textproduct: Reno

KEY MESSAGES

* Summer-like heat will maintain widespread moderate to areas of major HeatRisk today.

* Thunderstorm activity increases today and tomorrow, peaking Friday. This will bring concerns for impacts to fire, recreation, and aviation on both days.

* Cooler and drier weather is favored to return over the weekend followed warmer temperatures for next week.

DISCUSSION

The latest RAP analysis of the upper air pattern this morning shows an upper ridge over the region with a subtropical trough trailing it over the Pacific. Going through today, forecast guidance projects the trough moving closer to the West Coast and breaking down the ridge. In the afternoon, a shortwave disturbance moves through the flow over the CWA as well. While the ridge still remains over the region today, well-above normal temperatures are forecast for one more day with the NE CA and W NV valleys having highs in the middle to upper 90s (some portions of W NV possibly reaching the 100 degree mark) and Sierra communities having highs in the lower to high 80s. As such, the Heat Advisory for the W NV Basin and Range continues through early tomorrow with some portions seeing Major HeatRisk.

Another concern for today looks to come from potential thunderstorms within the region this afternoon. REFS SBCAPE values increase to around 500-1000 J/kg in the Sierra and the Sierra Front (higher values west of the Sierra crest). With this instability, the increased warmth in the afternoon providing lift, and PWAT values up to around 0.6 inches: these portions of the CWA have around a 15-35% chance for showers and thunderstorms today with the window opening around 1-2 PM PDT. The storms will provide increased fire weather concern within the Sierra Front today (please refer to the Fire Weather Section below or the Red Flag Warning in effect today for more information). Brief bouts of heavy rain could occur with these storms, but not anticipating major flooding issues as the ground probably can absorb a good amount of rain with the recent dry conditions. When looking at model forecast soundings, the Sierra Front also will have up to around 1500-1800 J/kg of DCAPE allowing for storms to produce increased outflow gusts up to ~50 mph later today. Please be weather aware today especially if you have outdoor plans and remember: when thunder roars, go indoors!

For Friday, models show the trough making its way over the W CONUS. This pattern aloft will allow shower and storm chances within the region to increase to around 25-65% for most of the CWA for tomorrow. Recent runs of the CAMs show some morning showers developing in NE CA, but stronger storms then beginning to develop in the Quad Counties region (especially along the Pine Nut Mountains) by around noon. These storms look to move north- northeast and may not exit the CWA completely until the late evening. These storms could be a bit wetter with current QPF values in W NV ranging between a trace to around 0.25 inches. But some storms could also be on the dry side with the SPC showing a 10% dry thunderstorm for most of the CWA on Friday. A Fire Weather Watch is in effect in areas seeing the higher chances for fire weather concern on Friday though this area could expand. With similar convective parameters as those forecast for today, Friday will see similar storm hazards including gusty erratic outflows to 50 mph, lightning outside of rain cores, fast moving storms, and heavy rain under storm cores. Will be monitoring trends in case the environment becomes more favorable for severe weather. Blowing dust is also possible near desert sinks and playas if stronger gusts occur in the NV Basin and Range. Please have a way to receive the latest weather updates on Friday especially if you have recreation and travel plans.

While daytime high temperatures are forecast to decrease around 5-10 degrees on Friday, they become closest to mid-June normals on Saturday. Saturday's forecast highs for the NE CA and NV valleys will be in the middle to upper 80s while the Sierra communities will be in the middle to upper 70s range. Forecast guidance then projects the trough moving eastward and away from the CWA on Sunday followed by high pressure building over the SW CONUS going into the middle of next week. This signals dry conditions for next week with temperatures warming again to where Moderate HeatRisk is seen within W NV beginning on Monday. -078

AVIATION

Density altitude concerns may continue today at terminals in NE CA and W NV due to increased heating. The main concern today expects to be with showers and storms developing within the region starting around 18/21-22Z. The Sierra and Sierra Front have around a 15-35% chance for precipitation today. MVFR conditions are possible at most TAF sites should a storm develop nearby. Storms may contain increased gusty outflow winds, brief periods of heavy rain and lightning. Terrain obscuration, LLWS and turbulence may also be present near storm cores. Another round of showers and storms is forecast for tomorrow with increased chances and coverage which expect to bring additional aviation concerns. -078

FIRE WEATHER

Fire weather concerns increase as the thunderstorm potential within the region rises today and tomorrow. Antecedent hot and dry conditions with poor overnight recoveries have helped in drying fuels further which also raises fire danger.

Storms will move quickly once developed, with a mix of wet and dry storm modes. This increases potential for dry lightning strikes outside of wet storm cores as well as dry storms that produce more lightning than moisture. Gusty, erratic outflows of 50+ mph are possible, increasing the threat of rapid wind direction shifts.

A Red Flag Warning is in effect today across the Sierra Front from 1 pm to 10 pm. A Fire Weather Watch still stands for Friday, in effect from 8 am through 11 pm. HRICH/078

REV Watches/Warnings/Advisories

NV...Fire Weather Watch from Friday morning through Friday evening NVZ458.

Red Flag Warning from 1 PM this afternoon to 10 PM PDT this evening NVZ420-421.

Heat Advisory until 5 AM PDT Friday NVZ004.

Fire Weather Watch from Friday morning through Friday evening NVZ423.

CA...Fire Weather Watch from Friday morning through Friday evening CAZ270-278.