July 19, 2021 - The National Weather Service reports deep, monsoonal moisture in the higher terrain of Central California will be responsible for the possibility of heavy to excessive rainfall today.
There is a marginal (5-10%) risk of excessive rainfall in the Sierra Nevada into this evening.
Area Forecast Discussion National Weather Service Hanford CA 1217 PM PDT Mon Jul 19 2021 .SYNOPSIS...Scattered showers and isolated thunderstorms will linger over the Sierra Nevada early this evening. Otherwise dry weather will prevail over the central California interior for the remainder of this week. A return of monsoonal moisture Saturday will renew the threat of thunderstorms over the mountains and desert this weekend. && .DISCUSSION...Thunderstorms are rumbling about over the foothills and higher elevations of the Sierra as of this writing. Although a few of them are producing heavy rain, they`re moving quickly northward and not staying in any location long enough to bring a big threat of flooding. The precipitation these storms have dropped over the mountains and desert during the past 24 hours has been largely beneficial with rainfall in the heavier storms totaling as much as four tenths of an inch. Most of the thunderstorm activity over the Sierra will come to an end by sunset as winds aloft become southwesterly, sweep monsoonal moisture into the Great Basin and bring a drier and more stable air mass into the CWA. This has already happened this afternoon across southern CA, including Kern County, as high pressure over the Four Corners region has built into this part of the state. As this ridge builds back over central California, we can expect this drying trend to take place over the remainder of our CWA tonight. The rest of this week will be considerably quieter as the Four Corners ridge dominates. Mostly clear skies, generally light winds and slightly above normal high temperatures will be the rule Tuesday through at least Friday, as a result. Tuesday looks as though it will be our warmest day this week, but only by a few degrees. Otherwise, high temperatures will flirt with the century mark in the San Joaquin Valley and lower foothills during mid to late week. In the Kern county desert, triple digit heat will be a mainstay this week, but nothing as extreme as the heat earlier this month. The ensembles haven`t wavered much from run to run during the past couple of days and still hint of a return of monsoonal moisture into central California this weekend. Hence, we can expect a renewed threat of mainly afternoon and evening thunderstorms over the desert and mountains Saturday and probably again Sunday into early next week while a southeasterly flow prevails aloft. Otherwise the presence of mid and high clouds in the 5 to 7 day period might lower maximum temperatures a bit but also keep nightly temperatures a bit warmer along with somewhat higher humidity levels. && .AVIATION...Isolated to scattered thunderstorms will continue over the Sierra until about 03z with local MVFR/IFR ceilings and mountain obscurations. VFR conditions will otherwise prevail over the central California interior during the next 24 hours. && .AIR QUALITY ISSUES... On Monday July 19 2021... Unhealthy for sensitive groups in Fresno... Kern... Kings... Merced and Tulare Counties and Sequoia National Park and Forest. Further information is available at Valleyair.orgSource: NWS
