A little cooler and a threat of thunderstorms in the higher elevations

July 19, 2019 – Little change in daytime temperatures next couple of days. A slight threat of afternoon thunderstorms over the northern Sierra crest Saturday and at the end of next week. A little warmer during the second half of next week. Breezy winds through the delta and over the Sierra Crest at times.

Discussion

A weak upper trough over the Pacific Northwest will keep high temperatures today a little below season normal. Travis AFB showing a healthy delta breeze this morning gusting to 30 mph. This combined with a marine layer of nearly 2000 feet deep will bring patchy coastal stratus into the delta this morning.

Westerly flow aloft should keep any afternoon monsoon moisture showers well east of the forecast area.

The upper trough is forecast to shift eastward into the northern Great Basin on Saturday as high pressure rebuilds over the west coast. this process will allow for a little warming on Saturday with daytime highs pushing up to about normal.

Southwest flow aloft should preclude afternoon Sierra thunderstorm development although latest SHEF model does show a small shortwave bringing thunderstorm threat to the Northern Sierra in the late afternoon or evening.

Upper ridge continues to amplify over the Great Basin on Sunday bringing up daytime highs a little more and may start to see daytime highs in the valley topping 100 in a few locations.

Temperatures warm just a bit more on Monday but upper ridge axis and maximum subsidence remain well east of the state so daytime highs will still stay within a few degrees of normal.

Extended Discussion (Tuesday through Friday)

Interior NorCal sandwiched between upper trough pushing into the PacNW Tuesday and large 4 corners high. Upper high then gradually expands westward through the remainder of the extended period. This will result in near normal high temperatures Tuesday slowly warming to about 3 to 7 degrees above normal towards the end of the week.

Monsoonal moisture flow around upper high could lead to afternoon deep moist convection over southern portions of the Northern Sierra Nevada Thursday and Friday.