textproduct: Reno

KEY MESSAGES

* A warming trend continues with near record high temperatures most likely from Sunday through Tuesday.

* Dry conditions are expected through early next week with typical afternoon west breezes most days.

* Some cooling returns by mid-late next week with isolated shower chances and periods of breezy winds.

DISCUSSION

Building upper level ridge over southern CA with a north-south axis near the Sierra crest today will shift east into the southwest US/Four Corners region from Sunday through Tuesday. With this pattern, very warm conditions will spread across the region, with highs Sunday-Tuesday around 15-20 degrees above seasonal normals (upper 80s-lower 90s in NE CA and W NV valleys, and upper 70s-lower 80s for Sierra communities). Record highs will be within reach--see the Climate section below for a list of the current temperature records at our two climate sites. The latest NWS HeatRisk forecast continues to show warmer valleys of western NV in the Moderate category, with the remainder of the region in the Minor category. Please take the time now to prepare for this heat especially if you have outdoor plans in the afternoon and are sensitive to heat. Also, use extra caution near rivers which remain cold and could be flowing fast, presenting a risk of hypothermia.

This ridge pattern will also allow for dry conditions to prevail through early next week. Increased daytime heating could allow for a few brief afternoon pop-up showers near the Sierra and south of US-50 in western NV, but chances look to be less than 10%. Light winds are expected today, then typical zephyr-type SW-W breezes (gusts around 25 mph) return each afternoon on Sunday through Tuesday. These winds may edge upward on Tuesday depending on the eventual ridge location in relation to an upstream trough/upper low off the CA coast, but confidence is lower on this wind trend.

The pattern is still on track to change Wednesday-Thursday as the upper level ridge moves east into Texas while the offshore low makes landfall in CA and eventually pushes across western NV. There continues to be variable scenarios with this low's track and timing, which would affect when and where the best chances of showers and thunderstorms occur. Currently, we're keeping our eyes on Wednesday through Thursday having the best potential for active weather. It may end up being more of a showery outcome with limited lightning coverage, especially if the best forcing moves through during the overnight/morning hours. Periods of increased winds (gusts 30-40 mph) are also in the mix for the Wednesday- Thursday time frame, either due to outflow gusts near showers/t-storms or increasing 700 mb flow over the Sierra with tighter pressure and temperature gradients.

We have more confidence in the near-record warmth ending from Wednesday onward, although highs should remain above mid-May averages through the end of next week, easing back to the mid 70s-near 80 for lower elevations and mid 60s-near 70 for Sierra communities. However, there's a 20-30% chance for additional cooling on Wednesday or Thursday if the upper low passes directly overhead with thicker cloud cover and showers. Overall precip potential decreases by late next week and through the May 16-17 weekend, although stray rain showers can't be fully ruled out as minor shortwave disturbances in a zonal flow pattern over the western US could brush across parts of eastern CA/western NV. MJD

AVIATION

Generally light NE-E winds through this evening, then typical SW-W breezes (gusts around 20 kt) return Sun-Tue, mainly between 20-04Z. VFR conditions are expected through early next week. Only possible exception is at KTRK where there's a 20% chance for patchy shallow fog developing between 10-15Z Sunday morning, which could cause intermittent sub-VFR conditions.

While dry conditions prevail, the warmest days Sunday-Tuesday could potentially bring density altitude concerns each afternoon, especially for the western NV terminals. MJD

CLIMATE

Current record high temperatures for Reno, NV that have potential to be broken or tied (Sunday-Tuesday):

May 10: 88 F, set in 1934. May 11: 90 F, set in 2001 and 2013. May 12: 89 F, set in 1959 and 2013.

Current record high temperatures for South Lake Tahoe, CA that have potential to be broken or tied (Sunday-Tuesday):

May 10: 75 F, set in 2025. May 11: 78 F, set in 2013. May 12: 79 F, set in 1988 and 1996.

MJD

REV Watches/Warnings/Advisories

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