June 2, 2017 – Warmer temperatures into Saturday, a little cooler Sunday then warming again though mid week. A slight chance of showers northern Shasta county mountains Saturday and Sunday afternoon or evening hours. Otherwise fair skies and dry conditions through the middle of next week.
Discussion
Flat upper level ridging over the west coast bringing fair skies across the forecast area this morning. Temperatures this morning are running a bit warmer than 24 hours ago after a day yesterday several degrees warmer than the day before. Fort Ord profiler indicating the marine layer is around 1000 feet this morning. Onshore surface gradient only moderate for a minor delta breeze.
With fairly shallow marine layer, weak onshore flow and a patchy stratus deck offshore, believe coastal stratus unlikely to reach inland significantly this morning.
Upper ridge amplifies over the west today bringing several degrees of warming with daytime highs expected to come in several degrees above normal. Upper trough digging into the eastern Pacific will nudge the upper ridge eastward on Saturday.
Overall airmass changes little from today but delta and near delta influenced areas may see a little cooling. GFS, ECMWF and NAM all painting isolated showers over the northwest corner of the state so can not rule out a slight threat of showers over northern Shasta county.
Upper shortwave trough swings through the north state on Sunday bringing cooler daytime highs with max temperatures dropping to around normal for this time of year. In addition to cooler temperatures, the far north state could see a few showers.
A stronger delta breeze and deeper marine layer could mean morning stratus well into the delta during the morning hours although forecast soundings do not indicate a deep enough marine layer for a significant intrusion into the valley. Upper ridge rebuilds over the west on Monday bringing a reduced delta breeze and the next warmup with highs bumping back up to several degrees above normal.
Extended discussion (Tuesday through Friday)
Dry weather is expected early next week as high pressure rebuilds over the region. The Mon-Wed timeframe looks to be the hottest days over the next week, with highs in the 90s across the Valley, and 70s to 80s over the mountains.
The ridge shifts eastward toward the end of next week as an upper trough approaches the West Coast. The GFS is considerably stronger with this system than the ECMWF, and brings some light precipitation across much of the region. Our forecast is a blend of the two solutions, as forecast confidence is low.