Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
409 FXUS66 KSTO 142023 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 123 PM PDT Sat Sep 14 2024 .Synopsis... Warm and dry weather continues today, then periods of unsettled weather Sunday into next Wednesday with scattered showers and isolated thunderstorms along with periods of gusty wind. Drier and warmer weather returns Thursday into next weekend. && .Discussion... Dry weather continues today with high temperatures expected to be close to the max temps Friday. Satellite shows a line of cirrus clouds making their way over Shasta County early this afternoon but overall a quiet weather day with dry Valley conditions. This looks to change tomorrow afternoon ahead of a weather system moving in from the Pacific NW. Chances for rain start Sunday afternoon over the Coastal Range and northern Shasta County. By mid-afternoon chances for rain spread north of I-80 with the NBM giving a 35-75% of seeing rain, higher as you travel northward. With this, there is a 15-25% chance of thunderstorms from Hwy. 32 northward, highest over northern Shasta County and Southern Cascades mountains. Currently, hi-res models are showing convection being constrained to mainly the Coastal Range and northern Shasta County. However, given the upper low`s track of moving from west to east across the Central Valley, there is the potential for showers and isolated thunderstorms to extend further down the Valley. Any thunderstorms that do develop will be capable of gusty winds, small hail, and lightning, as well as brief heavy rainfall which may lead to flooding/debris flow impacts for recent burn scar areas. Overall confidence is low, given the discrepancies in the model`s placement of convection versus the synoptic forcing possible further down the Valley. As the low moves through the Valley, it keeps the thunderstorm threat into Monday morning, more contained to higher terrain of the Sierra/Coastal Range. By Monday afternoon, chances will taper off giving a brief break in active weather and cooler temperatures over the area. From Sunday afternoon to late Monday morning, The next round of precipitation will start Tuesday PM into Wednesday as energy ahead of a larger trough passage occurs Tuesday evening. Late Tuesday evening will see rain begin over the Coastal Range before extending further into the Valley Wednesday morning bringing another round of showers, isolated thunderstorms, breezy winds, and cooler, moist air. Tomorrow through midweek will see below normal temperatures with Valley highs in the 70s and mid 50s to low 70s over the mountains and foothills. & .EXTENDED DISCUSSION (Wednesday THROUGH Saturday)... Another low pressure is projected to move into interior NorCal Wednesday morning, bringing another chance of showers and potential thunderstorms to NorCal. The NBM is showing more widespread showers/storms for the Central/Northern Valley and the Sierra Nevada. Current probabilities of exceeding 0.50" inches of rainfall from Wednesday-Thursday night are around 30-60%, with the highest probs in the northern Sierra and Burney Basin. Still some disagreement on the track of the low, so these probabilities will likely change as will the total QPF forecast as models come into better consensus. Low pressure will then move off into the Great Basin Thursday night/Friday morning and an upper level ridge will then develop in the eastern Pacific. Pressure gradients will be orientated north to south on Thursday, so the potential for breezy and locally gusty northerly winds will exist. High temperatures will then climb back into the mid 80s to low 90s as we move into the weekend as our heights rise and ridging dominates the synoptic pattern. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. Sfc wind mainly at or below 12 kts except vcnty of Delta SWly sfc wind up to 20 kts possible aft 00z Sun. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$