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FXUS65 KREV 022150 AFDREV

Area Forecast Discussion National Weather Service Reno NV 150 PM PST Sat Dec 2 2023

SYNOPSIS

Snow showers will continue across the northern Sierra into far northwest NV through tonight. Otherwise, showers will decrease Sunday with milder, drier and less breezy weather for Monday and Tuesday. Another storm system will bring breezy winds and additional chances for rain and mountain snow showers mid to late week.

DISCUSSION

Through Tuesday:

* Our northwest flow pattern will ease over the next 24-36 hours as heights rise in response to a building shortwave ridge that will dominate our weather Mon-Tue. Winds continue to be rather stout over the ridges with gusts 50-70 mph being observed at higher elevation sensors. These winds will likely stay up tonight into early Sunday morning as a shortwave drops southeastward from the PacNW into the eastern Great Basin.

* Showers increasing along the west slopes of the northern Sierra and close to the Oregon border will bring some light QPF this evening and overnight. QPF 0.25-0.50" will be limited to areas west of Hwy 89 and in the Surprise Valley near the Warners.
Amounts quickly taper to 0.10" or less in the Tahoe Basin and other areas of northeast CA/northwest NV. Meanwhile, little or no accumulation is expected for the eastern Sierra of Mono County or west central NV including the greater Reno-Carson City area. As far as snow levels, the Colfax profiler and Slide mountain temperature sensor indicate they have risen to 6500-7000 feet with latest blended guidance holding them there overnight. Given snowfall rates will generally be less than 0.5"/hr, snow accumulation for area passes near or below 7000 feet is unlikely. Watch for some light slushy conditions near Donner Pass and Echo Summit this evening, and slick roads across Mt Rose Summit.

* Winds decrease with weak valley inversions/limited mixing returning Mon-Tue. There will be some brief buildup of air pollutants, although the transient nature of this ridge will mitigate the degree of buildup early in the week. Temperatures will warm, especially for higher Sierra valleys with afternoon highs pushing 50s to around 60 degrees areawide by Tuesday (around 10 degrees above normal).

Wednesday-Next Weekend:

* The 500 mb height cluster analysis continues to show another system working through the region Wed-Fri, but are undecided on the exact depth and resultant speed of the system. The 12Z GFS/ECMWF have trended weaker and more progressive than their previous solutions and this trend is in line with their respective ensemble means. So for now, there is a good chance we will see mild and breezy conditions Wednesday with a few showers reaching the northern Sierra followed by cooler temperatures and chances for showers areawide Thursday and Thursday night, favoring areas north of Hwy 50. Snow levels Wednesday should be high enough to mitigate impacts, but then they are forecast to lower Thursday as the main trough moves into the area, possibly bringing travel impacts. Latest blended guidance still shows quite a range in amounts (for example, the 25th and 75th percentile for 48 hour snow amounts at KTRK range from 0.2" all the way up to near 6"). The faster trend would favor the lower end amounts, so stay tuned as we continue to adjust the forecast over the next few days. Temperatures will be cooler Thu-Fri, but again how cool depends on the eventual depth of this system.

* The trough will be departing, or will have already departed the region by next weekend, as the mostly likely scenario (60% chance) indicates heights rising along the West Coast. So next weekend favors dry and seasonably cool.

Hohmann

AVIATION

* Showers will continue through tonight in the northern Sierra and across northern NV with occasional terrain obscurement and MVFR conditions at KTRK/KTVL. Snow levels will remain above Sierra airport runways, so no accumulating snow is expected. Showers will taper Sunday morning with dry conditions prevailing through Tuesday.

* Gusty northwest flow aloft will keep wind ridge gusts up overnight into Sunday morning with gusts 50+ kts. This will bring periods of light to moderate turbulence and localized LLWS. Surface wind gusts to 20-25 kts will persist into this evening. Winds gradually taper Sunday afternoon/evening with locally breezy southwest winds persisting near the Oregon border. Light winds then return for all areas Mon-Tue.

* Another system will bring increasing winds and chances for showers Wed-Fri.

Hohmann

REV Watches/Warnings/Advisories
NV...None.
CA...None.

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