textproduct: Reno

KEY MESSAGES

* Dry conditions and mostly clear skies persist with cold temperatures through Sunday along with below zero wind chills near the Sierra crest with gusty breezes. * The next impactful storm arrives late on Monday with rain and high elevation mountain snow through Wednesday. Flooding potential exists with this atmospheric river event, but forecast confidence remains low at this time.

DISCUSSION

When looking at the current RAP upper air analysis, an upper ridge continues over the region with some small disturbances embedded within the upper air flow. Because of this pattern aloft, dry weather persists today with a good amount high cloud cover seen over W NV and NE CA. The dry conditions expect to continue though the region may see some lesser cloud cover going into the night. Low temperatures for tonight into tomorrow morning are forecast to be in the teens and 20s. Minimum wind chills in the Sierra crest areas of Mono County will drop as low as -5F tonight with a majority of the forecast area staying above zero.

This upper air pattern looks to continue into tomorrow allowing for slightly warmer daytime high temperatures compared to today. Model guidance still shows winds increasing with a system passing through the NW CONUS. In the portions of region closest to the system (NE CA and Northern Washoe County), the latest NBM run shows a 40-60% chance of gusts of 40+ mph. Sierra ridge gusts could also top off somewhere around 50 mph with the highest peaks reaching around 70 mph. Please keep this in mind in case you are in these areas tomorrow. Overnight low temperatures currently look to be a few degrees warmer than the previous night. Winds do look to decrease overnight, so minimum wind chills look to stay above freezing albeit only a few degrees in the highest elevations of Mono County.

The warming trend looks to continue going into the work week with the first half of Monday staying dry. But by the late afternoon and evening hours, precipitation chances look to move into NE CA that later spread both southward and eastward going into the night. Models show low pressure off the coast of BC slowly moving southeast in the beginning of the week which will funnel a good amount of moisture into the northern half of CA. Precipitation coverage expands into the Sierra Front on Tuesday morning with the NV Basin and Range seeing their chances around by the late afternoon and evening hours. When looking at the Center for Western Weather and Water Extremes (CW3E) Atmospheric River (AR) Landfall Tool, the probability of integrated water vapor transport (IVT) greater than 250 kg/ms is around 100% in NE CA and the Sierra especially on Tuesday. What does this mean you might ask? This storm shows signs to be an atmospheric river event and will bring a good amount of moisture to Sierra crest...on top of the snow that recently fell. When looking at the NBM QPF probabilities, the Sierra crest around the Tahoe region sees currently sees a 30-40% chance for 2 inches or more by Wednesday night with this storm. As this system will be a warmer storm, snow levels look to start around 8-8.5 kft late Monday and rise higher going into Tuesday. If the forecast holds, higher elevations will start with a rain-snow mix late Monday into early Tuesday (the exception being in the highest elevations in the Eastern Sierra as they may stay all snow) before transitioning to mostly rain while valley areas stay with a rain p-type. Stronger ridge winds gusting up to around 100 mph are possible on Tuesday with this system as well.

It still a bit too early to say for sure if there will be definite flooding issues with this early week storm, but the additional runoff due to snowmelt could potentially cause some problems especially in poor drainage areas. Several of the river gages in the area are showing rises in their latest forecast including the West Fork Carson River which shows a 5-25% chance of reaching monitor stage. Will keep an eye on this in case the flooding threat increases. Drier and warmer conditions look to follow this storm by Thursday that will last into next weekend. -078

AVIATION

VFR conditions look to persist at all TAF sites through the region today and tonight. Sierra winds will be mostly south-southwesterly with gusts up to around 20 kts though KMMH has mostly light and variable winds forecast. Low confidence in FZFG occurring tonight for KTRK with forecast calling for the increased surface winds and hindering fog formation. Not ruling it out completely in case winds do not pan out as expected. W NV TAF sites look to have generally winds under 10 kts with the exception of KMEV which may see gusts up to around 20 kts through the overnight and morning hours. While Sierra terminals see LLWS and turbulence persist, Sierra front terminals look to have LLWS begin around 22/05Z that continues into Sunday morning. Dry conditions are anticipated to persist through Sunday ahead of the next weather system arriving late Monday going into midweek. -078

REV Watches/Warnings/Advisories

NV...None. CA...None.