961
FXUS66 KMFR 011819
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
1119 AM PDT TUE SEP 1 2026
KEY MESSAGES
* THERE IS A SLIGHT CHANCE OF THUNDERSTORMS ALONG THE CASCADES AND
CASCADE FOOTHILLS THIS AFTERNOON.
* AN UNUSUALLY STRONG SYSTEM FOR EARLY SEPTEMBER WILL BRING
WETTING RAIN TO THE REGION WITH GUSTY WINDS ALONG THE COAST
WEDNESDAY.
* ROCK SLIDES ARE POSSIBLE ALONG HIGHWAYS 42, 138 AND 38.
* POCKETS OF FROST ARE POSSIBLE TONIGHT EAST OF THE CASCADES.
* TEMPERATURES WILL BE 15 TO 25 DEGREES COOLER THAN NORMAL
WEDNESDAY AND THURSDAY.
* COOLER CONDITIONS WITH SHOWER CHANCES PERSISTING INTO EARLY
NEXT WEEK.
DISCUSSION
A CLOSED LOW JUST OFFSHORE OF OREGON WILL OPEN UP
AND PASS OVERHEAD TODAY, PRODUCING A 20 TO 50 PERCENT CHANCE OF
SHOWERS OVER MUCH OF THE REGION. THUNDERSTORM CHANCES ARE LOW AS
THIS TROUGH PASSES OVERHEAD, BUT THERE SHOULD BE ENOUGH
INSTABILITY AND MOISTURE, ALONG WITH TERRAIN LIFTING PROCESSES,
FOR A FEW ISOLATED THUNDERSTORMS THIS AFTERNOON ALONG THE
CASCADES AND CASCADE FOOTHILLS.
AS THIS OCCURS, A MUCH STRONGER CLOSED LOW OVER THE GULF OF
ALASKA WILL DIG SOUTH, PUSHING A STRONGER COLD FRONT THROUGH
SOUTHERN OREGON AND NORTHERN CALIFORNIA WEDNESDAY, BEFORE MOVING
ONSHORE THURSDAY AND REMAINING OVERHEAD THROUGH THE WEEKEND. THIS
FRONT WILL PRODUCE GUSTY SOUTH WINDS ACROSS MUCH OF THE AREA,
ESPECIALLY ALONG THE COAST AND EAST OF THE CASCADES, AS WELL AS IN
THE SHASTA VALLEY. THIS IS AN UNUSUALLY STRONG EVENT SO EARLY IN
THE SEASON, MORE AKIN TO A TYPICAL DECEMBER FRONT IN TERMS OF WIND
AND RAIN, JUST NOT AS COLD.
SPEAKING OF RAIN, THIS FIRST FRONT WILL BRING WETTING RAIN TO
LOCATIONS ALONG AND WEST OF THE CASCADES, AND FOR A SIGNIFICANT
PORTION OF THE EAST SIDE AS WELL. AGAIN, THIS IS AN ATYPICAL
EVENT FOR SO EARLY IN THE SEASON, SO SOME DAILY PRECIPITATION
RECORDS WILL LIKELY FALL ON THE 2ND AND 3RD.
AS FOR THE IMPACTS, ROCK SLIDES ALONG HIGHWAYS 38,42 AND 138 ARE
POSSIBLE WITH THIS FIRST RAIN OF THE SEASON. ALSO, ROADS COULD BE
SLICK ON TUESDAY AS A LIGHTER RAIN BRINGS UP SOME OIL TO THE
SURFACE. THOSE SLICK ROADS COULD CONTINUE EARLY INTO THE FRONT
PASSAGE WEDNESDAY AFTERNOON. IT'S ALSO NOT OUT OF THE QUESTION FOR
A FEW POWER OUTAGES ALONG THE COAST AS THIS WIND HITS SOME
STRESSED VEGETATION, ESPECIALLY SINCE TREES REMAIN COVERED IN
LEAVES.
EVENTUALLY, TEMPERATURES WILL COOL BEHIND THE FRONT WITH LOWS
FALLING INTO THE 40'S EAST OF THE CASCADES AND UPPER 40'S AND
LOWER 50'S WEST OF THE CASCADES. THERE IS SOME CONCERN FOR FROST
ACCORDING TO THE NBM AS IT'S FORECASTING LOWS IN THE MID 30'S IN
KLAMATH FALLS. HOWEVER, AS THIS IS SO EARLY IN THE SEASON, AND
BECAUSE IT IS THE FIRST EVENT OF ITS TYPE IN SEVERAL MONTHS, THE
USUAL BIAS CORRECTION METHODS OF THE NBM ARE VERY UNLIKELY TO
REPRESENT EXPECTED CONDITIONS ACCURATELY. THEREFORE, WE WILL LEAN
HEAVIER ON DETERMINISTIC GUIDANCE, WHICH HAS WARMER LOWS WITH THE
SCATTERED TO WIDESPREAD CLOUD COVER AND WINDINESS. THIS DOES NOT
RULE OUT FROST OCCURING IN SOME LOCATIONS TUESDAY NIGHT BEFORE
THE BIG COLD FRONT. TEMPERATURES WILL BE 15 TO 25 DEGREES COOLER
THAN NORMAL FOR EARLY SEPTEMBER. MOUNT SHASTA CITY MAY ONLY HIT 57
DEGREES ON WEDNESDAY AND 59 DEGREES ON THURSDAY FOR HIGHS, WHICH
WOULD BE RECORD MINIMUM MAXIMUMS FOR THE RESPECTIVE DAYS.
MEANWHILE, HIGHS WEDNESDAY AND THURSDAY IN MEDFORD WILL BE IN THE
MID 60S, COOLER THAN NORMAL INDEED.
IT SHOULD BE MENTIONED THAT WE ARE NOT CONSIDERING THIS A "FIRE
SEASON ENDING EVENT" JUST YET, AS IT IS VERY EARLY IN SEPTEMBER,
AND CLIMATOLOGICALLY SPEAKING, CONDITIONS CAN STILL BE VERY WARM
AND DRY WELL INTO OCTOBER. IT IS VERY FAIR TO SAY, HOWEVER, THAT
THIS IS WILL GREATLY REDUCE FIRE WEATHER CONCERNS FOR AT LEAST
THE NEAR FUTURE.
FINALLY, ENSEMBLES KEEP THIS UPPER LEVEL LOW OVER US FOR A WHILE.
IT LOOKS LIKE IT COULD JUST LINGER INTO MONDAY WITH COOLER THAN
NORMAL TEMPERATURES AND SPOTTY SHOWERS PERSISTING ACROSS THE
FORECAST AREA. KIND OF HARD TO BELIEVE WE COULD SEE 5 TO 6 DAYS
OF RAIN AROUND THE REGION IN EARLY SEPTEMBER (AND SUCH A VAST
DIFFERENCE FROM CONDITIONS DURING THE LABOR DAY WEEK JUST 6 YEARS
AGO). ENSEMBLE MEMBERS VARY GREATLY ON LOCATION AND INTENSITY OF
THE QPF FROM FRIDAY ONWARD, SO DETAILS REMAIN UNCERTAIN, AND WILL
BE UPDATED AS NECESSARY.
AVIATION (18Z TAFS)
AHEAD OF AN INCOMING FRONT, EXPECTING CLOUD COVER TO BE COMMON WITH
INCREASING RAIN CHANCES TOMORROW. MVFR CONDITIONS ARE LIKELY ALONG
THE COAST THROUGH THIS CYCLE WITH INTERMITTENT PERIODS OF VFR. THE
BIG QUESTION AHEAD OF THE FRONT IS THE POTENTIAL FOR THUNDERSTORMS
TODAY WHICH COULD IMPACT KMFR, BUT MAY LIKELY STAY ROOTED OVER THE
HIGHER TERRAIN ALONG THE CASCADES EAST OF MEDFORD.
THAT SAID, DID HINT AT THIS POSSIBILITY (VCTS) FOR THIS
AFTERNOON/EARLY EVENING. OTHERWISE, EXPECTING WIDESPREAD SHOWERS AND
RAIN TO DEVELOP TONIGHT/WED MORNING ALONG THE COAST AND SPREAD
EASTWARD THROUGH THE DAY ON WEDNESDAY. HOWEVER, NOT EXPECTING
THUNDER AS THIS SHOULD BE MAINLY A SHOWERY TYPE PATTERN. LASTLY,
ENHANCED BREEZES ARE EXPECTED AHEAD OF THE FRONT TOMORROW AFTERNOON.
-GUERRERO
MARINE...UPDATED 1200 PM PDT TUESDAY, SEPTEMBER 1, 2026
SOUTH
WINDS WILL INCREASE TODAY AHEAD OF AN APPROACHING EARLY SEASON
FRONT. GUSTY WINDS AND STEEP SEAS WILL BEGIN IN THE OUTER WATERS
THIS AFTERNOON, THEN SPREAD TO THE INNER WATERS THIS EVENING INTO
TONIGHT. WINDS WILL INCREASE TO GALES WITH VERY STEEP AND HAZARDOUS
SEAS BY EARLY WEDNESDAY MORNING, PERSISTING UNTIL THE FRONT PASSES
ONSHORE WEDNESDAY AFTERNOON. WINDS WILL DIMINISH BEHIND THE FRONT,
BUT REMAIN GUSTY WITH STEEP SEAS THROUGH THURSDAY NIGHT. PERIODS OF
HEAVY RAIN AND LOW VISIBILITY ARE ALSO EXPECTED THROUGH THIS TIME.
CONDITIONS IMPROVE FRIDAY, AND REMAIN RELATIVELY CALM THROUGH THE
WEEKEND AND POTENTIALLY INTO EARLY NEXT WEEK.
MFR WATCHES/WARNINGS/ADVISORIES
OR...FROST ADVISORY FROM 4 AM TO 8 AM PDT WEDNESDAY FOR ORZ029>031.
CA...FROST ADVISORY FROM 4 AM TO 8 AM PDT WEDNESDAY FOR CAZ085.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY FROM 11 PM THIS EVENING
TO 5 AM PDT WEDNESDAY FOR PZZ350-356.
GALE WARNING FROM 5 AM TO 7 PM PDT WEDNESDAY FOR PZZ350-356-370-
376.
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 5 AM PDT
WEDNESDAY FOR PZZ370-376.
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