January 25, 2021 – Light rain and snow expected into early this morning as a cold system moves across Northern California. Freezing temperatures are expected across much the area Tuesday morning. A long duration, high impact winter storm is expected Tuesday evening into Friday bringing periods of gusty winds and moderate to heavy rain and mountain snow. Potential for significant low elevation snow and damaging winds Tuesday night and Wednesday.

Discussion

Radar shows continued rain and mountain snow showers across much of interior Northern California early this morning. Rain amounts for yesterday into this morning range anywhere from generally 0.10- 0.75″, with a few locally higher amounts seen. Scattered precipitation is expected to continue into the morning, with some lingering mountain precipitation possible into the evening. Any additional snow amounts for the afternoon and evening across the Central Sierra are expected to be light.

Behind this system, breezy north winds are expected this afternoon across the Valley with local gusts up to 30 mph possible. Skies clear this evening and overnight temperatures quickly fall to near or below freezing for most areas. Expect valley temperatures early Tuesday morning anywhere from the mid 20s to low 30s and mountain temperatures in the single digits to teens. A Hard Freeze Warning has been issued for the Valley as this may be the first long duration freeze event for the winter. This cold air precedes the next storm and is what will lead to the low elevation snow at the beginning of this next event.

The advertised high impact, cold winter storm arrives Tuesday early evening beginning in the northwest portion of the area and continues southeast overnight into Wednesday. The biggest changes with the forecast come with strong winds and low elevation snow across the far northern Sacramento Valley.

For the snow, snow levels begin extremely low on Tuesday especially in the Shasta County and northern Sacramento Valley area. Ensemble guidance indicates a good chance for low elevation snow in this area between Tuesday evening and Wednesday morning, possibly down to around 500 feet impacting areas such as Redding with even some possible light accumulation down to Red Bluff. Have expanded the Winter Storm Watch to include these areas until Wednesday morning before snow levels begin to rise through the day.

Southerly winds increase rapidly overnight as this storm moves in with 925mb NAM winds maxing out around 80 mph. This may translate to winds across the Valley of 35 to 45 mph with gusts of up to 60 mph. A High Wind Watch has been issued for these anticipated damaging winds. With widespread rain and snow also anticipated during these overnight hours, expect extremely poor visibilities and hazardous travel conditions.

Snow levels increase on Wednesday above 3000 feet with heavy snowfall expected to continue into Friday morning. By the end of the week, multiple feet of snow will be likely in the mountains with a few inches of rain in the Valley. There may be some breaks in Valley precipitation during this multiple day event and rain may vary from very light to extremely heavy at times. Local flooding may be of a concern especially on roadways.

Extended discussion (Friday through Monday)

Active storm pattern continues late this week into early next week as an upper trough remains off the coast bringing persistent moist southwest flow into NorCal.

Precipitation amounts likely to be significantly less than earlier in the week on Friday and Saturday giving a relative break to mountain travelers, but another round of impactful mountain snow looks likely Sunday into Monday.