Truckee, CA Weather

Key Messages

* A slow moving storm will bring widespread wetting rain with thunderstorms, and high elevation snow to the region today and Thursday.

* Cool but mainly dry Friday into early next week. A more active storm pattern may return by the end of October.

Discussion

Isolated light rain showers with a few lightning strikes moved through parts of western NV and the eastern Sierra yesterday afternoon-early evening. Through much of this morning, we'll have a break from significant shower activity, until the next wave of forcing and moisture associated with the low off the CA coast moves inland. The height of this storm is still targeted to arrive by this afternoon and continue through Thursday, when widespread showers, isolated-scattered thunderstorms and high- elevation snow impact the area. WPC has expanded a marginal (5-15%) risk of excessive/flood-producing rainfall to include areas from Reno-Fallon southward through early Thursday morning.

TODAY-THURSDAY, THE MAIN EVENT:

* PRECIPITATION: A solid rain event (80+% chance for at least 0.25" of total rainfall regionwide, except slightly lower 65-80% chance near the OR border), begins late this morning near the eastern Sierra and west central NV. By this afternoon, more organized bands of rain showers and thunderstorms form across the Tahoe basin, the main cities of far western NV, and eastward to the US-95 corridor, with this initial round of activity pushing north of I-80 through this evening. Stronger storms may produce locally heavy rainfall (1" or more) and accumulations of small hail capable of producing localized flooding in poor drainage areas and burn scars such as the Floriston, Hawk, Bull and Bug fires. This isn't the only round of rain and storms for the event, as multiple guidance sources favor another push of precip overnight into Thursday morning across the eastern Sierra and much of western NV. Shower bands with embedded t-storms then redevelop Thursday afternoon, with a final wraparound band of rain kicking eastward into west central NV Thursday night into Friday morning as the storm exits to central-eastern NV.

* HIGH ELEVATION SNOW: Higher highway passes such as Ebbetts, Tioga and Sonora have a 50-80% chance of 2-4" snowfall, with up to 25% chance for 8" storm totals through Thursday. Higher peaks in southern Mono County have up to 25% chance for 1 foot of new snow. Farther north around the Tahoe region, Mt Rose Summit and Carson Pass could receive a quick 1-2" burst of snow tonight or Thursday. During periods of convection-enhanced precipitation, snow may briefly fall at much lower elevations, but meaningful accumulations should be limited to areas above 8000 ft.

* TEMPERATURES: The cooling trend continues with the coldest temperatures expected Thursday, when highs only reach the 50s-near 60 for lower elevations and mid 40s-lower 50s for Sierra communities. As the storm departs Thursday night, a period of brisk W-NW winds with gusts 25-35 mph, locally 40+ mph will enhance the chilly conditions in areas north of US-50.

* PREPARING FOR THE STORM: Expect slick road travel and slower commutes from this afternoon through Thursday. Now is a good time to prepare your vehicles for winter travel and bring out the cold weather clothing, as well as clearing debris from gutters and storm drains before the rain begins today.

Aviation

* Widespread rain and embedded thunderstorms bring periods of MVFR/IFR conditions and terrain obscurations from 20-21Z this afternoon through much of Thursday at the main terminals. Thunderstorm chances peak at 25-30% this afternoon, dropping to 15-20% for Thursday.

* Although overall winds will be on the lighter side through Thursday afternoon, heavier shower/t-storm bands could produce brief gusts of 30+ kt. W-NW gusts then increase to 20-25 kt Thursday night for KRNO/KTRK with a cold front passage. MJD