Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 12/27/20

Area Forecast Discussion
National Weather Service Reno NV
232 PM PST Sat Dec 26 2020 .SYNOPSIS... A colder winter system will produce a chance for snow Sunday night through Monday mainly south of Highway 50. Additional fast moving storm systems may produce additional chances for snow and gusty winds for the upcoming week, with typical cool temperatures expected into the start of 2021. && .SHORT TERM... Bands of snow showers have lingered through parts of eastern CA and northwest NV, producing short periods of reduced visibility and snow or slush on portions of I-80 near Donner Summit. These showers are likely to wind down by sunset. After a quiet and cloudy day on Sunday with a favorable window for travel to end the holiday weekend, attention then turns to a closed low pressure system projected to reach the central CA coasts late Sunday into Monday. The wobbly track of this low continues to present varied scenarios which could range from a widespread swath of light to locally moderate snow accumulations, to a more spotty outcome with the majority of the snow splitting off into two areas: west of the Sierra crest and/or into central NV. Putting these pieces together, our most likely outcome currently suggests the best chance for accumulating snowfall would be in western NV and eastern CA south of US-50, with spotty lighter amounts extending northward to near I-80. Please see our latest Special Weather Statement for our current projected snowfall totals Sunday night-Monday. While this doesn`t appear to be a heavy snowfall event, the cold temperatures could present travel concerns into Monday evening especially across parts of Mineral, Lyon and eastern Churchill counties where snowfall during the daytime Monday lands wet on roads, but then freezes around/after sunset as temperatures drop quickly into the 20s before paved surfaces have a chance to dry out. Once again, the track and timing of the storm would determine whether this hazard will exist, or if the worse conditions shift more quickly into central NV. Otherwise, daytime temperatures will remain below average with overall light winds due to the widespread cloud cover for the next two days and the aforementioned snow potential on Monday. These same clouds will limit cooling Sunday night, then on Monday night as this storm departs, most areas will be notably colder with lows mainly in the single digits and teens, and near/below zero for typically cold valleys. MJD .LONG TERM...Tuesday through Saturday... Some minor adjustments were made to the previous forecast primarily concerning delaying the onset of the next wave by about 6 hours more into Wednesday evening rather than earlier Wednesday. Also, ridge winds were trended higher as a 50-60kt core of winds at 700mb progresses through the region Wednesday night into Thursday. No major implications from these changes with the exception that aircraft turbulence is more likely Wednesday night into Thursday. Otherwise, the forecast remains on track with a couple of waves for mid week and possibly late next weekend. The mid week wave is shaping up more of a nuisance event with light snow accumulations for the Sierra with a dusting possible for western Nevada. System trajectory favors shadowing, but upper level support is on the weaker end of the scale. Still, conditions could get breezy for Wednesday night and Thursday with valley gusts 20-35 mph. Temperatures will not be overly cold Thursday morning, but winds will make conditions feel brisk. After high pressure builds Thursday night into Friday, another system will begin to approach for the weekend. Models delayed this system by around 6 hours as well from previous runs, so just some slightly chances of snow showers will be edging down the Sierra by Saturday. Model spread continues to be wider with GFS/GEFS favoring a split wave with EC/EC ensemble being more consolidated. NBM splits the difference with middling chances. So, forecaster certainty for next weekend remains on the lower end as probabilities become less defined. Boyd && ...Aviation... Conditions largely improve tonight over last night and this morning; just some freezing fog potential at TRK for this cycle. However, expect some lingering mountain obscurations that could continue through Sunday morning. Another wave will bring accumulating snow to mountain terminals Sunday night into Monday morning with a dusting to around an inch or so for western Nevada valleys along the Sierra Front. Best chances for around an inch of snow accumulation remain south of Highway 50 for western Nevada. Winds will not be very strong by regional standards for this round, but expect MVFR/IFR conditions and mountain obscurations through Monday morning. Boyd && .REV Watches/Warnings/Advisories... NV...None. CA...None. && $$ For more information from the National Weather Service visit...