Eastern Madera and Mariposa Counties
June 22, 2021 - The National Weather Service Hanford Office says we are forecasting dry thunderstorms across the Sierra Wednesday and Thursday as sub tropical moisture moves north into the area.
Dry thunderstorms can cause wildfire starts in the mountains, especially in the dry conditions due to the drought.
Area Forecast Discussion National Weather Service Hanford CA 340 AM PDT Tue Jun 22 2021 .SYNOPSIS... A cooling trend expected through midweek will bring temperatures close to normal. Winds will be gusty at times through and below the mountain passes during the period. Although dry weather will prevail this week, isolated thunderstorms cannot be ruled out over the higher terrain from Tuesday night through Thursday. && .DISCUSSION... A change in the weather is finally here as the Valley is expected to remain below the Century Mark today. The upper level disturbance that is slowly drifting toward the California Coast is responsible for the downward trend in temperatures. The disturbance supported the growth of the marine layer (as observed on the Fort Ord profiler) to well over 3000 feet MSL. At that altitude, will see a continuation of marine air surge into the Central Valley as cooler conditions spread beyond Merced County. In addition to the cooler marine air, the surge also provided for locally windy conditions over some of the areas higher terrain. With little change in the upper air pattern, temperatures and winds will once again dominate the areas weather conditions. Yet, further changes are expected as moisture filters in the region ahead of the rebuilding ridge pattern returning this weekend. The trajectory of the moisture may reach the area by midweek as isolated thunderstorms may be possible over the mountains and deserts. Observational data and model analysis show the upper disturbance moving slowly with pieces of energy rotating through California. While these pieces of energy will influence temperatures and winds today, the northward movement of moisture may begin to interact with the energy on Wednesday. Current upper air model analysis has the orientation of the disturbance able to draw-up monsoonal type moisture from the Baja Gulf for locally convective conditions across the Sierra Nevada range on Wednesday and even on Thursday. Fire weather conditions may become critical on those days as moisture may be limited and the lack of significant moisture may produce dry lightning conditions. Appropriate statement will be issued if conditions come into phase to produce the dangerous situation of low precipitation thunderstorms. Models still showing some uncertainty growing toward the end of the week, models lean toward the return of the West Coast Ridge pattern. Between Friday and Saturday, models attempt to dissipate the upper level disturbance and reintroduce the ridge axis over California. By Saturday, temperatures over the San Joaquin Valley may return to triple digit values as the ridge dominates the area once again. By the weekend, models place the ridge axis more over the Great Basin and Desert Southwest. Along with warming temperatures, the mid level wind flow under the position of the ridge pattern may become southwesterly and allow convective activity to diminish. While the extended may return to dry, the heat will once again affect the Central California Interior.Source: NWS
