December 12, 2020
Showers have spread as far south as a Monterey/Merced line as of the time of this writing. The cold front and associated trough of low pressure are now sweeping into northern California and will move through central California this afternoon and tonight. most of the precipitation will be over by roughly midnight with the exception of possibly near the base of the Kern County mountains where upslope conditions will continue to squeeze out drizzle or light rain into Monday morning. potential rain fall amounts are discussed below.
On Monday, high pressure over the eastern Pacific will shift eastward into California, temporarily driving the storm track further north. With a warm air inversion developing above the valley floor Tuesday and Wednesday, areas of fog and low clouds will no doubt develop. Even this morning, as of 7:00am, there were pockets of fog out there. Both Bakersfield and Hanford were down to ¼ of a mile with Visalia at 1 mile.
The high will again shift back westward over the ocean Wednesday night and Thursday, allowing the next trough of low pressure to move into northern and central California. Some models have moved up the timing of this system to Wednesday night and Thursday. Since a definite trend has developed, the chance of additional precipitation now appears likely.
A zonal flow will develop Friday into early next week with a flat zone of upper level high pressure off the California coast extending inland into California. A strong west to east Jetstream will move into the Pacific Northwest, affecting perhaps the northern ¼ of California from time to time.
Forecast: Showers reaching Fresno County later this morning, spreading into the south valley this afternoon. Showers through the late evening hours, ending by midnight. Mostly cloudy later tonight and Monday morning with a chance of drizzle or light rain for a time Monday morning near the base of the Tehachapi. Partly cloudy Monday afternoon through Tuesday night with areas of fog and low clouds developing Tuesday and Wednesday morning. increasing cloudiness later Wednesday afternoon. A chance of showers again late Wednesday night and Thursday. Mostly cloudy Thursday night through Friday morning. partly cloudy Friday afternoon through Sunday with periods of night and morning fog and low clouds.
Short Term:
| Madera 58/40/54/34/55 | Reedley 59/41/54/33/55 | Dinuba 58/41/53/33/53 |
| Porterville 59/41/54/34/55 | Lindsay 59/41/54/33/54 | Delano 61/42/54/35/55 |
| Bakersfield 62/44/53/39/56 | Taft 62/47/53/54/45 | Arvin 63/44/53/37/56 |
| Lamont 63/44/53/36/56 | Pixley 60/41/54/34/55 | Tulare 58/41/53/33/53 |
| Woodlake 58/40/54/33/53 | Hanford 58/41/54/35/55 | Orosi 59/40/54/32/53 |
Seven Day Forecast:
| Wednesday
AM fog/partly cloudy 32/58 |
Thursday
Chance of showers 41/62 |
Friday
Mostly cloudy 38/54 |
Saturday
AM fog/partly cloudy 34/57 |
Sunday
Am fog/partly cloudy 34/59 |
Two Week Outlook: December 20 through December 26: 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 this morning. later this afternoon through tonight, winds will be mainly out of the northwest at 5 to 12 MPH with locally stronger gusts. Winds Monday through Wednesday will be generally at or less than 10 MPH late mornings and afternoons and generally at or less than 5 MPH during the night and early morning hours with periods of near calm conditions.
Rain Discussion: Showers have already spread into the northern San Joaquin Valley and will reach into Fresno County later this morning, spreading into the south valley later this afternoon. Most of the shower activity should be over by roughly midnight with the possible exception of the extreme south valley where upsloping against the Kern County mountains may squeeze out some drizzle or light rain into Monday morning.
Rainfall amounts in Madera County and eastern Fresno County should tally up to .25 to .33. In western Fresno County, perhaps .10 to .20 due to rain shadows. In much of Tulare County, between .10 to .25 seems plausible with a tenth or two in Kings County. Most locations over the valley portion of Kern County should record no more than .10.
Dry weather will prevail Monday through Wednesday. models continue to trend towards the next trough of low pressure moving through late Monday night and Thursday, a bit earlier than previously projected. For now, it appears precipitation amounts will be generally light.
After Thursday night, the storm track will migrate back into the Pacific Northwest and roughly the northern ¼ of California.
Frost Discussion: All locations will be above 32 degrees tonight. Tuesday morning will likely be quite variable with lows ranging anywhere from the low 30s to the low 40s due to variable amounts of residual cloud cover. Also, with additional moisture on the valley floor, and a warm air inversion developing, low clouds and fog will play their usual wintertime role.
The air mass moving in behind today’s storm system is colder, but not critically so. It’s possible that, on Wednesday morning, only where skies clear, unprotected river bottom and similar locations could drop down to 27 to 28 or so with most locations ranging from 29 to 35.
Thursday and Friday will likely be above freezing due to the next storm system. Over the weekend, a westerly flow will develop with generally above freezing conditions, although lower 30s cannot be ruled out under the proper conditions.
The freeze pattern we discussed yesterday afternoon does not show up nearly as much on models this morning, so keep praying the holiday season will be a mild one.
Air Quality Expectations: The San Joaquin Valley Air Pollution Control District has issued the following warning(s) for December 13, 2020:
Today’s air quality is listed as moderate for Merced County south. The air quality for the remainder of the valley is Good.
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: Upper 40s to the lower 50s. Kern, Upper 40s to the lower 50s.
Actual Humidity Range Yesterday: Delano, 95%/69% Porterville, NA
Percentage of Sunshine Today/Tomorrow: Visalia: Today: 0%, tomorrow 30%. Bakersfield: Today: 20% Tomorrow: 10%
ET Rates Over the Past Seven Days: Stratford .41, Parlier .37, Blackwell Corners .NA, Arvin .41, Orange Cove .37, Porterville .NA, Delano .36. Courtesy University of California *=estimate, NA=not available.
Seven Day Soil Temperatures: Stratford 54, Parlier 50, Blackwell 55, Arvin, 52, Orange Cove 55, Porterville 51, Delano 44
Record Temperatures: 72/23. Average Temperatures: 55/35
Heating Degree Days This Season: 578, -152
Courtesy of the NWS
Average Temperature for this month So Far: 48.5 +3.0
Precipitation: Seasonal total for Fresno, .62, or -1.64, Month to Date: .34, or -.22
Precipitation for Bakersfield, Season, .39, +or- -.89. Month to date .T, or -.34
Water year season is from October 1st through September.
Chilling Hours November 1st through February 28: Orange Cove, 317, Parlier, 389, Arvin, 307, Shafter, 345, Stratford, 363, Belridge 379, Delano, 392, Porterville, 445
Hours at 45 or below 45. Courtesy UC Davis
Sunrise: 7:04 am Sunset: 4:44 pm Hours of Daylight: 9:41
Yesterday’s Weather
MCE : Merced 153 : DH1600 / 52 / 47 / 0.65 /
MAE : Madera 253 : DH1600 / 52 / 47 / 0.33 /
FAT : Fresno Airport 333 : DH1600 / 54 / 46 / 0.34 /
HJO : Hanford Airport 242 : DH1600 / 59 / 45 / 0.14 /
NLC : Lemoore Naval AS 234 : DH1600 / 57 / 45 / 0.13 /
BFL : Bakersfield Airport 496 : DH1600 / 57 / 42 / T /
VIS : Visalia Airport 292 : DH1600 / 56 / 44 / 0.18 /
ATEC1 : Avenal 787 : DH1551 / 61 / 43 / 0.00 /
PTV : Porterville Airport 442 : DH1600 / 57 / 41 / 0.11 /
Rainfall: 24hr W.Y. % Last Y. % Ave. Year ave.
STOCKTON 0.13 0.55 17 4.00 122 3.28 14.06
MODESTO 0.19 0.69 25 2.78 102 2.72 13.11
MERCED 0.24 1.73 72 0.00 0 2.39 12.50
MADERA 0.17 0.49 20 0.00 0 2.50 12.02
FRESNO 0.26 0.62 27 0.00 0 2.26 11.50
HANFORD 0.08 0.27 15 0.00 0 1.81 10.10
BAKERSFIELD T 0.39 30 0.00 0 1.28 6.47
BISHOP 0.00 T 0 1.06 100 1.06 5.18
SALINAS T 0.53 20 4.09 154 2.65 12.83
PASO ROBLES 0.00 0.28 12 4.70 207 2.27 12.78
SANTA MARIA 0.01 0.26 10 2.68 102 2.62 13.95
Next report: December 14/am