Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
447 FXUS66 KSTO 180905 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 205 AM PDT Fri Oct 18 2024 .SYNOPSIS... Critical fire weather conditions are expected now and through Saturday evening due to gusty northerly winds and low humidities. Seasonal temperatures with generally quiet weather are forecast for next week. .DISCUSSION... Maximum wind gusts in the Valley yesterday maxed out between 30 and 45 mph. Today, while the area of highest concern for gusty winds has shifted slightly south, is still expected to have the higher overall wind gusts of the two days. Particularly, in the Delta, wind gusts up to 55 mph may be possible, with a 50 to 90% chance of winds 40 mph or higher. Elsewhere, in the southern Sacramento and northern San Joaquin Valleys (particularly west of the I-5 corridor), the NBM has probabilities of 40 mph or higher wind gusts at 20 to 70% today. Consequently, a Wind Advisory remains in effect for these specified areas of the Delta and Valley through 11pm tonight. In addition to gusty winds, daytime relative humidities are expected to drop severely today, bottoming out in the single digits to the mid-teens. These dry and gusty conditions will linger into Saturday, and therefore our Red Flag Warning remains in effect today through 5pm Saturday. Weak ridging begins to build back in on Sunday, bringing a return to light winds, dry weather and slightly warmer temperatures into next week. Temperatures should be near normal, with Valley highs around the high 70s to low 80s (60s to 70s at higher elevations). && .EXTENDED DISCUSSION (Tuesday THROUGH Friday)... Seasonable weather continues Tuesday and Wednesday of next week, as weak ridging continues over the area. There is potential for a new low pressure system to progress into part of interior NorCal mid to late next week, though cluster analysis and ensemble members disagree on the strength, placement, and overall trajectory of the trough. This is likely why the NBM mean solution is clinging on to precipitation chances, even though no measurable amount of precipitation is present until the 90th percentile on Thursday. This is also likely why there is a fairly wide spread of temperatures in the NBM late next week, with the upper range falling slightly above normal and the lower range falling below normal. For now, the most likely conditions remain dry with seasonable temperatures throughout the extended forecast. && .AVIATION... VFR conditions over interior NorCal next 24 hrs with wdsprd N-E sfc wind 15-25 kts with gusts 30-45 kts. Areas of LLWS til 18z Fri. && .STO WATCHES/WARNINGS/ADVISORIES... Red Flag Warning until 5 PM PDT Saturday for Carquinez Strait and Delta-Central Sacramento Valley in Glenn, Colusa, Yuba, Northern Sutter, and Butte County Below 1000 Ft-Eastern Portion of Shasta/Trinity NF-Northern Motherlode From 1000 to 3000 Ft. Includes portions of Nevada-Yuba-Placer-Amador and ElDorado Units-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-Southern Motherlode From 1000 to 3000 Ft. Includes portions of Calaveras-Tuolumne Unit-Southern Sacramento Valley in Yolo-Sacramento Far Western Placer, southern Sutter and Solano County Below 1000 Ft. Wind Advisory until 11 PM PDT this evening for Carquinez Strait and Delta-Northern San Joaquin Valley-Southern Sacramento Valley. && $$