Includes Eastern Mariposa and Madera Counties and Yosemite National Park
May 21, 2021 - The National Weather Service Hanford Office reports a few thunderstorms are possible along the Sierra Nevada and foothills starting late this morning through the afternoon and evening hours.
Small hail and wind gusts near 40 miles per hour are a couple of hazards associated with strong thunderstorms.
In addition to dangerous cloud to ground lightning strikes, any thunderstorm can produce intense rainfall rates, leading to localized flooding.
Area Forecast Discussion National Weather Service Hanford CA 355 AM PDT Fri May 21 2021 .SYNOPSIS...Unseasonably cool weather will continue over the district through Saturday with scattered showers and isolated thunderstorms over the Sierra during the afternoon and early evening hours both days. Dry weather can be expected Sunday through the end of next week. Temperatures will recover to seasonable levels Sunday. Much of next week will average slightly warmer than normal. && .DISCUSSION...Another exceptionally cool day is on tap for the central California interior, but at least it will not be as windy as Thursday. Although northwesterly breezes may still gust to about 25 mph on the west side of the San Joaquin Valley this afternoon and westerly winds could gust up to 40 mph through and below the Kern county mountain passes, wind speeds will remain below advisory levels in most locations. Otherwise, afternoon temperatures today will average a good ten degrees below normal. The storm system that brought this unseasonably cool air mass into the district is currently centered over Mono County. Although it is limited on moisture, it will produce showers over the Sierra today, primarily from midday into this evening. A few showers may also pop up over the coastal ranges west of I-5 this afternoon as well. By late this afternoon, a few showers will probably develop over the Sierra foothills, and as they wander toward the east side of the San Joaquin Valley, most will probably evaporate as they come into an otherwise very dry air mass that resides over the San Joaquin valley. Nonetheless, some sprinkles could fall out of these otherwise ominous looking clouds in the eastern third of the valley very late this afternoon or this evening. It will be cold enough for precipitation to fall as snow showers above 5500 feet today and it`s possible that a few inches could accumulate above this elevation in some locations by this evening. Backpackers and hikers in the Sierra high country should be prepared for wintry weather this afternoon and evening. In addition, a few showers may be accompanied by some thunder, lightning and small hail over the Sierra this afternoon into early this evening. By later this evening, the storm system will drift into the Great Basin where it will sit nearly idle through Saturday as a strong anticyclone over the Eastern U.S. slows its eastward movement this weekend. That being said, Saturday could bring a recurrence of mainly afternoon showers and higher elevation snow showers over the Sierra. Otherwise, a cool northerly flow aloft will reside over central California through the first half of this weekend. Although the air mass over the CWA modifies somewhat on Saturday, high temperatures will still run several degrees below normal. Sunday looks like the best day, weatherwise, this weekend, with mostly sunny skies. Despite another chilly start to the day, temperatures should finally rebound to seasonable levels Sunday afternoon. A weak upper level ridge will move over central California Monday and bring further warming. Thermometer readings will flirt with the 90 degree mark in many locations of the San Joaquin Valley, lower foothills and the Kern County desert Monday afternoon. The ensembles bring a short wave trough through the Pacific Northwest early next week which in turn will flatten the upper level ridge over central California and probably trim high temperatures a bit on Tuesday and Wednesday. The models become polarized in their solutions on days 6 and 7. Some of them forecast weak ridging aloft over central California while other ensemble members forecast a weak upper level trough to reside over the Golden State. Confidence in temperature trends during this period is medium at best, so we`re opting for a middle of the road solution and keeping high temperatures slightly above normal later next week. Otherwise, dry weather will be the rule.Source: NWS
