Chance of thunderstorms in the higher elevations, heat advisory in effect over the weekend

July 26, 2019 – A few thunderstorms possible over the Sierra today. Hot temperatures this weekend with widespread triple digits at the lower elevations. A Heat Advisory is in effect for this weekend. Temperatures cooling to average next week.

Discussion

NorCal under southerly flow aloft this morning between high pressure ridge centered over the four corners area and a weak trough off the Pacific Northwest coast. The southerly flow is bringing monsoon moisture northward into the Great Basin and radar showing some showers over the far southeast CWA at this time.

There is a chance that some of this shower activity may work its way up the Sierra later this morning. A shortwave rotating northeastward through NorCal may generate enough instability for some of these Sierra showers to develop into thunderstorms. Stability proggs indicate insufficient instability for thunderstorms elsewhere but may see a few very light showers this morning as the shortwave trough lifts through.

Otherwise, most CWA locations will see scattered clouds this morning. Skies should clear a little this afternoon as the upper flow becomes more westerly. Daytime highs today should come in similar to Thursday at just a little above normal.

Upper ridge builds over the west coast over the weekend bringing drier more stable conditions. It will also bring airmass warming with daytime highs Saturday and Sunday expected to top out about 6 to 10 degrees above normal.

Will leave heat advisory for this weekend up due to these above normal temperatures during these climatological warmest days of the year. An eastern Pacific trough dropping in to the Pacific Northwest and NorCal will bring a significant drop in daytime temperatures Monday. Most locations will see a drop in 5 to 10 degrees from the above normal temperatures over the weekend.

Extended Discussion (Tuesday through Friday)

Upper level high pressure will be centered over the Four Corners region Tuesday through late next week with weak ridging present along the west coast. The main impact of this feature will be to moderate temperatures back to near normal values with highs generally in the 90s in the Valley and the 70s in the mountains. Dry weather will persist next week.