December 17, 2018
Summary: Skies have cleared over sections of the west side of the valley north of Kern County. However, plenty of upslope clouds continued to be banked up against the valley facing slopes of the surrounding mountains. These clouds will more than likely remain through the night and into Tuesday morning. Where it clears this evening, with dew points in the low to mid 50s, fog will have no problem forming after midnight when winds die off. The air mass above the valley floor, despite the trough passage, is still mild. The freezing level over Oakland this morning was 7,600 feet and it was 8,200 feet over Vandenberg.
Beginning Tuesday, a strong upper level high will develop off the southern California coast and will ridge northward, moving the storm track back into the Pacific Northwest. As the high continues to build, a strong warm air inversion will develop, leading to widespread fog and/or low clouds by Wednesday morning. These low clouds and the fog will have a tough time burning off as we’re just about to the shortest day of the year with only nine hours and forty minutes of daylight.
Late Thursday night and Friday morning, a weak trough of low pressure will spread light precipitation over northern California, but for now it looks like it will be too weak to spread precip as far south as the growing area. It is possible it could temporarily break up the warm air inversion. If it does, it will more than likely return over the weekend as a high center several hundred miles out to sea extends eastward into California.
For the second model run in a row, there is some indication of a low pressure system and its associated cold front moving through northern and central California possibly as early as Christmas Eve night and Christmas Day. Currently, models project the wet/dry line to be right at Fresno County so right now the south valley will have just a slight chance of measurable rain.
More and more, it’s beginning to look like a colder weather pattern will set up about the 27th. A deep trough of low pressure is expected to move through. This type of trough wouldn’t necessarily bring rain to the valley, but would create a north/northwest flow between high pressure off shore and a low center over the interior west. This is not a classic freeze pattern, but it is one which does bear watching for possible below freezing low temperatures.
Forecast: Mostly cloudy tonight in Tulare and Kern Counties and locally elsewhere. Mostly clear to p artly cloudy along the west side north of Kern County. Mostly cloudy in the south valley Tuesday morning and partly cloudy elsewhere. Mostly clear Tuesday afternoon through Tuesday evening. Widespread fog and low clouds will develop after midnight Tuesday night, lifting into a low overcast by Wednesday morning with partial afternoon clearing possible. Widespread fog and/or low clouds Wednesday through Sunday with partial afternoon clearing. Increasing cloudiness Monday leading to a slight chance of showers Christmas Eve night and a chance of showers Christmas Day, mainly from Fresno County north.
Short Term:
| Madera 42/56/40/54 | Reedley 45/55/41/55 | Dinuba 43/54/39/53 | |
| Porterville 44/54/41/55 | Lindsay 42/55/39/55 | Delano 45/56/41/56 | |
| Bakersfield 48/54/43/56 | Taft 49/57/44/58 | Arvin 43/54/41/59 | |
| Lamont 44/56/42/57 | Pixley 42/55/41/55 | Tulare 43/53/40/54 | |
| Woodlake 43/54/41/53 | Hanford 43/56/41/54 | Orosi 42/55/40/53 | |
Winds: Winds this evening will be mainly out of the northwest at 5 to 10 MPH, diminishing by the late evening hours. Winds after midnight through Thursday will be generally at or less than 6 MPH with extended periods of near calm conditions.
Rain: Expect dry weather tonight and dry weather through the workweek and the coming weekend. Some models are suggesting a chance of rain from Fresno County northward Christmas Eve night and Christmas Day with only a minimal chance of showers further south. For the second day in a row, models are showing the pattern after Christmas becoming dry until about the 30th when the two week model suggests the possibility of precipitation.
Frost Discussion: All locations will be above 32 degrees tonight and each night through the coming weekend and more than likely through the 26th. The needle on models seems to be trending towards a colder pattern setting up around the 27th and lasting through the New Year. For now, this does not appear to be a classic freeze situation, but one which could potentially lower overnight temperatures below freezing, though not critically so. We will keep a close eye on it, though.
Next report: Tuesday morning/December 18