Mariposa projected high temperature for Wednesday: 90 degrees and Saturday: 65 degrees
Oakhurst projected high temperature for Wednesday: 90 degrees and Saturday: 65 degrees
Yosemite Valley projected high temperature for Wednesday: 83 degrees and Saturday: 57 degrees
September 22, 2019 - National Weather Service Hanford Office reports and increasing likelihood of a major pattern change coming next weekend.
Nearing 100F in the valley Wednesday, then maybe only 70s in the valley next Saturday.
Area Forecast Discussion National Weather Service Hanford CA 400 AM PDT Sun Sep 22 2019 .SYNOPSIS...Dry weather can be expected over the district through Thursday. Temperatures will warm to seasonable levels today then trend slightly cooler Monday in the wake of a dry cold front. A major warm up will occur by midweek with high temperatures near the century mark Wednesday in the hottest locations of the San Joaquin Valley and desert. A cold storm system will bring a change to unseasonably cool and possibly wet weather Friday through next weekend. && .DISCUSSION...The week ahead will bring some wild temperature swings in addition to some astounding weather extremes. One week from today many of us may look back in amazement and wonder how we could transition from Summerlike heat during midweek to unseasonably cool, unsettled weather at the end of the week and possibly Winterlike conditions over the high Sierra by next weekend. We`ll do our best to sort it all out for you in this discussion. Today, officially, is the last day of Summer. Thermometer readings will climb above the 90 degree mark in the San Joaquin valley, lower foothills and the Kern county desert this afternoon as a weak ridge of high pressure aloft moves over central California. When Fall officially arrives at 12:58 am PDT Monday, a cold front will be approaching from the northwest. This moisture starved front will sweep southward through our CWA Monday morning with little more than some mid and high clouds. In its wake, the rest of Monday will be breezy and slightly cooler than today with seasonable afternoon temperatures. A much stronger upper level ridge anchored over the Eastern Pacific will build into central California Tuesday through Wednesday and bring a major warming trend. High temperatures Tuesday will bounce back above the 90 degree mark in the San Joaquin Valley and the Kern county desert. As the ridge gains stronger footing over central California Wednesday, temperatures will soar well into the 90s in the valley and desert. Thermometer readings could top the century mark in the hottest locations. That`s pretty close to the records in Fresno and Bakersfield. (The record high in Fresno for Wednesday is 100 degrees which last occurred on that date in 2009. In Bakersfield, the record high for September 25th is 103, which last occurred on that date in 1975.) This might be Summer`s last hurrah before a storm system in the Gulf of Alaska chases it all away later this week. That storm will be a major pattern breaker when it arrives here Friday. As the cold front ahead of this storm approaches from the north on Thursday, the high pressure ridge will get squashed and there will be an increase in onshore flow across central California. A shallow intrusion of marine air will come into at least the northern half of the San Joaquin Valley by Thursday afternoon and lower high temperatures back to seasonable levels. Otherwise, Thursday will still be slightly warmer than normal over much of the CWA. That cold front will slip south of our CWA Thursday night and herald the arrival of a much cooler air mass Friday. Otherwise, the upper level trough that follows this cold front will deepen along the West coast Friday through Saturday. In doing so, our weather will turn sharply cooler/colder and the atmosphere will become increasingly unstable over the central California interior. Showers will become likely over the mountains Friday and could materialize over the lower elevations by Friday afternoon or evening. As the upper level trough moves inland Saturday, rain showers could turn to snow showers in the Sierra above 7,000 feet and isolated thunderstorms equipped with small hail could develop over the San Joaquin Valley and adjacent foothills Saturday afternoon, especially from Fresno county northward. Isolated funnel clouds are certainly possible on Saturday as well. Afternoon temperatures Friday and Saturday may be no higher than the lower 70s in the San Joaquin Valley and possibly as cool as the mid 60s. (Records for low max temperatures could be challenged in the San Joaquin Valley both days depending on cloud cover.) The models differ on the placement and the depth of this upper level trough along the West coast next weekend, so forecast confidence is low as to where and how much precipitation occurs over the CWA. The GFS continues to deepen the trough over the Golden State next Sunday while the ECM displaces the closed low off the Pacific Northwest coast and places much of central CA under a relatively drier southwesterly flow aloft. Whatever the case, our pattern looks potentially wet by Saturday, especially over the mountains. Hikers and campers in the Sierra will want to pay close attention to NWS forecasts during the later part of the week and be prepared for a drastic change to wintry weather by next weekend with the potential for several inches of snow in the Sierra above 8,000 feet.Source: NWS
