999
FXUS65 KREV 280936
AFDREV
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE RENO NV
136 AM PST SUN DEC 28 2025
KEY MESSAGES
* MUCH COLDER TEMPERATURES AND DRY WEATHER PREVAILS THIS WEEKEND
WITH POTENTIAL FOR FREEZING FOG IN THE SIERRA.
* QUIET WEATHER WITH MORNING INVERSIONS LEADING TO AIR STAGNATION
IS EXPECTED NEXT WEEK OVER WESTERN NV VALLEYS.
* THERE IS POTENTIAL FOR THE NEXT STORM SYSTEM ON NEW YEARS DAY
THROUGH NEXT WEEKEND, BUT THE SYSTEM LOOKS WEAK COMPARED TO THE
LAST ONE.
DISCUSSION
AS OF 1 AM THIS MORNING, A COLD AND DRY AIRMASS IS FIRMLY
ENTRENCHED ACROSS THE GREAT BASIN, WITH AN UPPER RIDGE BUILDING
FROM THE WEST. SATELLITE IMAGERY INDICATES MOSTLY CLEAR SKIES
ALONG WITH HIGH CLOUDS MOVING IN FROM THE NORTH, BUT FREEZING FOG
(FZFG) IS REPORTED NEAR TRUCKEE. CONDITIONS REMAIN FAVORABLE FOR
FOG WITH A 40% CHANCE OF DEVELOPMENT. HOWEVER, THE HIGH CLOUDS
MAY INHIBIT THE DEVELOPMENT OF FOG. IF IT DEVELOPS, IT IS EXPECTED
TO DISSIPATE BY LATE MORNING.
TEMPERATURES REMAIN BELOW SEASONAL NORMALS THROUGH MONDAY. MORNING
LOWS ACROSS THE SIERRA WILL DIP INTO THE SINGLE DIGITS TO MID-
TEENS, WITH WESTERN NEVADA VALLEYS IN THE MID-TEENS TO MID-20S.
DAYTIME HIGHS TODAY WILL BE IN THE LOW TO MID-30S FOR THE SIERRA,
AND UPPER 30S TO LOW 40S FOR WESTERN NV VALLEYS. THE COLDEST
MORNING IS EXPECTED TO BE MONDAY, WITH MANY LOCATIONS SEEING
SIMILAR OR SLIGHTLY COLDER LOWS THAN THIS MORNING. A GRADUAL
WARMING TREND BEGINS MONDAY AFTERNOON AS THE RIDGE STRENGTHENS AND
SHIFTS EASTWARD. WINDS WILL REMAIN LIGHT ACROSS THE ENTIRE AREA
THROUGH TUESDAY. THIS, COMBINED WITH CLEAR SKIES AND COLD MORNINGS,
WILL LEAD TO STRONG VALLEY INVERSIONS IN WESTERN NV.
THE UPPER RIDGE BREAKS DOWN BY NEW YEAR'S DAY AS PACIFIC STORM
SYSTEMS APPROACH THE WEST COAST. LATE ON NEW YEAR'S DAY (WEDNESDAY
NIGHT/THURSDAY) MARKS THE RETURN OF PRECIPITATION. NBM GUIDANCE
SHOWS POPS INCREASING TO 30-60% FOR THE SIERRA/NE CA, AND 10-20%
FOR WESTERN NV VALLEYS. SNOW LEVELS START RELATIVELY HIGH, BETWEEN
7-8 KFT, MEANING LOWER ELEVATIONS WILL LIKELY SEE RAIN. SNOW
LEVELS GRADUALLY LOWER THROUGH FRIDAY AND SATURDAY, INCREASING
SNOW CHANCES FOR PASSES AND POTENTIALLY SIERRA COMMUNITIES. PRECIP
CHANCES CONTINUE THROUGH FRIDAY AND SATURDAY.
MODEL GUIDANCE, INCLUDING THE NBM AND GFS/ECMWF ENSEMBLES, SHOWS
INCREASING AGREEMENT ON THE ARRIVAL OF PRECIPITATION FOR THE NEW
YEAR; ALTHOUGH TIMING, INTENSITY, AND SNOW LEVELS STILL EXHIBIT
CONSIDERABLE SPREAD. WE WILL CONTINUE TO MONITOR MODEL TRENDS TO
REFINE PRECIPITATION TIMING, AMOUNTS, AND SNOW LEVELS.
-HC
AVIATION
VFR CONDITIONS PREVAIL FOR MUCH OF THE REGION OVER THE NEXT 24
HOURS, WITH LIGHT WINDS AND FEW TO SCT MID TO HIGH LEVEL CLOUDS.
ANOTHER ROUND OF FZFG IS POSSIBLE FOR SIERRA VALLEYS BETWEEN
08-17Z THIS MORNING AND TOMORROW MORNING, BRINGING LIKELY
IFR/LIFR IMPACTS TO KTRK AND POTENTIALLY KTVL. WHILE THERE IS
CURRENTLY A 40-50% PROBABILITY OF FZFG, THE DEVELOPMENT MAY BE
INHIBITED BY AN INCREASE OF CLOUD COVER THIS MORNING.
-JOHNSTON/HC
REV WATCHES/WARNINGS/ADVISORIES
NV...NONE.
CA...NONE.
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