419
FXUS66 KMFR 232150
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
250 PM PDT WED OCT 23 2024
DISCUSSION
AN UPPER LEVEL COLD FRONT IS MOVING OVER NORTHERN
CALIFORNIA AND SOUTHERN OREGON THIS AFTERNOON. SHOWERS HAVE BEEN
OBSERVED AT ISOLATED LOCATIONS AND ACTIVITY WILL CONTINUE MOVING
EASTWARD AND OUT OF THE AREA THROUGH THE EVENING.
A FREEZE WARNING IS IN PLACE FOR THURSDAY MORNING FROM 2 AM THROUGH
10 AM AS COLD AIR BEHIND THE FRONT MOVES INTO AREA VALLEYS. IN
OREGON, THE WARNING COVERS THE ILLINOIS, APPLEGATE, AND ROGUE
VALLEYS AS WELL AS SOUTHERN DOUGLAS COUNTY INCLUDING THE CITIES OF
AZALEA AND GLENDALE. IN CALIFORNIA, THE WARNING COVERS THE LOWER
KLAMATH RIVER, SCOTT, AND SHASTA VALLEYS AS WELL AS THE MOUNT SHASTA
REGION. THESE AREAS HAVE HIGH CHANCES (50-90+%) TO EXPERIENCE
PERIODS OF FREEZING CONDITIONS DURING THE WARNING DURATION.
AN UPPER LEVEL RIDGE WILL START TO DEVELOP DURING THE DAY ON
THURSDAY, BRINGING A WARMING TREND THAT WILL CONTINUE INTO SATURDAY.
A THERMAL TROUGH WILL HELP PARTS OF SOUTHWEST OREGON (INCLUDING
BROOKINGS, GOLD BEACH, AND AGNESS) TO GET A HEAD START ON WARMING ON
THURSDAY. FRIDAY MORNING LOWS HAVE 40-80% CHANCES TO REMAIN NEAR
FROST CONDITIONS (33 TO 36 DEGREES) IN MOST AREAS AFFECTED BY THE
THURSDAY MORNING WARNING, WITH CITIES IN THE SOUTHERN ROGUE VALLEY
(ASHLAND, PHOENIX, TALENT) UNLIKELY TO SEE FROST CONDITIONS IN THIS
PERIOD.
MORE ACTIVE WEATHER WILL BEGIN ON FRIDAY EVENING INTO SATURDAY
MORNING, WHEN A LOW PRESSURE SYSTEM WILL MOVE DOWN FROM THE GULF OF
ALASKA AND LINGER OFF THE CANADIAN COAST. A WARM FRONT FROM THIS
SYSTEM WILL BRUSH ALONG THE OREGON COAST STARTING FRIDAY EVENING.
THIS FRONT WILL BRING A 60-95% CHANCE OF SHOWERS ALONG COASTAL AREAS
AND A 40-80% CHANCE OVER INLAND AREAS THROUGH THE DAY SATURDAY. WITH
THESE CONSTANT CHANCES FOR LIGHT SHOWERS, CURRY COUNTY AND COASTAL
COOS COUNTY ARE FORECAST TO GET BETWEEN 0.5 AND 1.0 INCHES OF
RAINFALL ON SATURDAY. OTHER INLAND AREAS WEST OF THE CASCADES WILL
SEE 0.2 INCHES OR LESS IN THIS PERIOD.
ON SUNDAY MORNING, A COLD FRONT FROM THE LOW PRESSURE SYSTEM WILL
START TO MOVE OVER THE AREA, BRINGING A WAVE OF ACTIVITY ACROSS THE
AREA. 70-95% CHANCES OF PRECIPITATION WILL MOVE EASTWARD THROUGH THE
DAY SUNDAY. CURRY COUNTY WILL SEE HEAVY RAINFALL LATE SATURDAY NIGHT
INTO EARLY SUNDAY MORNING, WITH ANOTHER 0.5 TO 1.0 INCHES EXPECTED
IN THIS SHORT PERIOD. A COLD UPPER TROUGH IS EXPECTED TO DEEPEN AND
MOVE OVER THE AREA BEHIND THE FRONT, SUPPORTING SCATTERED POST-
FRONTAL SHOWERS THROUGH MONDAY AND TUESDAY. OVERALL, COOS AND CURRY
COUNTIES AND THE CASCADES WILL GET BETWEEN 1 AND 2 INCHES OF
PRECIPITATION FROM SUNDAY TO TUESDAY. THE UMPQUA VALLEY IS FORECAST
TO GET ABOUT AN INCH OF RAINFALL AND THE ILLINOIS AND ROGUE VALLEYS
WILL GET BETWEEN 0.5 AND 0.75 INCHES OF RAINFALL IN THIS PERIOD.
OTHER AREAS WILL GET HALF AN INCH OR LESS OF RAINFALL INTO NEXT
WEEK.
SNOWFALL OVER THE CASCADES IS POSSIBLE BEHIND THE COLD FRONT, BUT
THE TIMING IS COMPLICATED. THE HEAVIEST PRECIPITATION OVER THE
CASCADES IS LATER IN THE MORNING ON SUNDAY, BUT SNOW LEVELS ARE
FORECAST TO BE ABOVE 7000 FEET AT THIS POINT. SNOW LEVELS ARE
EXPECTED DROP TO 5000-6000 FEET BY MONDAY MORNING AND 4000 FEET BY
TUESDAY MORNING. ECMWF AND GFS MODEL GUIDANCE SUGGESTS BETWEEN 3 TO
6 INCHES OF SNOW OVER THE CASCADES EARLY NEXT WEEK, WHILE THE NBM
EXPECTS 5 TO 10 INCHES ALONG THE RANGE AND 12 INCHES AT HIGHER
ELEVATIONS. THIS FAR OUT, THERE'S MANY VARIABLES THAT COULD IMPACT
TOTAL SNOWFALL THAT ARE DIFFICULT TO ACCURATELY FORECAST.
ADDITIONALLY, LINGERING SURFACE WARMTH AND RAIN/SNOW MIXES WOULD
LIKELY MINIMIZE WIDESPREAD ACCUMULATION. AT THE VERY LEAST,
WIDESPREAD WINTER WEATHER HAZARDS ARE NOT EXPECTED BUT SOME PRODUCTS
ARE NOT IMPOSSIBLE.
BEYOND TUESDAY, ACTIVITY IS EXPECTED TO DECREASE. BOTH GFS AND ECMWF
PRECIPITATION METEOGRAMS SUGGEST AN UNIMPACTFUL FRONT MOVING OVER
THE AREA LATE NEXT WEEK, THEN SPORADIC SIGNALS BEYOND THAT.
TEMPERATURE METEOGRAMS KEEP TEMPERATURES COOL THROUGH THE FIRST
COUPLE WEEKS OF NOVEMBER. -TAD
AVIATION...23/18Z TAFS
A FRONT FORMING OVER THE REGION LATE
THIS MORNING CONTINUES TO BRING WIDESPREAD CLOUD COVER, THOUGH
MOSTLY VFR AS OF THIS WRITING (1030 AM PDT). HOWEVER, LOWER CEILINGS
(MVFR) PERSIST IN THE UMPQUA/ROGUE VALLEYS ALONG WITH AREAS OF
HIGHER MOUNTAIN OBSCURATION.
THE FRONT WILL SLOWLY SHIFT EASTWARD THIS AFTERNOON, PUSHING EAST OF
THE CASCADES AFTER 22Z AND CLEARING EASTERN LAKE COUNTY BY AS LATE
AS 02Z. SOME LIGHT RAIN AND HIGHER ELEVATION SNOW WILL ACCOMPANY THE
FRONT AS IT MOVES THROUGH, PERHAPS BRIEFLY LOWERING CEILINGS TO MVFR
IN SOME AREAS THAT ARE VFR CURRENTLY.
CEILINGS IMPROVE RAPIDLY AFTER THE FRONT MOVES THROUGH LATE THIS
AFTERNOON/EVENING AS MUCH DRIER AIR MOVES IN ALOFT. WINDS WILL
GENERALLY REMAIN LIGHT FOR INLAND PORTIONS OF THE WEST SIDE INTO
THURSDAY MORNING, BUT WEST TO NORTHWEST WINDS WILL BE BREEZY THIS
AFTERNOON ON THE EASTSIDE, INCLUDING KLAMATH FALLS.
TONIGHT INTO THURSDAY MORNING, VALLEY MVFR/IFR IS EXPECTED EARLY
THURSDAY MORNING, PARTICULARLY IN THE UMPQUA VALLEY, BUT MOST
EVERYWHERE ELSE WILL BE VFR. -SPILDE
MARINE...UPDATED 200 PM PDT WEDNESDAY, OCTOBER 23, 2024
A
THERMAL TROUGH NEAR THE COAST WILL BRING MODERATE NORTH WINDS AND
ELEVATED SEAS OVER THE MARINE WATERS TONIGHT THROUGH LATE THURSDAY
EVENING. THE WORST CONDITIONS WILL BE BEYOND 10 NM FROM SHORE AND
SOUTH OF CAPE BLANCO. A BRIEF PERIOD OF IMPROVED CONDITIONS IS
EXPECTED EARLY FRIDAY BEFORE A PATTERN CHANGE THAT IS EXPECTED LATE
FRIDAY THROUGH THE WEEKEND. LOW PRESSURE MOVING NORTH TOWARD
VANCOUVER ISLAND WILL BRING INCREASING SOUTHERLY WINDS AND BUILDING
SEAS LATE FRIDAY AFTERNOON AND FRIDAY NIGHT, WITH GALES AND VERY
STEEP, HAZARDOUS SEAS POSSIBLE. STEEP SOUTHWEST SWELL IS THEN LIKELY
TO CONTINUE BEHIND THE LOW SATURDAY WITH ACTIVE WEATHER PERSISTING
INTO EARLY NEXT WEEK. -SPILDE
MFR WATCHES/WARNINGS/ADVISORIES
OR...FREEZE WARNING FROM 2 AM TO 10 AM PDT THURSDAY FOR ORZ023-024-
026.
CA...FREEZE WARNING FROM 2 AM TO 10 AM PDT THURSDAY FOR CAZ080>082.
PACIFIC COASTAL WATERS...GALE WATCH FROM FRIDAY AFTERNOON THROUGH
LATE FRIDAY NIGHT FOR PZZ370-376.
SMALL CRAFT ADVISORY UNTIL 2 AM PDT FRIDAY FOR PZZ376.
TAD/MAS
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