December 19, 2018
Summary: Most of the southern half of the San Joaquin Valley is clear of low clouds and fog while from northern Fresno County up to the Delta region, the low overcast, as of 2:00pm, remained. Dew points up and down the line this afternoon are running in the mid to upper 40s, and with a mostly clear night ahead…other than high, thin clouds…widespread fog and/or low clouds will form during the later evening hours and will be widespread by sunrise. It will burn off into partial afternoon clearing in some areas by Thursday afternoon.
Strong upper level high pressure is currently centered several hundred miles off the southern California coast. The storm track goes up and over the high into the Pacific Northwest. This will continue through Friday then a weak trough will move through Friday which just might break up the inversion. If it does, the low clouds and fog will have no problem forming again over the weekend.
Speaking of the weekend, a west to east flow will continue across the eastern Pacific and into California with weak disturbances moving inland to our north. The most we will see is variable cloudiness from time to time and at least areas of night and morning fog and low clouds.
On Christmas Eve, rain will be spreading over northern California, possibly reaching Fresno County Christmas Eve. Models have backed off somewhat on both the strength and the southern limit of possible precipitation. We’ll go along with this and call for a chance of showers for the southern half of the valley, especially Christmas Day.
A strong north/northwest push of air will move down the valley the day after Christmas which will likely pile up a bunch of lower level clouds against the north facing slopes of the Kern County mountains with plenty of cloud cover over Kern and Tulare Counties and possibly Fresno County. A week from today, a second system will quickly move out of the Gulf of Alaska, but some of the new models are showing this low moving southeast just off shore then into the Desert Southeast by Friday. This would reduce somewhat the chance for a hard freeze as the winds aloft would be more north/northwest rather than north/northeast. Still, the period from the 28th through the 1st bears close watching as it’s normal for models to change the positions of players and the possible ramifications.
Forecast: Widespread fog and/or low clouds developing as the night progresses. Fog and/or low clouds Thursday with possible afternoon clearing. Areas of fog and low clouds Friday morning, otherwise it will be partly to mostly cloudy. Areas of fog and low clouds Saturday through Monday mornings, otherwise partly cloudy. Increasing cloudiness Christmas Eve with a chance of light rain as far south as Fresno County with a chance of light showers in the south valley Christmas Day through Christmas evening. Mostly to partly cloudy Christmas night through Wednesday morning. Becoming partly cloudy Wednesday afternoon through Thursday with areas of night and morning fog and/or low clouds.
Short Term:
| Madera 37/58/41/59 | Reedley 37/58/42/60 | Dinuba 36/56/41/57 | |
| Porterville 36/59/41/60 | Lindsay 35/58/40/61 | Delano 38/60/42/61 | |
| Bakersfield 42/63/44/63 | Taft 46/62/46/63 | Arvin 38/62/41/61 | |
| Lamont 39/63/43/63 | Pixley 36/59/42/59 | Tulare 35/57/41/58 | |
| Woodlake 36/58/41/59 | Hanford 37/60/42/61 | Orosi 36/59/40/60 | |
Winds: Winds will be generally at or less than 6 MPH through Saturday with periods of near calm conditions.
Rain: Expect dry weather to continue through at least Monday morning. The latest models this afternoon are not as robust in their portrayal of the Christmas Day storm. There is still a decent chance of light rain from Fresno County north, but we must back off and use the term chance of light showers south of Fresno County from Christmas Eve night through Christmas Day. There is a chance of lingering showers, mainly in the south valley, Christmas Eve night and in the foothills Christmas morning. The second system we had previously discussed for about the 27th now is looking like the low will drop down the coast far enough off shore to remove the chance of rain from the forecast.
From the 28th through the first few days of 2019, models show a strong ridge off shore, blocking storms from moving into California.
Frost Discussion: Coldest locations tonight may drop down to 33 to 36 degrees with most locations ranging from 37 to 42. A lot of tonight’s outcome will be determined by the formation of fog and low clouds, which haven’t even burned off towards Merced County all day.
On Friday morning, fog and low clouds will also determine the outcome with variable cloudiness above the low clouds. Where it clears, mid to upper 30s are possible Saturday through Monday mornings.
Overcast skies and the chance of showers will keep things comfortable Christmas morning. For the day after Christmas, I would anticipate upslope clouds against the valley facing slopes of the Sierra Nevada and the Tehachapi Mountains. Wind conditions will also help.
Beginning about a week from today, the chance for frost nights will begin to increase. There is one piece of good news this afternoon. Some models are showing more of a north/northwest flow over California rather than a north/northeast flow. This would make a great deal of difference. Still, we could very well see frost nights during this time frame. At this point, we’re taking the chance of a hard freeze out of the forecast, but subfreezing conditions are likely.
Next report: Thursday morning/December 20