471
FXUS66 KMFR 252046
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
146 PM PDT SAT APR 25 2026
KEY MESSAGES
-SLIGHTLY COOLER WEATHER CONTINUES THIS WEEKEND (AND INTO MON)
WITH ISOLATED TO SCATTERED SHOWERS FROM THE CASCADES EASTWARD.
-ISOLATED PM/EVE THUNDERSTORMS ARE ALSO POSSIBLE, BUT PRIMARILY
ACROSS NORCAL (MT SHASTA REGION EASTWARD).
-SHOWERS CHANCES ARE LOWER WEST OF CASCADES, BUT CAN'T RULE ONE
OUT HERE OR THERE SUN/MON, ESPECIALLY HIGHER TERRAIN.
-ACTIVITY SHIFTS EASTWARD TUE/WED WITH WARMING TREND WED- FRI.
-NEXT INCREASED CHANCE OF SHOWERS IS NEXT SATURDAY.
DISCUSSION
SATELLITE IMAGERY THIS AFTERNOON IS VERY REVEALING OF
THE UPPER AIR PATTERN ACROSS THE NORTHWEST UNITED STATES. A THIN
VEIL OF HIGH THIN CIRRUS IS DROPPING SOUTHWARD ACROSS SOUTHERN
OREGON AT THIS TIME AND IS THE LEADING EDGE OF AN UPPER TROUGH
DIGGING INTO WA/OR. MEANWHILE, CUMULUS DEVELOPING ACROSS NORCAL
ARE INDICATIVE OF INCREASED MID-LEVEL MOISTURE AND INSTABILITY
ASSOCIATED WITH ANOTHER UPPER TROUGH MOVING ONSHORE JUST SOUTH
OF SAN FRANCISCO.
AS THESE TWO AREAS COME TOGETHER THIS AFTERNOON/EVENING, WE
EXPECT SHOWERS AND ISOLATED THUNDERSTORMS TO DEVELOP, MAINLY FROM
THE HORN OF TRINITY COUNTY (THAT JUTS NORTHWARD INTO SOUTHERN
SISKIYOU COUNTY) EASTWARD ACROSS THE MT. SHASTA REGION (NEAR AND
SOUTH OF MEDICINE LAKE) AND INTO MODOC COUNTY. MOISTURE AVAILABLE
IN THESE AREAS ISN'T THAT IMPRESSIVE, GENERALLY PWS OF AROUND 0.50
OF AN INCH OR SO. NEITHER IS INSTABILITY, FOR THAT MATTER (~250
J/KG). BUT, DUE TO THE PERSISTENT ALIGNMENT OF THE UPPER FLOW
(W->E), ACTIVITY COULD REDEVELOP OVER THE SAME AREAS WELL INTO THE
EVENING. THE HIGHEST PROBABILITY OF THIS OCCURRING IS TO THE
SOUTH IN SHASTA/NORTHERN LASSEN COUNTIES. EVEN SO, SOME OF THE
STRONGER CELLS THAT DEVELOP COULD BRING BRIEF DOWNPOURS (IN
ADDITION TO CLOUD TO GROUND LIGHTNING, GUSTY WINDS AND EVEN PEA-
SIZE HAIL) AROUND MT. SHASTA CITY, DUNSMUIR, MCCLOUD, DAY, LOOKOUT
AND ADIN. WHILE A SHOWER OR TWO CAN'T REALLY BE RULED OUT FARTHER
NORTH, THAT'S WHERE MOST OF THE ACTIVITY WILL BE THROUGH TONIGHT
AND EVEN PERHAPS INTO SUNDAY MORNING.
WITH THE TROUGH AXIS OVERHEAD ON SUNDAY, SHOWERS/ISOLATED
T-STORMS CONTINUE IN NORCAL. THERE IS A LITTLE BETTER CHANCE OF
SHOWERS EXTENDING INTO SOUTHERN OREGON, BUT THESE WILL BE MOSTLY
FOCUSED NEAR ELEVATED HEAT SOURCES (MOUNTAINS/HIGHER TERRAIN),
WHERE THE BEST INSTABILITY IS LOCATED. VALLEY POPS WILL BE
GENERALLY 10% OR LESS. OVERALL, TEMPS THE NEXT 2 DAYS WILL BE NEAR
TO SLIGHTLY BELOW NORMAL -- WITH THE LOWEST MAXTS COMPARED TO
NORMAL IN AREAS WHERE THE MOST CLOUD COVER/PRECIP IS -- IN EASTERN
SISKIYOU/MODOC COUNTIES. SNOW LEVELS THIS WEEKEND COULD DROP TO
AROUND 5000 FEET, BUT ANY SNOW ACCUMULATIONS WILL BE MINIMAL AND
CONFINED TO THE HIGHER MOUNTAINS AROUND MT. SHASTA AND ALSO THE
WARNERS. ACTIVITY SUNDAY SHOULD WANE AFTER SUNSET WITH THE LOSS
OF INSTABILITY.
BY MONDAY, WITH A KICKER TROUGH SWINGING SOUTHWARD JUST OFFSHORE,
THE MAIN TROUGH AXIS WILL PUSH EAST OF THE CASCADES. THERE COULD
STILL BE PM/EVE SHOWERS OVER THE EAST SIDE THEN, BUT MOST AREAS
WILL BE DRY WITH SEASONABLE TEMPERATURES. ONSHORE FLOW COULD LEAD
TO THE DEVELOPMENT OF STRATUS ALONG THE COAST BOTH MONDAY AND
TUESDAY MORNINGS, ESPECIALLY NORTH OF CAPE BLANCO. DEPENDING ON
THE DEPTH OF THE MOIST LAYER, THIS MAY IMPACT PORTIONS OF THE
UMPQUA BASIN AS WELL.
A STRONG UPPER RIDGE IS FORECAST TO DEVELOP AND MOVE INTO THE AREA
MID-LATE NEXT WEEK AND THIS WILL BRING A PERIOD OF DRY AND WARMER
WEATHER WITH HIGH TEMPERATURES (AREAS INLAND FROM THE COAST)
GENERALLY 10-15F ABOVE NORMAL FOR LATE APRIL AND EARLY MAY.
COASTAL AREAS COULD CONTINUE TO EXPERIENCE INTRUSIONS OF LATE-
NIGHT/MORNING MARINE STRATUS.
LATEST 12Z LONG RANGE DETERMINISTIC GUIDANCE IS HINTING AT THE
POTENTIAL FOR A TROUGH TO APPROACH THE COAST BY NEXT WEEKEND WITH
THE POSSIBILITY OF SHOWERS AND THUNDERSTORMS. BUT, ENSEMBLE
GUIDANCE IS SPLIT ON THIS WITH A MAJORITY (60%) OF MEMBERS
MAINTAINING A DRY PATTERN. -SPILDE
AVIATION...25/18Z TAFS
VFR CONDITIONS PREVAIL ACROSS THE REGION
WITH THE EXCEPTION OF SOME SCATTERED MVFR CEILINGS IN THE BROOKINGS
AREA AND SOME LOW END VFR CEILINGS ACROSS THE MODOC PLATEAU AND
AROUND THE MEDICINE LAKE AREA IN SOUTHEASTERN SISKIYOU COUNTY.
OVERALL, VFR CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD FOR MOST
LOCATIONS WITH SOME BREEZY WEST TO NORTHWEST WINDS DEVELOPING THIS
AFTERNOON. SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED TO
DEVELOP JUST SOUTH OF THE OR/CA BORDER THIS AFTERNOON AS WELL,
MAINLY FROM THE MT SHASTA REGION AND AREAS EASTWARD. SHOWER ACTIVITY
LOOKS TO CONTINUE INTO THE OVERNIGHT HOURS, BUT ONCE THEY CLEAR,
AREAS OF MVFR CEILINGS WILL LIKELY LINGER ACROSS FAR NORTHEASTERN CA
INTO SUNDAY MORNING.
ALONG THE COAST, MARINE STRATUS WILL RETURN TO THE COASTAL WATERS
AND ALONG THE COAST/COASTAL VALLEYS. EXPECT MVFR/IFR CEILINGS TO
RETURN AROUND 06-08Z AND PERSIST INTO SUNDAY MORNING. /BR-Y
MARINE...UPDATED 1215 PM PDT FRIDAY, APRIL 24, 2026
HIGH PRESSURE
OFFSHORE AND A LOW PRESSURE TROUGH ALONG THE COAST WILL MAINTAIN
GUSTY NORTH WINDS TODAY. ADVISORY LEVEL WINDS ARE EXPECTED THIS
AFTERNOON SOUTH OF CAPE BLANCO, RESULTING IN CONTINUED STEEP SEAS
DUE TO WIND WAVES COMBINED WITH A LOW BACKGROUND NORTHWEST SWELL.
NORTH WINDS WILL PERSIST THROUGH THE WEEK, BUT THE PATTERN WEAKENS
SOME SUNDAY INTO MONDAY, RESULTING IN LESS STEEP SEAS AND IMPROVED
CONDITIONS THROUGH EARLY TUESDAY.
NORTHERLY WINDS INCREASE AGAIN LATE TUESDAY, ESPECIALLY SOUTH OF
CAPE BLANCO, AND PERSIST THROUGH MUCH OF THE WEEK. STEEP SEAS COULD
RETURN AROUND MID-WEEK DUE TO INCREASING WIND WAVES AND ANOTHER 4-6
FT NORTHWEST SWELL MOVING INTO THE WATERS. HIGH END ADVISORY LEVEL
WINDS ARE POSSIBLE LATE IN THE WEEK, WITH AREAS OF GALES SOUTH OF
GOLD BEACH ALSO POSSIBLE. /BR-Y
MFR WATCHES/WARNINGS/ADVISORIES
OR...NONE.
CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM PDT SUNDAY
FOR PZZ356-376.
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