Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 740 AM PDT Fri May 1 2026 ...LOW PRESSURE IMPACTS THE REGION THIS WEEKEND INTO EARLY NEXT WEEK... .METEOROLOGICAL CONDITIONS (FRI AM - THU AM)... A narrow wavelength upr ridge is situated from just off the southern CA coast north-northeast to the interior of the Pacific Northwest stretching up into west-central Canada. This feature is sandwiched between two areas of low pressure with the first over the Great Basin moving off toward the southeast and another upstream just west of Vancouver Island. This second area of low pressure will drop southward through the weekend...increasing the likelihood of precip each day into early next week with the peak being Sunday into Monday. For today...the exiting low over the Great Basin may generate some build ups over the southern Sierra with the potential for some stray showers developing. Also...with afternoon heating and the approaching system down the west coast...there may be some scattered showers and even a thunderstorm per SPC across the northern CA coastal mountains mainly from the Eel River basin northward. The area of low pressure will settle off the CA coast on Saturday into Sunday with increasing diffluent flow aloft in the northeast quadrant of this feature. This places the best opportunity for precip from the Trinity Mountains eastward across the Shasta Lake drainage and northeast CA Plateau along with the northern/central Sierra. The SPC Day 2 Convective Outlook does highlight these areas for the potential of general thunderstorm activity. Monday into Tuesday sees the primary circulation reaching its farthest south location off the central CA coast before slowly swinging inland and exiting the region across the lower Colorado River basin. On Monday...best precip will be aligned along the length of the Sierra and then points east across the northern half of NV. These locations are also inside a broad area of general thunderstorms drawn on the SPC Day 3 Convective Outlook. After this system exits to the east...an upr ridge will slide across the area for dry and warmer conditions during the middle of next week. Freezing levels are currently from 9000-feet across northeast NV to 12000-feet or so along coastal locations. Into Saturday...as the Great Basin low moves out...a broad area of 11000- to 13000-feet will spread across the entire area. Then as the area of low pressure moves across central and southern CA into southern NV...the core of the system will bring freezing levels down to 7000- to 8000-feet from later Sunday into later Tuesday. Please Note: This product may NOT be routinely updated. Please refer to the following product issued by the CNRFC www.cnrfc.noaa.gov/Daily-Briefing for a graphical summary of weather and hydrologic conditions. |