April 15, 2018
Summary: There is a considerable amount of high clouds this morning streaming in from the subtropics which are not really associated with a big weather change that will occur tonight through Monday night. In fact, today will be quite warm with temperatures reaching or even surpassing the 80 degree mark, despite the high cloud cover.
A cold low is moving out of the Gulf of Alaska and will move into the Pacific Northwest later this afternoon and evening. The associated upper trough and cold front will move into central California late tonight and Monday morning with widespread light shower activity, gusty winds, and much cooler temperatures. In fact, to give you an idea of what will happen to the atmosphere over the next 36 hours, the freezing level is currently at 12,300 feet and will dip as low as 4,300 feet by Monday evening, lowering snow levels possibly down to 3,500 feet or so, even over the Kern County mountains. This same cold air mass will be unstable enough Monday afternoon and evening for more scattered showers and the chance of isolated thunderstorms. If thunderstorms occur they will be accompanied by heavy rain and small hail.
The atmosphere and wind conditions will begin to settle down somewhat after midnight Monday, allowing isolated locations to drop into the mid to upper 30s with a slight chance of the very lowest spots brushing with the 32 degree mark for short periods of time. However, a significant frost threat simply does not exist.
A weak high aloft will build in from the west Tuesday through Wednesday, allowing for a minor warming trend. We will reverse rudders again Thursday as a new low moves out of the Gulf of Alaska and into California. This doesn’t appear to be a significant weather event, but rather one which will result in just a small chance of light showers and another temporary dip in temperatures.
After Thursday, a zone of high pressure will develop over the eastern Pacific, extending eastward over California. This will result in a westerly flow aloft, allowing for yet another warming trend. This time, though, dry weather and above average temperatures should hold through next weekend and probably through the next week.
Forecast: Variable high clouds today. Increasing cloudiness tonight with light showers spreading down the valley, mainly after midnight. Light showers likely Monday morning. Scattered showers Monday afternoon and evening with a chance of isolated thunderstorms. Partly to mostly cloudy later Monday night through Tuesday morning with a chance of light showers near the foothills, especially in Kern County. Mostly clear Tuesday afternoon through Wednesday. Increasing cloudiness Wednesday night with a small chance of light showers Thursday and Thursday night. Mostly clear Friday through Sunday.
Short Term:
High temperatures this afternoon will warm into the lower 80s, falling into the mid 40s to the lower 50s tonight. Temperatures will warm into the low to mid 60s Monday, dipping into the mid 30s to the lower 40s Monday night then rising into the mid to upper 60s Tuesday.
Winds: Winds will be generally less than 12 MPH today then will be out of the southeast at 5 to 15 MPH this evening. Winds late tonight through Monday evening will be out of the northwest at 15 to 25 MPH with gusts possibly approaching 40 MPH along the west side. Winds later Monday night will decrease to 5 to 15 MPH with light winds Tuesday through Wednesday. The next periods of elevated wind conditions will be Wednesday night and Thursday.
Rain: Models this morning are moving the next cold weather system into central California a bit more slowly than previously indicated. The chance of light showers will reach into Fresno and Madera Counties possibly around midnight, spreading southward during the early morning hours. Expect generally light showers over the entire region Monday morning, turning to scattered showers with a chance of isolated thunderstorms Monday afternoon and evening. Any thunderstorm activity will likely be accompanied by heavy rain and small hail. Showers will end by late Monday evening. Precipitation amounts in Madera and eastern Fresno Counties could tally up to as much as a quarter to a third of an inch with perhaps a tenth or two along the east side of Tulare County and generally less than a tenth of an inch along the west side and over the valley portion of Kern County. If isolated thunderstorms develop, as much as a third to a half inch is not out of the question. Dry weather will return later Thursday night and continue through Wednesday evening. There will be a relatively small chance of light showers late Wednesday night and Thursday but for now, this system does not appear impressive. Dry weather will return Thursday night and continue through the weekend and at least through the middle of the following week.
Frost: A fairly radical change in temperatures will occur over the next 36 hours. Lower 80s today will be replaced by lower 60s Monday and as a cold, dry air mass dives southward through the valley on the wings of northwesterly winds, dew points may fall enough to allow temperatures in the cold spots to dip into the mid to upper 30s, assuming skies are clear and winds are near calm. This would only be in the river bottom and similar cold spots. There’s a slight chance of lower 30s for very short durations in those cold spots but no real frost is expected. After Tuesday morning, expect above freezing conditions each day for the foreseeable future.
Next report: Monday morning, April 16