December 12, 2019
Summary: For midDecember, central California remains in a very warm environment. The freezing level taken earlier above Vandenberg was all the way up to 13,000 feet. Tehachapi, at an elevation of 4,000 feet, was reporting a reading of 55 as of 1:00pm while Shaver Lake at 5,600 feet was reporting 57. Widespread mid 60s are prevalent above the valley floor, a good 10 degrees above average.
High pressure at the upper levels of the atmosphere continues to stretch from northern Baja to 1,500 miles out over the ocean to the west. The jet stream is running from west to east, coming on shore just north of a California/Oregon border. Winds are zipping along at 150 knots at that latitude. The flow aloft over central California also remains out of the west. Light precipitation has been confined today to parts of northern California and the Sierra Nevada from Tahoe north. Even though a batch of high clouds continue stream over central California, there’s still been plenty of sunshine. Over the next 24 hours, the pattern will show little change with the higher clouds being rather thin. This should allow enough radiational cooling for fog to develop again Friday morning.
A pattern change will occur over the weekend as a fairly weak low drops out of the Gulf of Alaska then moves rapidly into the Pacific Northwest and then the Great Basin as an inside slider Sunday morning. This system will generate a weakening cold front which will move down the valley Saturday. showers will spread down the Sierra Nevada with light showers over the valley floor. Models are still suggesting that where measurable precipitation occurs, most will record no more than .10 with higher amounts over the higher elevations of the Sierra Nevada.
Behind the front, winds will begin to pick up out of the northwest as the mild westerly flow becomes northwesterly, spreading a cooler air mass into California. Instead of temperatures 10 degrees or more above average, more normal temperatures will return as highs drop into the low to mid 50s early next week. Lows will be well down into the 30s. more on t his in the frost discussion below.
Models continue to indicate a lower latitude storm will move to off a position off the north central coast by Wednesday afternoon. It will then move inland Thursday in the form of a trough of low pressure. If this trend continues, we’d see widespread precipitation. Medium range models for the 19th through Christmas Day are still pointing towards wet weather with the possibility of a large low developing off the coast of the Pacific Northwest. There would be a strong west/southwest flow moving across the Pacific and into California. We could even see the development of a pineapple connection.
Forecast: Variable mid and high level clouds tonight and Friday. Areas of ground fog developing, mainly north of Kern County, later tonight and Friday morning. Increasing cloudiness Friday night. mostly cloudy Saturday and Saturday night with the risk of light showers Saturday through Saturday evening and a slight chance of showers Saturday night and Sunday morning. Partly cloudy Sunday afternoon through Monday morning. Patchy fog developing Monday morning. Mostly clear Monday afternoon through Tuesday with areas of fog and low clouds possible Tuesday morning. Increasing cloudiness Tuesday night. an increasing chance of rain Wednesday into Thursday.
Short Term:
| Madera 42/62/47/57 | Reedley 42/64/46/59 | Dinuba 41/62/46/58 | |
| Porterville 41/64/45/59 | Lindsay 40/63/44/59 | Delano 43/65/47/58 | |
| Bakersfield 48/66/52/60 | Taft 51/65/53/60 | Arvin 42/66/47/61 | |
| Lamont 44/65/48/60 | Pixley 42/64/47/59 | Tulare 40/62/45/58 | |
| Woodlake 41/63/45/58 | Hanford 43/63/47/59 | Orosi 40/63/45/58 | |
Winds: Winds will be generally at or less than 6 MPH with periods of near calm conditions through Friday night. Winds Saturday will begin to increase out of the northwest at 10 to 20 MPH with stronger gusts along the west side and from Fresno County north. Winds will be 8 to 15 MPH with stronger gusts elsewhere. Winds Saturday night and Sunday will be mainly out of the northwest at 10 to 15 MPH along the west side with stronger gusts and generally at or less than 12 MPH elsewhere. Winds Sunday will decrease to around 5 to 10 MPH with light winds returning Sunday evening.
Rain: The chance for mainly scattered light showers will pick up Saturday through Saturday evening with a slight chance of showers Saturday night and early Sunday. This system is quite weak so anticipate no more than .10 at any given location with many locations picking up possibly just a few hundredths of an inch. Dry weather will return Sunday and will last through at least Tuesday night. models continue to indicate a strong low will approach the north central coast Wednesday then opening up into a trough of low pressure before moving inland Thursday. It this occurs, rain will become likely sometime Wednesday, lasting through Thursday. The latest medium range models are still indicating the potential for a very active pattern between the 19th and Christmas Day with the potential for a big low off the coast of the Pacific Northwest and a very moist jet stream flanked into California.
Frost Discussion: All locations will be above 32 degrees through Sunday morning. a colder air mass will follow a weakening cold front moving through central California Saturday. temperatures will actually drop to what is more typical for the season with highs Monday and Tuesday in the low to mid 50s. We could see widespread low to mid 30s as early as Monday morning with a slight chance of some upper 20s. one model is spitting out a low temperature of 31 Tuesday morning in Porterville. This could put coldest locations in the 27 to 31 degree range, assuming skies remain clear. Only Monday and Tuesday of next week appear to be the days when frost is possible as clouds will begin to increase Tuesday night and more rain possible Tuesday and Wednesday. the flow behind the Wednesday/Thursday system will again be out of the west, continuing mild conditions. The pattern from Christmas Day and for several days thereafter is certainly up for speculation. Some models show a deep low over California with very cold air moving in from the Yukon Territory of Canada then sliding southward just off the California coast. This would not result in a critical pattern, but could lead to a series of chilly nights. Between Christmas and New Year’s. Considering that the time frame from now through mid January is typically the coldest of the year, we’re certainly overdue for cold weather.
Next report: Friday morning/December 13