textproduct: Reno

KEY MESSAGES

* Widespread showers and isolated thunderstorms are expected within the region today, along with much cooler temperatures. * Drier weather with mild temperatures are forecast through the weekend.

* Breezier winds are on tap for early next week with below- average temperatures through the week.

DISCUSSION

According to the latest RAP upper air analysis, a southwesterly flow continues over the CWA being between a ridge over the SW CONUS and a Pacific trough. There is also an upper low feature over the SW Canadian coast that models project moving closer to the Canada-U.S. border through the day. With this setup aloft, a cooler system moves through the region today, giving the CWA widespread shower chances of around 30-80%. When looking at the 06Z run of the HRRR, chances for precipitation begin to increase the window for the main bulk of the precipitation opens around 9-10 AM and ends around 7 PM, though there is a 10-40% chance for light showers along I-80 prior this window opening. Precipitation chances from this system expect to taper off completely early Saturday morning. The latest QPF values look to range from a trace to around 0.3-0.4 inches in the Sierra crest. With increased cloud cover expected today, the forecast also shows daytime highs that will be around 5-15 degrees below seasonal normals today. NE CA and W NV valleys will see high temperatures in the middle 70s to lower 80s range while the Sierra communities will have highs in the middle 60s to around the 70 degree mark.

As for thunderstorm chances, the latest NBM probabilities show around a 10-40% chance today with portions of the region along and south of US-50 having the higher end chances. When looking at convective parameters for later today, there is around 100-500 J/kg in the aforementioned higher chance areas, with pockets of CAPE values over 1000 J/kg in the NV Basin and Range today. Forecast soundings do look to be pretty moist today as more tropical moisture is pumped into the area with the upper air setup. Stronger thunderstorms will be capable of frequent lightning and outflow wind gusts up to 50 mph. Storms can produce periods of heavy rainfall today too with PW values of 0.8-1.2 inches, though the higher PW values could just translate into the increased cloud cover today. Expected storm motions look to be quick today, but flash flooding will still be possible where storms train, especially if they do so over vulnerable burn scars and/or steep terrain. The WPC currently has a marginal risk (5%) for excessive rainfall generally along and south of a line from Winnemucca to Portola today. Please be weather aware today and have a way to receive the latest weather updates!

Going through the weekend, forecast guidance shows the upper low moving eastward along the international border with the Pacific trough progressing over the CWA. Skies over the weekend will clear up quite a bit following the departure of today's system, which will allow for area temperatures to rebound slightly. NE CA and W NV valleys will see high temperatures in the lower to middle 80s with Sierra high temperatures in the upper 60s to middle 70s. While mostly dry conditions prevail through the weekend, there is a 10-20% chance for a diurnal shower or two during the afternoon hours in the NV Basin & Range and Mono County.

For next week, ensemble guidance begins to show another Pacific trough entering the picture. This pattern looks to possibly cause winds on Monday and Tuesday afternoons to increase with gusts up to around 25-35 mph again, though confidence is low at this time. Wind gusts of this magnitude could cause fire weather concerns to return to the region with conditions mostly drying out after today. Will continue to monitor this as well as some possible precipitation chances for the middle of next week. The forecast is also showing high temperatures beginning the month of September that will be mild, yet still 5-10 degrees cooler than normal highs for this time. -078

AVIATION

A cooler system moves through the region today, bringing widespread shower chances (30-80%) along with isolated thunderstorm chances (10- 40%). While isolated showers are possible early this morning, the 06Z HRRR model shows the window for the bulk of the showers and storms to be 28/16Z-29/03Z. There may be some lingering showers in the NV Basin and Range through 29/06Z with the system exiting overnight. The higher end chances for thunderstorms today generally look to be along and south of US-50. Thunderstorms near terminals today will have the capability of producing erratic outflow winds gusting up to around 30+ kts. While not currently anticipating sub-VFR conditions at area TAF sites, will be monitoring for stronger thunderstorm today as periods of heavier rainfall are possible which will reduce visibility. Also, Sierra ridge winds will gust up to around 40 kts this afternoon.

Drier conditions are in the forecast through the weekend, with decreased chances (10-20%) for an isolated shower or two during the afternoon hours in the NV Basin and Range and S. Mono County. Saturday afternoon winds gusting up to around 20-30 kts are in the forecast, followed by typical afternoon zephyr breezes on Sunday. -078

REV Watches/Warnings/Advisories

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