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Hydrometeorological Discussion
National Weather Service / California Nevada RFC / Sacramento CA
700 AM PDT Sun Apr 27 2025

...COOL CONDITIONS WITH PRECIP FOCUSED MAINLY NORTHERN NV TODAY...
...WEAK SYSTEM LATER TUE-LATE THU WITH LIGHT PRECIP MAINLY EAST...
...ANOTHER COLD CORE SYSTEM POSSIBLE FOR THE FOLLOWING WEEKEND...

.METEOROLOGICAL CONDITIONS (SUN AM - SAT AM)...

The last weekend in April continues with cooler than normal 
temperatures across the region with afternoon highs expected to be 
anywhere from about 5- to 25-degF below seasonal averages. 
Also...radar imagery shows a rather solid area of light to 
locally moderate precip spreading from northeast to southwest 
rotating around the upr low situated across central NV...affecting 
the northern/central Sierra down to portions of the Central Valley 
around the Sacramento area. Since 27/12Z...automated gauges have 
reported anywhere from a few hundredths of an inch to 0.15-inch or 
so. With the cool air in place with the core of the system moving 
across the region...snow levels have fallen to 4500-feet at Colfax 
and 5000-feet at Oroville according to the latest NOAA PSD S-Band 
Radars. This matches will with the 27/12Z KREV RAOB that indicated a 
freezing level of 5900-feet. 

Through today...the upr low will slowly make its way to the 
northeast and cross the NV/UT border this afternoon. Models continue 
to indicate the best precip will fall in the northwest quadrant of 
this feature...which will bring northern NV from about US-50 
northward the highest amounts ranging anywhere from 0.10-inch at the 
driest locations to 1.00-inch at the wettest places. Back across 
CA...precip should taper off through the afternoon and early evening 
hours as the better forcing shifts off to the east. 

Into Monday...as the best forcing with the upr low moves north and 
east of the region across the northern Rockies and eventually the 
northern Plains states...an elongated upr trof will extend all the 
way back toward southern CA and northern Baja. This should be enough 
cyclonic flow to keep some light showers going across northeast NV 
and possibly even the southern Sierra. Freezing levels should 
quickly recover as the core of the system vacates the area...jumping 
up to 9000- to 11500-feet by the end of Day 2.

Models continue to indicate a weak disturbance moving through the 
northwest flow aloft and crossing from coastal Pacific Northwest to 
northern CA by Wednesday...eventually forming a weak cutoff low 
across central/southern CA. This feature looks to have just enough 
forcing and moisture to generate some light precip mainly over the 
Sierra and points east across NV. 

Things once again get a bit more interesting for the end of the 
week as another elongated upr trof with polar origins sets up just 
off the west coast. This is once again promising to bring cooler 
than normal temperatures and another chance at scattered precip with 
lowered freezing levels. 

And with that...la fin.