Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
953 FXUS66 KSTO 142039 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 139 PM PDT Tue May 14 2024 .SYNOPSIS... Patches of moderate HeatRisk in the Valley through Wednesday with above normal temperatures expected throughout the remainder of the week. A few showers and thunderstorms possible over the Sierra this afternoon and evening with locally breezy conditions. && .DISCUSSION (Today through Friday)... Another warm day continues today with widespread upper 80s and 90s throughout the Valley. Temperatures peak tomorrow with most Valley locations being at or above 90 degrees with 70s and 80s across the mountains and foothills. Areas north of Sacramento including portions of the northeast foothills will be under Moderate HeatRisk. Those sensitive to heat or working in heat-sensitive industries should take extra precautions like regularly taking breaks in the shade and staying hydrated. NBM probabilities show a 25-55% chance of afternoon highs greater than 100 degrees across portions of the Valley between Sacramento and Red Bluff, including Chico and Willows. Temperatures are set to cool several degrees Thursday and Friday with Valley highs in the mid 80s and low 90s late week. There is a chance for a few pop-up showers and thunderstorms south of Hwy. 50 as things develop along the crest and westerly- southwesterly flow moves them across Tuolumne County. Satellite imagery as of 1245 PM PDT shows areas of cumulus clouds bubbling along the Sierra, which points to the instability in the area. There is a fair amount of uncertainty as high resolution models show differing solutions regarding the extent and intensity of any convective development. Given conditions over-performed models yesterday and smaller scale influences weighing heavier this time of the year, things point to a few discreet showers developing by this evening. The latest run of the NAM forecasted reflectivity showed this best with everything reminding south of I-80 and peak development being 4-7 PM. Overall, best chances for any development will be between 2 and 7 PM this evening and with any storm that does develop small hail, gusty winds, lightning, and brief heavy rain showers are possible. The Delta Breeze looks to strengthen slightly tomorrow and throughout the work week with gusts of 20-30 MPH, strongest in the late afternoon and evening. Areas along I-5 westward can expect some locally elevated fire conditions with breezy north winds (10-15 kts) on Wednesday with minimum RH values near 15% along I-5. && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... Hark! A cooling trend doth approaches and is expected to henceforth continue as we venture through the weekend and into next week. High temperatures will be 5 to 10 degrees above normal in the Valley and 10 to 15 degrees in the mountains on Saturday. By Sunday, upper level troughing descending down from Canada will merge with a cutoff low off the Southern California coast which will reinforce the cooling trend and increase onshore flow through the Valley and Delta. Increased instability and moisture availability associated with the trough, will lead to the potential for afternoon/evening isolated mountain thunderstorms along the Sierra crest. The National Blend of Models (NBM) has a 15-20% chance of thunderstorms Saturday-Tuesday. && .AVIATION... VFR conditions across interior Northern California over the next 24 hours. There is a 15-20% chance of isolated mountain thunderstorms this afternoon/evening, south of I-80 from 21Z Tues-02Z Wed. Sustained winds in the Valley will be under 12 kts. Throughout the Delta, sustained west-southwesterly winds 15-20 kts with gusts 20-25 kts through 18Z Wed. Over the foothills/mountains, northeasterly winds will gust 20-25 kts from 09Z-18Z Wed. North winds in the Valley are expected to increase tomorrow. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$