May 7, 2019 - The National Weather Service Hanford Office reports a few strong thunderstorms are possible in the Southern Sierra Nevada and adjacent foothills, extending into the extreme eastern portions of the San Joaquin Valley.
Funnel clouds, small hail, and wind gusts near 40 miles per hour are some of the hazards associated with strong thunderstorms.
In addition to dangerous cloud to ground lightning strikes, any thunderstorm can produce intense rainfall rates, leading to very localized flooding.
Area Forecast Discussion National Weather Service San Joaquin Valley - Hanford CA 335 AM PDT Tue May 7 2019 .SYNOPSIS... A low pressure system over Southern California will provide cooler temperatures and unsettled weather over the Southern Sierra Nevada and adjacent foothills today through Wednesday. The greatest potential for rain this week in the San Joaquin Valley looks to be Thursday afternoon through Friday afternoon. && .DISCUSSION... The upper low that has influenced the weather over the region continues to shift slowly southeastward today. In its wake, clouds and a few thunderstorms invaded Central California on Monday. Yet, due to the weak lift generated from a distant disturbance, storm activity was confined to the Sierra Nevada. However, the cloud cover did manage to keep temperatures on the cooler side as the San Joaquin Valley struggled to reach the 80 degree-F mark. In addition, surface pressure gradients from KSFO to KLAS supported strong winds under the change in temperature. Yet, now that the cool air has overspread the region, pressure gradients have relaxed as winds continue to diminish. The wind advisory from Monday will be allow to expire this morning. While the upper continues to slow move into the Desert Southwest today, another round of mountain convection may bee seen as the environment is still primed with the needed ingredients for afternoon thunderstorms. Short range models progging the upper low over Southwestern Arizona this morning and shifting it toward the AZ/NM state line by the afternoon hours. During this time, a very weak piece of energy will cross Central California. Even with the weak lift from this piece of energy enough instability and moisture will exist over the region to support the generation of mountain convection. Therefore, will follow the Storm Prediction Center Guidance and place the Mountains and Foothills under the treat of convection while debris clouds float out into the valley locations. No significant precipitation is therefore expected over the valley as down-slope flow from an easterly direction dry out the lower atmosphere. And, just like Monday, the atmosphere will stabilize this evening and allow for some clearing overnight. Toward the middle of the week, models show the upper low merging back into the main flow as the West Coast remains in the cyclonic flow pattern. While an almost meridional flow pattern develops over the west, weak pieces of energy will continue to rotate around the cyclonic flow to generate additional convective events over the Sierra Nevada on Tuesday and possibly Wednesday. Later in the week, models still attempting to form a closed low that drops toward California from the Inter-mountain West. The current trajectory has changed little during the last few days and its cuts through Yosemite. While confidence is growing on the development of the upper low, high uncertainty exist on the time of when the low will cross the region. Will favor the faster timing of the GFS/Canadian and NOGAPS models and expect widespread precipitation by Thursday night. All models place the upper low offshore by the start of the weekend and begin drying out the region. While mountain convection may continue into the weekend, the remaining parts of the region will see dry and cool conditions going into the middle of May.Source: NWS
