textproduct: Reno

KEY MESSAGES

* A weather system continues to bring showers, thunderstorms, and cooler temperatures today. Be prepared for recreation and travel impacts due to gusty winds, rain, hail, and mountain snow.

* Cool, showery weather with additional thunderstorm chances expected Monday and Tuesday. Snow may impact travel over mountain passes above 8000 feet Monday.

* Warm and dry weather returns mid-week.

DISCUSSION

Today: A Pacific closed low resides west of the Central CA coast today. Forecast guidance keeps this low from making landfall today, but has it moving closer to the coast throughout the day. At the surface, showers and thunderstorms have already kicked off in portions of the Sierra and Sierra Front according to the latest radar returns. Shower chances for the rest of today look to be around 30-50% in NE CA, 70-90% in the Sierra, 50-70% in the Sierra Front, and 20-60% in the W NV Basin and Range. While the entire region sees some risk for thunderstorms today, the Sierra and Sierra Front portions have the best chances of 25-45% this afternoon. Potential storm hazards today include lightning strikes, small hail & ice pellets, erratic & gusty winds, and brief periods of heavy rain. Storm motion looks to be quick (~15-25 kts to the N/NW), so this will lower potential flooding concerns today. Severe thunderstorm chances do look low (<5%), but cannot be ruled out completely as the latest RRFS run shows convective parameters that could support it especially around the Greater Tahoe area this afternoon. Please have a way to receive the latest weather information especially if you have outdoor plans for the rest of today. Area-wide precipitation chances look to diminish to around 10-30% overnight with the exception of portions of W NV south of US-50 which sees a 40-70% chance continuing around midnight. Snow levels also will drop to around 8 kft overnight which will change precipitation type to snow in higher portions of the Sierra. Higher elevations in Mono County potentially have a 40-50% NBM probability of 1+ inches of snowfall by Monday morning.

Monday and Tuesday: Model guidance has the aforementioned Pacific upper low take a southwest track along the CA coast on Monday. The low then begins a more eastward track staying south of the CWA as it opens up into trough on Tuesday. With this pattern aloft, precipitation chances will continue on Monday (60-90% across the region) and Tuesday (20-60% along and south of I-80, around 20% or less to the north). Thunderstorm chances for Monday afternoon look to be around 20-30% areawide with Tuesday seeing the same chances along and south of I-80 and <15% to the north. Similar storm hazards to those on Sunday will be seen on both days with severe potential (storms containing 58+ mph wind gusts and/or large hail of 1+ inches in diameter) being low, but still possible. Remember: when thunder roars, go indoors. Area high temperatures cool down a bit on Monday (NE CA and W NV valleys in the middle 50s to middle 60s range, Sierra Communities in the upper 40s) before rebounding a bit on Tuesday. Another concern is the potential for mountain snow at some of the Sierra Passes in Mono County as snow levels look to drop to around 7.5-8 kft during Monday and then down to around 7 kft overnight Monday. This may allow for accumulating snow at recently open Sierra Passes that could cause some hazardous traveling conditions. While the high sun angle at this time of year may inhibit some of the accumulation, the latest NBM probabilities show around a 45-65% chance of 6+ inches of snowfall at the Sierra Crest in Mono County by late Tuesday morning. As active weather expects to continue into the first half of the week, please watch for forecast updates as they become available.

Wednesday and beyond: As the trough is absorbed into a larger trough out in the E CONUS, an upper ridge moves over the W CONUS starting Wednesday. This ridge looks to be part of an omega blocking pattern through much of the rest of the work week. This will allow for dry conditions to prevail for the rest of the week with temperatures warming to around 5-10 degrees above seasonal normals. Currently, NE CA and W NV valleys have highs forecast in the lower to middle 80s while Sierra communities have daytime high temperatures in the 70s beginning Thursday and going though the weekend. There is some model uncertainty in the upper air pattern over the weekend though as the GEFS shows a weak trough moving through the NW CONUS while the ECMWF Ensemble shows this feature being merging with a trailing Pacific low. While the dry pattern and the above normal temperatures expect to continue over the weekend, the GEFS solution may result in a slight uptick in winds though there is low forecast confidence at this time. -078

AVIATION

Showers and thunderstorms continue within the region today. Most area TAF sites see around a 30% chance for a thunderstorm to occur through 04/03Z which would cause IFR conditions. The exception is at KMMH which would has similar -SHRA chances bringing MVFR restrictions during this time. Potential hazards with these storms include frequent lightning, brief heavy rainfall, gusty outflow winds around 35 kts, and small hail (less than one inch in diameter). Severe thunderstorm chances are low today (<5%), but are still possible (storms with gusts up to 60 mph and/or large hail of one inch in diameter). Shower chances lessen overnight, but increase again in the morning as more shower and thunderstorm chances are in the forecast on Monday and Tuesday. Lower cloud heights are expected today, which may cause mountaintop obscurations. -078

REV Watches/Warnings/Advisories

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