March 6, 2019 – Occasional showers and thunderstorms with mountain snow today. Mountain travel will be impacted and additional rain may increase flood potential. Showers continue Thursday into the weekend.
Front moving inland early this morning accompanied by a line of showers with mainly light to moderate rain. Gusty south to southeast winds have increased ahead of the front and are currently gusting around 25-35 mph across much of the region. Snow levels remain fairly high (around 6000-7000 ft per profiler data) and KBLU precip remains rain.
Front and widespread precipitation moves through early this morning followed by scattered showers and thunderstorms from late morning through the afternoon as weaker upstream short-wave approaches. Forecast soundings in the post-front environment this afternoon indicate the potential for a few longer-lived storms with their attendant risks, heavy rain, hail and gusty winds.
Higher res models also continue to indicate the potential for a persistent line of showers and thunderstorms over Shasta County this afternoon into this evening with the setup of the north valley convergence zone.
12 to 18 inches of additional snow can be expected across the passes today, with 2 feet or more over the peaks, before snow tapers a bit tonight. Showers may bring another foot or more of accumulation through Thursday morning. Additional valley rainfall of 1/4 to 1/2 inch is expected today with much lighter amounts expected tonight and Thursday.
With saturated soils, and streams, creeks and main stem rivers running high, additional rain may increase the potential for flooding, especially near thunderstorms which are capable of bringing higher amounts in a short period of time.
Showers will persist Thursday and Friday as a longer wave trough moves through the West. Lowering snow levels during this time will result in some snow below the BLU level which could lead to a downgrade of the winter storm warning to an advisory.
Extended Discussion (Sunday through Wednesday)
A broad positively-tilted upper trough will settle offshore of the state on Sunday. Forecast guidance has been fairly consistent in carrying the parent upper low toward northern Baja California by early next week. Some snow showers are possible over the mountains (primarily from Highway 50 southward) to conclude the weekend. Given the general lack of moisture, perhaps an inch of snow could be squeezed out over regions which see such a shower.
As the axis of lower heights exits toward northern Mexico, dry northerly winds are anticipated to commence next week. The next system to keep an eye on would be Tuesday as a longwave trough advances through the Pacific Northwest. It remains to be seen where the southern extension of this storm will reside. Currently the 00Z ECMWF is flatter while the 06Z/00Z GFS shows a more amplified solution. While the latter does have ensemble support, would like to see the ECMWF join this wetter scenario. Thus, have kept the forecast mainly dry for the early/middle part of next week for now.
The temperature forecast supports slightly below average temperatures for early to mid March. Valley high temperatures should sit anywhere from the mid 50s to low 60s while mountain locales remain in the 30s and 40s.