Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
292 FXUS66 KSTO 242145 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 245 PM PDT Mon Jun 24 2024 .SYNOPSIS... Seasonably warm and periodically breezy weather persists across the early week period, with a slight cooling trend to near normal from mid to late week and into the weekend. Slight chance of isolated thunderstorms through Tuesday evening. && Key Points - Decreasing Moderate HeatRisk today and Tuesday, and then primarily Minor HeatRisk mid-week into the weekend. - Slight chance of isolated thunderstorms through Tuesday evening, best chances over the Sierra Crest south of Highway 50. - Potential for another warming trend late in the weekend and into next week. Short-Term Discussion (Today THROUGH Thursday)... Current GOES-West visible satellite imagery shows a band of mid level moisture creeping northward from the south, as well as some cumulus clouds developing over the northern Sierra Crest this afternoon. Temperatures are currently trending approximately 1 to 6 degrees cooler than this time yesterday afternoon across interior northern California, valid at 230 PM PDT. Moderate HeatRisk continues today for much of the Valley and foothills, as seasonably warm temperatures prevail and high pressure continues across the Desert Southwest. An area of low pressure will approach the Pacific Northwest over the next several days, bringing some cooling to the area, back to around normal for this time of year, and HeatRisk down to around Minor for the rest of this week. There is some monsoonal moisture moving into the area today and Tuesday that we will be keeping an eye on. The best chances for thunderstorm development would be over the Sierra Crest south of Highway 50, where there is a 10-15% probability this afternoon, and a 15-30% probability Tuesday afternoon. Confidence is low, but there is also potential for a stray thunderstorm in the Valley and foothills this afternoon and overnight into Tuesday as well. High resolution models are struggling to capture what is developing to the south this afternoon, so we have introduced a slight chance of thunderstorms in the lower elevations through Tuesday evening to address the nonzero potential for a stray thunderstorm. Otherwise, mid level clouds and some virga may be observed over the same timeframe. Potential impacts with any thunderstorms that develop would be lightning, gusty winds, small hail, brief heavy rain, and possible fire starts. When thunder roars, go indoors! && .EXTENDED DISCUSSION (Friday THROUGH Monday)... Ensemble guidance and cluster analysis are in general agreement for mainly westerly flow over the extended forecast period, with heights increasing later in the weekend and into early next week as weak ridging starts to develop over the Great Basin area this weekend, and then stronger ridging developing over the Eastern Pacific by early next week with a weaker trough in between. As a result, slightly warmer temperatures are forecast on Sunday, and into early next week as well, although there is still a spread for high temperatures over this timeframe. Valley temperatures look like they will trend from the upper 80s and low to mid 90s on Friday and Saturday to the high 90s and low 100s by Monday. The National Blend of Models (NBM) suggests a 30 to 70 percent probability of reaching or exceeding 100 degrees for the daytime high in the Valley on Monday. && .AVIATION... VFR conditions expected over the next 24 hours across Northern California. Surface winds 10-15 kts with gusts up to 20 kts through 03z Wednesday, southerly through the Sacramento Valley and northwesterly through the northern San Joaquin. In the Vicinity Delta, westerly winds 10-15 kts with gusts up to 20 kts thru 14z Tuesday. Additionally, there is a 10-30% chance of isolated thunderstorms over the Valley, foothills, & mountains. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$