July 10, 2019 – Gradual warming this week with temperatures returning to above average by the end of the week. Breezy wind at times through the Delta and over the Sierra crest. Temperatures returning back down to near normal early next week.
Discussion
Northern California under southwest flow aloft between high pressure centered over the southwest U.S. and a low pressure system off the Pacific Northwest coast. A couple of weak frontal bands pivoting through the southwest flow north of the state are bringing scattered to broken high to mid level cloud cover the northern CWA. The southern CWA is under mainly clear skies this morning although some patchy coastal stratus may make it into the western delta later this morning. Upper ridge over the southwest U.S. will continue to build back westward over the next few days bringing rising Heights and a continued warming trend.
Stable southwest flow aloft and building high pressure will keep any precipitation out of the short term forecast. Daytime highs today will warm a few degrees but are still expected to come in a little below normal.
On Thursday, highs push up just a bit above normal then up several more degrees on Friday putting highs about 5 degrees above normal for mid July. Temperatures level off on Saturday as an upper low over the eastern Pacific pushes closer to the coast. A few locations may even see a slight drop in temperatures.
GEFs ensembles in fairly good agreement in this trough movement towards the coast so have good confidence in this transition to cooler temperatures going into next week. Winds during the short term period should remain relatively light but will be breezy at times through the delta and over the higher Sierra locations.
Extended Discussion (Sunday through Wednesday)
Little change to the forecast as ensemble guidance continues to show high pressure over the desert southwest through Monday. This ridge will eventually sink farther south as a broad trough sets up over the Pacific Northwest. Temperatures will still be hot this weekend, but will then gradually decrease a few degrees each day starting on Sunday.