Summary: Orographics are playing a huge role in our weather this afternoon. The jet stream over extreme northern California is running from west to east, zipping along at 107 MPH. the flow aloft over central California has the winds aloft at 30,000 feet out of the west at around 90 MPH. When all this moist air rushes in from the Pacific, it’s lifted by the Sierra Nevada, creating clouds and precipitation. Doppler radar is showing light precipitation all along the Sierra Nevada as far south as the high country of Sequoia National Park.
A cold front will move down the valley Saturday. as pressures fall as the main trough of low pressure moves into the Great Basin Saturday night and Sunday morning, northwest winds will pick up down the valley behind the front, issuing in a cooler air mass. Temperatures will drop to pretty close to mid December averages. Areas of frost are possible Monday and Tuesday mornings. This is discussed in the frost summary below.
Upper level high pressure will be overhead Sunday afternoon through Tuesday night, so areas of fog will again form Monday, but more especially Tuesday morning. on Wednesday, a lower latitude storm will be a few hundred miles west of the Golden Gate. I must say, however, models show this system really washing out as it advances eastward across central California Wednesday night and early Thursday. In fact, some models confine any precipitation to the Sierra Nevada.
Upper level high pressure will again take hold next Thursday night through Friday night. beginning next Saturday, models are still pointing towards a developing cold trough of low pressure digging southward from the Gulf of Alaska. This trough, on the majority of models, will remain in place for roughly 3 to 4 days then will turn into a closed low either over southern California or just off shore. The bottom line is, Saturday through Christmas Eve will see a chance of rain on any given day. A colder pattern may set up after Christmas, but we’ll leave that in the frost summary, as well.
Forecast: A chance of light showers tonight through Saturday night, mainly on the far eastern flank of the valley near the Sierra Nevada foothills. Mostly cloudy Sunday morning then partly cloudy Sunday morning through Monday morning, but possibly remaining mostly cloudy over portions of Tulare and Kern Counties. Mostly clear to occasionally partly cloudy Monday afternoon through Tuesday night with areas of fog and low clouds Tuesday morning. increasing cloudiness Wednesday with a small chance of light showers through early Thursday. Partly cloudy Thursday night and Friday with areas of night and morning fog and low clouds.
Short Term:
| Madera 49/57/37/53 | Reedley 50/58/38/53 | Dinuba 49/57/36/52 | |
| Porterville 49/58/38/54 | Lindsay 49/57/36/53 | Delano 50/58/40/52 | |
| Bakersfield 53/60/41/52 | Taft 53/59/42/53 | Arvin 49/61/41/52 | |
| Lamont 50/60/41/52 | Pixley 48/58/37/53 | Tulare 50/58/39/52 | |
| Woodlake 49/59/37/53 | Hanford 50/59/39/53 | Orosi 48/58/36/52 | |
Winds: Winds later this evening will be out of the east to southeast at 5 to 10MPH. later Saturday and Saturday night, winds will be mainly out of the northwest at 10 to 15 MPH with gusts to 25 MPH possible, mainly from Fresno County north and along the west side of Kern and Kings Counties. Winds Sunday will be out of the northwest at 5 to 12 MPH. Winds Sunday night and Monday will be generally less than 7 MPH with periods of near calm conditions.
Rain: The jet stream is slowly sagging southward into northern California as is that band of subtropical moisture which has been feeding into northern California the past few days. Light showers will spread down the Sierra Nevada as far south as the back country of Sequoia National Park. No radar echoes are occurring on the valley floor. There is a minimal chance of light showers, mainly along the east side, tonight through Saturday night. any location that happens to receive anything measurable will likely not pick up more than .10. dry weather will return Sunday and continue through at least Tuesday night. the storm system we’ve been talking about for several days off the Golden Gate is beginning to look pretty anemic on projections. In fact, some models show al the precipitation confined to the Sierra Nevada. For now, we’ll call for a minimal chance of light showers Wednesday into Thursday morning. dry weather can be expected Thursday afternoon through Friday night. models have been pretty consistent in showing the development of a deep trough of cold low pressure off the coast beginning next Saturday and indicate it will be there through Christmas Eve. The result will be a reasonably decent chance of rain any given day from the 20th through the 24th. The weather may dry out just in time for Santa Christmas Eve night. However, that’s a low confidence forecast as some models show a low center developing over southern California or just off shore. Theoretically this would result in unsettled weather through the 26th. Models after the 26th look dry out through New Year’s.
Frost Discussion: All locations will be above 32 both Saturday and Sunday mornings. Finally, a somewhat colder air mass will arrive behind a front that will move down the valley Saturday. the front will be followed by a fairly cold trough of low pressure but instead of moving into California, it’s expected to dive into the Great Basin. Pressure differences between the coast and the interior will create gusty northwest winds down the valley over the weekend, issuing in a colder air mass with much lower dew points. Widespread low to mid 30s are anticipated Monday and Tuesday mornings. We may see upslope clouds Monday morning along the west facing slopes of the Sierra Nevada and the north facing slopes of the Tehachapi Mountains which may hold temperatures in the upper 30s to the lower 40s there. On Tuesday morning, it’s possible much of the cloud cover will have dissipated for a mostly clear night. it’s not out of the realm of possibility that coldest locations could dip to 27 to 29 for a few hours with most locations between 30 and 34. We should see increasing amounts of cloud cover Wednesday from an approaching storm which should return us to above freezing conditions. Even though high pressure follows, so does a westerly flow aloft, resulting in fairly mild conditions. Longer term, an active pattern will set up about a week from tomorrow and is expected to continue through Christmas Eve. I’m still monitoring closely models for the period after Christmas as it’s possible a low center could develop either over southern California or off shore while a narrow ridge of high pressure builds northward into western Canada. The squeeze play would create a northeasterly flow aloft and a strong off shore flow which could lead to some chilly nights. We’re still talking about a week and a half away so at this point I’m just in a stay tuned mode.
Next report: Saturday morning/December 14