textproduct: Reno

KEY MESSAGES

* Gusty winds will impact holiday travel and recreation, with elevated fire concerns across Mono and Mineral counties.

* Chances of rain and isolated thunderstorms increase across Lassen, the Surprise Valley, and N Washoe County this afternoon.

* Warmer and drier weather is favored next week with low shower and thunderstorm chances along the E Sierra around midweek.

DISCUSSION

A quick-moving shortwave will drag a dry cold front through the Sierra and western Nevada today. Primary weather concerns will be with gusty winds, including impacts to recreation, travel, fire, and aviation sectors. The secondary weather concern will be the increased potential for some showers and thunderstorms across the northern tier of the forecast area, right along the CA/NV/OR border.

WINDS: Ridge winds have already been trucking along today with gusts in the 40-55 mph range. The ridge winds will remain elevated through the late afternoon with gusts 60+ mph possible. This will result in impacts to aviation, including increased risk for wind shear and mountain turbulence. See the AVIATION discussion for details on timing. Surface wind gusts have already arrived in some areas, especially in the foothills and Eastern Sierra, where observations are approaching 40 mph. Plan on wind gusts 30-40 mph across much of the area this afternoon, but I wouldn't be shocked to see gusts 50+ mph, particularly for the more typically windy spots. The 12z sounding had a rather stout stable layer just above the ridgeline that forecast soundings lower steadily through the day. The combination of the tightening surface pressure gradient along the dry front and the stable layer "kicking" upper level strong winds to the surface may compound the strength of the winds today. Be prepared for rough lake waters, turbulent flights, and blowing dust/reduced visibilities near desert sinks and playas. Dry and windy conditions will also elevate fire concerns from Mono County into S.Lyon/Mineral counties this afternoon (more details below). Winds will drop off considerably after 8pm, reducing the impacts as we journey into Monday.

PRECIPITATION: Shower and thunderstorm potential will be limited to areas near the Oregon border. Rain chances increase to 30-60% across N Lassen County, the Surprise Valley, and far N Washoe County this afternoon, with hi-res ensembles suggesting a 20-40% probability of isolated thunderstorms. Potential thunderstorm hazards include brief heavy rain, strong outflow gusts of 45+ mph, small hail/graupel, and occasional lightning. Strong outflow gusts may kick off blowing dusts resulting in degraded visibility near playas/dry lake beds through the evening.

Labor Day and Beyond: Monday will be dry and mild. Ensemble clusters are leaning toward a drier and warmer week ahead as high pressure takes hold across the region. There will be low (10-30%) chances for rain and storms each afternoon for areas from Lake Tahoe southward into the Eastern Sierra. Otherwise, plan on more typical September temperatures with highs in the upper 70s to 80s. Ensemble clusters highlight the potential for another cool, windy and possibly damp weekend as the next low pressure system approaches the West. There's quite a bit of uncertainty with the location for now, as some ensembles maintain the ridge and block the low from reaching our area.

-Edan

AVIATION

A quick moving cold front will pass through later this afternoon with an increase in gusty winds to the Sierra and western Nevada as well as low chances for showers and thunderstorms along the OR border today.

WINDS: Plan on SW FL100 winds 30-35 kts through 0z Monday with LLWS risk for KTRK-KTVL-KMMH as well as mountain wave turbulence from the Sierra crest eastward into far W Nevada. S-SW surface gusts 25-35 kts will persist through 03z Monday. Impacts include areas of blowing dust in the afternoon, with reduced visibilities at KHTH- KNFL-KLOL. For KRNO and KCXP/KMEV, SW winds will shift after the dry frontal passage to W/NW after between 0-03z Monday. The quick shift will provide another round of LLWS concerns during the front passage and behind it. FL100 winds will begin to weaken by 03-06z which will help to reduce the threats of LLWS and mountain wave turbulence by 06z.

PRECIPITATION: Chances of showers and thunderstorms increase to 30- 60% this afternoon near the Oregon border, otherwise VFR conditions will prevail today.

-Edan

FIRE WEATHER

UPDATE- Red Flag Warnings are in effect for fire weather zones 274, 421, and 429 through 8PM for Gusty Winds and Low Humidity.

A dry frontal passage is producing 40-50 mph S/SW gusts this afternoon across the Sierra Front, and Mono and Mineral counties. RH reductions of 7-20% will be focused from valley and midslope areas of Mono County into S.Lyon and Mineral counties. Plan on 4-6 hours of critical fire weather conditions through the evening. Some locations in Mono County (Lundy Canyon and Mammoth Airport) are already hitting this criteria with humidity values 8-10%.

While afternoon RH will be slightly elevated (20-25%) across the Sierra Front and portions of west-central Nevada, it will be dry enough to warrant elevated fire concerns across these areas today.

Fortunately, nighttime recoveries will be moderate to good (up to 50- 80%) tonight into Monday morning. However, the exception to this will be across of the Chalfant Valley and other lower elevations near the Mono/Inyo Co border where RH will struggle to exceed 40%.

-Salas

REV Watches/Warnings/Advisories

NV...Lake Wind Advisory until 11 PM PDT this evening NVZ001>004.

Red Flag Warning until 8 PM PDT this evening NVZ421-429.

CA...Lake Wind Advisory until 11 PM PDT this evening CAZ071>073.

Red Flag Warning until 8 PM PDT this evening CAZ274.