387
FXUS66 KPQR 052152
AFDPQR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PORTLAND OR
252 PM PDT TUE AUG 5 2025
SYNOPSIS
BROAD TROUGHING WILL BRING CONTINUED BELOW-NORMAL
TEMPERATURES THROUGH THURSDAY WITH CLOUDS AND CHANCES FOR A
WIDESPREAD WETTING RAIN SPREADING FROM WEST TO EAST STARTING
TUESDAY NIGHT AND CONTINUING THROUGH EARLY THURSDAY. AS THE
LATTER PART OF THIS WEEK APPROACHING, HIGH PRESSURE WILL BUILD
OVER THE REGION AND RESULT IN A WARMING AND DRYING TREND THURSDAY
THROUGH THE WEEKEND AND POTENTIALLY HAZARDOUS HEAT BY EARLY
NEXT WEEK.
SHORT TERM...TONIGHT THROUGH THURSDAY NIGHT
A WEAK SURFACE
LOW OFFSHORE OF VANCOUVER ISLAND WILL OCCLUDE AND FILL AS MOVES
EASTWARD TONIGHT. A PAIR OF SURFACE FRONTS EXTENDING SOUTHWARD
FROM THIS SURFACE LOW WILL BRING PERIODS OF RAIN TO THE COAST
THIS EARLY THIS EVENING AND INTO TONIGHT, WITH THE FRONTS
PUSHING FURTHER INLAND BY WEDNESDAY MORNING. CAM GUIDANCE HAS A
START TIME FOR PRECIPITATION ALONG THE COAST AROUND MIDNIGHT
TONIGHT AND A START TIME FOR THE WILLAMETTE VALLEY AROUND 3 AM
WEDNESDAY WITH AN INITIAL PERIOD OF STEADIER STRATIFORM RAIN.
PRECIPITATION WILL TAKE ON A MORE SHOWERY PATTERN WEDNESDAY
MORNING. MODEL SOUNDINGS ARE SHOWING SOME WEAK INSTABILITY, WITH
THE NAM AND CANADIAN SHOWING AROUND 100 J/KG OF CAPE, SO THIS
IS NOT A FAVORABLE SYSTEM FOR THUNDER, BUT CAN'T RULE OUT THE
PROBABILITY OF A FEW RUMBLES. CURRENTLY, THERE IS A 5%-10%
PROBABILITY FOR THUNDERSTORMS ALONG THE SOUTHERN WASHINGTON
CASCADES STARTING WEDNESDAY AFTERNOON THROUGH WEDNESDAY NIGHT.
LINGERING POST-FRONTAL SHOWERS MAY CONTINUE INTO THURSDAY
MORNING BEFORE SEASONABLY COOL AND DRY WEATHER RETURNS THURSDAY
AFTERNOON INTO THURSDAY NIGHT.
ABUNDANT MOISTURE ASSOCIATED WITH THIS SYSTEM, AS EVIDENCED BY
PRECIPITABLE WATER VALUES APPROACHING 1.5 INCHES. IF THIS WERE
TO OCCUR, THIS WOULD TIE OR POSSIBLY BREAK THE DAILY RECORD FOR
PRECIPITABLE WATER FOR AUG 6TH, WHEN LOOKING AT THE UPPER AIR
SOUNDING FOR KSLE. FOR REFERENCE, THE NORMAL AMOUNT OF
PRECIPITABLE WATER AROUND THIS TIME OF YEAR IS AROUND 0.80
INCHES. PRECIPITABLE WATER CAN BE DESCRIBED AS THE AMOUNT OF
WATER VAPOR CONTAINED WITHIN THE ENTIRE COLUMN OF THE ATMOSPHERE
ABOVE ONE GIVEN LOCATION. NOW, THIS DOESN'T MEAN THAT YOU CAN
GET MORE PRECIPITATION THAN WHAT IS IN THE COLUMN AS THE
ATMOSPHERE IS NOT A STATIC ENVIRONMENT AND A MULTITUDE OF
FACTORS/SYSTEMS CAN ADD OR REMOVE PRECIPITABLE WATER.
STORM TOTAL PRECIPITATIONS ACROSS THE REGION ARE AS FOLLOWS:
WILLAPA HILLS, MOUNT ST. HELENS AND WASHINGTON CASCADES:
0.50-1.10 INCHES
COAST AND COAST RANGE:
0.10-1.00 INCHES
WILLAMETTE VALLEY:
0.01-0.40 INCHES
OREGON CASCADES:
0.01-0.75 INCHES
THE HIGHER ACCUMULATIONS ARE EXPECTED FOR AREAS NORTH OF SALEM,
OR AND IF A THUNDERSTORM DEVELOPS, THAT WOULD ALSO RESULT IN AN
INCREASE IN OVERALL PRECIPITATION TOTALS. OVERALL, SLIGHTLY
COOLER AND WETTER WEATHER IS IN THE FORECAST OVER THE NEXT 24-36
HOURS. /42-PICARD
LONG TERM...FRIDAY THROUGH MONDAY
WHILE NEAR SEASONAL TO
SLIGHTLY COOLER TEMPERATURES WERE A NICE REPRIEVE A PATTERN
SHIFT TOWARDS THE END OF THE WEEK WILL SEE HIGH PRESSURE
RETURNING. NEAR SEASONAL DAYTIME HIGHS ON FRIDAY WILL CONTINUE
TO RISE AS EARLY NEXT WEEK APPROACHES. MID TO UPPER 90S ACROSS
INLAND AREAS BY SUNDAY AND MONDAY ARE EXPECTED. MODELS ARE ALSO
SHOWING THAT SOME AREAS COULD SEE DAYTIME HIGHS REACH INTO THE
TRIPLE DIGITS. FOR SUNDAY, THERE IS A 20% PROBABILITY OF 100
DEGREE DAYTIME HIGH IN PORTLAND, 45% PROBABILITY FOR SALEM AND
CORVALLIS AND 55% PROBABILITY FOR EUGENE AND COTTAGE GROVE.
MONDAY THE PROBABILITIES FOR 100 ARE: 50% PROBABILITY OF 100
DEGREE DAYTIME HIGH IN PORTLAND, 75% PROBABILITY FOR SALEM AND
CORVALLIS AND 80% PROBABILITY FOR EUGENE AND COTTAGE GROVE.
TUESDAY, WHILE BEING 8 DAYS IN THE FUTURE, MODELS ARE SHOWING A
50% PROBABILITY FOR DAYTIME HIGHS REACHING 100 DEGREES AS WELL.
THROUGH THE SAME TIME PERIOD, DEWPOINT TEMPERATURES IN THE UPPER
50S TO LOW 60S WILL ALSO MAKE CONDITIONS FEEL NOTICEABLY
HUMID/STICKY. IN ADDITION, OVERNIGHT LOWS IN THE MID TO UPPER
60S ARE MOST LIKELY IN THE CENTRAL WILLAMETTE VALLEY,
PORTLAND/VANCOUVER METRO, LOWER COLUMBIA AND COWLITZ VALLEYS,
AND THROUGH THE COLUMBIA RIVER GORGE SUNDAY AND MONDAY NIGHTS,
RESULTING IN AREAS OF MAJOR HEATRISK FOR THE AFOREMENTIONED
AREAS.
A LACK OF SUFFICIENT OVERNIGHT COOLING CAN RAISE THE CUMULATIVE
HEAT STRESS AND ELEVATE THE RISK FOR HEAT ILLNESS. THEREFORE,
RESIDENTS OF THE AFOREMENTIONED AREAS WITHOUT ACCESS TO
ADEQUATE COOLING SHOULD BEGIN TO PLAN FOR THIS PERIOD OF
HAZARDOUS HEAT. /42-PICARD
AVIATION
A FRONTAL SYSTEM IS BEGINNING TO MAKE LANDFALL WHICH
WILL SLOWLY CAUSE STRATUS TO FILL THE REGION. WILL SEE VFR
CIGS/VIS OVER THE NEXT FEW HOURS, BUT WILL FALL TO MVFR LEVELS
STARTING ALONG THE NORTH OREGON COAST, MOVING TO THE CENTRAL
OREGON CASCADES. WILL SEE PRECIPITATION WITH THIS FRONT WHICH WILL
CAUSE VIS TO DEGRADE THROUGH THE EVENING. RAIN WILL BE HEAVIEST
ALONG THE COAST, CASCADES, COAST RANGE, AND NORTH OF KUAO. COASTAL
TERMINALS WILL SEE IFR CIGS/VIS WITH PASSING STORMS. CONFIDENCE
IS LOW IN REGARDS TO JUST HOW LOW CIGS WILL FALL IN THE LATER HALF
OF THE FORECAST FOR INLAND TERMINALS. HOWEVER, AREAS SOUTH OF
KUAO WILL LIKELY STAY DRIER, AND VFR.
PDX AND APPROACHES...EARLIEST ARRIVAL OF RAIN IS 05Z WED, WITH
THE LATEST BEING AROUND 12Z WED. WILL SEE A DECREASE IN CIG
HEIGHTS AFTER THE FRONT ARRIVES, BUT MODELS ARE TRENDING
SLIGHTLY HIGHER ON THE FL OF THOSE CLOUDS. THERE MAY BE A FEW
HOURS AFTER 16Z WED WHERE VIS WILL BE REDUCED. THIS IS LIKELY
DUE TO THE PRESENCE OF STRONGER SHOWERS, AND HIGHER CONFIDENCE
IN THE TIMING. HAVE TRENDED TOWARDS A GRADUAL REDUCTION IN CIGS.
UNLESS A HEAVY SHOWER ESTABLISHES ITSELF RIGHT OVER KPDX, VIS
SHOULD BE UNAFFECTED.
-MUESSLE
MARINE
SATELLITE IMAGERY SHOWS THE FRONTAL SYSTEM SITTING OVER
THE NORTHERN AND CENTRAL WATERS WITH INCREASING SOUTHERLY WINDS.
BUOYS HAVE YET TO RESPOND, BUT AREA OBSERVATIONS ARE SHOWING GUSTS
TO AROUND 20 KT. THE PEAK WIND SPEEDS WILL BE WITH THE INITIAL
ONSET OF THE FRONT, BUT WILL CONTINUALLY SEE 10 TO 15 KT WINDS
WITH AREAS OF GUSTS TO 20 KT - ESPECIALLY CLOSER TO SHORE. CANNOT
RULE OUT AN ISOLATED GUSTS TO 25 KT OR TWO, BUT NOT EXPECTED TO BE
WIDESPREAD OR FREQUENT. SEAS WILL BE GENERALLY UNAFFECTED WITH
THIS SYSTEM AND REMAIN NORTHWESTERLY AT 4-6 FT. THESE CONDITIONS
WILL PERSIST THROUGH WEDNESDAY.
HIGH PRESSURE DEVELOPS IN THE LATER HALF OF THE WEEK CAUSING A
WIND REVERSAL AND ELEVATED SPEEDS STARTING THURSDAY EVENING.
-MUESSLE
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
WWW.WEATHER.GOV/PORTLAND
INTERACT WITH US VIA SOCIAL MEDIA:
WWW.FACEBOOK.COM/NWSPORTLAND
X.COM/NWSPORTLAND
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