Rain and snow in the mountains tonight through Saturday, bouts of choppy weather next week – YubaNet


Persistent showers in the Sierra, otherwise a break in weather today. Precipitation returns to the region this evening and Saturday before another break on Sunday. the unstable the trend continues next week with the potential for more rain and snow in the mountains.


Relative break in weather across most of the NorCal interior early this morning like yesterday hollow pushed east. The exception is the prosecution scattered light showers over the northern Sierra. The snow level continues to gradually increase as the precipitation has changed to light rain at KBLU, and radar indicates that the level is currently around 6500 ft along I-80.

Today’s break will be brief like the next one hollow rapidly approaching. The next one will bring another round of significant precipitation to the region as another relatively weak AR transit, but the duration is expected to be considerably shorter compared to yesterday’s system, with most precipitation forecast to occur tonight through at noon on Saturday.

QPF an additional 1 to 2.5 inches will be possible over the mountains, with a quarter to a half inch possible in the Sacramento Valley. The northern San Joaquin Valley should see a tenth or two like the hollow swings inland further south.

Snow amounts likely won’t be as impressive as the last system over the northern Sierra (and snow levels will stay around 5-6k ft). Nevertheless, significant impacts on travel likely develop again this evening and persist for much of Saturday, and winter weather advisories have been issued.

We see some CAP Saturday afternoon construction primarily on the northern Sierra and Sierra foothills north of I-80. The forcing will be rather weak in the afternoon and the thunderstorm the threat seems low but not zero. A isolated cell or two will be possible. Saturday’s environment will be very similar to today’s and similar threats can be expected with any thunderstorms that eventually develop.

Our asset and the unsettled weather will pause on Easter Sunday as weak ridges build up and we will see temperatures warm to near average. Another system is expected to move Monday afternoon.

In-depth discussion (Tuesday to Friday)

A cooler than Ordinary wx model is planned on Norcal with periods of unstable wx. Currently, later in the day Tuesday and Wednesday morning seems to be the mildest/driest wx period before the next AR/TPW plume moves landward/inland.

The WEF Probability IVT/IVT plume forecasts indicate that another “weak” AR/TPW plume will bring more rain and mountain snow to Norcal late on the 20th or 21st.

Deterministic models vary the onset of the frontal band of precipitation moving through NorCal with the ECMWF faster than the SFP. Apparently these models “reversed their scripts” to handle this wx system with the ECMWF now very gradual in sweeping this AR/Plume through NorCal followed by another shortwave too much around the 23rd, while the SFP follow yesterday ECMWF suggesting a prolonged shower pattern as a parent closed low from NErn Pac descends SEwd in the center California/Srn California Fri. Although confidence is low at the moment, this scenario would have greater potential for “strong” California convectionespecially on SOCAL.

Since the Day 3-7 prototype cluster page is based on Thursday April 14th 12Z runs, Day 7 ends at 00z Friday April 22nd, leaving some speculation for the Friday forecast.

All clusters except #4 follow yesterday’s ECMWF and tonight SFP usually a longer wave too much and deep closed low forming on the Ern Pac continue the downpour, unstable wx model on NorCal for Fri.


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