Scattered showers possible today, drier and warmer for the remainder of the week

April 30, 2019 – Cooling trend continues today with temperatures near or a little below average. Dry conditions except for a chance of showers or isolated thunderstorms over the foothills and mountains today. Temperatures trend warmer through the remainder of the week with a chance for showers returning to the higher terrain this weekend.

Discussion

Strong short-wave pivoting into southwest OR early this morning with scattered showers and a few thunderstorms developing out ahead of it across northeast CA. The approaching system has induced a strong onshore gradient and allowed the marine layer to deepen resulting in gusty onshore winds into the Central Valley and a stratus intrusion into the southern Sacramento Valley and foothills.

Shower chances will spread southward through the foothills and northern Sierra today as short-wave energy carves the trough eastward into the Great Basin and the cold front drops southward. QPF is expected to be generally under a quarter of an inch with perhaps an inch or two of snow accumulation possible along the northern Sierra crest. Temperatures today will drop to below average from a combination of synoptic cooling and continued onshore flow.

Beginning Wednesday, dry weather and gradually milder temperatures are forecast for the remainder of the work week as high pressure rebuilds.

Extended Discussion (Saturday through Tuesday)

Upper ridge axis shifts through early Saturday as closed upper low in the EPAC approaches the CA Coast. Models differ with how quickly the low progresses with the GFS moving some showers into the higher elevations by the evening, while the EC holds off until Sunday morning. Either way, Sunday looks to be unsettled over Interior NorCal with showers in the foothills and mountains and possibly into portions of the Central Valley. Model CAPE attm looks to be relatively low so for now will advertise only showers and continue to monitor. Progs differ on track and progression of low into early next week so will keep a threat of showers over the northern and eastern foothills and mountains into Tuesday.