textproduct: Reno

KEY MESSAGES

* Dry weather prevails through early next week with above average daytime temperatures and typical chilly nights.

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

* Sierra ridges can expect periodic breezy to gusty east winds through Friday, mainly during the night and morning hours.

DISCUSSION

The high pressure ridge responsible for this dry and stagnant weather pattern remains centered over northern CA-NV through today. This ridge will then retreat to off the Pacific NW coast Thursday-Friday but return inland by the weekend.

In general, the weather that has been occurring for the past few days will persist this week and through the holiday weekend, with valley inversions keeping hazy conditions and some reductions in air quality especially around urban areas. The dry air mass and limited cloud cover will keep typically chilly nights for mid- January. For areas not affected by freezing fog, daytime high temperatures will remain above average for the next several days, with highs in most western NV and Sierra valleys settling in the lower-mid 50s, although a few sites above the inversion-trapped valley floors have a reasonable chance at 60 degrees, especially by the weekend. Unfortunately for those more persistent foggy areas, most notably around Mono Lake, highs are unlikely to reach 30 degrees with the fog producing poor visibility and even depositing a touch of snow at times, leading to patchy slick conditions on paved surfaces. Some shores of Mono Lake may see a short period of clearing each afternoon, followed by fog returning after sunset. Smaller scale shallow fog could also develop near other lakes and sources of standing water each night/morning this week.

Winds remain light for lower elevations, while for Sierra ridges, a steady east flow will keep gusts in the 20-35 mph range through Friday. Periods of enhanced 40+ mph wind gusts are expected each night/morning due to a slight tightening of the 700 mb gradient. As we get to the weekend, these ridge winds will subside although one more round of increased east winds could return Monday, as the ridge center is currently projected to make a brief return to the similar northern CA/NV location as today.

For next week, dry and conditions continue through midweek, with a westerly flow over the Sierra possibly helping to disperse the freezing fog around Mono Lake. Longer range guidance still shows a signal of more active weather returning later next week. However, the latest ensemble data is less aggressive with this potential pattern change as dry scenarios remain in play, while the wetter scenarios hint more toward weaker storm systems without a robust tap of Pacific moisture. MJD

AVIATION

VFR conditions with light winds continue this week at the main terminals. The only exception is KTRK where patchy freezing fog continues to develop each night/morning mainly between 08-17Z with IFR/LIFR conditions at the observation site, although this fog could be shallow and/or limited in coverage across the airport grounds. Haze due to inversions in western NV continues through at least Friday, which may lower slantwise visibilities.

E/NE FL100 wind gusts will continue through Friday, with overall lighter gusts (below 30 kt) during each afternoon/early evening and increasing to 30-40 kt during the overnight and morning hours, leading to areas of turbulence for flights crossing the Sierra. MJD

REV Watches/Warnings/Advisories

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