828
FXUS66 KPQR 061712 AAA
AFDPQR
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE PORTLAND OR
1011 AM PDT SAT SEP 6 2025
UPDATED AVIATION DISCUSSION...
SYNOPSIS
THUNDERSTORMS PRODUCING FREQUENT LIGHTNING, SMALL HAIL
AND LOCALLY HEAVY RAIN WILL CONTINUE OVER MUCH OF NORTHWEST OREGON
AND SOUTHWEST WASHINGTON THIS MORNING. ANOTHER ROUND OF SHOWERS AND
STORMS IS EXPECTED LATE THIS AFTERNOON INTO TONIGHT, ALBEIT MORE
FOCUSED OVER THE CASCADES/FOOTHILLS AND EASTERN PORTIONS OF THE
WILLAMETTE VALLEY. TRENDING COOL, WET AND SHOWERY MONDAY THROUGH
TUESDAY AS A CLOSED UPPER LEVEL LOW SETTLES OVER THE AREA.
SHORT TERM...NOW THROUGH SUNDAY NIGHT
SINCE 12 AM SATURDAY,
NUMEROUS THUNDERSTORMS HAVE BEEN OBSERVED OVER THE COAST RANGE,
WILLAMETTE VALLEY AND PORTIONS OF THE CASCADE FOOTHILLS. THESE STORMS
ARE PRODUCING FREQUENT LIGHTNING, LOCALLY HEAVY RAIN, AND HAIL
ANYWHERE FROM THE SIZE OF PEAS TO DIMES PER RADAR SIGNATURES AND
TRAINED WEATHER SPOTTER REPORTS. SHOWERS AND STORMS ARE NOW SPREADING
NORTHWARD TOWARDS ASTORIA, THE LONG BEACH PENINSULA, WILLAPA HILLS
AND PORTLAND/VANCOUVER METRO. NOTE HI-RES MODELS ARE NOT HANDLING THE
EXTENT OF THIS AREA OF CONVECTION WELL, AND POPS AND THUNDER
PROBABILITIES HAD TO BE MANUALLY ADJUSTED UPWARDS TODAY TO BETTER
REFLECT CURRENT OBSERVATIONS. IT DOES APPEAR THERE IS A VERY SUBTLE
500 MB SHORTWAVE HELPING AID FORCING FOR ASCENT, AS WELL AS FAVORABLE
JET STREAK DYNAMICS AS THE AREA CURRENTLY EXPERIENCING CONVECTION IS
UNDER THE LEFT EXIT REGION OF A 250 MB JET MAX. THIS JET MAX IS
FORECAST TO LIFT NORTHWARD OVER SOUTHWEST WA LATER THIS MORNING IN AN
ENVIRONMENT FEATURING SUBSTANTIAL MID-LEVEL INSTABILITY/MOISTURE,
SUGGESTING THE AREA OF ONGOING CONVECTION WILL LIKELY CONTINUE
LIFTING NORTHWARD. WILL ALSO NOTE ANY LOCATION IS NORTHWEST OR AND
SOUTHWEST WA IS FAIR GAME TO SEE SHOWERS AND STORMS TODAY AND
TONIGHT, NOT SOLELY THE LOCATIONS THAT HAVE BEEN MENTIONED ABOVE.
CHANCES FOR SHOWERS REMAIN IN THE FORECAST SUNDAY AND SUNDAY NIGHT,
WITH THE HIGHEST PROBABILITIES OVER THE CASCADES. THUNDERSTORM
CHANCES PLUMMET BELOW 10-15% ON SUNDAY, WHICH SEEMS REASONABLE AS THE
LREF MEAN SHOWS MUCAPE VALUES FALLING BELOW 100 J/KG AS MID-LEVEL
LAPSE RATES BECOME LESS STEEP PER BUFKIT SOUNDINGS. THE MAIN
EXCEPTION TO THAT IS OVER THE LANE AND LINN COUNTY CASCADES WHERE
THERE APPEARS TO BE A BIT MORE INSTABILITY WITH SLIGHTLY HIGHER
CHANCES FOR THUNDERSTORMS. -TK
LONG TERM...MONDAY THROUGH FRIDAY NIGHT
A COOL, WET AND SHOWERY
FALL-LIKE WEATHER PATTERN DEVELOPS MONDAY AND CONTINUES THROUGH
AT LEAST TUESDAY IN RESPONSE TO A CLOSED UPPER LEVEL LOW THAT IS SET
TO SETTLE OVER THE REGION DURING THAT TIME. THIS LOW WILL BRING
WIDESPREAD SHOWERS WITH SIGNIFICANT RAIN AMOUNTS FOR THIS TIME OF
YEAR. THE NBM CONTINUES TO SHOW HIGH PROBABILITIES FOR AT LEAST
0.25-0.5" OF RAIN OVER ALL OF NORTHWEST OR AND SOUTHWEST WA FROM THE
COAST TO THE CASCADES, RANGING FROM 60-90% FOR THE 48-HOUR PERIOD
ENDING AT 5 AM WEDNESDAY, EXCEPT 40-70% OVER SOUTHWEST WASHINGTON.
NOTE THE HIGHEST PROBABILITIES ARE OVER THE OREGON CASCADES, WHICH
WILL HELP DAMPEN ONGOING WILDFIRE ACTIVITY. WITH THE CLOUDY/SHOWERY
CONDITIONS IN PLACE, HIGH TEMPERATURES WILL BE WELL BELOW NORMAL,
LIKELY ONLY IN THE UPPER 60S TO LOWER 70S.
THE FORECAST BECOMES MORE UNCERTAIN FROM WEDNESDAY ONWARD, ESPECIALLY
IN REGARDS TO THE EXACT LOCATION OF THE AFOREMENTIONED UPPER LOW AT
THAT POINT IN TIME, WHICH WILL ULTIMATELY IMPACT PRECIPITATION
CHANCES, CLOUD COVER, AND TEMPERATURES. WILL NOTE THERE ARE CHANCES
FOR SHOWERS WEDNESDAY THROUGH FRIDAY, HOWEVER CHANCES ARE HIGHEST ON
WEDNESDAY AT 40-60%. CHANCES FOR SHOWERS DECREASE TO 20-30% FOR
THURSDAY AND FRIDAY. IF SHOWERY WEATHER DOES OCCUR, EXPECT
TEMPERATURES TO REMAIN COOLER THAN AVERAGE. IF CONDITIONS TREND DRY
WITH BREAKS OF SUN, TEMPERATURES WOULD MOST LIKELY REBOUND WELL INTO
THE 70S. -TK
AVIATION
EXPECT IFR/LIFR CIGS TO CONTINUE ALONG THE COAST
THROUGH MOST OF THE TAF PERIOD, WITH POTENTIAL FOR BRIEF MVFR
CIGS BETWEEN 21Z SATURDAY AND 01Z SUNDAY. INLAND, MOST TERMINALS
ARE UNDER MVFR CIGS DUE TO ONSHORE FLOW EARLIER THIS MORNING
PUSHING MARINE STRATUS THROUGH THE COAST RANGE GAPS AND COLUMBIA
RIVER. EXPECT THESE DETERIORATED INLAND CONDITIONS TO IMPROVE TO
VFR BY 20-21Z SATURDAY. EXPECT A RETURN OF MVFR CIGS TO INLAND
TERMINALS AROUND 11-13Z SUNDAY (30-50% CHANCE OF MVFR).
ADDITIONALLY, THERE IS POTENTIAL FOR SHOWERS AND ISOLATED
THUNDERSTORMS THIS EVENING AND TONIGHT FOR INLAND LOCATIONS, BUT
CONFIDENCE FOR TIMING AND LOCATION REMAINS UNCLEAR AT THE MOMENT.
ANY THUNDERSTORM ACTIVITY THAT MAY DEVELOP WILL BE MOVING IN FROM
THE SOUTH-SOUTHEAST.
PDX AND APPROACHES...EXPECT CURRENT MVFR CONDITIONS TO IMPROVE
TO VFR BY 20-21Z SATURDAY. VFR CONDITIONS WILL THEN CONTINUE
THROUGH THE EVENING AND DROP BACK DOWN TO MVFR BY 11-13Z SUNDAY
(40-60% CHANCE OF MVFR). THERE IS POTENTIAL FOR SHOWERS AND
ISOLATED THUNDERSTORMS THIS EVENING AND TONIGHT, BUT CONFIDENCE
FOR TIMING AND EXACT LOCATION REMAINS UNCLEAR AT THE MOMENT. ANY
THUNDERSTORM ACTIVITY THAT MAY DEVELOP WILL BE MOVING IN FROM THE
SOUTH- SOUTHEAST. ~HALL
MARINE
AN AREA OF LOW PRESSURE IS EXPECTED TO PROGRESSES
THROUGH THE WATERS THIS WEEKEND ALLOWING FOR A SWITCH TO SOUTHERLY
WINDS AS THROUGH THE WATERS THIS WEEKEND, WHICH WILL FACILITATE A
SWITCH TO SOUTH TO SOUTHWEST WINDS BY THE AFTERNOON HOURS ALBEIT
FAIRLY LIGHT OVERALL. WE'LL CONTINUE TO HAVE TO WATCH FOR SLIGHT
CHANCES (15-20%) FOR THUNDERSTORMS THROUGH TODAY AS WELL. EXPECT
THESE SOUTHERLY WINDS TO PERSIST THROUGH MONDAY AND TUESDAY BEFORE
TURNING NORTHERLY AGAIN ON WEDNESDAY AS THE LOW PRESSURE MOVES
OFF TO THE EAST AND SURFACE HIGH PRESSURE RETURNS TO THE WATERS.
SEAS WILL GENERALLY HOLD IN THE 3-5 FT RANGE INTO EARLY NEXT WEEK.
THERE IS A 30-40% CHANCE OF COMBINED SEAS CLIMBING ABOVE 5 FT
DURING THE MIDDLE NEXT WEEK WITH THOSE PROBABILITIES CLIMBING TO
60-75% BY THE END OF NEXT WEEK. -SCHULDT
PQR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
WA...NONE.
PZ...NONE.
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