textproduct: Reno

KEY MESSAGES

* Patchy fog may reduce visibilities in and around Truckee this morning.

* Isolated showers along the Sierra crest today with slight (30-40%) chances for showers Saturday.

* Pattern shift to cooler and more showery weather early next week with a 40-50% chance for thunderstorms along the Sierra and Sierra Front Sunday and Monday.

DISCUSSION

Persistent southerly flow aloft from the combination of an upper level ridge and an incoming low pressure system off the West Coast will give our CWA a few days of temperatures 5-10 degrees above average (mid-70s for NV valleys) today and Saturday. Due to the lack of nocturnal cloud coverage and light winds overnight, Martis Valley and Truckee could see freezing fog again this morning (30% chance). Winds today will be light and east/southeasterly, then shifting out of the west with gusts 15-20 mph on Saturday. Fairly light winds generally out of the west continue into early next week. Temperatures take a hit on Monday to a few degrees below average (mid-60s in NV valleys), then bounce right back up into the low 80s across western NV by Wednesday or Thursday.

The highlight of forecast over the next 5 days will be afternoon showers and thunderstorms. As the closed low approaches our area and moves down the coast, we'll see an area of upper level diffluence setup over our CWA this afternoon. This, in conjunction with increased PV this weekend, will be the main forcing behind the storms this weekend. Today, the storms will be concentrated south of US-50 along the Sierra. Current chances to see a rain shower around Alpine and Mono counties is around 15%.

Stronger showers and thunderstorms are expected Saturday and Sunday due to increased forcing aloft and more available moisture to tap into. PWATs Saturday and Sunday are forecast to be around 0.6-0.7" which is right around the sweet spot for our area. Storm coverage will expand Saturday and Sunday over western NV and northeast CA. Current precip chances are 30-40% Saturday (15% chance t-storms) and 50-80% Sunday (30% chance t-storms), with the higher end being along the Sierra crest around the Greater Lake Tahoe area. Latest CAM guidance is showing MUCAPE values of 100-300 J/kg on Saturday and an eyebrow raising 500-800 J/kg on Sunday. Storm motions appear on the slower end around 10-15kt Saturday, then a bit faster around 20-25kt on Sunday. Model soundings show DCAPE values around 700-1000 J/kg Saturday and Sunday, which puts estimated wind gusts near thunderstorms around 30-40 mph. Overall, main concerns with these storms will be brief heavy rainfall, occasional-frequent lightning, small hail and ice pellets, and brief gusty winds from outflows.

The storms look to continue after Sunday, with Monday possibly being another strong thunderstorm day. Long range models such as the GFS and Euro are showing MUCAPE values upwards of 600-800 J/kg on Monday, and the EC EFI for CAPE also highlights this. Later this week, at least one more cut-off low is expected to follow a similar path as the one this weekend, allowing storm chances to continue through the end of next week. Of course, there remains some uncertainty in timing and exact placement of that low as it makes its way onshore, but it's very likely we'll stay active through the end of next week.

-Justin

AVIATION

VFR conditions continue today with light east winds. KTRK has a 30% chance to see FZFG tonight through sunrise. An incoming system on Saturday will increase FL100 winds out of the SW to 20-30kt in the afternoon. Chances for showers jump up to 30-40% on Saturday and 50-80% on Sunday, each with a 15% and 30% chance of lightning, respectively.

-Justin

REV Watches/Warnings/Advisories

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