textproduct: Reno

KEY MESSAGES

* Showers and thunderstorms will persist through Friday and possibly Saturday along with cooler than normal temperatures.

* Snowfall is likely in the Sierra and mountains in Nevada above 7000 feet today and tomorrow.

* Temperatures will warm back to near or above normal next week.

DISCUSSION

* Cold upper low meandering over California and Nevada will keep showers and t-storms in the forecast through Friday and possibly Saturday, depending on the speed that the low moves out this weekend. In many past years, this cool and wet pattern has coincided with the Memorial Day weekend. This year, it was a close call.

* While the afternoons will have the most widespread showers and isolated t-storms due to destabilization, with the various waves rotating around the upper low, overnight and morning showers are likely. For example: HREF showing 70%+ odds of at least 0.1" rainfall between 6 AM and Noon Thursday from Hawthorne to Reno/Tahoe. Regarding t-storms, today and tomorrow have the best chances for stronger cells per SPC outlook and HREF. Even some updraft helicity tracks showing up in HREF over Pershing, N Washoe, and Modoc Counties each day - an indication more organized storms and increased severe potential. Even more impressive tomorrow further north over Oregon.

* Rain-snow lines will vary between 6000-8000' through Friday based on the NBM guidance. With the coolest days being today and tomorrow, that's when we'll have the best chances for mountain snowfall. NBM showing 60-80% chances for at least 1" new snow in the Sierra between Tahoe and Mammoth today and tomorrow, with up to 40% chance of 4" especially above 7000'. So any mountain roads that are open above 7000' could have travel impacts due to snow, with some of that coming down in higher intensity snow/pellet showers. Any nighttime snow even on well-travel roads like I-80 could result in slick conditions.

* The trend has been for a slower exit of the upper low, with NBM now showing showers possible Saturday, which also keeps the warm-up more gradual with 80s holding off until Sunday or even Monday in lower elevations. Even with cooler than normal temps through the weekend, the odds of hard freezes in lower valleys and urban areas appear limited due mainly to cloud cover. Even at a typical cold spot like Minden, the NBM is only showing about 20% chance of sub-freezing temps Thursday and Friday mornings.

* Increasing confidence in a solid warm up next week to typical or above normal temperatures, especially the second half of the week. Can't rule out isolated showers or even t-storms over the higher terrain each day with that warmth. NBM t-storm POPs running 10-20% each day. -Chris

AVIATION

* High chances (80%+) for MVFR to IFR rain showers across the region through Thursday, including overnight and early morning periods. Mountain obscuration is also expected.

* Thunderstorms are also expected (20-40% chances) - today mainly from WMC/LOL to AAT and tomorrow from AAT-SVE-TVL-MMH over the Sierra. Main threats are erratic outflows to 40 knots, lightning, small hail, and heavy rains.

* Rain-snow lines varying between 6000-8000', so snow showers can't be ruled out at mountain airfields like TRK/TVL and MMH. NBM showing anywhere from 10-25% chances for 0.1 to 1" snowfall at these sites today and/or tomorrow.

-Chris

REV Watches/Warnings/Advisories

NV...None.

CA...None.