Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
624 FXUS66 KSTO 172000 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 100 PM PDT Mon Jun 17 2024 .SYNOPSIS... Critical fire weather conditions continue through early Tuesday across the Valley and Delta from gusty northerly winds and low minimum relative humidity. Dry and generally seasonable weather then continues through midweek, with a warming trend expected late week and through the weekend. && Key Points - A Red Flag Warning is in effect until 8 AM Tuesday across the majority of the Delta region, Valley, and adjacent foothills below 2000 ft, due to low daytime relative humidity, gusty northerly winds, and poor overnight recoveries. - Generally seasonable temperatures continue through most of the week, with a gradual warming trend late week into the weekend. - Widespread Moderate HeatRisk is expected from Friday through Monday, with some Major HeatRisk in the foothills on Saturday. Short-Term Discussion (Today THROUGH Thursday)... Dry and mostly clear conditions continue to prevail over the area this afternoon. Already, relative humidities across the Valley are starting to reach below 20%, with values forecasted to potentially reach single digits locally in some areas. Winds, too, have already gusted up to 37 mph at locations such as Red Bluff and Stockton, with more gusty winds expected for the remainder of today and into Tuesday. Ensembles show the trough causing these critical fire weather conditions today through early Tuesday to be moving eastward over the next couple of days. Until the low pressure system moves out of the area however, it will continue to bring breezy northerly winds and dry relative humidities to the area. As such, a Red Flag Warning remains in effect for areas in the Delta region and Valley below 2000 ft until 8 AM on Tuesday. Late Tuesday and into Wednesday, as the current trough moves out and a more broad troughing pattern covers the area, winds will decrease and relative humidities will rise a little (though still remaining in the 20-30% range in the daytime, and even lower in the northern Sacramento Valley). Temperatures will remain near or slightly below seasonable levels through Tuesday, though they will begin to warm slowly mid-week, with Wednesday and Thursday seeing Valley temperatures around the 90s, and upper 60s to upper 80s at higher elevations. && .EXTENDED DISCUSSION (Friday THROUGH Monday)... As we move into the weekend, weak broad troughing aloft is suggested by ensembles and cluster analysis while a ridge of high pressure will attempt to build in the Great Basin. Heights aloft should continue to rise over our area in response, and lead to a gradual warming trend Friday and Saturday. High temperatures on Friday and Saturday are expected to be in the low 90s to around 105F across the Valley, with 70s to mid 80s for the Valley and Foothills. Widespread Moderate HeatRisk will accompany both days, with isolated areas of Major HeatRisk in the Foothills and portions of the northern Sacramento Valley. On Sunday, heights will lower slightly, which will bring slightly cooler air into the area, although the cooldown will only be a few degrees. Generally, still anticipating 90s to low triple digits (100-103) in the Valley and 70s to low 80s in the Foothills and mountains. The slight drop in afternoon temperatures will also bring widespread Moderate HeatRisk on Sunday and Monday, with the Delta and Sacramento areas in Minor HeatRisk as the Delta Breeze will help keep things cooler in these areas. && .AVIATION... VFR conditions across interior NorCal for the next 24 hours. In the Valley, widespread northerly surface winds up to 20 knots with gusts 25-35 knots until around 03Z. In the Delta, winds shifting westerly around 04Z with speeds of 5-15 knots. In the mountains, expect surface winds from the northwest to northeast with gusts up to 35 knots. && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 8 AM PDT Tuesday for Carquinez Strait and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-Eastern Mendocino NF- Northern Sacramento Valley to Southern Tehama County Line Below 1000 Ft-Northern San Joaquin Valley in San Joaquin and Stanislaus Counties Below 1000 ft-Northern Sierra Foothills from 1000 to 3000 Ft. Includes portions of Shasta-Trinity and Butte Units-Northern Sierra Including Lassen NP and Plumas and Lassen NF/S West of the Sierra Crest (West of Evans Peak-Grizzly Peak- Beckworth Peak)-Southeast Edge Shasta-Trinity NF and Western Portions of Tehama-Glenn Unit-Southern Sacramento Valley in Yolo- Sacramento Far Western Placer, southern Sutter and Solano County Below 1000 Ft. && $$