985
FXUS65 KREV 240413 AAA
AFDREV
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE RENO NV
813 PM PST THU JAN 23 2020
UPDATE
INITIAL SHOWERS WITH THE WEAK INCOMING SYSTEM HAVE JUST PRODUCED
TRACE AMOUNTS. HOWEVER, RADAR TRENDS AND HI RES MODELS SUGGEST A
BETTER CHANCE OVERNIGHT. BEST CHANCES WILL BE ALONG THE SIERRA
CREST TO NEAR THE OREGON BORDER AS WELL AS EASTERN PERSHING
COUNTY. AMOUNTS STILL LOOK TO BE LIGHT AND GENERALLY LESS THAN A
TENTH OF AN INCH, BUT ISOLATED SPOTS COULD SEE UP TO A QUARTER
INCH. SNOW LEVELS REMAIN HIGH, NEAR 8000 FEET SO ONLY THE HIGHEST
PEAKS AND RIDGES WILL SEE SNOW LEAVING THE PASSES JUST WET. X
PREVIOUS DISCUSSION
/ISSUED 127 PM PST THU JAN 23 2020/
SYNOPSIS...
MAINLY LIGHT WINDS WITH ABOVE AVERAGE TEMPERATURES WILL PREVAIL
THROUGH WEEK'S END WITH SOME VERY LIGHT RAIN OR SNOW LATE THURSDAY
NIGHT INTO EARLY FRIDAY. THIS WEEKEND ANOTHER SYSTEM WILL BRING
CHANCES OF VALLEY RAIN AND MOUNTAIN SNOW ALONG WITH GUSTY WINDS.
EXTENSIVE CLOUD COVER AND A COUPLE OF WEAK STORMS ARE POSSIBLE
INTO NEXT WEEK.
SHORT TERM...
THERE ARE TWO MAIN FEATURES OF NOTE IN THE SHORT TERM PART OF THE
FORECAST TODAY. EACH...WHILE NOT STRONG AS FAR AS WINTER STORMS
GO...PRESENTS ITS OWN SET OF PROBLEMS.
THE FIRST IS A WAVE THAT MOVES THROUGH THE REGION TONIGHT. THE
MAIN PART OF THE WAVE CAN CURRENTLY BE SEEN ON WATER VAPOR
SATELLITE IMAGERY NEAR 130W. AHEAD OF THE THE MAIN WAVE IS A WEAK
AREA OF WARM AIR ADVECTION NOTED BY ENHANCED MOISTURE AND SLIGHTLY
COOLER CLOUD TOPS IN THE SATELLITE IMAGERY. THE WARM AIR
ADVECTION PORTION OF THIS FEATURE SHOULD BEGIN IMPACTING NORTHEAST
CALIFORNIA AND THE NORTHERN SIERRA BY EARLY EVENING WHILE THE
MAIN PART OF THE WAVE MOVES THROUGH JUST AFTER DAYBREAK FRIDAY.
LOW CLOUDS AND FOG KEPT SOME OF THE COLDER VALLEYS IN THE SIERRA
FROM COMPLETELY MIXING OUT TODAY. THE PRESENCE OF CLOUD COVER AND
THE WARM AIR ADVECTION ALOFT CREATING AN INVERSION MAY RESULT IN
A FEW POCKETS OF TEMPERATURES NEAR FREEZING IN THESE COLDER
VALLEYS THIS EVENING. SO WHILE OVERALL SNOW LEVELS SHOULD BE
RISING THIS EVENING THERE IS THE POSSIBILITY THAT A FEW VERY
REMOTE LOCATIONS COULD SEE A BRIEF PERIOD OF VERY LIGHT FREEZING
RAIN BELOW 7500 FEET BEFORE EVERYTHING CHANGES TO RAIN. THE SNOW
LEVELS RISE TO NEAR 8000-8500 FEET BRIEFLY THIS EVENING AS MIXING
INCREASES THEN FALL WELL BELOW 7000 FEET WITH THE PASSAGE OF THE
MAIN WAVE BY EARLY FRIDAY.
MOISTURE IS NOT OVERLY ABUNDANT WITH THIS SYSTEM AND THE HIGHER
SNOW LEVELS WILL LIMIT ACCUMULATIONS ON THE PASSES...BUT THERE
COULD BE A PERIOD OF SLICK/SNOW COVERED ROADS FOR THE TRANS-
SIERRA PASSES LATE THIS EVENING AND EARLY FRIDAY.
A BRIEF BREAK BRINGS DRY WEATHER FRIDAY AFTERNOON INTO EARLY
SATURDAY MORNING BEFORE THE NEXT WAVE AFFECTS THE AREA. THE MODEL
SOLUTIONS HAVE BEEN HAVING A DIFFICULT TIME WITH THIS SYSTEM...AND
TODAY WAS NO EXCEPTION.
THE PREVIOUS FORECAST CYCLE SAW A FASTER SYSTEM WITH LESS DWELL
TIME OVER THE REGION AND LESS QPF. WELL...NOW SOME OF THE MODEL
SOLUTIONS HAVE SLOWED THE INITIAL ONSET OF PRECIPITATION FROM LATE
SATURDAY AFTERNOON TO SATURDAY EVENING (SATURDAY NIGHT FOR MOST
AREAS EAST OF THE SIERRA). BUT THE SYSTEM STILL MOVES THROUGH
RATHER QUICKLY WITH STEADY PRECIPITATION OUT OF THE AREA BY MID-
TO LATE-MORNING SUNDAY. THIS SLOWER ENTRY INTO THE REGION RESULTS
IN HIGHER SNOW LEVELS AT THE ONSET OF PRECIPITATION. THAT MEANS
LESS TOTAL SNOW ACCUMULATION IN THE HIGHER ELEVATIONS. WHILE THE
HEAVIEST BURST OF PRECIPITATION IS STILL IN THE MIDNIGHT TO 6 AM
TIME FRAME SATURDAY NIGHT INTO SUNDAY MORNING...THERE IS SLIGHTLY
LESS PRECIPITATION OVERALL. SNOW TOTALS BELOW 8000 FEET AT THE
CURRENT TIME DO NOT REACH THE LEVEL OF AN ADVISORY...BUT THERE
COULD BE HAZARDOUS DRIVING CONDITIONS BY SUNDAY MORNING OVER THE
HIGHER PASSES OF THE SIERRA AS A FEW INCHES PILE UP.
WINDS DO NOT LOOK OVERLY STRONG WITH THIS SYSTEM EITHER. GUSTS
AHEAD OF THE MAIN WAVE COULD REACH 30-35 MPH SUNDAY MORNING. THEN
AFTER THE PRECIPITATION HAS ENDED WINDS COULD GUST 30-40 MPH
SUNDAY AFTERNOON IN THE LEE OF THE SIERRA. WE MAY NEED A LAKE WIND
ADVISORY FOR LAKE TAHOE.
SHOWERS LINGER IN THE SIERRA AND THE FAR EASTERN PART OF THE
FORECAST AREA SUNDAY AFTERNOON AND EVENING. THEN ANOTHER WEAK WAVE
BRINGS VERY LIGHT RAIN/SNOW TO AREAS NEAR THE OREGON BORDER BEFORE
DAYBREAK MONDAY MORNING.
AS STATED...NONE OF THESE INDIVIDUAL SYSTEMS RISE TO THE LEVEL OF
EVEN A WINTER WEATHER ADVISORY...BUT THEY ALL HAVE THE POTENTIAL
TO CAUSE SOME TRAFFIC DELAYS DUE TO JUST A SMALL AMOUNT OF SNOW ON
THE HIGHER ELEVATION ROADS.
LONG TERM...MONDAY THROUGH THE END OF JANUARY...
FOR THE EARLY AND MIDDLE PART OF NEXT WEEK, A FEW WEAK
DISTURBANCES WILL MOVE THROUGH THE NORTHWEST US. CURRENTLY THE
BEST OVERALL CHANCES FOR LIGHT RAIN AND SNOW ARE ANTICIPATED FOR
TUESDAY, BUT A FEW LIGHTER SHOWERS ARE ALSO POSSIBLE MAINLY FOR
FAR NORTHEAST CA-NORTHWEST NV AT TIMES FROM MONDAY THROUGH
WEDNESDAY. DAYTIME TEMPERATURES ARE EXPECTED TO BE ABOUT 4-8
DEGREES ABOVE AVERAGE THROUGH MIDWEEK.
FOR TUESDAY WHEN THE MAIN DISTURBANCE MOVES THROUGH, PRECIP
AMOUNTS STILL LOOK RATHER MODEST, WITH THE WETTER SCENARIOS
SHOWING AROUND 0.50" FOR WESTERN LASSEN AND PLUMAS COUNTIES AND
0.25" NORTHWARD TO SURPRISE VALLEY, WHILE DRIER SCENARIOS SHOW
LESS THAN HALF THESE VALUES. SNOW LEVELS ARE PROJECTED TO START
NEAR 4500-5000 FEET, SO THE HIGHER ELEVATION ROADS AND PASSES OF
NORTHEAST CA COULD HAVE SOME SNOW ACCUMULATIONS IN THE MORNING,
BEFORE SNOW LEVELS RISE TO NEAR 6000 FEET DURING THE DAY. FROM
I-80 SOUTHWARD, THESE PRECIP VALUES DROP OFF SO THE SIERRA/TAHOE
AREAS MAY ONLY SEE A SMALL AMOUNT OF SNOW WHILE MUCH OF WESTERN NV
LIKELY GETS SHADOWED OUT WITH ONLY A FEW SPRINKLES OR FLURRIES.
LATER NEXT WEEK, THE MAJORITY OF MODEL/ENSEMBLE GUIDANCE FAVORS A
STRONGER RIDGE OF HIGH PRESSURE BUILDING INTO CA-NV. THIS WOULD
SHUT DOWN PRECIP CHANCES FOR ALL OF EASTERN CA-WESTERN NV,
ALTHOUGH CIRRUS COVERAGE LOOKS WIDESPREAD AT LEAST FOR THURSDAY.
TEMPERATURES WILL BE ON THE RISE WITH HIGHS WELL ABOVE AVERAGE
(60+ DEGREES FOR LOWER ELEVATIONS AND 50+ DEGREES FOR SIERRA
VALLEYS) AS JANUARY COMES TO A CLOSE. MJD
AVIATION...
HIGH RESOLUTION MODEL GUIDANCE BRINGS AN AREA OF MOISTURE WITH
LIGHT RAIN SHOWERS THROUGH EASTERN CA-WESTERN NV MAINLY NORTH OF
US-50 TONIGHT INTO EARLY FRIDAY. HIGH SNOW LEVELS NEAR 8000 FEET
AND LIGHT INTENSITY WILL LIMIT IMPACTS TO MAINLY PERIODIC
OBSCURATION OF TERRAIN IN MVFR CIGS/VSBY FOR THE TAHOE TERMINALS
AND INTO KRNO-KCXP-KMEV, MAINLY BETWEEN 01-06Z, THEN PUSHING
ACROSS WEST CENTRAL NV FROM 04-09Z. MORE ISOLATED SHOWER ACTIVITY
IS POSSIBLE OVERNIGHT. IF SUFFICIENT RAIN FALLS AT KTVL/KTRK THIS
EVENING, PATCHY FOG COULD PRODUCE IFR/LIFR CONDITIONS OVERNIGHT
INTO FRIDAY MORNING IF CLOUD COVER DIMINISHES. KMMH IS EXPECTED TO
REMAIN DRY WITH VFR CONDITIONS TONIGHT. LIGHT SURFACE WINDS WILL
PREVAIL AT ALL TERMINALS THROUGH SATURDAY, ALTHOUGH SIERRA RIDGE
GUSTS MAY INCREASE TO NEAR 45 KT LATE TONIGHT AND FRIDAY.
ANOTHER STORM SYSTEM WILL MOVE THROUGH THE REGION LATE SATURDAY
EVENING THROUGH SUNDAY MORNING. PERIODS OF MVFR/IFR CIG/VIS,
MOUNTAIN OBSCURATION, LIGHT SNOW AT THE SIERRA TERMINALS AND LIGHT
RAIN FOR WESTERN NV TERMINALS ARE EXPECTED, ALONG WITH GUSTY
WINDS, TURBULENCE AND POSSIBLE LLWS. MJD
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
FOR MORE INFORMATION FROM THE NATIONAL WEATHER SERVICE VISIT...
HTTP://WEATHER.GOV/RENO
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