This report last updated
Tuesday, August 04, 2015 07:32 AM
A cool as the marine layer has increased and the onshore flow has strengthened. This morning we are enjoying temperatures in Magalia running about 6° cooler than 24 hours ago. The low temperature so far has been 59°. Dew point temperatures are running in the lower 50°s which is very comfortable. Winds overnight have been nearly nonexistent.
Today could get interesting as a strong shortwave of energy will lift into Northern California as it rotates around the base of a parent low pressure cell offshore. This shortwave is expected to interact with some subtropical moisture from Tropical Storm Guillermo which is currently east of Hawaii. This scenario could bring clouds and a chance of some showers or thunderstorms to Magalia later today. The current prognosis has a 10% chance of precipitation later this afternoon into late evening as the shortwave passes through the region and destabilizes the atmosphere. Those odds are predicted to decrease to a 5% chance later tonight into early Wednesday morning. Any deviation from the current expected trajectory of the shortwave could have an impact of Magalia's chances of precipitation. A secondary effect of this shortwave is a general cooling of the atmosphere and the increased onshore air flow through the Delta which should bring a cooler day compared to Monday. As the subtropical moisture spreads over our area, dew point temperatures may elevate somewhat and feel a bit more muggy.
Today's high temperature is predicted to reach 82° here in Magalia at 2400'. Historical normal for this time of year is 90° (at De Sabla Res.). In contrast, yesterday's high reached 88°. The low tonight is predicted at 61°. Winds this afternoon are expected to generally be out of the south at 5-7 mph. Localized gusty winds are possible in any thunderstorm activity. Let's hope some of the thunderstorms drop rain on some of the many wildfires across the north state.
Wednesday and Thursday looks as though the shortwave will have passed through and precipitation odds should drop back to a 0% chance by sunrise Wednesday and continue at those odds through most of Thursday. A shortwave ridge of high pressure should build in behind today's weather system and bring slightly warmer temperatures both days. By late Thursday night, the low pressure cell offshore should push to the east and bring us another slight chance of precipitation. There's a 15% chance of showers or thundershowers late Thursday night into Friday as the low passes through the region. A slight cooling trend will likely accompany the low as it nears. Precipitation odds drop back to a 5% chance this weekend.
There are some discrepancies regarding next week's weather as a low pressure area out of the Gulf of Alaska drops south along the coast. For now, the forecast has a chance of showers over far northern Shasta County late Sunday afternoon and evening. The trajectory of the low is not set in stone at this time, so predicting next week's weather is not very confident at this time. Have a good Tuesday. Bob