December 18, 2018
Summary: Skies over the valley this afternoon are mostly clear except for over or near the foothills. There are pockets of clouds based at between 3,500 and 4,000 feet over portions of Kern County, but even they seem to be waning with time. With only high, thin clouds overhead tonight and high dew points, fog should become fairly widespread possibly as early as midnight. By sunrise, the Tule fog should cover much of the valley then lift into a low overcast by late morning with partial afternoon clearing. We can pretty much ditto that for Wednesday night through Thursday evening.
A weak wave of low pressure will move through northern and central California late Thursday and Friday, but any precipitation should remain north of a Bay Area/Sacramento/Yosemite line. It’s entirely possible, however, that it may generate enough low level wind energy to break up the warm air inversion, thus less fog Friday.
For Saturday through Christmas Eve, a moist zonal flow, or a westerly flow, will sweep inland over central California with mostly cloudy skies, but for now no precipitation is expected. A rather robust cold low from the Gulf of Alaska will slide southeastward Christmas Eve night, sliding into California Christmas Day for a good chance of lower elevation rain and lowering snow levels.
We are still on track for colder weather between Christmas and New Year’s as the possibility of a southwest to northeast oriented high pressure system builds into the Pacific Northwest, possibly as far north as the Canadian Rockies. While that’s occurring, a low pressure system will develop over central or southern California, creating a northeast flow into northern California, meaning the origins of the air mass may be from the Canadian Rockies. That poses a possible freeze threat before New Year’s. by freeze, I don’t mean teens to low 20s but possibly mid to upper 20s. I’m probably going out on a limb talking numbers this far away from the event, but it is something to be aware of.
Forecast: Some lingering cloud cover in Kern County and southeastern Tulare County tonight, slowly clearing later. Otherwise, it will be mostly clear with areas of ground fog developing before midnight. Widespread fog and/or low clouds Wednesday morning, lifting into a low overcast by midday with areas of clearing possible Wednesday afternoon. Fog and/or low clouds will continue Wednesday night through Friday morning with afternoon clearing possible. Variable cloudiness later Friday through Sunday night with patchy night and morning fog. Cloudy Christmas Eve through Christmas night with a small chance of rain from Fresno County north Christmas Eve night. periods of rain after midnight into Christmas night. mostly cloudy Wednesday with a chance of showers.
Short Term:
| Madera 38/56/37/56 | Reedley 37/55/36/54 | Dinuba 37/54/36/55 | |
| Porterville 38/57/37/58 | Lindsay 36/56/35/57 | Delano 40/57/39/57 | |
| Bakersfield 43/61/43/63 | Taft 46/61/46/64 | Arvin 41/61/38/63 | |
| Lamont 42/62/41/63 | Pixley 38/57/37/58 | Tulare 38/55/38/56 | |
| Woodlake 38/57/38/58 | Hanford 40/57/37/57 | Orosi 36/57/36/57 | |
Winds: Winds will be generally at or less than 6 MPH through Friday with periods of near calm conditions.
Rain: Expect dry weather to continue through Sunday night. there will be a minimal chance of light rain as far south as Fresno County Christmas Eve with periods of rain after midnight into Christmas night. Some models show a low center developing over central or southern California the 26 or 27 with limited moisture, but it still deserves to be considered as a chance of showers. Dry weather will return from the 27th into possibly the first few days of the new year.
Frost Discussion: Expect above freezing conditions through the day after Christmas. Models this afternoon are a bit more ominous from the 27th through the first of January. As we’ve discussed the past few days, a southwest to northeast oriented high is projected to build through the Pacific Northwest. This afternoon, some models are showing the high building into the southern Canadian Rockies with the possibility of a low center developing over central or southern California. This squeeze play around the eastern side of the high and western side of the low would turn the winds aloft out of the northeast over northern California, driving the air mass from possibly the Canadian Rockies right down into our region. This is a borderline freeze pattern, one we’ll simply have to monitor as we move closer in time. For now, I don’t want to get specific with numbers as this potential event is still a number of days out. This is, though, something to be aware of.
Next report: Wednesday morning/December 19