119
FXUS66 KMFR 210405
AFDMFR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE MEDFORD OR
805 PM PST WED NOV 20 2024
DISCUSSION
SNOW LEVELS ARE SLOW TO RISE IN SOME PLACES THIS
EVENING, PARTICULARLY WESTERN SISKIYOU COUNTY, AROUND MT SHASTA,
AND UP AROUND SISKIYOU SUMMIT. THIS IS DUE TO ANOTHER WAVE OF
MODERATE TO HEAVY PRECIPITATION THAT HAS MOVED NORTHEASTWARD ALONG
THE STALLED FRONT/AR. PRECIP INTENSITY HAS BEEN PERSISTENT ENOUGH
TO OVERCOME MODEST WARMING ALOFT AND IS RESULTING IN A WET-BULB
DOWN TO 32F AND AN ISOTHERMAL LAYER KEEPING SNOW AS THE MAIN
P-TYPE. BUT, THIS IS CHANGING PER LATEST WEB CAMS DOWN ALONG I-5
FROM WEED SOUTH TO DUNSMUIR, WHERE IT APPEARS RAIN IS MIXING IN
BELOW 4000 FEET. INDEED, A RECENT SPECIAL OBSERVATION FROM KMHS
AIRPORT IS SHOWING MODERATE RAIN NOW AND A TEMPS OF 35F. SNOWMAN
SUMMIT ON HIGHWAY 89 IS STILL VERY SNOWY AT THIS TIME. WINTER
STORM WARNINGS REMAIN IN EFFECT FOR THESE AREAS UNTIL 10 PM PST,
BUT AS THE AIR ALOFT CONTINUES TO WARM SLIGHTLY OVERNIGHT, SNOW
IMPACTS WILL BE MOSTLY ABOVE 4500 FEET. WE ISSUED A WINTER WEATHER
ADVISORY FOR SNOW DURING THE OVERNIGHT PERIOD FOR THE
CASCADES/SISKIYOUS AND ALSO PORTIONS OF ZONE 30 (NORTH OF
CHILOQUIN), WHERE SEVERAL INCHES COULD STILL ACCUMULATE BEFORE
SNOW LEVELS RISE ABOVE 5000 FEET DURING THURSDAY.
THE STRONG WINDS EXPERIENCED ACROSS A LARGE PORTION OF THE AREA
YESTERDAY, LAST NIGHT AND EVEN INTO TODAY IN SOME AREAS HAVE
EASED A BIT. HOWEVER, GUSTY WINDS ARE EXPECTED TO CONTINUE IN
PORTIONS OF THE SCOTT AND SHASTA VALLEYS AS WELL AS OVER THE EAST
SIDE TONIGHT THROUGH FRIDAY MORNING. THE HIGH WIND WARNINGS WERE
SET TO EXPIRE AT 7 PM PST EARLIER THIS EVENING, BUT WE DECIDED TO
EXTEND THEM SINCE MANY OF THESE AREAS WILL STILL HAVE ADVISORY
LEVEL WINDS TONIGHT INTO THURSDAY. WITH LOW PRESSURE EXPECTED TO
DEVELOP OFFSHORE AND INTENSIFY RAPIDLY AS IT MOVES NORTHWARD, THE
GRADIENT WILL TIGHTEN AND WE EXPECT POTENTIAL 60 MPH WIND GUSTS
AGAIN THURSDAY EVENING/NIGHT INTO FRIDAY MORNING. A HIGH WIND
WATCH REMAINS IN EFFECT ALONG THE COAST FOR A SIMILAR TIME PERIOD.
ADDITIONAL WIND ADVISORIES ARE LIKELY, ESPECIALLY FOR THE ROGUE
VALLEY, WHERE SOME GUSTS TO 45-50 MPH ARE POSSIBLE AGAIN.
WINTER IMPACTS WILL BE MUCH LESS TOMORROW SINCE SNOW LEVELS WILL
BE HIGH. THE ONLY SNOW WILL BE AT THE HIGHEST PEAKS, BUT RAIN
WILL CONTINUE TO DELUGE PORTIONS OF NORCAL AND SW OREGON. WE HAVE
AN AREAL FLOOD WARNING FOR PORTIONS OF SW OREGON AND INTO WESTERN
SISKIYOU COUNTY. WITH ANOTHER 3-5 INCHES OF RAIN LIKELY (PERHAPS
EVEN MORE IN SOME AREAS), THERE IS CONCERN FOR FLOODING IN AND
AROUND THE MT SHASTA REGION AS WELL WITH ALL THE RAIN ON TOP OF
THE SNOW THAT HAS ALREADY FALLEN. WE'LL SEE IF WE NEED TO EXPAND
THE WARNING TO INCLUDE ZONE 82.
WHILE THE WEATHER PATTERN WILL REMAIN ACTIVE, THINGS SHOULD CALM
DOWN A BIT THIS WEEKEND. -SPILDE
AVIATION...21/00Z TAFS
LEVELS CONTINUE TO VARY UNDER SHOWERY
WEATHER OVER NORTHERN CALIFORNIAN AND SOUTHERN OREGON. WHILE AREA
TERMINALS ARE GENERALLY STAYING AT VFR CEILINGS, PASSING SHOWERS
HAVE BROUGHT PERIODS OF MVFR LEVELS. WHILE SNOW LEVELS ARE AT 4500
TO 5500 ACROSS MOST OF THE AREA, SNOW SHOWERS CONTINUE AROUND THE
MOUNT SHASTA REGION. SNOW LEVELS ARE EXPECTED TO REACH 7000 TO 8000
FEET BY EARLY THURSDAY MORNING. WITH THOSE CONDITIONS, RAIN SHOWERS
ARE FORECAST TO CONTINUE ACROSS THE AREA. ADDITIONALLY, GUSTY WINDS
AND LOW LEVEL WIND SHEAR REMAIN IN THE FORECAST OVER HIGHER TERRAIN
AND ACROSS AREAS EAST OF THE CASCADES.
GUIDANCE SUGGESTS MVFR OR IFR CEILINGS ARE POSSIBLE FOR ROSEBURG AND
MEDFORD OVERNIGHT AND INTO THURSDAY MORNING. CONFIDENCE IN THESE
OUTCOMES IS SLIGHT TO MODERATE, BUT POSSIBLE TIMING HAS BEEN
INCLUDED IN THE TAF FORECAST TO ACKNOWLEDGE THE POSSIBILITY. -TAD
MARINE...UPDATED 800 PM PST WEDNESDAY, NOVEMBER 20, 2024
VERY
STEEP AND HAZARDOUS SEAS CONTINUE IN THE WAKE OF AN IMPACTFUL
SYSTEM, WITH THE HIGHEST SEAS GENERALLY IN WATERS BEYOND 10 NM
FROM SHORE AND NORTH OF GOLD BEACH. SEAS WILL IMPROVE STEADILY
TONIGHT AND THROUGH THE DAY FRIDAY, WITH STEEP SEAS EXPECTED
PERSISTING. A SMALL CRAFT ADVISORY IS IN PLACE FOR TONIGHT AT 10
PM THROUGH FRIDAY AT 7 PM TO HIGHLIGHT THESE CONDITIONS.
LATE THURSDAY NIGHT, A SMALL DEEPENING LOW PRESSURE SYSTEM WILL
APPROACH THE AREA AND BRING ANOTHER ROUND OF STRONG SOUTHERLY WINDS.
CURRENT GUIDANCE SUPPORTS GALE FORCE WINDS ACROSS ALL WATERS, WITH A
FEW MODELS SUGGESTING LOCALIZED AREAS OF STORM FORCE WINDS MAY BE
POSSIBLE AS MARINE WINDS GET "SQUEEZED" BETWEEN THE SYSTEM AND
COASTAL TOPOGRAPHY. A GALE WARNING WILL REMAIN IN PLACE FOR ALL
WATERS, WITH THE HOPE THAT ADDITIONAL MODEL GUIDANCE WILL IMPROVE
CONFIDENCE IN THE PATH OF THE SYSTEM AND HOW WINDS WILL BEHAVE NEAR
THE OREGON COAST.
CONDITIONS LOOK TO IMPROVE AFTER THIS SYSTEM CONTINUES NORTHWARD.
UNSETTLED SEAS MAY CONTINUE INTO SATURDAY. WHILE SHOWERY WEATHER
DOES LOOK TO CONTINUE INTO THE END OF DECEMBER, IMPACTFUL WEATHER IS
NOT IN THE FORECAST AS OF RIGHT NOW. -TAD
BEACH HAZARDS
UPDATED 800 PM PST WEDNESDAY, NOVEMBER 20,
2024...WE DOWNGRADED THE HIGH SURF WARNING TO AN ADVISORY
EARLIER. OCEAN WAVES ARE CURRENTLY 18 FEET AT 14 SECONDS AT BOTH
BUOY 15 AND 27. THIS COULD STILL BRING LARGE BREAKING WAVES OF
20-24 FEET TO THE BEACHES. THESE SHOULD TEND TO SUBSIDE OVERNIGHT
WITH AN END TIME OF 4 AM PST. -SPILDE
PREV DISCUSSION
/ISSUED 407 PM PST WED NOV 20 2024/
.UPDATED AVIATION DISCUSSION
SHORT TERM (TONIGHT THROUGH THURSDAY NIGHT)...
OVERVIEW:
LINGERING IMPACTS ARE EXPECTED THROUGH TONIGHT WITH REGARDS TO
SNOWFALL, MAINLY IN SISKIYOU COUNTY WHERE HAZARDOUS ROAD CONDITIONS
ALREADY EXIST FROM PREVIOUS 24 HOUR SNOWFALL. WE ARE ALSO EXPECTING
WIND SPEEDS TO BE STRONG THROUGH TONIGHT, AND THIS WILL LEAD TO AT
LEAST SOME VISIBILITY RESTRICTIONS WITH SNOWFALL. ADDITIONALLY, WE
WILL SEE RAINFALL IMPACTS, ESPECIALLY AREAS WITHIN THE FLOOD WATCH
WHERE SEVERAL INCHES OF RAINFALL IS EXPECTED OVER THE NEXT 24-48
HOURS. AREAS IN CURRY COUNTY AND WESTERN SISKIYOU COUNTY COULD SEE
UPWARDS OF 3-7 INCHES OF ADDITIONAL RAINFALL FROM THIS AFTERNOON
UNTIL FRIDAY NIGHT. THIS WILL BE FALLING ON ALREADY SATURATED
GROUNDS AND RECENT SNOWFALL AS WELL. THE RAINFALL ON TOP SNOWPACK
IS A LITTLE TRICKY TO FORECAST, BUT WE ARE EXPECTING AT LEAST SOME
MELT AND RUNOFF WHICH IS ALSO PART OF THE FLOOD WATCH.
FURTHER DETAILS:
UPPER LEVEL PATTERN SHOWS A VERY SIMILAR PATTERN THROUGH THE
SHORT TERM (AND REALLY BEYOND THAT) AS AN H5 CLOSED LOW WOBBLES
OFF SHORE OF THE VANCOUVER ISLAND AREA. THIS WILL LEAD TO A FRESH
SURFACE LOW DEVELOPING AND KICKING OUT THURSDAY NIGHT INTO
FRIDAY. THIS LOW WONT HAVE ENOUGH TIME TO "BOMB OUT" LIKE THE
PREVIOUS SURFACE LOW, BUT WE WILL SEE IMPRESSIVE PRESSURE FALLS ON
THE ORDER OF ABOUT 10MB OVER 6 HOURS. THIS WILL RESULT IN A
STRONG PRESSURE GRADIENT, ESPECIALLY NEAR AND ALONG COASTAL AREAS.
WE MAY NEED ANOTHER WIND HAZARD TO HIGHLIGHT THIS THREAT THURSDAY
NIGHT INTO FRIDAY MORNING WHEN THE PEAK WINDS AREA EXPECTED. THIS
WOULD ALSO INCLUDE SOME OF THE HIGHER TERRAIN ON THE EASTSIDE
(TYPICAL WINDY SPOTS).
REGARDING SNOWFALL, WE ARE EXPECTING SNOW LEVELS TO RISE OVERNIGHT
AND THROUGH THE DAY TOMORROW, SO WE HAVE THE WINTER STORM WARNING
ENDING TONIGHT AT 10PM. THAT SAID, COULD STILL HAVE SOME
LINGERING SNOWFALL THROUGH THURSDAY MORNING, BUT THIS WILL BE
MAINLY FOR AREAS ABOVE 5000 FEET.
-GUERRERO
LONG TERM (FRIDAY MORNING THROUGH WEDNESDAY)...
ANOTHER MAJOR CYCLONE WILL BE WRAPPING NORTHWARD THROUGH THE
MARINE WATERS FRIDAY MORNING. A BROAD REGION OF 50-65KT 850 MB
SOUTHERLIES WILL BE IMPACTING THE COASTAL WATERS AND BEACHES.
WE'VE ISSUED A HIGH WIND WATCH FOR THE NEAR-COAST REGION OF COOS
AND CURRY COUNTIES TO COVER UNCERTAINTIES IN THE TIMING AND
STRENGTH OF THE LOW. BEST ESTIMATES ARE IN THE BALL PARK OF 975 MB
FOR THE DEPTH OF THE SURFACE LOW JUST INSIDE 130W OFF THE OR
COAST 12-18Z FRIDAY MORNING.
AS THIS LOW MOVES NORTH, A SURGE IN WARMER LOWER ATMOSPHERIC
TEMPERATURES WILL SURGE NORTHWARD ACROSS THE WARNING AREA ALLOWING
SNOW LEVELS TO RISE CONSIDERABLY. ATMOSPHERIC RIVER CONDITIONS
ABATE BY FRIDAY AFTERNOON BUT LIKELY NOT BEFORE SOME APPRECIABLE
RAINFALL TOTALS FALL UPON RECENT SNOWS. WE'LL BE KEEPING OUR EYE
ON SOME FLOOD POTENTIAL HERE. STAY TUNED.
LOW PRESSURE WILL REMAIN OFF THE COAST SATURDAY THROUGH EARLY
NEXT WEEK ALLOWING FOR CONTINUED SHOWER ACTIVITY HOWEVER NOTHING
OF THE NATURE OF THAT WE'VE SEEN LATELY.
-STAVISH
AVIATION...21/00Z TAFS...LEVELS CONTINUE TO VARY UNDER SHOWERY
WEATHER OVER NORTHERN CALIFORNIAN AND SOUTHERN OREGON. WHILE AREA
TERMINALS ARE GENERALLY STAYING AT VFR CEILINGS, PASSING SHOWERS
HAVE BROUGHT PERIODS OF MVFR LEVELS. WHILE SNOW LEVELS ARE AT 4500
TO 5500 ACROSS MOST OF THE AREA, SNOW SHOWERS CONTINUE AROUND THE
MOUNT SHASTA REGION. SNOW LEVELS ARE EXPECTED TO REACH 7000 TO 8000
FEET BY EARLY THURSDAY MORNING. WITH THOSE CONDITIONS, RAIN SHOWERS
ARE FORECAST TO CONTINUE ACROSS THE AREA. ADDITIONALLY, GUSTY WINDS
AND LOW LEVEL WIND SHEAR REMAIN IN THE FORECAST OVER HIGHER TERRAIN
AND ACROSS AREAS EAST OF THE CASCADES.
GUIDANCE SUGGESTS MVFR OR IFR CEILINGS ARE POSSIBLE FOR ROSEBURG AND
MEDFORD OVERNIGHT AND INTO THURSDAY MORNING. CONFIDENCE IN THESE
OUTCOMES IS SLIGHT TO MODERATE, BUT POSSIBLE TIMING HAS BEEN
INCLUDED IN THE TAF FORECAST TO ACKNOWLEDGE THE POSSIBILITY. -TAD
MARINE...230 PM PST WEDNESDAY, NOVEMBER 20, 2024...VERY STEEP
AND HAZARDOUS SEAS CONTINUE IN THE WAKE OF AN IMPACTFUL SYSTEM,
WITH THE HIGHEST SEAS GENERALLY IN WATERS BEYOND 10 NM FROM SHORE
AND NORTH OF GOLD BEACH. SEAS WILL IMPROVE STEADILY TONIGHT AND
THROUGH THE DAY FRIDAY, WITH STEEP SEAS EXPECTED PERSISTING. A
SMALL CRAFT ADVISORY IS IN PLACE FOR TONIGHT AT 10 PM THROUGH
FRIDAY AT 7 PM TO HIGHLIGHT THESE CONDITIONS.
LATE THURSDAY NIGHT, A SMALL DEEPENING LOW PRESSURE SYSTEM WILL
APPROACH THE AREA AND BRING ANOTHER ROUND OF STRONG SOUTHERLY WINDS.
CURRENT GUIDANCE SUPPORTS GALE FORCE WINDS ACROSS ALL WATERS, WITH A
FEW MODELS SUGGESTING LOCALIZED AREAS OF STORM FORCE WINDS MAY BE
POSSIBLE AS MARINE WINDS GET "SQUEEZED" BETWEEN THE SYSTEM AND
COASTAL TOPOGRAPHY. A GALE WARNING WILL REMAIN IN PLACE FOR ALL
WATERS, WITH THE HOPE THAT ADDITIONAL MODEL GUIDANCE WILL IMPROVE
CONFIDENCE IN THE PATH OF THE SYSTEM AND HOW WINDS WILL BEHAVE NEAR
THE OREGON COAST.
CONDITIONS LOOK TO IMPROVE AFTER THIS SYSTEM CONTINUES NORTHWARD.
UNSETTLED SEAS MAY CONTINUE INTO SATURDAY. WHILE SHOWERY WEATHER
DOES LOOK TO CONTINUE INTO THE END OF DECEMBER, IMPACTFUL WEATHER IS
NOT IN THE FORECAST AS OF RIGHT NOW.
-TAD
MFR WATCHES/WARNINGS/ADVISORIES
OR...WINTER WEATHER ADVISORY UNTIL 4 AM PST THURSDAY FOR ORZ027-
028-030.
HIGH WIND WARNING UNTIL 10 AM PST FRIDAY FOR ORZ029>031.
HIGH SURF ADVISORY UNTIL 4 AM PST THURSDAY FOR ORZ021-022.
HIGH WIND WATCH FROM THURSDAY EVENING THROUGH SATURDAY AFTERNOON
FOR ORZ021-022.
CA...WINTER WEATHER ADVISORY UNTIL 10 PM PST THIS EVENING FOR CAZ080.
HIGH WIND WARNING UNTIL 10 AM PST FRIDAY FOR CAZ081-084-085.
WINTER STORM WARNING UNTIL 10 PM PST THIS EVENING FOR CAZ082-
083.
PACIFIC COASTAL WATERS...HIGH SURF ADVISORY UNTIL 4 AM PST THURSDAY
FOR PZZ350-356.
HAZARDOUS SEAS WARNING UNTIL 10 PM PST THIS EVENING FOR PZZ350-
356-370-376.
SMALL CRAFT ADVISORY UNTIL 7 PM PST THURSDAY FOR PZZ350-356-370-
376.
GALE WATCH FROM THURSDAY EVENING THROUGH LATE FRIDAY NIGHT FOR
PZZ350-356-370-376.
MAS/MAS/MAS
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