943
FXUS66 KMFR 260322
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
822 PM PDT FRI JUL 25 2025
DISCUSSION
TONIGHT'S RADAR WAS STILL ACTIVE WITH THUNDERSTORMS
MAINLY IN NORTHERN CALIFORNIA. THERE HAVE BEEN REPORTS OF SMALL
HAIL IN A COUPLE OF THESE STORMS SO FAR, ALTHOUGH MORE OF THE
STORMS FELL ONTO MORE SECLUDED AREAS. THERE ARE A FEW CELLS TO
STILL TRACK TONIGHT, NAMELY NEAR WEED AND TENNANT. THESE COULD
STILL BRING GUSTY WINDS, SMALL HAIL AND LIGHTNING. OUTFLOWS WILL
ALSO NEED TO BE MONITORED AS THEY HAVE BEEN FORMING NEW CELLS
BEHIND.
TOMORROW'S RAIN CHANCES WILL FOCUS ON CENTRAL TO EASTERN SISKIYOU
AND MODOC COUNTIES, AS WELL AS EASTERN LAKE COUNTY. -HERMANSEN
MARINE...UPDATED 800 PM PDT FRIDAY, JULY 25, 2025
SUB-ADVISORY
NORTH WINDS AND LOW SEAS OF 5 FT OR LESS, WILL PERSIST THROUGH THE
WEEKEND INTO EARLY NEXT WEEK. OF NOTE, WINDS WILL BRIEFLY APPROACH
SMALL CRAFT ADVISORY LEVELS THROUGH THIS EVENING, BETWEEN PORT
ORFORD AND GOLD BEACH, 2 TO 20 NM FROM SHORE. WINDS THEN LOWER
OVERNIGHT. AREAS OF FOG AND LOW STRATUS WILL ALSO PERSIST THROUGH
THIS TIME. WINDS AND SEAS MAY TREND SLIGHTLY HIGHER AROUND TUESDAY
OF NEXT WEEK.
PREV DISCUSSION
/ISSUED 521 PM PDT FRI JUL 25 2025/
UPDATE...UPDATED AVIATION DISCUSSION.
AVIATION...26/11Z TAFS...IFR ALONG THE COAST WILL BECOME WIDESPREAD
THIS EVENING AND PERSIST THROUGH SATURDAY MORNING. AREAS OF MVFR
MAY SPREAD INTO THE NORTHWEST UMPQUA BASIN EARLY SATURDAY MORNING,
MAINLY NEAR AND NORTH OF ROSEBURG. THEN EXPECT CLEARING TO VFR IN
THE UMPQUA AND ALONG THE COAST LATE SATURDAY MORNING AND EARLY
SATURDAY AFTERNOON. HOWEVER, LOCAL MVFR MAY PERSIST INTO THE
AFTERNOON ALONG THE COAST.
ELSEWHERE OVER INLAND AREAS, VFR PREVAILS BUT SCATTERED
THUNDERSTORMS ARE DEVELOPING AGAIN THIS AFTERNOON/EVENING,
MAINLY IMPACTING SISKIYOU, MODOC, LAKE AND SOUTHEAST KLAMATH
COUNTIES. THESE COULD LOCALLY AND TEMPORARILY REDUCE
VISIBILITY/CEILINGS TO IFR/MVFR. ANY THUNDERSTORMS WILL HAVE THE
ABILITY TO PRODUCE CLOUD TO GROUND LIGHTNING, STRONG, GUSTY OUTFLOW
WIND GUSTS OF 40-60 MPH, BRIEF, HEAVY RAIN AND SMALL HAIL.
PREV DISCUSSION... /ISSUED 145 PM PDT FRI JUL 25 2025/
DISCUSSION...THE FIRST CELLS OF THE DAY ARE SHOWING UP ON
RADAR/SATELLITE EARLY THIS AFTERNOON. ONE FORMED DIRECTLY ATOP MT.
SHASTA WITH OTHERS DEVELOPING IN THE TRINITY ALPS, MEDICINE LAKE
REGION AND ALSO PARTS OF LASSEN/NORTHERN WASHOE COUNTIES. THE
EXPECTATION FOR THE REST OF THIS AFTERNOON AND EVENING IS ANOTHER
ROUND OF WIDESPREAD LIGHTNING ACROSS NORCAL AND INTO PORTIONS OF
SOUTH-CENTRAL OREGON (EAST OF THE CASCADES). ACTIVITY WILL BE IN
THE SAME GENERAL AREAS THAT IT OCCURRED YESTERDAY, WITH A SLIGHT
SHIFT IN THE MAIN FOCUS AREA OFF TO THE SOUTH AND EAST. GENERALLY
IF YOU DRAW A LINE FROM HAPPY CAMP TO KLAMATH FALLS TO SUMMER
LAKE, LOCATIONS NORTH AND WEST OF THERE SHOULD MISS OUT ON THE
THUNDERSTORMS ALL TOGETHER. HI-RES MODELS ARE SHOWING THE
BULLSEYE OF HIGHEST LIGHTNING PROBABILITY (>80%) ACROSS PORTIONS
OF SOUTHEASTERN SISKIYOU AND INTO MODOC COUNTY. STORMS TODAY WILL
BE SLOW-MOVERS, WITH MID-LEVEL STEERING FLOW OF ONLY AROUND 5-15KT
(VERY SIMILAR TO YESTERDAY). SO, THEY SHOULD HAVE THE ABILITY TO
PRODUCE BRIEF, HEAVY RAINFALL. WPC SHOWS MARGINAL RISK FOR
EXCESSIVE RAINFALL, WHICH, IF CELLS TRAIN OVER A SPOT FOR MORE
THAN AN HOUR, COULD LEAD TO URBAN AND SMALL STREAM FLOODING WITH A
LOW CHANCE (5-14%) OF FLASH FLOODING. THIS SEEMS MOST LIKELY FOR
STORMS IN SOUTHERN SISKIYOU COUNTY, BUT ALSO WESTERN MODOC WHERE
PWATS ARE IN SOME CASES GREATER THAN 1.00". FARTHER EAST,
INVERTED-V PROFILES OVER THE FAR EAST SIDE INDICATE HIGHER-BASED
STORMS (BASES OF 10-12K FT) WITH MODEL DCAPE (DOWNDRAFT CAPE) OF
MORE THAN 1000 J/KG. THIS IS A GOOD INDICATOR OF STRONG, GUSTY
OUTFLOW WINDS. NOTABLY, THE SPC HAS BEEFED UP THE SEVERE
THUNDERSTORM RISK TO MARGINAL FOR THIS AFTERNOON/EVENING IN SE
PORTIONS OF THE AREA (MODOC), WHERE ISOLATED SEVERE WIND GUSTS
(5-14% CHANCE) ARE POSSIBLE. OF COURSE, GUSTY WINDS REALLY CAN
OCCUR WITH ANY STORM. MUCH LIKE YESTERDAY, STORMS THAT BUILD AND
MAINTAIN THEIR CORES SHOULD ALSO BE ABLE TO PRODUCE AT LEAST PEA
TO MARBLE SIZE HAIL. STRONGEST CELLS COULD BRING HAIL STONES UP TO
1.00" IN DIAMETER. ACTIVITY WILL ONCE AGAIN WANE AFTER SUNSET AND
PROBABLY END SOMETIME BETWEEN 10 AND 11 PM.
MARINE LAYER STRATUS HAS BROKEN UP AND IS MOSTLY OFFSHORE NORTH OF
CAPE BLANCO EARLY THIS AFTERNOON, BUT IT PERSISTS SOUTH OF PISTOL
RIVER. A COASTAL EDDY CAN BE SEEN IN VISIBLE SATELLITE IMAGERY
OFF CRESCENT CITY. EXPECT MAINLY SUNNY SKIES WEST OF THE CASCADES
THROUGH VERY EARLY THIS EVENING, THEN STRATUS/FOG WILL PUSH BACK
ONSHORE. MODELS ARE SHOWING A BIT DEEPER MARINE LAYER TONIGHT, SO
STRATUS SHOULD PUSH A BIT FARTHER INTO THE UMPQUA BASIN AND COULD
END UP CLOSER TO OR EVEN TO ROSEBURG FOR A FEW HOURS SATURDAY
MORNING. THE REST OF THE AREA INLAND FROM THE COAST AND WEST OF
THE CASCADES WILL REMAIN CLEAR TONIGHT.
WHILE SATURDAY WON'T BE QUITE AS ACTIVE AS IT WAS YESTERDAY AND
WILL BE TODAY, THE AREA WON'T BE DEVOID OF THUNDERSTORMS. MODELS
SHOW A BIT MORE OF A DRIER WSW FLOW ALOFT AS AN UPPER TROUGH
APPROACHES THE PACNW COAST. THIS WILL, ONCE AGAIN, SHIFT THE AXIS
OF ACTIVITY A BIT FARTHER TO THE SOUTH AND EAST. BUT, THERE STILL
CAN BE ISOLATED THUNDERSTORMS FROM AROUND THE TRINITY ALPS ENE
ACROSS EASTERN SISKIYOU INTO MODOC AND SOUTHERN LAKE COUNTIES
SATURDAY AFTERNOON/EVENING. HIGH TEMPERATURES WILL BE FAIRLY
TYPICAL FOR LATE JULY, MOSTLY IN THE 80S AND LOW 90S FOR WEST SIDE
VALLEYS, AND GENERALLY 80-85F OVER THE EAST SIDE.
MODEL GUIDANCE INDICATES A RELATIVE DROP IN THUNDERSTORM POTENTIAL
ON SUNDAY/MONDAY (AT LEAST COMPARED TO TODAY/YESTERDAY). BUT,
CHANCES DON'T GO AWAY COMPLETELY. IT APPEARS THERE'S JUST ENOUGH
MOISTURE, INSTABILITY AND UPPER FORCING FOR ISOLATED STORMS.
WE'VE ACTUALLY ADDED SLIGHT CHANCES (15-24%) INTO THE FORECAST
FOR BOTH AFTERNOONS/EVENINGS. WHILE CONFIDENCE IN EXACTLY WHERE
STORMS WILL BE IS ON THE LOW SIDE, AREAS THAT STAND THE BEST
CHANCE CONTINUE TO BE IN THE MOUNTAINS OF WESTERN SISKIYOU COUNTY,
BUT ALSO FROM THE WARNER MTNS OF MODOC COUNTY UP INTO SOUTH-
CENTRAL OREGON FROM AROUND CRATER LAKE EASTWARD.
A MORE POTENT UPPER TROUGH/DISTURBANCE IS THEN FORECAST TO
APPROACH THE CENTRAL CA COAST AGAIN BY TUESDAY TAKING ON A
NEGATIVE TILT AS IT HEADS TOWARD THE GREAT BASIN AT MIDWEEK. MODEL
PROBABILITIES OF SHOWERS AND THUNDERSTORMS INCREASE ACROSS A
LARGER PORTION OF THE AREA THEN ALONG WITH SOME POTENTIAL FOR WEST
SIDE STORMS. TUESDAY/WEDNESDAY LOOKS LIKE THE BEST CHANCE FOR
THAT TO HAPPEN. WE'LL CONTINUE TO HONE IN ON THIS AS WE GET
CLOSER. THERE'S STILL PLENTY OF UNCERTAINTY WITH HOW QUICKLY THIS
TROUGH ARRIVES. -SPILDE
FIRE WEATHER...UPDATED 100 PM PDT FRIDAY, JULY 25, 2025...THE
MAIN FIRE WEATHER CONCERN FOR THE NEXT WEEK WILL BE THUNDERSTORMS.
TEMPERATURES, HUMIDITIES, AND BREEZY AFTERNOON WINDS WILL ALL
REMAIN NEAR SEASONABLE LEVELS.
SCATTERED TO NUMEROUS THUNDERSTORMS THIS AFTERNOON/EVENING ARE
EXPECTED TO RESEMBLE THOSE OF YESTERDAY IN STRENGTH, AND IN WHERE
THEY OCCUR. ABUNDANT LIGHTNING WITH SOME STRONG TO SEVERE STORMS IS
EXPECTED, ESPECIALLY IN NORTHERN CALIFORNIA. THESE WILL BE WET, SLOW
MOVING STORMS WITH THE REGION OF SCATTERED STORMS EXTENDING INTO
SOUTHEAST KLAMATH AND SOUTHERN LAKE COUNTIES. THOUGH A STEP DOWN OR
TWO IN THE LEVEL OF RISK OF THUNDERSTORMS, ADDITIONAL ISOLATED TO
SCATTERED STORMS ARE EXPECTED EACH DAY SATURDAY THROUGH TUESDAY.
THIS INCLUDES A FOCUS FOR STORMS ON SATURDAY FROM EASTERN SISKIYOU
INTO MODOC AND SOUTHERN LAKE COUNTIES. ON SUNDAY, A LESSER RISK OVER
A BROADER AREA WILL BRING A 10-20% PROBABILITY FROM NEAR THE SCOTT
VALLEY IN SISKIYOU COUNTY EXTENDING ACROSS THE SHASTA VALLEY INTO
KLAMATH, LAKE, AND ALSO MODOC COUNTIES.
ALTHOUGH ACTIVITY STILL LOOKS TO BE ISOLATED YET AGAIN. FORECAST
CONFIDENCE DROPS DOWN A NOTCH ON MONDAY, WITH UNCERTAINTY IN THE
LOCATION OF THE NEXT SHORTWAVE TROUGH EMBEDDED IN THE FLOW BETWEEN A
BROAD TROUGH IN THE GULF OF ALASKA AND RIDGING OVER THE ROCKIES. THE
HIGHEST PROBABILITY REMAINS FROM NORTHERN PORTIONS OF KLAMATH AND
LAKE COUNTIES INTO CENTRAL AND EASTERN OREGON. THE 12Z GFS HAS
TRENDED FASTER IN SWINGING YET ANOTHER TROUGH INTO CENTRAL
CALIFORNIA ON TUESDAY WHICH COULD LEAD TO A LARGER SCALE EVENT, BUT
FOR NOW WE WILL FOLLOW THE NBM WITH A BROAD BRUSH SLIGHT CHANCE
SOUTHWARD AND EASTWARD FROM THE CASCADES AND SISKIYOU MOUNTAINS.
THE COMPLEXITY OF THE PATTERN AND MODEL DIFFERENCES INCREASE AT MID-
WEEK WITH A TROUGH DOMINATED PATTERN LIKELY TO CONTINUE TO RESULT IN
LATE DAY INSTABILITY. -DW
MFR WATCHES/WARNINGS/ADVISORIES
OR...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR ORZ624-625.
CA...RED FLAG WARNING UNTIL 11 PM PDT THIS EVENING FOR CAZ280>282-284-
285.
PACIFIC COASTAL WATERS...NONE.
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