Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
383 FXUS66 KSTO 100937 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 237 AM PDT Thu Oct 10 2024 .Synopsis... Our cooling trend continues through this week with a weak weather system bringing light rain late Friday night into Saturday north of I-80. Below to near normal temperatures are expected to extend through next week. .Discussion... An onshore flow pattern continues today as an upper level trough approaches from the eastern Pacific. High temperatures will see a little more cooling today, with relative humidity also gradually trending higher. This pattern is also spreading high clouds across the area. Highs this afternoon will be in the mid to upper 80s to low 90s in the Valley and Delta, with 70s to mid 80s across the lower mountains to the foothills. A shortwave embedded within the trough along the coast will move closer Friday, bringing additional cooling. Highs Friday afternoon will drop another 3 to 4 degrees. By Saturday, highs cool to the upper 70s to around 80 in the Valley with 60s to 70s over the mountains and foothills. The NBM projects some warming highs (3-7 degrees) Sunday as weak eastern Pacific ridging briefly develops ahead of the next system. HeatRisk levels will remain in the Minor or less category over the area today through the weekend. The weak shortwave will bring breezy onshore winds, mainly late Friday afternoon and evening. It will also bring light precipitation chances to areas north of I-80. The rain is expected to begin late Friday night, with best potential early Saturday morning and then tapering off around mid-day Saturday. Rainfall totals with this system are forecast around 0.01-0.25", highest along the far western portions of the Sacramento Valley and the northern Coastal Range area. Much of the Sacramento Valley is currently expected to see amounts ranging from sprinkles to a tenth of an inch, highest over the north end of the Valley. Some low humidity conditions linger over the mountains and northern Sacramento Valley today, with afternoon minimums in the teens to around 20 percent. The onshore flow pattern will bring increasingly cool temperatures and higher humidity into the weekend, though, decreasing fire weather concerns further each day. && .EXTENDED DISCUSSION (Monday THROUGH Thursday)... Weak upper ridging progged over interior NorCal on Monday. Heights then trend down Tuesday as long wave trough and embedded short wave in the EPAC approaches. Models differ with progression of this feature as GFS tracks it through Tuesday night into Wednesday, while slower EC advertises a Wednesday/Thursday event. NBM leans towards GFS with timing. EC also showing a wetter wave with widespread precipitation, while GFS/NBM keep bulk of precip north of I-80 and mostly over the mountains. GFS then brings another short wave trough across northern portions of the CWA Thursday. Areas of gusty wind will accompany passage of short waves. High temperatures cool through the extended from near normal Monday to around 3 to 8 degrees below normal midweek. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. Sfc wind mainly below 12 kts except vcnty of Delta, SWly wind 15-20 kts til 17z and after 22z Thu. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$