Area Forecast Discussion
Issued by NWS Reno, NV
Issued by NWS Reno, NV
891 FXUS65 KREV 152031 AFDREV Area Forecast Discussion National Weather Service Reno NV 131 PM PDT Sun Sep 15 2024 .SYNOPSIS... * Windy conditions will persist into early evening, then winds decrease overnight with more typical breezes Monday. * Well below average temperatures expected Monday, in addition to widespread rain showers and high elevation snow. * Another cold system expected Tuesday night and Wednesday, bringing additional chances for rain and high elevation snow. && .DISCUSSION... * Winds have increased this afternoon with surface gusts 30-35 mph, locally to 40 mph and ridges around 60 mph. These winds are on track to continue into this evening before diminishing overnight. Fortunately, RH has remained elevated and generally above 20% in the Sierra and along the Hwy 395 corridor. Cannot rule out some locally critical conditions the remainder of the afternoon before winds decrease and moisture increases further this evening/overnight. * Latest guidance has not departed much from previous thinking with a couple of colder storm systems in line to bring much cooler weather and good chances for wetting precipitation through Wednesday (60-80% chance of seeing at least 0.25" by late Wednesday in any one spot). The first storm drops into northern CA tonight and moves across the Great Basin Monday- Monday night while the second one drops into the region Tuesday night and Wednesday. Temperatures will be much below normal for Monday and Wednesday when rain chances are highest. Where bands set up, afternoon highs will struggle to reach 50 degrees in the Sierra and 60 degrees for lower elevation sites. Highs both days will be around 20-25 degrees below average (more like late October) with hard freezes returning to Sierra valleys Tuesday morning as we see a brief clearing in between storms. * For the first storm, showers will increase late tonight across far western NV and the Tahoe Basin then shift into western NV during the afternoon/evening Monday. Latest blended guidance continues to favor west central NV, but some CAMS (particularly the HRRR) are bullish with convective bands over Reno-Tahoe Monday morning. This could result in some thunder as well as a brief lowering of the snow levels (as low as 6000 feet) - possibly bringing an inch or two of snow and impacts to higher passes. Antecedent conditions are quite warm, so accumulations would be brief - still worth watching if you have travel plans across Sierra passes in the morning. Otherwise, a good wetting rain is likely, especially across western NV east of Hwy 95 and over NW NV where the chance of seeing 0.50" of rain is 40-60%, locally higher near any storms. Lesser amounts are expected along the eastern Sierra towards Mammoth with this first storm. Snow levels outside convection will range between 7500-8000 feet with several inches of accumulation on the higher peaks of the Sierra above 8000 feet. * The second storm drops a bit farther west and south with showers/isolated storms favoring the Sierra and areas south of Hwy 50 Tuesday night/Wednesday as it tracks across southern NV. Snow levels are not as low with this system, so rain will be the predominant precipitation type outside elevations above 9000-9500 feet. Quite brisk northeast winds are possible across the Sierra ridges/higher terrain Wednesday night as the upper low exits. A drier and milder pattern returns late week into the weekend. Hohmann && .AVIATION... * Strong gusty southwest winds will persist into early evening with gusts at area terminals 20-30 kts through 01-03Z. FL100 winds will remain elevated 30-35 kts through 06-09Z (Mt top gusts 50-55 kts), then decrease overnight. This will lead to some moderate turbulence along with a short period of LLWS along the eastern Sierra (KMEV-KMMH) as surface winds weaken first (02-07Z). * Moisture and instability increase 06-12Z with an expanding area of showers near the Tahoe Basin/far western NV terminals, lasting through 16-18Z Monday. There is about a 10-15% chance of a thunderstorm in this area with heavier showers and cannot rule out light snow accumulation of 1-4 inches above 7000 feet. Higher terrain obscurement with periods of MVFR down at terminal levels where heavier bands develop. Showers and isolated storms (15-25% chance) then transition to western NV, favoring KLOL- KNFL-KHTH Monday afternoon/evening. * A second cold system will bring another round of rain and high elevation snow Tuesday night-Wednesday with daytime breezy conditions. We will have to watch Wednesday night for potential strong northeast ridge winds/increased turbulence as the systems exits. Hohmann && .REV Watches/Warnings/Advisories... NV...Lake Wind Advisory until 8 PM PDT this evening NVZ002. CA...Lake Wind Advisory until 8 PM PDT this evening CAZ072. && $$