December 6, 2019
Summary: We are still tracking a large Pacific storm located roughly 400 miles off the northern California coast. The frontal band from this system is moving very slowly towards the east but has spread precipitation over northern California from roughly Santa Rosa north. There is one rather unexpected element to this pattern. A batch of subtropical moisture is moving on shore over the coastal areas of southern California from Ventura southward to just west of San Diego. This batch of moisture will not affect the San Joaquin Valley as the main thrust will be east/northeast through inland sections of southern California.
The cold front off shore will begin to make its move inland through central California Saturday. models continue to show a strong rain shadow over the western and southern flanks of the valley, but with good orographic precipitation along the Sierra Nevada from mainly Kings Canyon north. After the front moves through, the colder sector, or the upper low, will begin to move into northern and central California for periodic showers Saturday night through Sunday evening. Some models have slowed the forward progression of this storm, so we could see showers last into Monday morning, especially on the east side of the valley.
Upslope clouds will follow this system, banking up against the west facing slopes of the Sierra Nevada and the north facing slopes of the Tehachapi Mountains. Clearing will be slow Monday. Assuming skies clear in a timely manner, which is somewhat doubtful, but if skies do clear, ground fog will have no problem forming after midnight Monday night and Tuesday morning.
A massive ridge of upper level high pressure will be anchored just off shore Monday night and Tuesday, extending into western Nevada. A sharp ridge will build northward to almost the Arctic Circle. Modified arctic air will plunge south/southeast into the Rocky Mountain region and the midwestern U.S. Monday and Tuesday. Models still show this air mass remaining well to the east of central California.
A weak trough of low pressure will move through Wednesday. precipitation is very unlikely with this system, however mid and high level clouds will move in from the west and could inhibit fog formation. Models show a flat zone of upper level high pressure over the eastern Pacific with the main storm track moving into the Pacific Northwest, affecting the northern ¼ of California from time to time. Central California will only observe variable cloudiness from time to time. On nights where skies are relatively clear, widespread fog and low clouds can be expected. On nights where cloud cover is dominant, the fog and low clouds will be patchy.
Temperatures next week will be governed by fog coverage.
Forecast: Increasing cloudiness tonight. periods of rain Saturday and Saturday night. showers Sunday with a chance of isolated thunderstorms Sunday afternoon and evening. A diminishing chance of showers after midnight Sunday with a chance of a few lingering showers for a time Monday morning. Partly to mostly cloudy Monday afternoon. Partly cloudy Monday night through Tuesday with areas of fog and low clouds developing. Increasing cloudiness Tuesday night. variable cloudiness Wednesday and Wednesday night. partly cloudy Thursday through Friday with areas of night and morning fog and low clouds.
Short Term:
| Madera 48/63/48/61 | Reedley 50/64/51/61 | Dinuba 49/64/48/60 | |
| Porterville 50/65/51/62 | Lindsay 48/65/49/62 | Delano 51/66/51/62 | |
| Bakersfield 53/68/53/63 | Taft 53/66/53/62 | Arvin 49/68/51/62 | |
| Lamont 50/67/51/63 | Pixley 50/65/51/62 | Tulare 49/63/48/60 | |
| Woodlake 48/64/48/61 | Hanford 50/65/48/61 | Orosi 48/63/48/60 | |
Winds: Winds tonight will be out of the southeast at 8 to 15 MPH before midnight. After midnight and from Fresno County north, winds will be out of the southeast at 15 to 25 MPH with stronger gusts. Winds in Kings County will be generally out of the southeast at 10 to 20 MPH with stronger gusts. IN Tulare County, winds will be out of the east or southeast at 8 to 15 MPH with stronger gusts. In Kern County, winds will be generally out of the east or southeast at 10 to 15 mph with local gusts to near 30 MPH possible near the base of the Grapevine and locally elsewhere. These winds will continue Saturday morning then will be out of the west or northwest late Saturday afternoon through Sunday at 10 to 15 MPH with stronger gusts, mainly near showers. Winds Sunday night will be out of the northwest at 8 to 15 MPH. Winds Monday will be generally at or less than 7 MPH with periods of near calm conditions.
Rain: Rain has spread over northern California as far south as Santa Rosa. There is also a batch of precipitation spreading over southern California from Ventura County southward to just off shore San Diego. That area of rain will not affect the San Joaquin Valley. A cold front is located about 300 miles off the central coast and will move through the valley Saturday with periods of rain. Rain shadows will definitely develop along the western and southern flanks of the valley where precip amounts are expected to be generally .25 or less. In Kern County, for now it appears a tenth or two is likely. There is greater potential for significant rain along the east side of the valley, especially from a Visalia/Exeter line north where .50 or more cannot be ruled out from Saturday through early Monday. Isolated thunderstorms are a possibility Sunday afternoon and evening. When and if these storms do occur, over .50 totals are certainly feasible. We may see some lingering showers lasting into Monday morning. The remainder of Monday and the remainder of next week should be dry.
Frost Discussion: All locations will be above freezing for at least the next seven to ten days.
Next report: Saturday morning/December 7