661
FXUS65 KREV 220927
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
127 AM PST MON DEC 22 2025
KEY MESSAGES
* HEAVY RAINS THAT COULD LEAD TO LOCALIZED FLOODING, AND HEAVY WET
SNOW IN THE SIERRA ABOVE 8000 FEET CONTINUES INTO THE LATE
EVENING.
* FOLLOWING THE BEGINNING WEEK SYSTEM, THERE WILL BE A BRIEF LULL
IN PRECIPITATION ON TUESDAY WITH GUSTY RIDGE WINDS.
* ANOTHER ROUND OF STORMY CONDITIONS COULD BRING SIGNIFICANT RAIN
AND SNOW ALONG WITH ENHANCED WINDS LATE TUESDAY THROUGH
CHRISTMAS DAY INTO THE WEEKEND.
DISCUSSION
FOR TODAY, PRECIPITATION CONTINUES FOR NORTHERN MONO COUNTY
NORTH INTO LASSEN COUNTY. MEANWHILE FOR WESTERN NV, LIGHT RAIN
SHOWERS WILL PERSIST MAINLY WEST OF US-95 AND NORTH OF I-80 INTO
THE LATE MORNING. OTHER AREAS IN THE INNER-BASINS AND EAST OF THE
CRESTS IN MONO COUNTY WILL REMAIN DRY. SNOW LEVELS WHICH HAVE BEEN
AROUND 8,000 FT ON SUNDAY WILL REMAIN STEADY AROUND 8,000 FT
TODAY. HIGH-RESOLUTION MODELS AND ENSEMBLES ARE ALL IN AGREEMENT
THAT THE PRIMARY BAND OF PRECIPITATION AFFECTING THE EASTERN
SIERRA WILL SLOWLY MOVE NORTH AS THE DAY PROGRESSES. PRECIPITATION
WILL FIRST END IN NORTHERN MONO COUNTY BY AROUND 11 AM TO 2 PM,
THEN EVENTUALLY IN THE TAHOE BASIN BY 4-7 PM. MEANWHILE,
PRECIPITATION WILL BECOME LESS INTENSE FOR EASTERN PLUMAS AND
LASSEN COUNTY, BUT MODELS SHOW THESE AREAS MAY KEEP LIGHT SHOWERS
INTO EARLY TUESDAY. AS FOR WIND, SOME OF THE WIND PRONE AREAS AND
RIDGES ARE STILL SHOWING GUSTS TO 50-70 MPH (AS OF 1 AM). WINDS
WILL STAY ELEVATED ALONG THE RIDGES TODAY WITH GUSTS OF 40-60 MPH,
BUT THE REMAINDER OF THE REGION WILL HAVE MUCH CALMER WINDS WITH
GUSTS BETWEEN 20-30 MPH. AS SUCH, THERE WILL NOT BE THE NEED FOR
ADDITIONAL WIND-RELATED PRODUCTS.
AS THE PRIMARY UPPER LEVEL TROUGH MOVES CLOSER TO THE COAST ON
TUESDAY, THE AFOREMENTIONED BAND OF PRECIPITATION WILL CONTINUE
TO SHIFT WEST, ALLOWING FOR A MOSTLY CLEAR DAY ACROSS THE REGION.
BUT, BY LATE TUESDAY EVENING INTO EARLY WEDNESDAY THE FIRST IN A
SERIES OF MULTIPLE SHORT-WAVE TROUGHS THAT ARE ROTATING AROUND
THE LARGER PARENT LOW WILL BEGIN TO IMPACT THE REGION. THIS WILL
LEAD TO MULTIPLE DAYS OF RAIN, SNOW, AND STRONG WINDS. IN
ADDITION, EACH SHORT-WAVE THAT MOVES THROUGH WILL BE COLDER THAN
THE PREVIOUS, ALLOWING FOR SNOW LEVELS TO DROP THROUGH CHRISTMAS
DAY INTO THE 26TH.
TO START WITH LATE TUESDAY INTO WEDNESDAY, THE FIRST SHORT-WAVE
MOVES INTO THE AREA WITH MORE HEAVY RAIN, AND HEAVY SNOW ABOVE
AROUND 6,000-6,500 FT. ONE THING TO NOTE FROM PRIOR GUIDANCE IS
THAT MODELS ARE STARTING TO HINT THAT THE SURFACE LOW AND UPPER
SHORT-WAVE TROUGH MAY BREAK OFF FROM THE COLD FRONT AND MOVE
NORTH INTO THE PACIFIC NORTHWEST. IF THIS OCCURS, WE MAY SEE
CLEARING IN LASSEN, EASTERN PLUMAS, AND POSSIBLY THE TAHOE AREA
LONGER THAN WHAT WE ARE CURRENTLY FORECASTING. THIS WILL BE
WATCHED AS WE GET CLOSER. BY LATE WEDNESDAY INTO EARLY FRIDAY, THE
NEXT PIECE OF SHORT-WAVE ENERGY MOVES INTO THE AREA. THIS FEATURE
WILL BE MUCH COLDER, ALLOWING FOR SNOW LEVELS TO DROP BELOW ALL
PASS LEVELS (<5,500FT) IN THE EASTERN SIERRA BY THURSDAY AFTERNOON
AND EVEN AS LOW AS THE VALLEY FLOORS (~4,500FT) IN WESTERN NV BY
FRIDAY. FOR THIS REGION, A WINTER STORM WATCH WILL REMAIN IN
EFFECT FROM LATE TUESDAY EVENING UNTIL FRIDAY MORNING FOR THE
SIERRA. -MCKELLAR
FOR DETAILS ABOUT THE WINTER STORM WATCH, PLEASE VISIT
WWW.WEATHER.GOV/REV/WINTER
IF YOU'RE PLANNING ON GOING OUT TO THE BACK COUNTRY IN THE
EASTERN SIERRA, PLEASE VISIT WWW.WEATHER.GOV/REV/AVALANCHE
AVIATION
* MODERATE TO AT TIMES HEAVY RAIN IS LIKELY AT KTRK AND KTVL
THROUGH AT LEAST TUES 00Z, WITH SCATTERED SHOWERS THROUGH AROUND
TUES 06Z. THIS WILL CAUSE VISIBILITIES TO DECREASE TO IFR/LIFR
WITH TERRAIN OBSCURATIONS IN AREAS OF HEAVY PRECIPITATION.
HIGHER ELEVATIONS GENERALLY ABOVE 8,000 FT IN THE SIERRA MAY SEE
SNOW TODAY. WESTERN NV TAF SITES MAY OCCASIONALLY DROP TO MVFR
VISIBILITY WHEN RAIN OCCURS THROUGH AROUND 20Z.
* AREA-WIDE LLWS, MOUNTAIN WAVE TURBULENCE, AND RIDGETOP WINDS
GUSTING UP TO 40-60 MPH ARE ALSO TO BE EXPECTED THIS AFTERNOON.
SURFACE WINDS ARE LIGHTER TODAY, WITH SUSTAINED WINDS OF 10-15
KTS WITH GUSTS UP TO 25 KTS. -MCKELLAR
HYDROLOGY
ONGOING MODERATE TO HEAVY RAINS ARE RESULTING IN SIGNIFICANT RISES
ON RIVERS AND STREAMS TODAY INTO MONDAY MOST NOTABLY FROM ALPINE
COUNTY NORTH THROUGH LASSEN COUNTY.
MINOR FLOODING OF SMALL STREAMS, URBAN AND POOR DRAINAGE AREAS AND
ROCKFALL IN STEEP TERRAIN ARE POSSIBLE DURING ANY PROLONGED PERIODS
OF HIGH INTENSITY RAINFALL.
WHILE NO MAINSTEM RIVER FLOODING IS CURRENTLY FORECAST, THE SUSAN
RIVER NEAR SUSANVILLE IS CURRENTLY EXPECTED TO EXCEED ACTION STAGE
AND MINOR FLOODING CAN NOT BE RULED OUT. REMAIN AWARE OF THE
POTENTIAL FOR ADDITIONAL RIVER AND STREAM RISES NEAR CHRISTMAS EVE
IN LARGE MOUNTAIN DRAINAGES BELOW ABOUT 6000 FEET, LIKE THE SUSAN
RIVER. IN THESE AREAS ADDITIONAL RAIN AND SATURATED CONDITIONS COULD
LEAD TO RAPID RISES AND RENEWED FLOODING CONCERNS. IN MOST OTHER
AREAS, LOWERING SNOW LEVELS WILL REDUCE FLOODING CONCERNS INTO NEXT
WEEK.
ENHANCED RUNOFF AND SEDIMENT TRANSPORT INCLUDING ROCK FALL ARE
LIKELY WITHIN AND BELOW RECENT BURN AREAS, INCLUDING, BUT NOT
LIMITED TO THE DAVIS AND BEAR BURN AREAS. POST-FIRE DEBRIS FLOWS ARE
NOT EXPECTED.
YOU CAN FIND RIVER FORECASTS UPDATED SUNDAY AT ~3PM AND ~9PM,
THEN ~ 9AM AND ~3PM MONDAY AND TUESDAY AT: WWW.CNRFC.NOAA.GOV
-TIM
REV WATCHES/WARNINGS/ADVISORIES
NV...FLOOD WATCH THROUGH THIS AFTERNOON NVZ002.
WINTER STORM WATCH FROM TUESDAY EVENING THROUGH FRIDAY MORNING
NVZ002.
WINTER WEATHER ADVISORY UNTIL 1 PM PST THIS AFTERNOON NVZ002.
CA...FLOOD WATCH THROUGH THIS AFTERNOON CAZ071-072.
WINTER STORM WATCH FROM TUESDAY EVENING THROUGH FRIDAY MORNING
CAZ071>073.
WINTER WEATHER ADVISORY UNTIL 1 PM PST THIS AFTERNOON CAZ072.
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