Version:  Current  |  Back 1  |  Back 2  |  Back 3  |  Back 4  |  Back 5  |
Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
1230 PM PST Sat Dec 4 2021

...DRY CONDITIONS THROUGH THE WEEKEND BEFORE A WEAK SYSTEM ARRIVES 
MONDAY...
...RENEWED RAINFALL CHANCES BY MID TO LATE NEXT WEEK...

.METEOROLOGICAL CONDITIONS (SAT PM - FRI AM)...

Minor updates to the forecast in the short term. Conditions have not 
changed much since this morning. An upper ridge remains the dominant 
weather feature, steering moisture northward into the Pacific 
Northwest, while a dry upper low approaches Baja and a weak surface 
low and cold front move into the Pacific Northwest. This front looks 
to move through the region on Sunday, though no precip is expected 
with this system. The next surface low still expected to move down 
along the Pacific Northwest coast on Monday. Still looks fairly 
unimpressive with only about 0.10"-0.25" expected for the wettest 
spots Monday into Tuesday. Freezing levels will also lower down to 
around 7-9 kft from NE to SW starting Monday morning. Levels should 
rebound from W to E later Tuesday back to 10-12 kft for most of the 
region. 

Another trough is then still on track to move into British 
Columbia/Pacific Northwest on Wednesday before expanding to engulf 
most of the western U.S. in a longwave pattern into late next week. 
A cold front extending southward from Canada over the eastern 
Pacific looks to also move through CA/NV late Wednesday through 
Thursday while an embedded shortwave approaches from the NW reaching 
northern CA on Thursday. Models keep another 1+" PW plume offshore 
associated with this feature, though disagreement regarding the 
timing and positioning persists. Forecast remains on track for 
precip on Thursday and into Friday morning with highest totals still 
over the Sierra. A good number of both model's ensemble members 
agree on higher amounts there as well, of course with differences 
still in magnitude, placement, and timing. Colder air moving in will 
also drop freezing levels from N to S down to 3.5-6 kft by early 
Thursday morning with these values then spreading across most of the 
region by the evening, and even down to 2-3 kft for the north by 
that time. Overall, looks like a potential wet pattern for mid to 
late next week. Will have a better idea of the details as we get 
closer.