December 22, 2018
Summary: Very little clearing has taken place over the valley, as of 2:00pm. Most locations are reporting a low overcast based between 1,600 and 2,400 feet. Highs will only end up in the mid 50s this afternoon. Considering that lows were only near 50 this morning, you can see very little difference between daytime and night time temperatures. For a fog regime type day, it was extraordinarily mild.
Variable mid and high level clouds are streaming over northern California and will spread over central California during the night. these clouds are riding a north/northwest flow across the Pacific and will be with us through Monday morning. On Monday afternoon, clouds will thicken and lower ahead of a low pressure system moving quickly southeastward from the Gulf of Alaska. Mainly light rain will spread over the valley Christmas eve night with showers continuing into Christmas morning. Lingering showers will be possible, especially in the south valley, Christmas afternoon.
Skies will be slow to clear as a northwest push of air moves down the valley and is lifted by the Kern County mountains and, to a lesser extent, the west facing slopes of the Sierra Nevada. If by chance some locations do clear Wednesday morning, near freezing temperatures will be possible.
Another low out of the Gulf of Alaska will drive through the Pacific Northwest and right down the spine of the Sierra Nevada about Thursday morning. For now, this system looks like a dry one with the possible exception of the Sierra Nevada. Behind this system, temperatures will fall even more as a north/south wind trajectory aloft spreads a colder air mass down from the north. The origins of this air mass will be from southwestern Canada, so even though cold it won’t be considerably so.
Beginning the 30th and 31st, a massive high is projected by models to cover the entire eastern Pacific Ocean with a ridge building into Alaska. Meanwhile, a low center will develop possibly as far south as northern Baja or somewhere over southern California or southwest Arizona. This will set up a pipeline of modified arctic air plunging southward into the western U.S. California will essentially be on the western rim of the north/south polar express. Most of this may or may not make it into Nevada and points eastward. This flow may actually become north/northeast January 1 and 2, which could possibly bring a greater risk of moving modified arctic air into the valley. On paper, anyway, by the 3 or 4, we should see a high center just to the west of San Francisco, hopefully ending the possible cold weather episode.
Forecast: Overcast tonight through Sunday morning. Variable cloudiness Sunday afternoon and night. increasing cloudiness Christmas Eve. Showers spreading down the valley Christmas Eve night, continuing through Christmas morning. A chance of lingering showers Christmas afternoon. Mostly cloudy Christmas night and Wednesday morning with patchy morning fog. Variable cloudiness Wednesday afternoon through Thursday. Becoming mostly clear Thursday afternoon through Saturday.
Short Term:
| Madera 49/56/42/58 | Reedley 50/56/43/57 | Dinuba 48/55/42/56 | |
| Porterville 50/57/43/58 | Lindsay 48/56/42/58 | Delano 50/57/44/59 | |
| Bakersfield 50/57/44/58 | Taft 51/58/47/59 | Arvin 50/57/44/59 | |
| Lamont 51/57/44/58 | Pixley 49/56/44/58 | Tulare 48/56/44/57 | |
| Woodlake 49/57/44/57 | Hanford 49/56/43/57 | Orosi 48/55/43/58 | |
Winds: Winds will be generally at or less than 6 MPH with periods of near calm conditions through Sunday night. Winds Monday will be out of the southeast at 5 to 15 MPH, continuing Christmas Eve night. winds Christmas Day will be out of the northwest at 10 to 20 MPH with stronger gusts, mainly along the west side.
Rain: The chance for showers will begin to pick up Christmas Eve night and will last well into Christmas morning with a chance of lingering showers Tuesday afternoon. Precipitation amounts are still anticipated to be on the light side with .25 amounts over Fresno and Madera Counties with locally more, as much as .25 could fall over portions of Tulare County with .10 or so in Kings County and generally .10 or less over the valley portion of Kern County. Dry weather will begin Tuesday night and in all likelihood will continue through the end of the year and possibly through the first week in January.
Frost Discussion: All locations will be above freezing tonight and each night through Christmas morning. The air mass behind the Christmas Day storm is colder, but not critically so. If skies happen to clear Tuesday night and Wednesday morning, lows could dip into the low to mid 30s. lows Thursday morning will depend upon cloud cover. A weather system will be moving through then with possibly enough cloud cover to keep readings in the low to mid 30s. if skies clear, upper 20s to lower 30s would be the result.
Friday morning, the air mass will be somewhat colder yet, but again not critically so. Widespread upper 20s and lower 30s would be a good bet for now, lasting through next weekend.
Models still indicate a massive Pacific upper high will be covering the eastern Pacific and building all the way northward into Alaska as a low center develops possibly as far south as northern Baja or perhaps over southern California. California is placed, on paper anyway, on the western rim of polar air diving southward. This event, if it occurs, could be determined by just where the air mass flows. Currently, it would be a given that the Great Basin and points eastward would be affected, and possibly California. I’ve seen many times where the Sierra Nevada did an efficient job of keeping polar air masses to the east. But, on less frequent occasions, the flow sets up with that modified arctic air flowing into California. You may remember this day in 1990 when temperatures plummeted into the teens, leading to ten days of temperatures ranging in the teens to the lower 20s. the coldest temperature recorded with that event was eleven and a half degrees at a location near Lindsay. I’m by no means even hinting at such an event, but rather to explain that historically, we’re in the most dangerous days of the year for cold weather and to be vigilant with these twice daily forecasts.
Next report: Sunday morning/December 23