151
FXUS66 KMFR 291901
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
1201 PM PDT TUE JUL 29 2025
UPDATE
UPDATED THE AVIATION AND MARINE SECTIONS.
AVIATION...29/18Z TAFS
IFR LOW CLOUDS AND PATCHY FOG ARE EXPECTED
TO RETURN TO THE COAST FROM BROOKINGS SOUTHWARD AND CAPE BLANCO
NORTHWARD (AS WELL AS INTO THE COQUILLE VALLEY) AFTER 03Z THIS
EVENING AND PERSIST THROUGH AROUND 17Z WEDNESDAY MORNING.
INLAND, VFR LEVELS LOOK TO CONTINUE THROUGH THE TAF PERIOD. HOWEVER,
ISOLATED TO SCATTERED THUNDERSTORMS WILL DEVELOP THIS EVENING,
MAINLY FROM THE SOUTHERN OREGON CASCADES EASTWARD AND ACROSS
NORTHERN CALIFORNIA. THERE IS ALSO A 10-15% CHANCE FOR THUNDERSTORMS
INTO SOUTHERN JOSEPHINE AND JACKSON COUNTIES. 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 MORE ACTIVE, THUNDERSTORM EPISODE IS
EXPECTED TO AFFECT A BROADER PORTION OF THE AREA ON WEDNESDAY
AFTERNOON AND EVENING. SCATTERED TO NUMEROUS STORMS WILL BE POSSIBLE
FOR ALL BUT THE COAST AND NORTHWEST DOUGLAS COUNTY. -DW
MARINE...UPDATED 800 AM PDT TUESDAY, JULY 29, 2025
A THERMAL
TROUGH WILL BRING GUSTY NORTHERLY WINDS AND STEEP SEAS BETWEEN
PORT ORFORD AND PISTOL RIVER THROUGH THIS AFTERNOON. THE THERMAL
TROUGH WILL STRENGTHEN SLIGHTLY EARLY THIS EVENING WITH STEEP SEAS
EXPECTED TO EXPAND OVER MUCH OF THE WATERS SOUTH OF PORT ORFORD
THROUGH WEDNESDAY EVENING.
CONDITIONS BRIEFLY IMPROVE WITH LOW PRESSURE IN THE AREA LATER
WEDNESDAY NIGHT INTO THURSDAY. SLIGHT STRENGTHENING OF A THERMAL
TROUGH IS LIKELY TO BRING A RETURN OF STEEP SEAS TO THE SOUTHERN
WATERS DURING THE AFTERNOON AND EVENING HOURS FROM THURSDAY
AFTERNOON INTO SATURDAY EVENING. -DW
PREV DISCUSSION
/ISSUED 458 AM PDT TUE JUL 29 2025/
DISCUSSION...SATELLITE SHOWS MARINE STRATUS MAKING ITS WAY INTO
PARTS OF THE COAST NEAR COOS BAY, AND THIS IS GROWING SOUTH
TOWARDS BANDON EARLY THIS MORNING. THERE IS ALSO LOWER CEILINGS
NEAR BROOKINGS, AND THIS IS SLOWLY MOVING NORTH INTO PISTOL RIVER.
THE NEAR TERM FORECAST STILL INCLUDES DAILY THUNDERSTORM CHANCES.
THE MAIN AREAS OF CONCERN FOR THIS AFTERNOON WILL BE EAST OF THE
CASCADES IN SOUTHERN OREGON AND INTO MODOC COUNTY. THESE CELLS WILL
FORM BETWEEN 2-4 PM IN MODOC COUNTY AND MOVE NORTHWARD. GUSTY WINDS,
SMALL HAIL, AND LIGHTNING IS POSSIBLE. STORMS IN RECENT DAYS HAVE
BEEN MOVING VERY SLOWLY (10 MPH OR LESS), SO THIS COULD RESULT IN
HEAVIER RAIN IN SPOTS BEFORE SOME CELLS PASS.
A TROUGH WEDNESDAY AFTERNOON WILL BRING THE CONCERN FOR
THUNDERSTORMS WESTWARD WITH A 20-30% CHANCE FOR LIGHTNING IN THE
ROGUE VALLEY AND INTO EASTERN DOUGLAS COUNTY NEAR TILLER AND
STEAMBOAT. LATER IN THE AFTERNOON AND INTO THE EVENING, SHOWERS AND
THUNDERSTORMS WILL START TO BUILD EAST OF THE CASCADES, ESPECIALLY
INTO LAKE COUNTY. PWATS ON THE WEST SIDE THE NEXT FEW DAYS ARE
NEARING 1.00", SO SOME LOCATIONS COULD ALSO SEE HEAVIER RAINFALL
WITH SLOW MOVING STORMS.
THERE ARE STILL MODEL DIFFERENCES FOR RAIN CHANCES THURSDAY
AFTERNOON AND ONWARD BECAUSE THE GFS HAS THE LOW PRESSURE SLIGHTLY
FARTHER NORTH, KEEPING MORE OF THE RAIN OUT OF THE AREA, WHILE THE
EURO ADDS MORE TO SOUTHERN OREGON.
LATER INTO THE WEEKEND, RIDGING WILL START TO TAKE HOLD OF THE
WEATHER PATTERN IN THE AREA. THIS WILL BRING WARMER TEMPERATURES TO
THE AREA ONCE AGAIN, AND THE 90TH PERCENTILE FORECAST HIGHS FOR
PORTIONS OF THE ROGUE VALLEY AND UMPQUA BASIN HAVE TRIPLE DIGITS
BACK THE MIDDLE OF NEXT WEEK. -HERMANSEN
FIRE WEATHER...UPDATED 200 AM PDT TUESDAY, JULY 29, 2025...THE
ATTENTION REMAINS ON THUNDERSTORM ACTIVITY EXPECTED THIS WEEK.
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. MAINLY ISOLATED COVERAGE IS
EXPECTED ALONG AND EAST OF THE CASCADES/NORTHERN CALIFORNIA WITH
SOME POCKETS OF SCATTERED ACROSS WESTERN SISKIYOU, NORTHERN KLAMATH
AND EASTERN LAKE COUNTIES.
FROM TODAY ONWARD, WE EXPECT A HEIGHTENED LEVEL OF THUNDERSTORM
ACTIVITY THROUGH AT LEAST THURSDAY, WITH THE GREATEST COVERAGE
EXPECTED TO BE WEDNESDAY AND STORMS CONTINUING OVERNIGHT FOR SOME
AREAS INTO THURSDAY MORNING. ANOTHER TROUGH (NEGATIVELY-TILTED)
SWINGS INTO CENTRAL CALIFORNIA, TURNING THE FLOW SOUTHERLY AS IT
TRACKS NORTHWARD THROUGH OREGON. THIS PATTERN WILL MAINTAIN DAILY
THUNDERSTORM CHANCES THROUGH AT LEAST THURSDAY, IF NOT INTO FRIDAY.
CONFIDENCE IS HIGHEST FOR AREAS ALONG AND EAST OF THE CASCADES AND
ACROSS NORTHERN CALIFORNIA TO SEE AT LEAST SCATTERED (IF NOT
WIDESPREAD) 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 TODAY. THERE IS A RED FLAG WARNING FOR
FWZS 285/623(EASTERN)/624/625. FOR FWZ 284, AND OTHER ZONES ACROSS
NORTHERN CALIFORNIA, COVERAGE LOOKS TO BE MOSTLY ISOLATED, THOUGH
ANOTHER POCKET OF SCATTERED IS POSSIBLE ACROSS WESTERN SISKIYOU (FWZ
280).
AREAL COVERAGE OF STORMS LOOKS GREATEST ON WEDNESDAY WITH THIS DAY
SEEING THE BEST POTENTIAL FOR STORMS WEST OF THE CASCADES. THIS IS
WHEN THE NEGATIVELY TILTED TROUGH NEARS THE FORECAST AREA AND
GUIDANCE SHOWS A SHORTWAVE AT THE BASE OF THIS TROUGH MOVING UP INTO
MODOC COUNTY FROM THE SIERRAS EARLY WEDNESDAY MORNING. THIS WOULD
LIKELY RESULT IN SOME SHOWER ACTIVITY ACROSS THE MODOC, BUT THERE
ISN'T A GOOD SIGNAL FOR LIGHTNING WITH THESE SHOWERS AT THIS TIME.
COULDN'T RULE OUT SOME STRIKES, HOWEVER, WITH ABOUT A 10% CHANCE OF
LIGHTNING. THIS SHORTWAVE STRENGTHENS DURING THE DAY WEDNESDAY WHILE
MOVING NORTHWESTWARD THROUGH THE REGION, RESULTING IN A RATHER
SIGNIFICANT TRIGGER FOR THUNDERSTORM INITIATION. SCATTERED TO
WIDESPREAD THUNDERSTORMS ARE LIKELY ON WEDNESDAY AND WE'VE GONE
AHEAD WITH A FIRE WEATHER WATCH FOR MUCH OF THE AREA (EXCLUDING
615/618/619/282). THE MAJORITY OF ACTIVITY IS EXPECTED DURING THE
AFTERNOON AND EVENING, BUT AS THIS SHORTWAVE SWINGS NORTHWARD IN THE
EVENING AND OVERNIGHT WEDNESDAY, THUNDERSTORM ACTIVITY COULD
CONTINUE ACROSS NORTHERN PORTIONS OF THE FORECAST AREA. WE'VE
STARTED THE WATCH FOR FWZ616 FOR WEDNESDAY EVENING, AND CARRIED IT
THROUGH THURSDAY MORNING. ADDITIONALLY, WE'VE HELD ONTO THE WATCH
FOR 617/623/624/625 THROUGH THURSDAY MORNING AS WELL. AS WE MOVE
INTO THE OVERNIGHT HOURS, THE FOCUS FOR CONCERN SHIFTS TO THE
NORTHERN PORTIONS OF 623/624/625, ROUGHLY NORTH OF A LINE FROM
CRATER LAKE TO SUMMER LAKE. AT THIS TIME, THE NOCTURNAL THREAT LOOKS
LIMITED TO THE NORTHERN AREAS, BUT SUBTLE CHANGES IN THE LOCATION OF
THIS SHORTWAVE COULD CHANGE THAT, SO STAY TUNED FOR UPDATES.
THE CURRENT FORECAST MAINTAINS SIMILAR CONDITIONS ON THURSDAY, BUT
THERE IS SOME UNCERTAINTY ON HOW MUCH THUNDERSTORM COVERAGE WILL
MATERIALIZE DUE TO ANY LINGERING CLOUD COVER FROM OVERNIGHT
ACTIVITY. ADDITIONALLY, WE'LL BE IN A LESS FAVORABLE DYNAMIC REGION
AS THE TROUGH WILL HAVE SHIFTED NORTH OF THE AREA. THE GREATEST
COVERAGE IS MORE LIKELY TO BE WHERE THERE ISN'T CLOUD COVER IN THE
MORNING, WHICH AT THIS TIME LOOKS TO BE EAST OF THE CASCADES AND
ACROSS NORTHERN CALIFORNIA. WE'LL TRY TO HONE IN ON THESE DETAILS
OVER THE COMING SHIFTS.
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...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY
EVENING FOR ORZ620>622.
RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ623>625.
FIRE WEATHER WATCH FROM WEDNESDAY EVENING THROUGH THURSDAY
MORNING FOR ORZ616.
FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
MORNING FOR ORZ623>625.
FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH THURSDAY
MORNING FOR ORZ617.
CA...FIRE WEATHER WATCH FROM WEDNESDAY AFTERNOON THROUGH WEDNESDAY
EVENING FOR CAZ280-281-284-285.
RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ285.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 8 PM PDT
WEDNESDAY FOR PZZ356-376.
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