675
FXUS66 KMFR 222135
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
235 PM PDT TUE OCT 22 2024
SHORT TERM...TUESDAY NIGHT THROUGH THURSDAY NIGHT
ZONAL UPPER
LEVEL FLOW IS CONTINUING TO SUPPORT SEASONAL TEMPERATURES ACROSS THE
AREA, WITH HIGH CLOUDS ALSO CONTRIBUTING TO COOLER CONDITIONS.
NIGHTTIME LOWS WILL BE VERY SIMILAR TO MONDAY'S ACROSS THE AREA.
A WEAK COLD FRONT WILL MOVE OVER THE AREA QUICKLY ON WEDNESDAY.
DAYTIME TEMPERATURES WILL FALL 5 DEGREES OR LESS ACROSS THE AREA.
COASTAL CITIES WILL STAY IN THE MID 60S AND INLAND VALLEYS WILL FALL
TO THE HIGH 50S. AREAS EAST OF THE CASCADES WILL BE IN THE LOW TO
MID 50S.
PRECIPITABLE WATER VALUES FOR THIS FRONT ARE AT 0.5 INCHES OR LESS,
WHICH WILL RESULT IN VERY LITTLE RAINFALL FOR THE AREA. CHANCES ARE
VERY LOW (10-30%) WEST OF THE CASCADES, AND SLIGHTLY BETTER (50-70%)
TO THE EAST. THE CASCADES AND PARTS OF LAKE COUNTY MAY SEE UP TO
0.25 INCHES, WITH MOST EAST SIDE AREAS GETTING 0.1 INCHES OR LESS.
COLD AIR BEHIND THE FRONT WILL BRING LOWER TEMPERATURES ON WEDNESDAY
NIGHT INTO THURSDAY MORNING. EAST SIDE AREAS WILL BE SAFELY BELOW
FREEZING, WITH NORTHERN LAKE AND KLAMATH COUNTIES FALLING INTO THE
LOW TEENS. THE UMPQUA VALLEY LOOKS TO STAY IN THE HIGH 30S, WHILE
COLDER TEMPERATURES ARE EXPECTED IN OTHER VALLEYS. IN OREGON, A
FREEZE WATCH IS IN PLACE FOR THE ILLINOIS, APPLEGATE, AND ROGUE
VALLEYS FROM 2 AM TO 9 AM ON THURSDAY MORNING. IN CALIFORNIA, A
FREEZE WATCH IS IN PLACE FOR THE LOWER KLAMATH RIVER, SCOTT, AND
SHASTA VALLEYS AS WELL AS THE MOUNT SHASTA REGION. EXPECTED
TEMPERATURES ARE BORDERLINE FOR A FULL FREEZE WARNING SO AN
ADDITIONAL DAY OF INFORMATION WILL GUIDE AN OFFICIAL ISSUANCE ON
WEDNESDAY MORNING.
AN UPPER LEVEL RIDGE WILL BUILD DURING THE DAY THURSDAY, BRINGING
WARMER TEMPERATURES THAT WILL CONTINUE INTO THE LONG-TERM FORECAST.
A DEVELOPING THERMAL TROUGH MAY BRING FURTHER WARMING IN
SOUTHWESTERN PARTS OF THE COVERAGE AREA, INCLUDING COASTAL AREAS
SOUTH OF GOLD BEACH, AGNESS, AND THE ILLINOIS VALLEY. A PERIOD OF
HIGH CLOUDS WILL BE POSSIBLE AS THE RIDGE DEVELOPS. NIGHTTIME
TEMPERATURES HAVE MODERATE (40-60%) OF FROST-CONDUCIVE CONDITIONS IN
MOST WEST SIDE VALLEYS ON THURSDAY NIGHT INTO FRIDAY MORNING, WITH
THE UMPQUA AND ROGUE VALLEYS EXPECTED TO BE WARMER THAN THOSE
THRESHOLDS. -TAD
LONG TERM...FRIDAY THROUGH TUESDAY, OCT 25-29, 2024
THE CHANGES IN THE EXTENDED FORECAST MOSTLY HAVE TO DO WITH THE
TIMING OF THE ACTIVE WEATHER PATTERN EXPECTED TO ARRIVE THIS WEEKEND
AND LAST INTO AT LEAST THE EARLY PART OF NEXT WEEK.
AFTER THE COLD MORNING FRIDAY, A THERMAL TROUGH WILL SHIFT INLAND
AND THE UPPER RIDGE AXIS WILL MOVE EAST OF THE CASCADES. MEANWHILE,
A VERY STRONG LOW/UPPER TROUGH WILL DIG INTO THE GULF OF ALASKA AND
THIS WILL ALLOW A FAIRLY VIGOROUS LOW OFFSHORE TO MOVE NORTHEAST
TOWARD VANCOUVER ISLAND WITH A WARM FRONT LIFTING NORTHWARD
OFFSHORE. WHILE SOME HIGH AND MID LEVEL CLOUDS WILL LIKELY INCREASE
ACROSS SW OREGON/NORTHERN CALIFORNIA IN ADVANCE OF THIS SYSTEM, IT
WILL ALSO PROBABLY BE THE WARMEST DAY OF THE PERIOD AS MID-LEVEL
TEMPS CONTINUE TO WARM. GUIDANCE CONTINUES TO SHOW WIDESPREAD HIGH
TEMPERATURES IN THE LOW TO MID 70S FOR THE VALLEYS WEST OF THE
CASCADES AND HIGHS LARGELY IN THE MID TO UPPER 60S OVER THE EAST
SIDE. RAINFALL, THOUGH, WILL MOSTLY REMAIN OFFSHORE.
THE FLOW ALOFT BECOMES LARGELY SOUTHWESTERLY AS THE LOW MOVES INTO
SW BRITISH COLUMBIA FRIDAY NIGHT AND THE COLD FRONT HANGS UP
OFFSHORE. RAIN CHANCES DON'T REALLY INCREASE UNTIL FRIDAY EVENING
ALONG THE COAST AND WEST OF THE CASCADES WITH THE HIGHEST POPS (20-
60%) FROM GRANTS PASS/ROSEBURG WESTWARD (HIGHEST ALONG THE COAST).
WITH THE INCREASE IN CLOUD COVER, FRIDAY NIGHT WON'T BE AS COLD AS
PREVIOUS NIGHTS, THOUGH IT WILL REMAIN DRY AND CHILLY FOR AREAS EAST
OF THE CASCADES. GRADIENTS AREN'T QUITE AS STRONG AS INDICATED
YESTERDAY (LIKELY DUE TO THE SLOWING OF THE INCOMING COLD FRONT), SO
JUST SOME LOCALLY BREEZY CONDITIONS FOR THE USUAL AREAS LIKE THE
SHASTA VALLEY AND OVER THE EAST SIDE. SNOW LEVELS WILL REMAIN QUITE
HIGH -- UP AROUND 8000 FEET.
SINCE THE FRONT ALONG THE COAST IS EXPECTED TO SLOW DOWN, THERE
WON'T BE MUCH ADVANCEMENT OF PRECIPITATION INLAND SATURDAY. LATEST
GUIDANCE IS SHOWING MOST, IF NOT ALL, PRECIPITATION REMAINING FROM
THE CASCADES WEST THROUGH MUCH OF SATURDAY. AND, POPS EAST OF
HIGHWAY 97 REMAIN MOSTLY BELOW 20%. AS SUCH, SATURDAY MAY ACTUALLY
BE THE WARMER DAY OVER THERE. LACK OF FORCING (OTHER THAN MOIST
ONSHORE FLOW) WILL KEEP PRECIP FROM GETTING TOO HEAVY ALONG THE
COAST, BUT WE DO EXPECT A HIGH PROBABILITY (>80%) OF RAINFALL.
AMOUNTS ARE LIKELY GOING TO BE HIGHEST IN THE COAST RANGES WHERE
OROGRAPHIC ENHANCEMENT IS MAXIMIZED. THE FRONT WILL WAIT FOR THE
KICKER TROUGH (THE UPPER TROUGH/LOW OVER THE GULF OF AK) TO GET ITS
PUSH ONSHORE. THIS APPEARS TO OCCUR SATURDAY NIGHT INTO SUNDAY WHEN
NEARLY ALL OF THE FORECAST AREA IS LIKELY (>60% CHANCE) TO SEE AT
LEAST SOME RAINFALL. DURING THIS TIME PERIOD, SNOW LEVELS FALL TO
AROUND 6000 FEET, SO WE MAY BEGIN TO SEE SOME SNOW MIX IN WITH THE
RAIN UP AT CRATER LAKE.
THE ACTIVE WEATHER PATTERN LIKELY CONTINUES SUNDAY NIGHT INTO MONDAY
AS THE UPPER TROUGH FROM THE GULF OF ALASKA SHIFTS INTO THE PACNW.
AN UPPER LEVEL DISTURBANCE WITHIN THE TROUGH WILL MOVE THROUGH
BRINGING A HIGH PROBABILITY OF PRECIPITATION AREA WIDE (60-90%
CHANCE), BUT WITH THE BEST CHANCE FOR MEANINGFUL (WETTING)
PRECIPITATION FROM THE CASCADES WEST. SNOW LEVELS CONTINUE TO
DROP, PERHAPS AS LOW AS 4500 FEET BY MONDAY MORNING. THIS WILL
PROVIDE A GOOD CHANCE FOR AT LEAST SOME ACCUMULATING SNOW IN THE
MOUNTAINS. RIGHT NOW, MODELS ARE SHOWING ABOUT 4-8" IN THE
CASCADES NORTH OF HIGHWAY 140. PRECIP AMOUNTS NEARING AN INCH
WOULD SUPPORT HIGHER ACCUMULATIONS, BUT WITH TIME OF YEAR AND WARM
GROUND PLAYING A ROLE, WE THINK THIS IS A GOOD ESTIMATE FOR THE
TIME BEING. WE DON'T THINK THIS WILL HAVE A HUGE IMPACT ON THE
HIGHER PASSES (LAKE OF THE WOODS/SISKIYOU SUMMIT), BUT THERE COULD
BE SOME SLIPPERY ROADS, ESPECIALLY ON 140 (WHERE IT'S A LITTLE
HIGHER ELEVATION) IN TIME FOR THE MORNING RUSH MONDAY. TOTAL
PRECIP AMOUNTS ARE SHOWN TO BE 1-3" ALONG THE COAST SAT-MON,
HIGHEST IN THE COAST RANGES. LOWER AMOUNTS HERE IN MEDFORD,
GENERALLY 0.25-0.50 OF AN INCH AND MOSTLY 0.10-0.25 OF AN INCH
SOUTH AND EAST OF THE MOUNTAINS.
BY TUESDAY, MODELS ARE SHOWING THE UPPER TROUGH AXIS SHIFTING EAST
OF THE AREA, BUT THE POTENTIAL FOR SHOWERS LINGERING (AT LEAST
BRIEFLY) BEHIND IT. OVERALL, WE'RE LOOKING AT HIGH TEMPERATURES
DURING THIS ACTIVE PERIOD RUNNING ABOUT 5-15F BELOW NORMAL. CLOUD
COVER AT NIGHT WILL KEEP LOW TEMPS CLOSER TO NORMAL VALUES. -SPILDE
AVIATION...22/18Z TAFS
VFR CONDITIONS UNDER A STEADY STREAM OF
CIRRUS CLOUDS WILL PREVAIL THROUGH THE TAF PERIOD FOR MUCH OF THE
AREA. THE EXCEPTION BEING IN THE UMPQUA BASIN WHERE LIFR STRATUS
LINGERS THIS MORNING. THE LOWER DECK SHOULD CLEAR AROUND 19-21Z,
WITH VFR THEN PREVAILING INTO THE OVERNIGHT HOURS. THE CIRRUS SHEILD
SHOULD LIMIT THE DEVELOPMENT OF LOW CLOUDS IN WEST SIDE VALLEYS
TONIGHT, BUT AMPLE MOISTURE IN THE UMPQUA BASIN WILL LIKELY LEAD TO
ANOTHER ROUND OF LIFR CONDITIONS LATE TONIGHT INTO EARLY WEDNESDAY
MORNING. ASIDE FROM SOME BREEZY NORTH WINDS ALONG THE COAST THIS
AFTERNOON, WINDS WILL GENERALLY REMAIN LIGHT THROUGH THE TAF PERIOD
FOR INLAND AREAS. A FRONT WILL AFFECT THE REGION TOWARDS THE END OF
THE TAF PERIOD (WEDNESDAY AFTERNOON/EVENING), BRINGING LOWERING
CLOUDS, TERRAIN OBSCURATIONS AND PRECIPITATION TO AREAS EAST OF THE
I-5 CORRIDOR. /BR-Y
MARINE...UPDATED 100 PM PDT TUESDAY, OCTOBER 22, 2024
A WEAK
THERMAL TROUGH PATTERN WILL MAINTAIN LOW END ADVISORY STRENGTH NORTH
WINDS THROUGH THURSDAY. THIS WILL BRING THE RETURN OF STEEP WIND
DRIVEN SEAS SOUTH OF CAPE BLANCO BY THIS AFTERNOON THAT WILL PERSIST
THROUGH AT LEAST WEDNESDAY NIGHT, LIKELY INTO THURSDAY AS WELL.
THERE COULD BE A BRIEF PERIOD OF IMPROVED CONDITIONS EARLY WEDNESDAY
A WEAK FRONT DISRUPTS THE THERMAL TROUGH PATTERN, BUT SEAS WILL
REMAIN WIND WAVE DOMINATED. STEEP SEAS ARE LIKELY TO PERSIST SOUTH
OF CAPE BLANCO THROUGH THURSDAY BEFORE A PATTERN CHANGE THAT IS
EXPECTED FRIDAY THROUGH THE WEEKEND. A LOW MOVING NORTH TOWARDS THE
GULF OF ALASKA WILL BRING INCREASING SOUTHERLY WINDS AND BUILDING
SEAS FRIDAY INTO THE WEEKEND. STEEP TO VERY STEEP SEAS AND GALES
WILL BE POSSIBLE IN THIS ACTIVE PATTERN. /BR-Y
MFR WATCHES/WARNINGS/ADVISORIES
OR...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY MORNING
FOR ORZ024-026.
CA...FREEZE WATCH FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY MORNING
FOR CAZ080>082.
PACIFIC COASTAL WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM PDT THURSDAY
FOR PZZ356-376.
TAD/MAS/MNF
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