662
FXUS66 KMFR 230531
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
1031 PM PDT TUE APR 22 2025
DISCUSSION...UPDATED AVIATION FORECAST
AVIATION...23/06Z TAFS
NORTHERLY WINDS HAVE INCREASED AT MOST
TERMINALS THIS AFTERNOON, WITH THE STRONGEST WINDS ALONG THE COAST.
WIND GUSTS THROUGH THE EVENING WILL PEAK AT 30-35KT AT NORTH BEND,
WHILE INLAND SITES WILL GENERALLY SEE WIND GUSTS IN THE 15-25KT
RANGE.
VFR CONDITIONS WILL REMAIN FOR INLAND AREAS TONIGHT. MVFR CEILINGS
HAVE BEEN TOGGLING AROUND COOS BAY AND BANDON AND WILL CONTINUE
TONIGHT. AN UPPER LEVEL SHORT WAVE WILL AMPLIFY AS IT MOVES ACROSS
THE AREA TONIGHT. THIS WILL CAUSE CLOUDS TO DEVELOP ACROSS SE
SECTIONS (NE CALIFORNIA INTO SOUTHERN KLAMATH/LAKE COUNTIES).
OVERALL, CONDITIONS LIKELY REMAIN VFR, THOUGH LOCAL MVFR AND TERRAIN
OBSCURATIONS ARE POSSIBLE IN ANY SHOWERS THAT DEVELOP, ESPECIALLY
NEAR THE WARNER MTNS. THESE CLOUDS PERSIST AND SHOWERS REMAIN
POSSIBLE THROUGH WEDNESDAY MORNING. A SLIGHTLY UPTICK IN WINDS NEAR
THE COAST ARE POSSIBLE TOMORROW AFTERNOON AS WELL.
-SPILDE/HERMANSEN
PREV DISCUSSION
/ISSUED 849 PM PDT TUE APR 22 2025/
DISCUSSION...AN UPPER LEVEL SHORTWAVE IS MOVING INTO THE AREA
TONIGHT THEN WILL SHIFT EASTWARD ON WEDNESDAY. THIS DISTURBANCE
WILL RESULT IN SOME SHOWERS DEVELOPING OVER THE PARTS OF THE AREA.
RADAR IMAGERY SHOWS SOME LIGHT SHOWERS EAST OF THE CASCADES THIS
EVENING, MAINLY ACROSS SOUTHERN LAKE COUNTY. MODELS CONTINUE TO
SUPPORT SHOWERS DEVELOPING OVER PORTIONS OF THE AREA FROM THE
SOUTHERN OREGON CASCADES EAST AND INTO SOUTHERN/EASTERN SISKIYOU
AND MODOC COUNTIES TONIGHT AND WEDNESDAY. WEAK INSTABILITY IS
EXPECTED IN THE AFTERNOON ON WEDNESDAY WITH LOW CHANCES (10-20%)
FOR THUNDERSTORMS TO DEVELOP, MAINLY IN SOUTHEAST SISKIYOU AND
MODOC COUNTIES. THE SHORTWAVE WILL GRADUALLY SHIFT EASTWARD,
EXITING THE AREA WEDNESDAY EVENING.
MEANWHILE, WEST OF THE CASCADES, WEAK RIDGING WILL BUILD INTO THE
AREA WEDNESDAY AS THE UPPER LEVEL DISTURBANCE GRADUALLY MOVES
EAST, RESULTING IN DRY WEATHER. AFTER SOME COOL MORNING
TEMPERATURES, EXPECT WARM AFTERNOON CONDITIONS WITH HIGHS NEAR OR
SLIGHTLY WARMER THAN TODAY.
THEN, AN UPPER LOW THEN APPROACHES THE AREA THURSDAY. AHEAD OF
THIS LOW EXPECT SOME WEAK INSTABILITY AND MID LEVEL MOISTURE UNDER
SOUTHWEST FLOW ALOFT. THIS WILL BRING SOME CHANCES (15-20%) FOR
SHOWERS INTO WESTERN SISKIYOU COUNTY ON THURSDAY MORNING, WITH
CHANCES FOR SHOWERS INCREASING AND EXPANDING ACROSS SISKIYOU
COUNTY AND NORTHWARD INTO SOUTHWEST OREGON (MAINLY FROM THE
SOUTHERN OREGON CASCADES WEST) ON THURSDAY AFTERNOON, THEN ACROSS
MUCH OF THE AREA THURSDAY EVENING. ADDITIONALLY, THE NATIONAL
BLEND OF MODELS SUPPORTS A SLIGHT CHANCE (10-20%) FOR
THUNDERSTORMS DEVELOPING ALONG WITH SHOWERS THURSDAY AFTERNOON
AND EVENING IN SISKIYOU COUNTY AND INTO THE SISKIYOU MOUNTAINS
AND SOUTHERNMOST PORTIONS OF THE SOUTHERN OREGON CASCADES. AREAS
FARTHER NORTH, INCLUDING CENTRAL/NORTHERN JACKSON, JOSEPHINE, AND
EASTERN DOUGLAS COUNTIES HAVE A 10% CHANCE FOR THUNDERSTORMS ON
THURSDAY AFTERNOON/EVENING. HAVE UPDATED THE FORECAST TO REFLECT
THE SLIGHT CHANCES FOR THUNDERSTORMS ON THURSDAY.
MARINE...UPDATED 815 PM TUESDAY, APRIL 22ND...MODERATE TO STRONG
NORTH WINDS WILL GRADUALLY DIMINISH TONIGHT, BUT SEAS WILL STILL
REMAIN ELEVATED ENOUGH FOR SMALL CRAFT CONDITIONS TO CONTINUE WITH
HAZARDOUS SEAS WARNING CONDITIONS SOUTH OF PORT ORFORD INTO
WEDNESDAY EVENING.
CALMER CONDITIONS ARE LIKELY THURSDAY AND FRIDAY. WEAK LOW PRESSURE
WILL MOVE INTO THE WATERS FRIDAY BRINGING SCATTERED SHOWERS. SEAS
ARE EXPECTED TO REMAIN ON THE LOW SIDE WITH NO MARINE HAZARDS ON
FRIDAY. -SPILDE/HERMANSEN
PREV DISCUSSION... /ISSUED 254 PM PDT TUE APR 22 2025/
DISCUSSION...NORTHWEST FLOW ALOFT CONTINUES TO SUPPORT SEASONABLE
TEMPERATURES AND UNEVENTFUL CONDITIONS ACROSS NORTHERN CALIFORNIA
AND SOUTHERN OREGON THIS AFTERNOON. A WEAK UPPER TROUGH WILL PASS
OVER THE AREA THIS EVENING AND THROUGH THE DAY WEDNESDAY. WINDS MAY
BE A LITTLE BREEZIER THAN NORMAL THIS EVENING, BUT NOTHING REMOTELY
HAZARDOUS IS EXPECTED. THERE WILL BE SOME MODERATE SHOWER CHANCES
(20-40%) ACROSS MODOC, EASTERN SISKIYOU, AND SOUTHERN LAKE COUNTIES
THROUGH THE DAY WEDNESDAY. ANY SHOWERS THAT DO FORM WILL BE ISOLATED
OR SCATTERED. RAINFALL WILL BE MEASURED IN THE HUNDRETHS OF AN INCH,
IF IT EVEN REACHES THE GROUND. INSTABILITY WILL BE WEAK, WITH
PERIODS OF 200-300 J/KG AT MOST ON WEDNESDAY EVENING. LIGHTNING IS
NOT WIDELY EXPECTED, BUT A STRAY STRIKE OR TWO IS NOT IMPOSSIBLE.
CONDITIONS CALM THROUGH THE DAY THURSDAY AS THE PATTERN CHANGES WITH
AN APPROACHING UPPER LEVEL LOW PRESSURE SYSTEM. SOUTHERLY FLOW ALOFT
ALONG THE LEADING EDGE OF THE SYSTEM WILL ALLOW FOR INITIAL SLIGHT
PRECIPITATION CHANCES (15-30%) OVER THE SISKIYOU RANGES AND THE
CASCADES ON THURSDAY AFTERNOON. COOLER DAYTIME TEMPERATURES ARE
FORECAST FOR FRIDAY AND CONTINUE THROUGH THE WEEKEND. WITH THE LOW
EXPECTED TO PASS TO THE SOUTH, GUSTY WINDS ARE NOT A CONCERN THROUGH
THE WEEKEND.
WIDESPREAD PRECIPITATION CHANCES (40-80%) ARE FORECAST FOR FRIDAY AS
THE LOW PASSES TO THE SOUTH. SOUTHERLY FLOW ALOFT ON FRIDAY WILL
BRING MORE SHOWERS TO AREAS WEST OF AND ALONG THE CASCADES AS WELL
AS NORTHERN KLAMATH AND LAKE COUNTIES. HIGHER TERRAIN COULD SEE
BETWEEN 0.5 TO 1.0 INCHES OF RAINFALL, WITH 0.3 INCHES OR LESS OF
RAINFALL FOR LOWER ELEVATION AREAS. SNOW LEVELS OF 5000 FEET WEST OF
THE CASCADES WILL ALLOW FOR 2-4 INCHES OF SNOWFALL OVER SOUTHWESTERN
SISKIYOU COUNTY PEAKS AND RIDGELINES. SNOW LEVELS OF 5500-6500 FEET
ALONG AND EAST OF THE CASCADES WILL KEEP UNREMARKABLE SNOWFALL TO
THE HIGHEST TERRAIN. RAINFALL OVER MODOC AND SOUTHERN LAKE AND
KLAMATH COUNTIES WILL GENERALLY BE 0.1 INCHES OR LESS.
40-80% PRECIPITATION CHANCES CONTINUE ACROSS THE AREA ON SATURDAY,
BUT FLOW ALOFT WILL BE MORE EASTERLY AS THE LOW PASSES OVER
CALIFORNIA. THIS WILL BRING HIGHER PRECIPITATION AMOUNTS TO LAKE AND
MODOC COUNTIES. AMOUNTS ARE STILL UNIMPACTFUL, WITH ONE-FOURTH OF AN
INCH OR LESS OF RAINFALL FORECAST FOR EAST SIDE BASINS. SNOW LEVELS
ALONG AND EAST OF THE CASCADES WILL DROP SLIGHTLY TO 5000-6000 FEET,
ALLOWING FOR 4-8 INCHES OF SNOWFALL OVER WARNER MOUNTAIN PEAKS
THROUGH THE DAY. BLY MOUNTAIN AND THE CASCADES MAY SEE 2-4 INCHES OF
SNOWFALL AT THE HIGHEST ELEVATIONS. THESE AMOUNTS ARE NOT NEAR
PRODUCT THRESHOLDS, BUT EXTRA CAUTION TRAVELING THROUGH THESE AREAS
ON SATURDAY WOULD NOT HURT. RAINFALL OVER WEST SIDE VALLEYS WILL
GENERALLY BE 0.1 INCHES OR LESS.
ACTIVITY STARTS TO DECREASE LATE SATURDAY NIGHT, WITH ANY SUNDAY
SHOWERS LIMITED TO THE CASCADES AND EASTERNMOST LAKE AND MODOC
COUNTIES. HIGH PRESSURE OVER THE PACIFIC OCEAN WILL BRING GENERALLY
DRIER CONDITIONS AND SEASONAL TEMPERATURES THROUGH NEXT WEEK.
METEOGRAM GUIDANCE FOR BOTH THE ECMWF AND GFS SHOW OCCASIONAL WEAK
AND BRIEF PRECIPITATION SIGNALS, AS WELL AS WIDE RANGES IN DAYTIME
HIGHS ACROSS ENSEMBLE MEMBERS. HOW THE HIGH DEVELOPS WILL BE
IMPORTANT FOR RESULTING CONDITIONS NEXT WEEK, BUT IMPACTFUL OR
HAZARDOUS CONDITIONS CURRENTLY LOOK UNLIKELY IN THE LONG-TERM.
-TAD
MFR WATCHES/WARNINGS/ADVISORIES
OR...CA...NONE.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 11 AM PDT
THURSDAY FOR PZZ350-356-370-376.
HAZARDOUS SEAS WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ350-
356-370-376.
GALE WARNING UNTIL 11 PM PDT THIS EVENING FOR PZZ356-376.
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