Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
947 FXUS66 KSTO 272013 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 113 PM PDT Mon May 27 2024 .SYNOPSIS... Periods of minor to moderate HeatRisk this week with locally elevated fire conditions across the northern and central Sacramento Valley Thursday. Onshore flow returns late this weekend into early next week. && .DISCUSSION... A relatively quiet remainder of Memorial Day expected with afternoon highs in the upper 80s and low 90s in the Valley. Showers along the Sierra crest are possible this afternoon and evening but should quickly move eastward off the crest if anything materializes. Current satellite shows growing cumulus clouds along the Sierra and Southern Cascades but no indication of any organized development as of early Monday afternoon. NBM probability shows a 10-25% chance of thunderstorm development south of I-80 along the Sierra. The dominant feature of the forecast early this week is an upper level trough moving through the Pacific NW that will maintain weak onshore flow over the area. Areas near the Delta will see west gusts 15 to 25 MPH, strongest in the afternoons. Afternoon highs on Tuesday will be in the mid to upper 80s in the Valley with 70s and 60s across the foothills and mountains respectively. The axis of the trough slides over Northern CA Tuesday with weak ridging developing over the Eastern Pacific that will induce breezy north winds in the Valley with warm, dry conditions. North winds 10 to 15 MPH with gusts up to 25 MPH start late Wednesday morning through the afternoon across the I-5 corridor, redeveloping stronger Thursday morning. North winds 15 to 20 MPH with gusts up to 30 MPH are forecasted, strongest late Thursday morning. NBM probabilities show a 15-40% chance of wind speeds exceeding 40 MPH on Thursday, highest across the Tehama and Glenn county. Combined with low RHs (10-20% Min. RH) across the Valley, elevated fire conditions are expected Thursday. Be sure to avoid outdoor burning, avoid equipment that creates sparks, keep vehicles off dry grass, and properly dispose of cigarettes. This switch in flow pattern will also see temperatures warm midweek. By Thursday areas of Moderate HeatRisk in the Valley are forecasted with highs in the low to mid 90s with 80s and 70s across the foothills and mountains respectively. NBM probabilities for afternoons higher than 100 degrees is only 10-30% chance, so triple digit highs have a better chance Friday and Saturday. Be sure to stay well hydrated and take breaks in the shade! && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Friday sees the continuation of the high temperatures on Thursday, as a transient ridge continues over the area. There is a chance we could see our first triple digit temperatures in the Valley on Friday, with 25 to 65% probabilities of temperatures at or greater than 100 degrees in the Sacramento Valley. Subsequently, Moderate HeatRisk continues in most of the Valley through Friday. A shortwave trough will flatten the ridging pattern over our area through the weekend, keeping temperatures from reaching any higher, though highs will still be in the 90s generally. The Sacramento metropolitan area and nearby Delta region will be slightly cooler, in the high 80s, due to onshore flow. The onshore flow will also bring breezy conditions in the late afternoon and evening. Areas of Moderate HeatRisk will also diminish during this time, leaving mostly Minor HeatRisk in its place. //SP && .AVIATION... VFR conditions next 24 hours. Local southwest surface wind gusts 15-25 kts in the vicinity of the west Delta, generally less than 12 kts elsewhere. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$