619
FXUS66 KMFR 272223
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
323 PM PDT SUN JUL 27 2025
DISCUSSION
ANECDOTALLY, THE CLIMATOLOGY OF OUR REGION TENDS TO
FAVOR ACTIVE PERIODS OF WEATHER TO ALTERNATE WITH QUIETER PERIODS.
BUT, IN THE CURRENT CASE, LAST WEEK'S WEATHER PRODUCED NEAR DAILY
THUNDERSTORM ACTIVITY (MAINLY OVER NORTHERN CALIFORNIA AND SOUTH
CENTRAL OREGON), AND THAT LOOKS TO CONTINUE THIS WEEK THROUGH AT
LEAST FRIDAY. AT THIS POINT, WEDNESDAY AND THURSDAY LOOK TO BE THE
MOST ACTIVE DAYS, WITH A POTENTIAL FOR ACTIVITY TO CONTINUE
OVERNIGHT ON WEDNESDAY NIGHT. OF COURSE, THE AMOUNT AND LOCATION
OF THUNDERSTORMS WILL SHOW DAILY VARIATION. A MAIN DRIVING FORCE
IS A PERSISTENT UPPER LEVEL TROUGH IN THE GULF OF ALASKA, WITH
ADDITIONAL DEVELOPING WAVES ROTATING AROUND THE BASE OF THE TROUGH
AND TRACKING EAST- NORTHEAST ACROSS NORTHERN CALIFORNIA.
WITH A TROUGH OFFSHORE, A FEW CONVECTIVE SHOWERS HAVE DEVELOPED
EARLY THIS AFTERNOON OVER LAKE AND MODOC COUNTIES. SEVERE WEATHER
IS NOT LIKELY TODAY, BUT ACTIVITY IS EXPECTED TO BROADEN ACROSS
NORTHERN CALIFORNIA AND SOUTH CENTRAL OREGON THIS EVENING WITH THE
SREF AND GFS MODELS IN AGREEMENT ON A FOCUS FROM THE
SISKIYOU/TRINITY COUNTY BORDER AREA (SOUTH OF THE SCOTT VALLEY)
NORTHEASTWARD ACROSS CENTRAL AND NORTHEAST SISKIYOU COUNTY INTO
SOUTHEAST KLAMATH AND SOUTHWEST LAKE COUNTIES.
WITH A NEW WAVE FOLLOWING A SIMILAR PATH, THE OVERALL AREA AND
CHARACTER OF ACTIVITY LOOKS TO BE SIMILAR ON MONDAY
AFTERNOON/EVENING, BUT WITH THE ADDITION OF A SLIGHT CHANCE FOR
JACKSON AND SOUTHEAST JOSEPHINE COUNTIES, AND THE FOCUS SHIFTED TO
THE SCOTT VALLEY INTO THE VICINITY OF YREKA, AND ALSO NORTHERN
KLAMATH COUNTY NEAR CRESCENT.
THE NEXT TROUGH ON TUESDAY WILL BE FARTHER SOUTH, ALONG THE
CALIFORNIA COAST. LATE DAY INSTABILITY LOOKS TO BE PRESENT INTO
SOUTHWEST OREGON, BUT THE SWATH OF SUFFICIENT MID-LEVEL MOISTURE
TO PRODUCE THUNDERSTORMS LOOKS TO EXTEND FROM SISKIYOU COUNTY
ACROSS THE CASCADES AND THE EAST SIDE. THUS, HAVE LIMITED THE
SLIGHT CHANCE MENTION OF SOUTHWEST OREGON STORMS TO THE APPLEGATE
AND CENTRAL AND SOUTHERN PORTIONS OF THE ROGUE VALLEY, FROM AROUND
MEDFORD SOUTHWARD.
THE AFOREMENTIONED TROUGH WILL SWING OVER OUR AREA WEDNESDAY, WITH
A BROADER COVERAGE OF MORE NUMEROUS, AND POTENTIALLY MORE POWERFUL
STORMS. AN EASTERLY STEERING FLOW COULD SEND THUNDERSTORMS INTO
SOUTHERN DOUGLAS, CURRY, AND SOUTHERN COOS COUNTIES. BUT,
CONFIDENCE IS HIGHER FOR A STILL VERY BROAD COVERAGE OF SCATTERED
STORMS TO THE SOUTH AND EAST OF THAT AREA.
CONFIDENCE IS INCREASING THAT THE TROUGH WILL REMAIN IN PLACE OVER
OUR AREA WEDNESDAY NIGHT WITH THE POTENTIAL FOR NOCTURNAL
THUNDERSTORMS. MODEL DIFFERENCES BECOME SIGNIFICANT ON THURSDAY
WITH DISAGREEMENT ON THE EXTENT TO WHICH THE TROUGH WILL SHIFT
EAST-NORTHEASTWARD. RESIDUAL CLOUD COVER MAY ALSO LIMIT THE
CONVECTIVE POTENTIAL. CONSIDERING THE CONTINGENT OF MODELS THAT
INDICATE THE WEST SIDE WILL BE ON THE BACK SIDE OF THE TROUGH BY
THURSDAY, THE PROBABILITY WILL BE HIGHER FOR THE EAST SIDE ON
THURSDAY AFTERNOON/EVENING. WITH THAT SAID, A LESS PROGRESSIVE
SOLUTION WOULD SET US UP FOR ANOTHER ROUND OF WIDESPREAD
THUNDERSTORMS.
THE NEXT TROUGH IS LIKELY TO FINALLY KICK ITS PREDECESSOR EASTWARD
ON FRIDAY. A WEST-SOUTHWEST FLOW ALOFT WOULD FAVOR INSTABILITY ON
THE EAST SIDE WITH A LESSER DEGREE OF INSTABILITY, LOWER RISK OF
SEVERE STORMS.
MODEL DIFFERENCES INCREASE FURTHER FOR NEXT WEEKEND WITH A NEAR
EVEN SPLIT BETWEEN ENSEMBLE MEMBERS FAVORING WARMING AND DRYING
FROM A RIDGE, AND THOSE FAVORING A CONTINUATION OF SEASONABLE
TEMPERATURES AND EAST SIDE FOCUSED LATE DAY THUNDERSTORMS.
AVIATION...27/18Z TAFS
ALONG THE COAST, AREAS OF IFR/LIFR
LINGER NEAR BROOKINGS. THESE LOW CLOUDS WILL CLEAR TO VFR THIS
AFTERNOON. LIFR/IFR IS EXPECTED TO RETURN TO THE COAST SOUTH OF GOLD
BEACH AROUND 04Z THIS EVENING, WITH A BROADER AREA OF IFR EXPECTED
ALONG MOST OF THE REMAINDER OF THE COAST AROUND 09Z, INCLUDING NORTH
BEND, AND SPREADING INTO THE COQUILLE AND LOWER UMPQUA VALLEYS. THIS
STRATUS WILL DIMINISH RATHER QUICKLY DURING MONDAY MORNING.
INLAND, OVERALL, SKIES ARE VFR AND WILL REMAIN THAT WAY THROUGH THE
TAF PERIOD. HOWEVER, ISOLATED TO SCATTERED THUNDERSTORMS THIS
AFTERNOON AND EVENING, MAINLY FROM THE SISKIYOU MOUNTAINS AND
CASCADES EASTWARD AND ACROSS NORTHERN CALIFORNIA. THESE COULD
TEMPORARILY LOWER CEILINGS AND/OR VISIBILITY, BUT THE MAIN RISKS
WITH THUNDERSTORMS WILL BE GUSTY OUTFLOW WIND GUSTS, CLOUD TO GROUND
LIGHTNING AND SMALL HAIL. A SIMILAR SCENARIO IS EXPECTED FOR MONDAY
AFTERNOON AND EVENING, WITH THE ADDITION OF A SLIGHT CHANCE OF
THUNDERSTORMS FOR JACKSON AND SOUTHEAST JOSEPHINE COUNTIES.
-DW
MARINE...UPDATED 200 PM PDT SUNDAY, JULY 27, 2025
SUB-
ADVISORY NORTH WINDS AND LOW SEAS OF 5 FT OR LESS, WILL PERSIST
INTO TUESDAY MORNING WITH NIGHTLY STRATUS AND FOG THAT WILL LAST
AT LEAST INTO THE MORNING HOURS EACH DAY. WINDS AND SEAS MAY TREND
SLIGHTLY HIGHER TUESDAY THROUGH THURSDAY, ESPECIALLY SOUTH OF
CAPE BLANCO. -DW
FIRE WEATHER...UPDATED 100 PM PDT SUNDAY, JULY 27, 2025
TEMPERATURES, HUMIDITIES, AND BREEZY AFTERNOON WINDS WILL ALL REMAIN
NEAR SEASONABLE LEVELS THIS WEEK, SO THE MAIN FIRE WEATHER CONCERN
WILL BE DAILY THUNDERSTORM CHANCES. WE'LL BE IN A RELATIVE LULL IN
TERMS OF THUNDERSTORM COVERAGE TODAY AND MONDAY, THOUGH WILL
SLIGHTLY MORE COVERAGE TODAY COMPARE TO YESTERDAY AND WHAT'S
EXPECTED MONDAY. THEN, FROM TUESDAY ONWARD, WE EXPECT A HEIGHTENED
LEVEL OF THUNDERSTORM ACTIVITY THROUGH AT LEAST THURSDAY. THIS WILL
LIKELY INCLUDE AREAS WEST OF THE CASCADES AT SOME POINT ALONG WITH A
NOCTURNAL THREAT, BOTH OF WHICH LOOK MOST LIKELY WEDNESDAY/WEDNESDAY
NIGHT.
FOR TODAY, A RED FLAG WARNING IS IN EFFECT FOR PORTIONS OF FWZS
280/281/284/624/625, MAINLY FROM THE SCOTT VALLEY EASTWARD TO THE
MEDICINE LAKE AREA THEN NORTHWARD INTO KLAMATH/LAKE COUNTIES. THIS
WILL BE THE FOCUS OF SCATTERED THUNDERSTORMS FOR TODAY, WITH
ISOLATED STORMS EXPECTED ACROSS THE MODOC, AND MAYBE EVEN AS FAR
WEST AS THE CASCADES AND ROGUE VALLEY (10-20% CHANCE) THIS
AFTERNOON/EVENING. GUIDANCE HOLDS STEADY WITH ISOLATED THUNDERSTORMS
ANTICIPATED ON MONDAY, FOCUSED OVER WESTERN SISKIYOU COUNTY, UP
ALONG THE CASCADES AND ACROSS NORTHERN KLAMATH AND EASTERN LAKE
COUNTIES. THERE ARE SOME SIGNALS POINTING TO MORE SCATTERED COVERAGE
OVER PORTIONS OF FWZ 280 AND FAR NORTHERN 624. HAVE DECIDED TO JUST
HEADLINE THIS IN THE FIRE WEATHER PLANNING FORECAST TO CONTINUE THE
MESSAGE OF A RELATIVE LULL IN THUNDERSTORM ACTIVITY COMPARED TO
TUESDAY-THURSDAY.
FOR THE UPCOMING WEEK, ATTENTION REMAINS FOCUSED ON ANOTHER TROUGH
THAT SWINGS INTO CENTRAL CALIFORNIA AND TURNS THE FLOW SOUTHERLY AS
IT TRACKS NORTHWARD INTO EASTERN OR/WESTERN ID. THIS PATTERN WILL
MAINTAIN DAILY THUNDERSTORM CHANCES THROUGH AT LEAST THURSDAY, IF
NOT INTO FRIDAY. CONFIDENCE IS HIGHEST FOR AREAS EAST OF THE
CASCADES AND ACROSS NORTHERN CALIFORNIA TO SEE AT LEAST SCATTERED
COVERAGE DURING THIS PATTERN, BUT THE MORE CHALLENGING ASPECT IS HOW
FAR WEST WILL STORMS MAKE IT, AND WILL THERE BE ANY OVERNIGHT
(NOCTURNAL) THUNDERSTORM POTENTIAL THIS WEEK. FOR NOW, THE FORECAST
SUPPORTS INCREASED THUNDERSTORM ACTIVITY FOR EAST SIDE/NORCAL
BEGINNING ON TUESDAY. WE'VE MOVED FORWARD WITH A FIRE WEATHER WATCH
FOR FWZS 623 (EASTERN PORTION IN KLAMATH COUNTY), 624/625/285 AND
THE NORTHERN PORTION OF ZONE 284. UNCERTAINTY INCREASES THE FARTHER
WEST YOU GO, SO DESPITE FWZ 280 BEING A TYPICAL THUNDERSTORM HOT
SPOT, WE'VE LEFT THAT ZONE OUT OF THE WATCH FOR NOW.
AREAL COVERAGE OF STORMS LOOKS GREATEST ON WEDNESDAY WITH THIS DAY
SEEING THE BEST POTENTIAL FOR STORMS WEST OF THE CASCADES. CURRENT
FORECAST MAINTAINS SIMILAR CONDITIONS ON THURSDAY, AND IS EVEN
HINTING AT SOME NOCTURNAL POTENTIAL FOR THE WEST SIDE WEDNESDAY
NIGHT INTO THURSDAY MORNING. WHILE GUIDANCE LOOKS SIMILAR FOR
THURSDAY, THERE IS SOME UNCERTAINTY ON HOW MUCH THUNDERSTORM
COVERAGE WILL MATERIALIZE DUE TO ANY LINGERING CLOUD COVER FROM
OVERNIGHT ACTIVITY. WE'LL BE TRYING TO HONE IN ON THESE DETAILS OVER
THE COMING SHIFTS, AND BE PREPARED FOR ADDITIONAL FIRE WEATHER
WATCHES THIS WEEK.
BY FRIDAY, ACTIVITY SHOULD TREND LESS, HOWEVER, GUIDANCE SHOWS
ADDITIONAL SHORTWAVES MOVING THROUGH IN A WESTERLY FLOW PATTERN.
THIS WOULD RESULT IN DECREASING CHANCES OF STORMS WEST OF THE
CASCADES WHILE MAINTAINING THUNDERSTORM CHANCES EAST OF THE CASCADES
AND ACROSS NORTHERN CALIFORNIA. ON THE OTHER HAND, TEMPERATURES WILL
REMAIN NEAR SEASONAL NORMS, IF NOT A FEW DEGREES BELOW OVER THE
UPCOMING WEEKEND. /BR-Y
MFR WATCHES/WARNINGS/ADVISORIES
OR...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ624-625.
FIRE WEATHER WATCH FROM TUESDAY AFTERNOON THROUGH TUESDAY
EVENING FOR ORZ623>625.
CA...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ280-281-
284.
FIRE WEATHER WATCH FROM TUESDAY AFTERNOON THROUGH TUESDAY
EVENING FOR CAZ284-285.
PACIFIC COASTAL WATERS...NONE.
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