textproduct: Reno

KEY MESSAGES

* Light winds and valley inversions will keep hazy skies and air quality reductions through the remainder of the holiday weekend with patchy freezing fog in some Sierra valleys.

* Dry weather prevails going into this week with above average daytime temperatures and slightly below average low temperatures.

* A pattern change is possible for the latter half of the week allowing gusty mountain ridge winds to return.

DISCUSSION

A high pressure ridge still resides over the western CONUS and eastern Pacific today, which allows the light winds and dry conditions to continue in the region. There is a slight shortwave disturbance in the upper air pattern causing the cloud cover going into today. Forecast guidance projects the disturbance to depart the region tonight, which will let the skies to mostly clear up by tomorrow morning. Some of the latest CAM runs particularly the NAM Nest appear to be treating this disturbance a little differently and may be over-convecting in their projections as they show some spotty light showers in the late morning and afternoon today. Low confidence that this will be the case though with ensemble guidance and other deterministic models just keeping it dry with the cloud cover. Valley inversions expect to remain in place allowing hazy skies and localized lower air quality in particularly around urban areas to begin the week. Another concern looks to be the freezing fog that is still occurring in the Martis Valley as well as the Mono Lake area and around Lake Crowley. While the Martis Valley will see the patchy fog dissipate later this morning, the fog around the Mono County lakes will continue its pattern of staying in place going into the afternoon and keeping temperatures cooler before lifting for a few hours. These areas then expect to have the foggy pattern repeat tonight and into tomorrow.

Going through the middle of the week, forecast guidance shows the ridge pattern persisting for the region. With this setup, the dry conditions and light winds will continue at least through Wednesday. Daytime high temperatures in the 40s and 50s are forecast with the exception of the aforementioned Mono County lake areas that may not climb out of the 30s on Monday (similar to today) due to fog hindering daytime heating. Chilly overnight lows are also in the forecast with Monday night looking to be the coldest by a few degrees when compared to the other forecast low temperatures during the week.

By Thursday, ensemble guidance shows the upper air pattern changing slightly by introducing a Pacific trough into the southwestern CONUS. This may make ridge winds gusting up to around 45 mph possible for the second half of the week. The latest NBM run has also pushed light precipitation chances (~15%) into next weekend and placed them more into NE CA. There's good forecast uncertainty at this time due to the inconsistency between model runs, but will continue to monitor this going forward. -078

AVIATION

VFR conditions persist for area TAF sites going through the holiday weekend. The only exception is at KTRK where patchy and mainly shallow FZFG is expected through this morning around 15Z and then again tonight into Monday morning. Haze in W.NV may lead to reduced slantwise visibilities. Area cloud cover is forecast to generally diminish by overnight tonight. -McKellar/078

REV Watches/Warnings/Advisories

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