December 16, 2020
There is a good combination of frost and fog out there this morning. some areas have dense fog while other locations are generally clear. Most ag stations this morning were reporting temperatures in the upper 20s to the lower 30s with some mid 30s in Kern County. A temporary ridge of high pressure is upwelling ahead of a trough of low pressure approaching the Pacific Northwest. This will result in a fairly pleasant mid December day. The high will be ejected further out over the ocean tonight as a fast moving trough of low pressure and its associated cold front move into northern California. Rain will spread to a Bay Area/Stockton line by midnight. Light showers could reach as far south as Fresno by sunrise, spreading over the remainder of the valley, mainly north of Kern County, by Thursday. This is a fast moving system and, with the main dynamics remaining over northern California, light amounts of precipitation is all that’s expected.
The trough will move inland pretty much perpendicular to the Sierra Nevada, so lift along the mountain range should squeeze out some decent amounts of rain and snow, especially from Fresno County northward.
The storm will move into the Great Basin late Thursday night and Friday. A northwest push of air will generate upslope clouds against the Kern County mountains and the west facing slopes of the Sierra Nevada, especially in Tulare County.’
Over the weekend, a flat zone of high pressure will stretch from the eastern Pacific across
California and into the Great Basin. A warm air inversion will quickly develop over the valley floor, setting the stage for widespread fog and low clouds nights and mornings. The fog and low clouds may persist through the day in some areas.
I’m watching models closely for the period the 23 through the 26. Some models show a sharp ridge along the Pacific coast building as far north as northwest Canada and Alaska while a low dives into the Great Basin. This could set up a strong off shore surface flow and a north/northeast flow aloft, conceivably pumping colder and drier air into central California while an arctic air mass dives into the Rockies and the Midwest. Hopefully this air mass will remain east of the Sierra Nevada, but considering we’re heading into the most dangerous time of year I’ll be watching this pattern very closely.
Forecast: Areas of fog and low clouds this morning, otherwise it will be mostly clear. Increasing cloudiness tonight leading to a chance of showers by 3:00am as far south as Fresno County. Light showers for a time Thursday, mainly north of Kern county. Overcast Thursday night and Friday morning. clearing Friday afternoon. Mostly clear Friday night through Monday night with increasing amounts of night and morning fog and low clouds, possibly persisting through the day in some areas. Partly cloudy Tuesday and Wednesday with areas of night and morning fog and low clouds.
Short Term:
| Madera 57/40/57/34/55 | Reedley 57/41/58/34/54 | Dinuba 56/40/57/33/54 |
| Porterville 59/41/58/33/54 | Lindsay 57/40/58/33/54 | Delano 59/41/57/40/56 |
| Bakersfield 59/43/57/41/56 | Taft 58/46/57/47/56 | Arvin 60/42/57/42/54 |
| Lamont 59/41/58/35/55 | Pixley 57/41/58/34/55 | Tulare 57/40/57/34/54 |
| Woodlake 57/41/58/33/55 | Hanford 57/41/58/35/55 | Orosi 57/39/58/33/55 |
Seven Day Forecast:
| Saturday
AM fog/PM sun 32/56 |
Sunday
AM fog/partial clearing’ 33/53 |
Monday
AM fog/partial clearing’ 35/55 |
Tuesday
AM fog/partly cloudy 37/59 |
Wednesday
Am fog/partly cloudy 33/55 |
Two Week Outlook: December 23 through December 29: This model has central California on the dividing line between dry weather over southern California and potentially wet weather over northern California and the Pacific Northwest. I need to introduce a chance of showers from main Fresno north during this period with above average temperatures.
December: This model shows above average temperatures during the month of December. Southern California should experience below average precipitation. There is some hope for northern and central California, however, as this model spits out equal chances of above or below average rainfall. We’re hoping for the above average side of things.
December, January, February: This model definitely reflects a La Nina pattern, which is when ocean temperatures are below average through the equatorial waters off of Peru, extending into the mid Pacific. Typically, this results in above average temperatures for much of the southern half of the U.S., including California, with unfortunately below average precipitation for California including the valley.
Winds Discussion: Winds will be light and variable through this evening. Late tonight through Thursday evening, winds will be out of the northwest at around 8 to 15 MPH. local gusts to near 25 mph will be possible north of Kern County and mainly along the west side. Winds late Thursday night through Sunday will be no more than 10 MPH and variable late mornings and afternoons and generally no more than 5 MPH during the night and early morning hours with periods of near calm conditions.
Rain Discussion: A fast moving trough of low pressure and its associated cold front will move rapidly through the valley Thursday. Light showers may reach as far south as Fresno County after roughly 3:00am Thursday, spreading over the remainder of the valley, mainly north of Kern County, Thursday morning. Dry weather will return by later Thursday afternoon or evening. It’s possible light rain or drizzle may occur near the base of the Tehachapi Mountains Thursday night into Friday morning due to upsloping. All indications are that this system will not be a prolific precipitation producer. In Madera and eastern Fresno County, expect no more than .10 to .25. Most of Tulare County could pick up between .05 and .15 with no more than a few hundredths over the valley portion of Kern County, if it rains there at all. Western Fresno and Kings counties will be under a rain shadow, so expect no more than .10. dry weather will return Thursday night and at least through the middle of next week. Models continue to show a blocking ridge along the coast through late December with little hope of precipitation.
Frost Discussion: All locations will be above freezing Thursday and Friday mornings as a weataher system traverses the region. Beginning Friday, a flat ridge of high pressure will build overhead, creasing a warm air inversion and setting the stage for night and morning valley fog possibly persisting through the day in some areas through at least Monday. The air mass following Thursday’s frontal system is not very cold, just pretty typical for mid December. From Saturday through Tuesday, typical low lying frost pockets could potentially drop into the upper 20s to the lower 30s with mostly mid 30s. if the fog and low clouds completely take over, readings will remain in the 30s. I am carefully perusing model information from the 23 through after Christmas. From model run to model run there are significant differences, however it’s possible a sharp ridge of high pressure will build along the Pacific coast all the way into Alaska and northwest Canada while a cold low drops into the Great Basin. Theoretically, this pattern would create a strong off shore flow and also a strong north/northeast flow aloft, potentially driving colder, drier air into central California. Usually, when arctic air masses drop southward, the lion’s share of the time they remain east of California and hopefully that will be the case this time around. Even so, from now to mid January is the most risky time of year for citrus, so obviously I’ll keep a close eye on developments.
Air Quality Expectations: The San Joaquin Valley Air Pollution Control District has issued the following warning(s) for December 16, 2020:
Today’s air quality is listed as The air quality for the entire valley is Moderate.
The District’s Real-time Air Advisory Network (RAAN) can be used to track air quality at any Valley location by visiting myRAAN.com. The option to use a specific address is available.
In addition, anyone can follow air quality conditions by downloading the free “Valley Air” app on their mobile device
Afternoon Dew Points Today: Low to mid 40s. Kern, low to mid 40s.
Actual Humidity Range Yesterday: Delano, 97%/49% Porterville, NA
Percentage of Sunshine Today/Tomorrow: Visalia: Today: 80%, tomorrow 0%. Bakersfield: Today: 90% Tomorrow: 0%
ET Rates Over the Past Seven Days: Stratford .37, Parlier .29, Blackwell Corners .NA, Arvin .38, Orange Cove .28, Porterville .NA, Delano .33. Courtesy University of California *=estimate, NA=not available.
Seven Day Soil Temperatures: Stratford 54, Parlier 50, Blackwell 55, Arvin, 52, Orange Cove 54, Porterville 51, Delano 45
Record Temperatures: 70/25. Average Temperatures: 54/35
Heating Degree Days This Season: 636, -157
Courtesy of the NWS
Average Temperature for this month So Far: 47.9 +2,7
Precipitation: Seasonal total for Fresno, 1.07, or -1.34, Month to Date: .79, or +.08
Precipitation for Bakersfield, Season, .40, +or- -.98. Month to date .01, or -.43
Water year season is from October 1st through September.
Chilling Hours November 1st through February 28: Orange Cove, 337, Parlier, 417, Arvin, 331, Belridge, 395, Shafter, 362, Stratford, 388, Delano, 424, Porterville, 468
Hours at 45 or below 45. Courtesy UC Davis
Sunrise: 7:06 am Sunset: 4:45 pm Hours of Daylight: 9:40
Yesterday’s Weather
MCE : Merced 153 : DH1600 / 54 / 33 / 0.00 /
MAE : Madera 253 : DH1600 / 56 / 34 / T /
FAT : Fresno Airport 333 : DH1600 / 55 / 38 / 0.00 /
HJO : Hanford Airport 242 : DH1600 / 55 / 33 / 0.00 /
NLC : Lemoore Naval AS 234 : DH1600 / 57 / 30 / 0.00 /
BFL : Bakersfield Airport 496 : DH1600 / 58 / 37 / 0.00 /
VIS : Visalia Airport 292 : DH1600 / 56 / 34 / 0.00 /
ATEC1 : Avenal 787 : DH1600 / 56 / 34 / 0.00 /
PTV : Porterville Airport 442 : DH1600 / 59 / 31 / 0.00 /
TFTC1 : Taft 759 : DHM / M / M / M /
LOSC1 : Los Banos 120 : DH1600 / 55 / 34 / 0.00 /
Rainfall: 24hr W.Y. % Last Y. % Ave. Year ave.
STOCKTON 0.00 1.38 40 4.05 119 3.41 14.06
MODESTO 0.00 1.20 42 2.79 98 2.84 13.11
MERCED 0.00 1.91 77 0.00 0 2.47 12.50
MADERA 0.00 0.55 21 0.00 0 2.60 12.02
FRESNO 0.00 1.07 45 0.00 0 2.36 11.50
HANFORD 0.00 0.49 26 0.00 0 1.89 10.10
BAKERSFIELD 0.01 0.40 30 0.00 0 1.34 6.47
BISHOP 0.00 0.01 1 1.06 96 1.10 5.18
SALINAS 0.00 0.66 24 4.12 149 2.76 12.83
PASO ROBLES 0.00 0.30 13 4.70 197 2.39 12.78
SANTA MARIA 0.03 0.30 11 2.68 97 2.75 13.95
Next report: December 16/pm