Area Forecast Discussion
Issued by NWS Sacramento, CA
Issued by NWS Sacramento, CA
385 FXUS66 KSTO 250919 AFDSTO Area Forecast Discussion National Weather Service Sacramento CA 144 AM PDT Tue Jun 25 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 this evening. && Key Points - Decreasing Moderate HeatRisk today, and then primarily Minor HeatRisk mid-week into the weekend. - Slight chance of isolated thunderstorms through this 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 Friday)... Mid-level monsoonal moisture continues to move in and across our area early this morning, bringing continued chances for isolated thunderstorms through this evening. Highest chances will occur along the Sierra crest (15-30% probability) this afternoon, though it is still possible that an isolated storm may pop up in the Valley and foothills well (10-15% probability). Confidence is low in the potential for storms outside of the mountains, however some high resolution models are showing some weak reflectivities in the late morning/early afternoon and therefore the potential for stray thunderstorms cannot be ruled out in that area entirely. Otherwise, scattered to broken mid-level clouds and virga will be primarily what is observed over the lower elevations. Impacts from any storms that do occur, in the mountains or at lower elevations, include lightning, gusty winds, small hail, brief heavy rain, and possible fire starts. Beyond the potential for isolated thunderstorms today, an area of low pressure continues to move towards the Pacific Northwest over the next few days, keeping the slight cooling trend on track for the week. HeatRisk will continue to decrease today, and by Wednesday conditions should be cool enough that primarily Minor HeatRisk will cover the area. By the end of the week, temperatures still look to be near normal for the time of year, with highs around the high 80s to mid 90s in the Valley, high 70s to low 90s in the foothills, and high 60s to high 70s in the mountains. && .EXTENDED DISCUSSION (Saturday THROUGH Tuesday)... 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; weak ridging will start to develop over the Great Basin area, followed stronger ridging over the Eastern Pacific early next week with a relatively weak trough in between. As a result, temperatures are forecast to warm slightly on Sunday and to continue to warm into early next week (though there is still a spread for high temperatures over this timeframe). NBM currently has probabilities of temperatures reaching or surpassing 100 degrees at 20 to 60% in the Valley on Monday, and 40 to 75% on Tuesday. && .AVIATION... VFR conditions over interior NorCal next 24 hrs. Isolated -tsra possible, mainly over SierNev btwn 19z-03z. Sfc wind mainly at or below 12 kts except vcnty of Delta SWly sfc wind up to 20 kts aft 00z Wed. && .STO WATCHES/WARNINGS/ADVISORIES... None. && $$