428
FXUS66 KMFR 041032
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
332 AM PDT THU SEP 4 2025
DISCUSSION
SATELLITE IMAGE SHOWS THE UPPER LOW MOVING NORTH OF
THE FORECAST AREA. THIS MORNING IT WILL BE DRY FOR MOST LOCATIONS. A
FEW ISOLATED SHOWERS ARE POSSIBLE IN EASTERN LAKE COUNTY, BUT THAT'S
IT.
THERE WILL BE A LACK OF CLOUD COVER THROUGH EARLY THIS AFTERNOON
COMPARED TO YESTERDAY. THIS WILL ALLOW TEMPERATURES TO HEAT UP MORE
EFFICIENTLY WITH AFTERNOON HIGHS IN THE UPPER 90S FOR THE INTERIOR
WESTSIDE VALLEYS.
THESE WARM TEMPERATURES WILL ALSO RESULT IN INCREASED INSTABILITY
THIS AFTERNOON. AT THE SAME TIME ANOTHER WEAK DISTURBANCE WILL MOVE
INTO THE AREA AHEAD OF A AN UPPER TROUGH OVER THE EASTERN PACIFIC.
THIS COULD TRIGGER ISOLATED STORMS AGAIN THIS AFTERNOON AND EVENING,
WITH THE HIGH RESOLUTION MODELS SHOWING CELLS FORMING OVER THE
KLAMATH AND SISKIYOU MOUNTAINS IN THE AFTERNOON, THEN DRIFTING NORTH
AND EAST WITH ADDITIONAL DEVELOPMENT ALONG THE CASCADES AND EAST
SIDE. IT IS WORTH NOTING THAT ALL BUT ONE MEMBER OF THE CAMS
(CONVECTIVE ALLOWING MODELS) THAT SHOW SIMULATED RADAR REFLECTIVITY
DEPICT ISOLATED CELLS MOVING SOUTH TO NORTH INTO THE ROGUE VALLEY,
AND PORTIONS OF JOSEPHINE COUNTY IN THE AFTERNOON.
FRIDAY, MODELS ARE GOOD AGREEMENT SHOWING AN UPPER LEVEL TROUGH
APPROACHING THE AREA FRIDAY AFTERNOON. GUIDANCE IS IN PRETTY GOOD
AGREEMENT SHOWING THE BEST CHANCE FOR THUNDERSTORMS SHOULD BE IN THE
NORTHERN CASCADES, AND PORTIONS OF KLAMATH AND LAKE COUNTY. MODELS
SHOW INSTABILITY AND FAVORABLE CAPE VALUES IN PORTIONS OF WESTERN
SISKIYOU COUNTY, AND PORTIONS OF JOSEPHINE AND JACKSON COUNTY , BUT
THE MID LEVELS ARE DRY, THUS THE MOST LIKELY SCENARIO WILL BE
BUILDING CUMULUS.
FRIDAY NIGHT THE UPPER TROUGH COULD BECOME NEGATIVELY TILTED AND
DESPITE THE FACT SOME OF THE GUIDANCE DOES NOT SCREAM OUT NOCTURNAL
STORMS, EXPERIENCE AND PATTERN RECOGNITION SUGGEST THE POTENTIAL FOR
A "SURPRISE" EVENT. MEANING THE POTENTIAL FOR NOCTURNAL ISOLATED
STORMS, AND THIS HAS BEEN ADDED TO THE FORECAST. THERE ARE SOME
INDICATIONS THUNDERSTORMS COULD SET UP AS FAR WEST AS THE COAST AND
OVER THE MARINE WATERS WITH THIS SHORTWAVE. STAY TUNED FOR UPDATES
AS DETAILS BECOME MORE CLEAR. -PETRUCELLI
SATURDAY AND BEYOND. THE PARENT TROUGH THAT HAS DRIFTED AROUND OVER
THE EASTERN PACIFIC FIRING SHORTWAVES AT US THIS WEEK WILL FINALLY
MOVE ONSHORE AND STICK AROUND THROUGH MOST OF NEXT WEEK. MODELS
AGREE MORE AND MORE ON THIS PATTERN CHANGE THAT WILL RESULT IN BELOW
NORMAL TEMPERATURES AND SEVERAL DAYS OF LIGHT, BUT BENEFICIAL,
PRECIPITATION CHANCES THAT WOULD MAKE THE AREA FEEL MORE LIKE
OCTOBER THAN EARLY SEPTEMBER. IT IS STILL YET TOO EARLY IN THE
SEASON, AND PRECIPITATION MAY BE TOO SPOTTY, TO CALL THIS A SEASON
ENDING EVENT, BUT GUIDANCE IS SHOWING A RANGE OF 0.5 TO 1 INCH
ACROSS THE ENTIRE AREA WITH UP TO AN INCH AND A HALF POSSIBLE ALONG
THE CASCADES AND SISKIYOUS. THIS SEEMS HIGH GIVEN THE TIME OF YEAR,
THOUGH SHOULD IT MATERIALIZE IT WOULD CERTAINLY PUT A LARGE DENT IN
FIRE WEATHER CONCERNS. THERE ARE STILL SOME DIFFERENCES BETWEEN THE
MODELS ON THE COVERAGE, TIMING, AND AMOUNT OF THIS BENEFICIAL
RAINFALL, SO ALTHOUGH CONFIDENCE IN COOLER AND WETTER WEATHER IS
HIGH, CONFIDENCE IN THE DETAILS REMAINS LOW. EXPECT FURTHER DETAILS
TO BECOME APPARENT OVER THE NEXT FEW DAYS. -BPN
AVIATION...04/12Z TAFS
AT THE COAST AND JUST OFFSHORE, IFR TO
LIFR CONDITIONS ARE EXPECTED THROUGH THE TAF PERIOD. CEILINGS COULD
COME UP TO MVFR FOR A BRIEF PERIOD BETWEEN 22--1Z, BUT CONFIDENCE IS
NOT HIGH ENOUGH TO INCLUDE IT IN THE NORTH BAND TAF.
INLAND, MARINE STRATUS WILL PERSIST IN THE COQUILLE BASIN THROUGH
17Z, THEN IT SHOULD BURN OFF TOWARDS THE COAST IN THE AFTERNOON.
ELSEWHERE. VFR CONDITIONS WILL CONTINUE THROUGH THE TAF PERIOD,
EXCEPT IN THE VICINITY OF THE EMIGRANT FIRE, AND FIRES IN CENTRAL
AND WESTERN SISKIYOU COUNTY. THE MAIN CONCERN FOR THIS AFTERNOON AND
EARLY THIS EVENING WILL BE ISOLATED THUNDERSTORMS. ISOLATED STORMS
COULD BE IN THE VICINITY OR OVER THE KLAMATH FALLS AND MEDFORD
AIRFIELD BETWEEN 21-3Z. HOWEVER, GUSTY AND ERRATIC WINDS WILL BE A
CONCERN AWAY FROM THE CORE OF THUNDERSTORMS ALONG LIGHTNING.
-PETRUCELLI
MARINE...UPDATED 200 AM PDT THURSDAY, SEPTEMBER 4, 2025
MODERATE
NORTH WINDS AND STEEP SEAS WILL CONTINUE FOR MOST AREAS THROUGH
EARLY THIS AFTERNOON AS THE THERMAL TROUGH GRADUALLY WEAKENS.
CONDITIONS ARE EXPECTED TO IMPROVE THIS EVENING THROUGH THE WEEKEND,
WITH WINDS BECOMING SOUTH AHEAD OF AN AREA OF LOW PRESSURE MOVING
ONSHORE EARLY NEXT WEEK. -BPN/PETRUCELLI
FIRE WEATHER
UPDATED 200 AM PDT THURSDAY, SEPTEMBER 4,
2025...SATELLITE IMAGE SHOWS AN UPPER LOW NORTH OF THE FORECAST AREA
WITH A DRY SLOT MOVING INTO THE AREA. OTHER THAN A FEW ISOLATED
SHOWERS IN EASTERN FIRE ZONE 625 THIS MORNING IT WILL BE DRY FOR THE
MORNING HOURS. THERE'S FAIRLY GOOD AGREEMENT AMONG THE HIGH RES CAMS
(CONVECTIVE ALLOWING MODELS) WHICH SHOW SIMULATED RADAR REFLECTIVITY
POPPING UP DURING THE EARLY TO MID AFTERNOON HOURS. THIS LINES UP
WELL WHERE MID LEVEL MOISTURE IS HIGHEST AND GREATEST INSTABILITY
WHICH PUTS THE BEST CHANCE FOR ISOLATED STORMS ALONG THE CASCADES,
SISKIYOUS, PORTIONS OF THE EASTSIDE AND NORTHERN CALIFORNIA. THERE'S
EVIDENCE SUGGESTING STORMS THAT POPS UP OVER THE SISKIYOUS COULD
COME OFF THE TERRAIN AND DRIFT NORTH OR FORM OVER PORTIONS OF THE
WESTSIDE IN PORTIONS OF FIRE ZONES 620 AND 622 LATE THIS AFTERNOON
AND EARLY EVENING. THIS IS NOT LOCKED IN STONE, BUT IT'S SOMETHING
THAT FOLKS SHOULD BE AWARE OF.
ISOLATED STORMS END EARLY THIS EVENING WITH NOT MUCH MORE THAN A FEW
SHOWERS OVERNIGHT TONIGHT, BUT MOST HOURS AND LOCATIONS WILL BE DRY.
FRIDAY, MODELS ARE GOOD AGREEMENT SHOWING AN UPPER LEVEL TROUGH
APPROACHING THE AREA FRIDAY AFTERNOON. GUIDANCE IS IN PRETTY GOOD
AGREEMENT SHOWING THE BEST CHANCE FOR THUNDERSTORMS SHOULD BE IN
PORTIONS OF FIRE ZONES 617, NORTHERN 623, AND 624 AND PORTIONS OF
625. MODELS SHOW INSTABILITY AND FAVORABLE CAPE VALUES IN PORTIONS
OF FIRE ZONES 280, 620 AND 622, BUT THE MID LEVELS ARE DRY, THUS THE
MOST LIKELY SCENARIO WILL BE BUILDING CUMULUS.
THE ABOVE MENTIONED UPPER TROUGH IS EXPECTED TO BECOME NEGATIVELY
TILTED FRIDAY NIGHT WHICH RAISES THE CONCERN FOR NOCTURNAL STORMS
FRIDAY NIGHT. THE HREF HINTS AT THIS POTENTIAL AND DESPITE THAT FACT
THE MODELS AREN'T REALLY HINTING AT THIS, THEY SOMETIMES CAN LEAD US
ASTRAY AND THERE COULD BE A "SURPRISE" EVENT THAT DOES INDEED OCCUR.
THEREFORE TO LEAN ON THE SIDE OF CAUTION, A SLIGHT CHANCE OF
THUNDERSTORMS WILL BE ADDED IN THE FORECAST FRIDAY NIGHT.
THE UPPER TROUGH WILL MOVE INTO THE AREA SATURDAY, WITH INSTABILITY
AND MID LEVEL MOISTURE EXPECTED TO BE GREATEST EAST OF THE CASCADES,
THIS THE BEST CHANCE FOR THUNDERSTORMS WILL BE IN THESE AREAS.
THERE'S SUFFICIENT EVIDENCE POINTING TOWARDS A COOLER AND UNSETTLED
PATTERN SUNDAY INTO THE FIRST PART OF NEXT WEEK. DURING THIS TIME,
WERE LIKELY TO HAVE COOLER AFTERNOON TEMPERATURES. SHOWERS, AND
HIGHER RELATIVE HUMIDITY DURING THE DAY AND EXCELLENT OVERNIGHT
RECOVERIES AT NIGHT. THE CHANCE FOR WETTING RAIN IS ALSO GOING TO BE
HIGHER FOR MOST LOCATIONS. -PETRUCELLI
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 2 PM PDT THIS
AFTERNOON FOR PZZ356-376.
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page