968
FXUS66 KMFR 052125
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
225 PM PDT FRI SEP 5 2025
DISCUSSION
A FEW STORMS ARE JUST STARTING TO POP UP ON RADAR
THIS AFTERNOON OVER LAKE AND NORTHERN KLAMATH COUNTIES. MORE ON
THAT BELOW. MEANWHILE, A DEEP MARINE LAYER WITH FOG, LOW STRATUS,
AND DRIZZLE LIES FIRMLY ENTRENCHED ALONG THE COAST AND OVER THE
COASTAL WATERS. THIS MARINE LAYER IS LIKELY TO STAY IN PLACE FOR
A WHILE, AND SOME LOCATIONS ALONG THE IMMEDIATE COAST MAY NOT
FULLY BREAK OUT OF THE CLOUDS FOR SEVERAL DAYS.
A COOLING TREND HAS STARTED TODAY AND WILL CONTINUE INTO NEXT
WEEK, WITH HIGH TEMPERATURES EVENTUALLY REACHING 10-15 DEGREES
BELOW NORMAL BY MONDAY/TUESDAY. HIGHS TODAY WILL BE AROUND 5
DEGREES COOLER THAN YESTERDAY FOR WEST SIDE VALLEYS WITH SIMILAR
TEMPERATURES FOR THE REST OF THE AREA. OUR DAILY THUNDERSTORM
CHANCES WILL CONTINUE THIS AFTERNOON AND INTO THE WEEKEND, WITH
THE FOCUS OF ACTIVITY TODAY EXPECTED TO BE IN THE NORTHERN
CASCADES, AND SOUTHEASTWARD INTO PORTIONS OF KLAMATH/LAKE/EASTERN
MODOC COUNTIES. LATER THIS EVENING AND OVERNIGHT INTO SATURDAY
MORNING, GUIDANCE SHOWS THE POTENTIAL FOR SOME OVERNIGHT
THUNDERSTORMS AGAIN WEST OF THE CASCADES. WHILE NONE OF THE CAMS
ARE SHOWING ACTIVITY TONIGHT, THEY ALSO DIDN'T SHOW THE STORMS
LAST NIGHT OVER DOUGLAS AND COOS COUNTIES. CONSIDERING THIS
MORNING'S ACTIVITY LINED UP WITH MODEL INDICATED ELEVATED
INSTABILITY, AND MODELS AGAIN SHOW THIS FOR TONIGHT COMBINED WITH
A NEGATIVELY TILTED SHORTWAVE APPROACHING AND MOVING THROUGH THE
REGION, IT'S REASONABLE TO BELIEVE THAT THERE COULD BE
THUNDERSTORMS DURING THE OVERNIGHT PERIOD TONIGHT. ISOLATED
SHOWERS/THUNDERSTORMS WILL BE POSSIBLE JUST ABOUT ANYWHERE WEST OF
THE CASCADES, INCLUDING THE COAST AND OVER THE MARINE WATERS.
THUNDERSTORM CHANCES CONTINUE INTO THE DAYTIME SATURDAY, FOCUSED
ALONG AND EAST OF THE I-5 CORRIDOR, AND SOME GUIDANCE IS REALLY
HONING IN ON THE AREA BETWEEN I-5/US-199 AND THE CASCADE CREST AS
THE MOST LIKELY LOCATION FOR DEVELOPMENT, WHICH INCLUDES MEDFORD,
ROSEBURG, AND GRANTS PASS. EXPECT ANOTHER 5 DEGREES OR SO OF
COOLING FOR AFTERNOON TEMPERATURES, INCLUDING AREAS EAST OF THE
CASCADES AND IN NORTHERN CALIFORNIA, WHICH WILL BRING THE AREA
DOWN TO TEMPERATURES MORE IN LINE WITH WHAT WE TYPICALLY SEE THIS
TIME OF YEAR. SUNDAY IS EXPECTED TO BE VERY SIMILAR TO SATURDAY,
ASIDE FROM A FURTHER FEW DEGREES OF COOLING.
LATE SUNDAY, 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 EARLY NEXT WEEK. THIS
PATTERN CHANGE WILL RESULT IN BELOW NORMAL TEMPERATURES AND
SEVERAL DAYS (ROUGHLY SUNDAY NIGHT THROUGH WEDNESDAY) OF LIGHT,
BUT BENEFICIAL, SHOWERY PRECIPITATION (WITH SOME EMBEDDED
THUNDERSTORMS POSSIBLE) THAT WOULD MAKE THE AREA FEEL MORE LIKE
OCTOBER THAN EARLY SEPTEMBER. WE ARE CONFIDENT THAT HEALTHY
MEASURABLE RAINFALL WILL OCCUR ACROSS THE AREA OVER THE FIRST HALF
OF NEXT WEEK, WHICH WOULD DEFINITELY BE HELPFUL WITH LOCAL
FIREFIGHTING EFFORTS, AND WOULD PUT A LARGE DENT IN FIRE WEATHER
CONCERNS. /BR-Y/BPN
AVIATION...05/18Z TAFS
MARINE STRATUS IS KEEPING LEVELS ALONG THE
OREGON COAST AT IFR TO LIFR, ALTHOUGH BRIEF PERIODS OF MVFR TO VFR
LEVELS ARE POSSIBLE IF CEILINGS BRIEFLY BREAK UP THIS AFTERNOON OR
EVENING. THE LAYER LOOKS TO SOLIDIFY AND REMAIN AT IFR/LIFR TONIGHT
INTO SATURDAY MORNING.
INLAND AREAS LOOK TO REMAIN VFR THROUGH THE TAF PERIOD. SMOKE FROM
AREA FIRES MAY PERIODICALLY IMPACT VISIBILITIES FOR INLAND
TERMINALS, BUT ANY LOWER FLIGHT LEVELS WOULD BE BRIEF. ISOLATED TO
SCATTERED THUNDERSTORMS ARE EXPECTED ACROSS LAKE AND NORTHERN
KLAMATH COUNTIES AS WELL AS OVER THE CASCADES THIS AFTERNOON AND
EVENING. WHILE TERMINALS ARE NOT EXPECTED TO BE DIRECTLY AFFECTED,
THUNDERSTORMS MAY PRODUCE GUSTY AND ERRATIC OUTFLOWS THAT COULD MOVE
ACROSS INLAND AREAS. -TAD
MARINE...UPDATED 200 PM PDT FRIDAY, SEPTEMBER 5, 2025
NORTH WINDS
WILL TURN SOUTH THROUGH TODAY, WITH MARINE FOG AND LOW CLOUDS
PERSISTING FOR THE NEXT SEVERAL DAYS. AN UPPER LEVEL LOW WILL PASS
OVER THE AREA LATE TODAY INTO SATURDAY, WITH SHOWERS AND DRIZZLE
LIKELY, AND A STRAY THUNDERSTORM OR TWO POSSIBLE. OUTSIDE OF
POTENTIAL SHOWERS/THUNDERSTORMS, EXPECT GENERALLY CALM CONDITIONS
WITH NO SIGNIFICANT SWELL, LIGHT WINDS, AND WIDESPREAD SHOWERS AHEAD
OF AN AREA OF LOW PRESSURE MOVING ONSHORE EARLY NEXT WEEK. -BPN
FIRE WEATHER...UPDATED 200 PM PDT FRIDAY, SEPTEMBER 5, 2025
A RED FLAG WARNING IS IN PLACE FOR FIRE WEATHER ZONES
617/623/624/625/285 FROM 1 PM THROUGH 9 PM TONIGHT. AN UPPER TROUGH
MOVING OVER THE AREA LOOKS TO PROVIDE INSTABILITY FOR ISOLATED TO
SCATTERED THUNDERSTORMS THIS AFTERNOON AND EVENING. LAKE COUNTY IS
EXPECTED TO SEE THE MOST ACTIVITY, WITH STORMS ALSO POSSIBLE OVER
EASTERN MODOC, NORTHERN KLAMATH, AND EASTERN DOUGLAS COUNTIES.
ISOLATED STORMS MAY ALSO DEVELOP WEST OF THE CASCADES. LESSER
CHANCES FOR ACTIVITY ARE ALSO IN THE FORECAST FOR AREAS WEST OF THE
CASCADES. WHILE WINDS ALOFT GO FROM SOUTH TO NORTH AND SHOULD GUIDE
MOST STORM MOTION, SOME MODELS SHOW ISOLATED WEST SIDE CELLS MOVING
TO THE SOUTHWEST. THIS MOVEMENT MAY RESULT FROM OUTFLOW CROSSING THE
CASCADES AND CONTINUING WESTWARD. THE EARLY MORNING THUNDERSTORMS
OVER ROSEBURG AND NORTH BEND TODAY WERE CAUSED BY OUTFLOW FROM
THURSDAY NIGHT'S ACTIVITY. OUTFLOW IS TOUGH TO PREDICT AND DEPENDENT
ON INDIVIDUAL STORM CHARACTERISTICS, SO SEEING THE POSSIBILITY IN
MODELING MAY BE SIGNIFICANT. OTHER AREAS NOT MENTIONED SO FAR
(EASTERN SISKIYOU, WESTERN MODOC, AND SOUTHERN KLAMATH COUNTIES)
LOOK TO AVOID ACTIVITY TONIGHT DUE TO DRIER AIR ALOFT. ISOLATED
ACTIVITY MAY CONTINUE INTO SATURDAY MORNING.
FOR SATURDAY AND SUNDAY, DRIER AIR ALOFT LOOKS TO LIMIT THUNDERSTORM
CHANCES EAST OF THE CASCADES. NORTHERNMOST LAKE AND KLAMATH COUNTIES
MAY SEE ISOLATED ACTIVITY. FOR SATURDAY, SLIGHT CHANCES (15-25%) FOR
THUNDERSTORMS ARE PRESENT ALONG THE CASCADES AND INTO WESTERN
SISKIYOU COUNTY AS WELL AS JACKSON, EASTERN JOSEPHINE, AND EASTERN
DOUGLAS COUNTIES. MODELS SHOW GOOD AGREEMENT ON THE AREA. WHILE
ISOLATED COVERAGE IS GENERALLY EXPECTED, SOME MODELS SHOW BORDERLINE
SCATTERED COVERAGE. A RED FLAG WARNING IS NOT NEEDED AS OF THIS
AFTERNOON, BUT ANY SIGNIFICANT INCREASE IN FORECAST ACTIVITY MAY
SUPPORT A WARNING BEING ISSUED ON SATURDAY MORNING. ON SUNDAY,
THUNDERSTORM CHANCES ALONG AND WEST OF THE CASCADES CONTINUE BUT
DECREASE (10-15%), WITH THE HIGHEST CHANCES LIMITED TO EASTERNMOST
DOUGLAS COUNTY. BEYOND THUNDERSTORM CHANCES, GUSTY SOUTHERLY WINDS
MAY DEVELOP OVER EAST SIDE TERRAIN AND INTO THE SOUTHERN SHASTA VALLEY
IN THE AFTERNOON AND EVENING OF BOTH SATURDAY AND SUNDAY. THE
COMBINATION OF THESE WINDS AND FORECAST RH VALUES DOES NOT REACH
CRITICAL CONDITIONS, BUT THE WINDS ARE WORTH ACKNOWLEDGING.
A PATTERN CHANGE REMAINS IN THE FORECAST FOR MONDAY, BRINGING COOLER
TEMPERATURES AND WIDESPREAD RAIN SHOWER CHANCES THAT MAY CONTINUE
INTO MIDWEEK. OCCASIONAL EMBEDDED THUNDERSTORMS ARE POSSIBLE, BUT
RELIABLE SIGNALS ARE NOT YET PRESENT IN GUIDANCE. -TAD
MFR WATCHES/WARNINGS/ADVISORIES
OR...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR ORZ617-623>625.
CA...RED FLAG WARNING UNTIL 9 PM PDT THIS EVENING FOR CAZ285.
PACIFIC COASTAL WATERS...NONE.
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