Hydrometeorological Discussion National Weather Service / California Nevada RFC / Sacramento CA 650 AM PDT Wed Apr 29 2026 ...SCATTERED SHOWERS CENTRAL/SOUTHERN SIERRA INTO NV WED-FRI... ...COOL LOW PRESSURE SYSTEM IMPACTS THE REGION SAT-TUE... .METEOROLOGICAL CONDITIONS (WED AM - TUE AM)... The s/wv trof that moved down the northern CA coast before swinging inland across central CA on its way toward southern NV yesterday has exited the region and is currently approaching the 4-Corners region. Scattered showers and thunderstorms associated with this feature developed over portions of the Sierra during the afternoon hours before dissipating around sunset. Cyclonic flow aloft continues over the interior with a secondary disturbance dropping southward from the Pacific Northwest toward the Great Basin. This is expected to generate another round of scattered showers and possibly a thunderstorms today mainly over the central/southern Sierra and portions of eastern NV. However...coverage is looking to be less than what occurred on Tuesday. This overall setup continues into Thursday...while an offshore narrow wavelength upr ridge nudges its way toward the west coast. With the cyclonic flow over the interior...and another disturbance making its way across the Great Basin...look for more afternoon and early evening showers and possibly a thunderstorm for similar areas to Day 2 over the southern Sierra and eastern NV. For the Friday into the weekend...a s/wv trof moving across the northeast Pacific will reach close to Vancouver Island before changing directions and diving southward generally along or just inside of 130W. This will help to shove the cyclonic flow and narrow wavelength upr ridge downstream of the area. Once the upr low reaches the latitude of northern CA the look for increasing unsettled conditions to spread across the region...especially in the diffluent flow of the northeast quadrant of the circulation. This will bring the best precip over areas near the CA/OR border and down the northern/central Sierra. Into early next week...the upr low will slowly drift to off the central CA coast before finally shifting eastward and inland...which will continue the unsettled conditions through Tuesday. Overall amounts currently show 0.25- to 0.50-inch at the wettest locations near the CA/OR border and northern/central Sierra. However...if convective precip does develop with this feature...which is a possibility...localized heavier amounts would occur. Freezing levels this morning are lowest over the upper Klamath River basin over toward the Great Basin with 7500- to 8500-feet. These increase up to about 10000- to 12500-feet along coastal locations. As the narrow wavelength upr ridge approaches the coast...these will bump up and peak on Friday into early Saturday as the high pressure slides overhead from 11000- to 13000-feet. Then with the upr low moving toward the region into early next week...freezing levels will slowly drop with the core of the system bringing them down to 6000- to 7000-feet on Monday into 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. |