Includes Eastern Mariposa and Madera Counties and Yosemite National Park
May 29, 2021 - The National Weather Service reports isolated thunderstorms are possible this afternoon and early evening for the higher elevations of the Sierra Nevada, primarily from Fresno county north into the Yosemite area.
Small hail, heavy downpours, and dangerous lightning will be the primary hazards with these storms.
Area Forecast Discussion National Weather Service Hanford CA 456 AM PDT Sat May 29 2021 .SYNOPSIS...High temperatures today will remain slightly above average for this time of year. A few thunderstorms are possible in the Sierra this afternoon and Sunday afternoon. Conditions will trend much warmer Sunday and Monday with maximum temperatures forecast to be around 15 to 20 degrees above normal then little change through midweek. && .DISCUSSION...A weak shortwave trough is currently pushing into central and southern California. This is providing an onshore flow across the region and has deepened the marine layer to over 2500 feet. This is deep enough to allow some cooler marine air to trickle into the Valley. This will keep some locations around Merced County at or even a degree or so below high temperature readings from yesterday, but across most of our area the passing weak trough will just help keep high temperatures from climbing too much above yesterday`s readings. Expect highs mostly a few degrees warmer, topping out around 3-6 degrees above normal for the end of May. The trough can also trigger a few afternoon thunderstorms over the Sierra. As the trough drops toward northern Baja by Sunday there may be a few thunderstorms near the Sierra crest, and temperatures will start an upward journey, with afternoon highs a few degrees above Saturday`s highs. While a closed low is developing in the northern Baja area, Pacific high pressure will build along the west coast, and our temperatures will increase more significantly for Memorial Day and into midweek. This will be the hottest stretch of weather we have experienced since early September of last year and highs will be as much as 20 degrees above normal, with some records threatened. This will lead to a moderate to high level of heat risk across the San Joaquin valley, lower foothills and westside hills Monday and Tuesday. A developing northeast Pacific trough will begin to weaken and displace the ridge on Wednesday and highs will start to trend downward. After Wednesday, as the trough further flattens the ridge overhead, the latter half of the week will see more significant cooling, with highs lowering to around 7-10 degrees above normal by the end of the week. With the anticipated heat impacts for at least Monday and Tuesday, we have issued an Excessive Heat Watch for these days. Wednesday may also require special attention to the heat, as it will see just the beginning of the downward temperature trend, and high temperatures will likely be down only a couple of degrees.Source: NWS
