077
FXUS66 KMFR 011149
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
449 AM PDT FRI MAY 1 2026
DISCUSSION
UPDATED AVIATION DISCUSSION.
AVIATION...01/12Z TAFS
IFR/MVFR CEILINGS PERSIST ALONG THE OREGON
COAST AND UMPQUA VALLEY THIS MORNING WITH VFR ELSEWHERE. THE LOWER
CEILINGS SHOULD TEND TO LIFT/BREAK UP LATER THIS MORNING/THIS
AFTERNOON.
MEANWHILE, WE EXPECT CONVECTIVE ACTIVITY TO BEGIN THIS AFTERNOON
WITH SOME CUMULUS BUILDUPS DURING THE MID-LATE AFTERNOON. ISOLATED
SHOWERS AND THUNDERSTORMS SHOULD DEVELOP LATE AFTERNOON/EVENING NEAR
AND JUST WEST OF THE CASCADES, INCLUDING AROUND THE ROGUE VALLEY.
THE CHANCE OF THUNDERSTORMS IS ABOUT 20-30% AROUND THE MFR TERMINAL
FRIDAY AFTERNOON, SO GUSTY OUTFLOWS ARE POSSIBLE WITH CLOUD TO
GROUND LIGHTNING. THE CHANCES FOR THUNDERSTORMS ARE SLIGHTLY LOWER
NEAR ROSEBURG. -SPILDE
PREV DISCUSSION
/ISSUED 325 AM PDT FRI MAY 1 2026/
KEY MESSAGES...
-MARINE LAYER STRATUS ON THE COAST AND IN THE UMPQUA BASIN THIS
MORNING.
-ISOLATED THUNDERSTORMS LATE THIS AFTERNOON AND EVENING, MAINLY
SISKIYOU COUNTY NORTHWARD TO THE SISKIYOUS/CASCADES AND ALSO
WEST SIDE VALLEYS ALONG I-5.
-THUNDER POTENTIAL CONTINUES THIS WEEKEND INTO MONDAY.
-HIGH PRESSURE BRINGS WARMER, DRIER WEATHER AGAIN TUESDAY AND
WEDNESDAY.
-SHOWER/THUNDER CHANCES COULD INCREASE AGAIN LATE NEXT WEEK.
DISCUSSION...SATELLITE IMAGERY IS SHOWING A BIT DEEPER OF A
MARINE PUSH THIS MORNING WITH LOW STRATUS FOR ALL COASTAL AREAS
AND ALSO PORTIONS OF THE UMPQUA BASIN. CLEAR SKIES (WITH SOME
HIGH CIRRUS) PERSIST ELSEWHERE. THE LOWER CLOUDS SHOULD GRADUALLY
BREAK UP/LIFT THIS AFTERNOON. WITH THE UPPER RIDGE AXIS SHIFTING
TO THE SOUTH AND EAST, AN UPPER TROUGH WILL CLOSE OFF JUST OFF THE
PACNW COAST AND MOVE SOUTHWARD (INSIDE 130W, BUT JUST OFFSHORE).
INCREASING SOUTHERLY FLOW IN ADVANCE OF THIS DISTURBANCE WILL
BRING HIGHER MOISTURE (PWS OF 0.5-0.8") AND INSTABILITY (CAPE
200-500 J/KG) OVER THE AREA LATE THIS AFTERNOON/EVENING. HI-RES
GUIDANCE SHOWS DECENT SOME CUMULUS BUILDING DURING THE LATE
AFTERNOON/EVENING OVER THE MOUNTAINS, ESPECIALLY FROM WESTERN
SISKIYOU COUNTY, UP ACROSS JACKSON COUNTY AND INTO THE CASCADES. A
CAPPING INVERSION DOES EXIST, SO IT'LL LIKELY TAKE MOST OF THE
DAY BEFORE WE SEE MUCH ACTIVITY (IT MAY HOLD OFF TIL EVENING).
EVEN SO, THESE AREAS STAND A DECENT CHANCE (20-40%) OF SHOWERS
ALONG WITH A SLIGHT CHANCE (15-20%) OF THUNDERSTORMS. WHILE
CONVECTIVE PARAMETERS AREN'T BULLISH ON SEVERE POTENTIAL (BULK
SHEAR ONLY IN THE 20-30KT RANGE), ANY CELLS THAT DO FORM COULD
PRODUCE GUSTY WINDS, CLOUD TO GROUND LIGHTNING AND SMALL HAIL. SOME
ACTIVITY (MOSTLY JUST SHOWERS) COULD LINGER NEAR AND WEST OF THE
CASCADES INTO TONIGHT SINCE THE CORE OF THE CLOSED LOW WILL BE
JUST OFF THE OREGON COAST AT THAT TIME.
SHOWERS AND STORMS WILL BE IN THE SAME GENERAL AREAS SATURDAY,
BUT WITH THE FLOW BECOMING MORE SSE AS THE CLOSED LOW HEADS DOWN
THE COAST, ACTIVITY COULD BECOME MORE WIDESPREAD AND INCLUDE EAST
SIDE AREAS DURING THE AFTERNOON/EVENING. LATEST GUIDANCE SHOWS THE
HIGHEST PROBABILITIES NEAR THE CASCADES AND OVER THE HIGHER
TERRAIN OF THE EAST SIDE. THE LOW SETTLES SOUTHWARD TO A POSITION
ABOUT ~300 MILES WSW OF SAN FRANCISCO SATURDAY NIGHT INTO SUNDAY
MORNING AND SHOWERS SHOULD WIND DOWN OVER OUR AREA WITH THE LOSS
OF INSTABILITY.
SUNDAY INTO MONDAY, THE LOW IS FORECAST TO ELONGATE AND SHIFT
EASTWARD -- MOVING ONSHORE INTO CALIFORNIA JUST SOUTH OF SF BAY
DURING THIS TIME. THE FOCUS FOR SHOWERS AND STORMS WILL BE
DIRECTED INTO NORCAL, BUT ALSO STILL INTO PORTIONS OF SOUTHERN
OREGON. WE'LL PROBABLY START OFF SUNNY SUNDAY AND IT WILL REMAIN
QUITE WARM/EVEN HUMID. THERE SHOULD BE ENOUGH MOISTURE,
INSTABILITY AND FORCING FOR MORE WIDESPREAD SHOWERS AND
THUNDERSTORMS DURING THE AFTERNOON/EVENING. HIGHEST POPS AND
THUNDER CHANCES WILL BE ACROSS NORCAL AND UP THE CASCADES WITH
LOWER CHANCES IN NW SECTIONS (NORTHWEST OF ROSEBURG). BY MONDAY,
WE'LL BE DECIDEDLY ON THE NORTHERN PERIPHERY OF THE LOW WITH UPPER
RIDGING TO THE NORTH AND MID-LEVEL FLOW AROUND THE LOW FROM THE
ENE. MOST AREAS WILL BE AT LEAST SLIGHTLY COOLER, BUT ESPECIALLY
NORCAL WHERE CLOUDS/SHOWERS WILL BE MOST PERSISTENT. THERE'S STILL
A CHANCE OF THUNDERSTORMS, BUT BEST CHANCE IS EAST OF THE
CASCADES. RAIN AMOUNTS WITH THIS ENTIRE SYSTEM WILL LIKELY VARY
QUITE A BIT DUE TO THE SHOWERY NATURE OF THE PRECIPITATION (AND
ALSO THE POTENTIAL FOR THUNDERSTORMS). SOME PLACES COULD END UP
WITH NOTHING AT ALL, WHILE THOSE THAT GET UNDER MORE PERSISTENT
SHOWERS COULD HAVE 0.25-0.50 OF AN INCH (MOST LIKELY IN SISKIYOU
COUNTY OF NORCAL) WITH UP TO AN INCH IN AREAS THAT MANAGE TO GET
BENEATH A THUNDERSTORM CORE FOR A WHILE.
TUESDAY INTO WEDNESDAY, THE UPPER RIDGE TO THE NORTH WILL WIN OUT
AS THE CLOSED LOW SETTLES INTO THE GREAT BASIN AND DESERT
SOUTHWEST. THIS WILL ALLOW THINGS TO WARM UP AGAIN, WITH
SHOWER/THUNDER CHANCES STAYING MOSTLY TO OUR SOUTH AND EAST. LONG
RANGE GUIDANCE IS HINTING AT THE POTENTIAL FOR ANOTHER TROUGH TO
ARRIVE SOMETIME LATE NEXT WEEK (THU/FRI) WITH PERHAPS AN INCREASE
IN SHOWER/THUNDER CHANCES AGAIN. -SPILDE
AVIATION...01/06Z TAFS...MVFR CEILINGS PERSIST ALONG THE OREGON
COAST TONIGHT AND SOME OF THOSE CEILINGS COULD SPILL INTO THE UMPQUA
VALLEY OVERNIGHT. OTHERWISE, VFR CEILINGS CONTINUE OTHER AREAS
THROUGH THE NIGHT.
WE'LL HAVE SOME SHOWERS AND THUNDERSTORMS DEVELOP IN THE AFTERNOON
HOURS WEST OF THE CASCADES IN THE ROGUE VALLEY. THE CHANCE OF
THUNDERSTORMS IS ABOUT 20-30% AROUND THE MFR TERMINAL FRIDAY
AFTERNOON, SO GUSTY OUTFLOWS ARE POSSIBLE CLOUD TO GROUND LIGHTNING.
THE CHANCES FOR THUNDERSTORMS ARE SLIGHTLY LOWER NEAR ROSEBURG.
-SMITH
MARINE...UPDATED 230 AM PDT FRIDAY, MAY 1, 2026....A THERMAL TROUGH
PATTERN WILL BRING GUSTY NORTH WINDS INTO SATURDAY EVENING. THE
STRONGEST WINDS AND VERY STEEP SEAS ARE EXPECTED SOUTH OF OPHIR
AGAIN TODAY. SEAS WILL BE STEEP ELSEWHERE. WINDS DIMINISH WHILE A
LONGER PERIOD NORTHWEST SWELL BUILDS LATE SATURDAY NIGHT, THEN
BECOMES DOMINANT LATER SUNDAY INTO MONDAY.
BEACH HAZARDS...A SHORT PERIOD NORTHWEST SWELL AND A BUILDING
LONG PERIOD NORTHWEST SWELL MAY COMBINE THEIR ENERGY TO PRODUCE
UNPREDICTABLE WAVES WASHING UP ON AREA BEACHES. THE RISK WILL BE
HIGHEST AROUND SUNRISE ON SUNDAY MORNING.
SNEAKER WAVES CAN RUN UP SIGNIFICANTLY FARTHER ON BEACHES THAN
NORMAL, INCLUDING OVER ROCKS AND JETTIES. THESE WAVES CAN SUDDENLY
KNOCK PEOPLE OFF OF THEIR FEET AND SWEEP THEM INTO THE OCEAN. THE
WAVES CAN ALSO MOVE LOGS OR OTHER OBJECTS WHICH COULD CRUSH OR
TRAP ANYONE CAUGHT UNDERNEATH. NEVER TURN AWAY FROM THE OCEAN!
MFR WATCHES/WARNINGS/ADVISORIES
OR...BEACH HAZARDS STATEMENT FROM SATURDAY EVENING THROUGH SUNDAY
MORNING FOR ORZ021-022.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 11 PM PDT
SATURDAY FOR PZZ350-356-370-376.
HAZARDOUS SEAS WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ356-
376.
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