNIGHT AND INTO THE MORNING
BOTH DAYS THIS WEEKEND AND WHERE THE STRATUS INTERSECTS THE
TERRAIN IN THE COAST RANGE. ALL IN ALL, A PATTERN NOT OUT OF THE
ORDINARY FOR THIS TIME OF YEAR. -SCHULDT
LONG TERM...MONDAY THROUGH THURSDAY
GOING FORWARD THROUGH THE
LONG TERM PERIOD SOMEWHAT LOWER CONFIDENCE PERSISTS AS
NUMERICAL GUIDANCE DIVERGES BEGINNING MONDAY ONWARD THROUGH THE
WEEK. TROUGHING INITIALLY PRESENT OVER THE PACIFIC NORTHWEST
LOOKS TO BECOME MORE ELONGATED AS A SHORTWAVE DIVES SOUTH ON ITS
WESTERN FLANK ON MONDAY. WHILE THIS WAVE MAY SUPPORT LIGHT RAIN
REACHING INTO THE REGION TO START THE WORK WEEK, CHANCES REMAIN
FAIRLY LOW OVERALL, ONLY 10-24% ALONG THE COAST AND IN THE
HIGHER TERRAIN OF THE CASCADES AND COAST RANGE WHILE THE
LOWLANDS SEE LESS THAN A 10% CHANCE. ECMWF BASED DETERMINISTIC
AND ENSEMBLE SOLUTIONS, INCLUDING THE ECMWF AIFS, REMAIN THE
MOST BULLISH ON LIGHT PRECIPITATION ACROSS THE AREA ON MONDAY
COMPARED TO OTHER MODELING SOLUTIONS WHICH KEEP THE UPPER-LEVEL
WAVE LESS DEVELOPED AND FURTHER EAST. ENSEMBLE MEMBERS THEN SHOW
A WIDE VARIETY OF POSSIBLE SCENARIOS INCLUDING A CUTOFF LOW
DEVELOPING OVER THE FAR EASTERN PACIFIC OR A DEAMPLIFICATION OF
THE TROUGH WITH AN ASSOCIATED WARMING TREND AS COOLER AIR IN THE
MID-LEVELS MODERATES. SHOULD THE FORMER CUTOFF LOW SOLUTION
MATERIALIZE MID TO LATE WEEK (ROUGHLY 40-50% OF THE ENSEMBLE
SPACE) WE'LL HAVE TO KEEP AN EYE OUT FOR CASCADES THUNDERSTORM
CHANCES. AT LEAST AT THIS POINT THE MAJORITY OF MEMBERS FAVOR
THE TREND BACK TOWARD A MORE ZONAL FLOW ALOFT AND THE FORECAST
THEREFORE WARMS BACK ABOVE SEASONAL NORMS COME THE MIDDLE OF THE
WEEK. -SCHULDT/PICARD
AVIATION
MIXED MVFR/IFR CIGS AND INTERMITTENT RESTRICTED VIS
WITHIN MARINE STRATUS CONTINUE AT COASTAL TERMINALS (KONP, KTMK,
KAST), BUT WILL BEGIN TO BREAK UP AND LIFT TOWARD PREDOMINANTLY
MVFR CIGS AND UNRESTRICTED VIS THROUGH THIS AFTERNOON. RESURGENT
STRATUS COVERAGE WILL SEE A RETURN TO IFR CIGS AFTER 06Z SAT.
INLAND, VFR CONDITIONS ARE EXPECTED BENEATH INCREASING CIRRUS
COVERAGE AT OR ABOVE 25 KFT THROUGH THIS EVENING. A STRONGER
MARINE PUSH MAY SEE FEW-SCT LOW STRATUS REACH UP THE COLUMBIA
RIVER TO PORTLAND-AREA TERMINALS (KPDX, KHIO, KVUO, KTTD), BUT
SUFFICIENT COVERAGE TO YIELD MVFR CIGS IS UNLIKELY, ONLY A 15-25%
CHANCE AFTER 12-15Z SAT. DIURNAL WEST TO NORTHWEST WINDS BUILD TO
5-10 KT WITH OCCASIONAL GUSTS OF 15-20 KT THIS AFTERNOON, THEN
DIMINISH TO 5 KT OR LESS TONIGHT.
PDX AND APPROACHES...CONTINUED VFR CONDITIONS EXPECTED THROUGH THE
PERIOD. HIGH CIRRUS COVERAGE INCREASES THROUGH THIS AFTERNOON,
THEN LOW CLOUDS DEVELOP OVERNIGHT AS A MORE VIGOROUS MARINE PUSH
REACHED THE VICINITY. THERE IS A 20% CHANCE FOR SUFFICIENT STRATUS
COVERAGE TO YIELD MVFR CIGS AFTER 12-15Z SAT BEFORE STRATUS MIXES
OUT BY 18Z SAT. NORTHWEST WINDS BUILD TO AROUND 10 KT OUT OF THE
NORTHWEST THIS AFTERNOON WITH GUSTS OF 15-20 KT, BEFORE EASING TO
5 KT OR LESS AFTER 06Z SAT. -PICARD
MARINE
WHILE WINDS REMAIN WEAK ACROSS THE WATERS, A SMALL
CRAFT ADVISORY REMAINS IN EFFECT ACROSS THE OUTER WATERS UNTIL
1100 FRIDAY DUE TO CHOPPY SEAS. SEAS SHOULD GRADUALLY FALL TO
AROUND 5-7 FT AT 8-9 SECONDS TODAY. HIGH PRESSURE WILL MAINTAIN
NORTHERLY TO NORTHWESTERLY WINDS THROUGH NEXT WEEK. SEAS CONTINUE
TO SUBSIDE THIS WEEKEND WITH MINIMAL IMPACTS EXPECTED. -ALVIZ
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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