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. |