663
FXUS66 KMFR 101013
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
313 AM PDT WED SEP 10 2025
DISCUSSION
SATELLITE IMAGERY IS SHOWING THE CORE OF THE UPPER
LOW OVER NORCAL CURRENTLY. A SHORT WAVE DISTURBANCE MOVING OUT OF
NW NEVADA AND INTO NE CALIFORNIA/SOUTH-CENTRAL OREGON IS BRINGING
SHOWERS AND ALSO ISOLATED THUNDERSTORMS EARLY THIS MORNING. THESE
WILL EXPAND IN COVERAGE TO THE NORTH AND WEST AROUND THE LOW'S
CIRCULATION TODAY, BUT WITH THE AXIS OF ACTIVITY A BIT FARTHER
EAST COMPARED TO YESTERDAY. WHILE ACTIVITY IS EXPECTED TO BE
GREATEST FROM THE CASCADES EASTWARD (60-90% POPS), WEST SIDE AREAS
STILL STAND A DECENT SHOT (30-60%) AT SHOWERS AND AN ISOLATED
STORM OR TWO. SOUNDINGS REMAIN MOIST WITH PWS AROUND OR EVEN A
BIT ABOVE 0.75" EAST OF THE CASCADES AND NEAR OR GREATER THAN
1.00" OVER THE WEST SIDE. STORM MOTIONS WILL BE SLOW AGAIN TODAY,
GENERALLY 10 KT OR LESS, SO CELLS THAT DO SIT FOR A WHILE WILL
HAVE THE ABILITY TO PRODUCE HEAVY RAINFALL. THIS POSES A MARGINAL
RISK (5-15%) FOR EXCESSIVE RAINFALL THAT COULD LEAD TO FLASH
FLOODING, BUT THE RISK REMAINS ON THE LOW SIDE FOR ANY FLASH FLOOD
PRODUCTS. MODELS ARE SHOWING TWO AREAS OF HEIGHTENED PROBABILITIES
FOR LIGHTNING (30-40%), ONE ACROSS NORCAL AND ANOTHER ACROSS
NORTHERN KLAMATH/LAKE COUNTIES, BUT A LARGE PORTION OF THE AREA
(ASIDE FROM THE COAST) STANDS A 15-25% CHANCE OF THUNDER TODAY.
LIKE YESTERDAY, RAIN AMOUNTS WILL BE HIGHLY VARIABLE DEPENDING ON
WHERE EXACTLY THE STORMS SET UP. BUT, MODELS ARE PUTTING THE FOCUS
FOR PRECIPITATION FROM THE CASCADES EASTWARD ACROSS NORTHERN
KLAMATH/LAKE COUNTIES WHERE AMOUNTS OF 0.25-0.50" APPEAR MOST
LIKELY. SIMILAR AMOUNTS ARE EXPECTED IN THE MOUNTAINS OF NORCAL.
OVER-ACHIEVING CELLS COULD PRODUCE LOCALLY 1.00"+ INCH OF
RAINFALL. TEMPERATURES WILL REMAIN ON THE COOL SIDE, GENERALLY
10-15F BUT AS MUCH AS 20F BELOW NORMAL, EXCEPT AT THE COAST WHERE
IT WILL BE RIGHT AROUND NORMAL.
THE BROAD CIRCULATION MOVES INTO THE GREAT BASIN ON THURSDAY AND
WILL CONTINUE TO WRAP SHOWERS AND THUNDERSTORMS BACK ACROSS THE
AREA. AGAIN, THE FOCUS WILL BE OVER THE EAST SIDE, BUT SOME COULD
DEVELOP BACK TO THE CASCADES AND PERHAPS EVEN THE WEST SIDE
VALLEYS. THEY SHOULD BE MORE ISOLATED THIS FAR WEST, HOWEVER.
TEMPERATURES WILL BE SIMILAR TO TODAY, PERHAPS A FEW DEGREES
WARMER WHERE CLOUDS ARE FEWER COMPARED TO TODAY.
ON FRIDAY, A SHORT WAVE UPPER RIDGE OFFSHORE WILL BUILD IN.
CYCLONIC FLOW AROUND THE SYSTEM OVER THE GREAT BASIN WILL KEEP A
CHANCE OF SHOWERS/T-STORMS OVER FAR EASTERN SECTIONS WHILE OTHER
AREAS DRY OUT AND TURN WARMER. THE RIDGE AXIS WILL MOVE IN
OVERHEAD ON SATURDAY RESULTING IN A NICE, WARM, DRY AFTERNOON FOR
INLAND AREAS. HIGH TEMPS SHOULD BE WITHIN A FEW DEGREES EITHER
SIDE OF NORMAL.
MODELS CONTINUE TO PEG LATE SATURDAY NIGHT INTO SUNDAY FOR THE
NEXT UPPER TROUGH TO APPROACH THE COAST AND MOVE ONSHORE. TIMING
AND STRENGTH DIFFERENCES REMAIN, BUT THIS SYSTEM SHOULD BRING A
CHANCE OF SHOWERS TO THE AREA ALONG WITH A SLIGHT COOL DOWN.
EFFECTS FROM THIS SYSTEM COULD LAST INTO MONDAY, BUT THE NEXT
UPPER RIDGE IS EXPECTED TO BUILD TUE/WED NEXT WEEK WITH THE STORM
TRACK REMAINING TO THE NORTH. THIS SHOULD ALLOW FOR A PERIOD OF
WARM WEATHER TO RETURN WITH HIGH TEMPS HERE IN MEDFORD UP AROUND
90F AGAIN. -SPILDE
AVIATION...10/12Z TAFS
A MOIST PATTERN CONTINUES. THE RECENT
RAINFALL IS RESULTING IN FOG AND LOW CLOUDS IN A LOT OF AREAS
THAT TYPICALLY DON'T HAVE THEM THIS EARLY IN SEPTEMBER. VALLEYS IN
NORCAL AND EVEN OVER PORTIONS OF THE EAST SIDE COULD EXPERIENCE
IFR/LIFR FOG AT LEAST BRIEFLY THIS MORNING BEFORE IMPROVING TO
VFR. THIS IS HAPPENING AT KLAMATH FALLS AND MONTAGUE CURRENTLY.
MEANWHILE, MOISTURE DEPTH IS GREATER AT MEDFORD AND ROSEBURG, SO
CEILINGS VARY FROM MVFR IN THE UMPQUA BASIN TO VFR LOCALLY. AREAS
OF HIGHER TERRAIN ARE OBSCURED. EXPECT IMPROVEMENT TO VFR BY LATE
MORNING IN THESE LOCATIONS. ALONG THE COAST, CONDITIONS ARE VFR
FROM GOLD BEACH UP TO AROUND PORT ORFORD, BUT IFR PREVAILS AT
NORTH BEND WITH LIFR AT BROOKINGS. CONDITIONS SHOULD IMPROVE TO
VFR IN THOSE AREAS LATE THIS MORNING/EARLY THIS AFTERNOON.
SHOWERS AND THUNDERSTORMS, SOME OCCURING THIS MORNING OVER THE FAR
EAST SIDE, WILL EXPAND AND DEVELOP WESTWARD TO AROUND THE CASCADES
AND EVEN OVER SOME WEST SIDE LOCATIONS THIS AFTERNOON/EVENING.
THESE COULD TEMPORARILY LOWER CEILINGS/VISIBILITY TO MVFR OR EVEN
IFR IN HEAVIER SHOWERS. MAIN RISKS WITH THUNDERSTORMS WILL BE
HEAVY DOWNPOURS AND LIGHTNING, BUT GUSTY WINDS ALSO CANNOT BE
RULED OUT. -SPILDE
MARINE...UPDATED 300 AM PDT WEDNESDAY, SEPTEMBER 10, 2025
NORTHERLY WINDS BE STRONGER IN THE FAVORED LOCATION SOUTH OF PORT
ORFORD AND BETWEEN 5 AND 30 NM FROM SHORE THROUGH THIS EVENING AND
AGAIN THURSDAY AFTERNOON/EVENING. WHILE SUB-ADVISORY CONDITIONS
ARE LIKELY TO PERSIST THROUGH THE END OF THE WEEK AND INTO THE
WEEKEND, SEAS DO INCREASE SOME DURING THE LATTER HALF OF THE WEEK
(FROM 3-5 FT TO 5-7 FT) AS A LOW NORTHWEST SWELL (5-6 FT @ 12-14
SECONDS) BUILDS INTO THE WATERS STARTING THURSDAY AND PERSISTING
INTO THE WEEKEND. -SPILDE
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...NONE.
MAS/MAS/MAS
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