textproduct: Reno

KEY MESSAGES

* Patchy fog may impact this morning's commute, especially near Truckee.

* Warmer and drier weather into the weekend with low chances of afternoon showers near the Sierra crest today and Thursday.

* Chances of rain and mountain snow showers, thunderstorms, and gusty winds increase this weekend and linger into early next week.

DISCUSSION

Clear skies and minor warming above the surface should allow pockets of fog/freezing fog to redevelop overnight in NE California and the E Sierra -- especially after another afternoon of light showers. Most notably, freezing fog is favored near Truckee where the morning commute may be met by reduced visibilities and slick roads. This includes the stretch of I-80 between Boca and Donner Lake. Be sure to drive slow and leave extra space between cars if encountering fog.

Exiting low pressure will allow dry, N/NW flow to overspread the region today, encouraging a warming and drying trend that lasts into the weekend. Drier air and a stable upper layer will largely suppress shower and thunderstorm potential until the weekend, but there is a low chance (10% or less) of isolated showers near the Sierra crest in the afternoon today and Thursday. Otherwise, warmer days are in store as daytime highs go from 60-70F today to upper 60s and upper 70s on Saturday. Some communities in NE CA and W NV valleys may even see highs reach 80F Saturday afternoon.

Potential for unsettled weather increases over the weekend as a closed low approaches the western states. However, questions still remain on how this low will evolve next week given existing model disagreements, lending to higher uncertainty in timing and intensity of storm impacts. Generally, more isolated shower activity begins Saturday afternoon -- favoring the eastern Sierra -- before increasing in likelihood and coverage each day through Monday or Tuesday. Thunderstorm potential follows a similar trend, although Sunday stands out as a more favorable day based on the location of an upper level jet and attendant large scale ascent.

Sierra snowfall will be quite sensitive to the low's progression as snow levels remain well above mountain passes until a pocket of cold air at the low's center moves inland. Guidance suggests this happens Monday or perhaps early Tuesday, however the window for accumulating snow at pass level (or lower) is rather brief as rising snow levels will confine snow to highest Sierra peaks on Wednesday of next week. As mentioned, forecast confidence is low at this point, and any variations in the storm's passage can shift when what was described above occurs and how impactful it will be.

-Salas

AVIATION

The primary near-term concern will be periods of FZFG and IFR/LIFR conditions overnight at KTRK. Like yesterday, the most favorable timeframe for fog will be between 10Z and 16Z before mixing out/increasing CIGS and VIS. Minimal change in the weather pattern should allow FZFG to redevelop tonight into Thursday.

Otherwise, VFR conditions and light breezes today with increasing low/mid clouds in the afternoon. Sole concern will be terrain obscuration and a 10% chance of showers at KTRK-KTVL-KMMH this afternoon.

-Salas

REV Watches/Warnings/Advisories

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