textproduct: Reno

KEY MESSAGES

* Light winds and valley inversions will keep hazy skies and air quality reductions to begin this week with patchy freezing fog in some Sierra valleys.

* Dry weather prevails this week with above average daytime temperatures and near average low temperatures.

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

DISCUSSION

The latest RAP analysis of the upper air pattern shows generally the same pattern that has been the case for a good number of the previous days: a high pressure ridge residing over the western CONUS and eastern Pacific. Forecast guidance shows this setup continuing through at least midweek, which will allow dry conditions and light winds to persist across the region. The daily widespread freezing fog that has been experienced around the Mono Lake area looks to continue at least today and tomorrow, so please be prepared for lower visibilities if traveling in the area. There may be a few hours in the afternoon today where it dissipates, but the forecast calls for it to return tonight. The Martis Valley and Lake Crowley area also expect to see morning freezing fog continue this morning as well as tomorrow morning. Valley inversions still remain in place allowing hazy skies and localized lower air quality in particularly around urban areas to begin this week. Daytime high temperatures to begin the week are forecast to be in the 40s and 50s with the exception of the Mono Lake area and some other areas where the fog will hinder daytime heating and keep the temperatures from climbing out of the 30s. Overnight low temperatures look to be more or less similar to those experienced over the weekend.

By late Wednesday into Thursday, ensemble guidance is picking up on a pattern change with an Pacific upper low making its way across SoCal before opening up into a trough as it reaches AZ on Friday. There is still some model uncertainty in the exact placement and timing of this low's progression, which does lower forecast confidence. But there is potential for mountain ridge gusts to increase slightly as a result on these two days. The latest NBM run now has a slight chance for light snow in the highest elevations of the Eastern Sierra on Thursday and Friday afternoon. Not the greatest confidence in this occurring due to the run-to-run model differences seen, but little to no accumulating snow is expected should these showers occur. By the weekend, a trailing upper ridge looks to move back over the region allowing for more dry weather. -078

AVIATION

VFR conditions and light surface winds continue for area TAF sites to begin the week. The only exception is at KTRK where patchy and mainly shallow FZFG is expected through around 15Z today that may return again tonight. Haze in W.NV may lead to reduced slantwise visibilities. -078

REV Watches/Warnings/Advisories

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