December 17, 2020
A trough of low pressure and its associated cold front are marching down the valley this morning. doppler radar returns are not impressive. In fact, as of the time of this writing, only a few hundredths has been recorded from Fresno County north with just trace amounts further south. The trough will move into Nevada later tonight. a relatively cold air mass will follow the front, but it’s nothing unusual for mid December.
A flat zone of high pressure over the eastern Pacific will begin to build inland over California Friday. The northwest flow behind today’s system will generate upslope clouds against the valley facing slopes of the Tehachapi and the southern Sierra Nevada. Some sunshine should begin to peek through later this afternoon, mainly along the west side. These upslope clouds should regenerate through the night and into Friday morning.
As the high builds inland Friday, the storm track will be driven back north into the Pacific Northwest. Models indicate the high wild dominate our weather through Tuesday. As a warm bubble of subsiding air creates a warm air inversion, extensive fog and low clouds will develop nights and mornings. It remains to be seen whether or not this will turn into a full fledged fog regime, however that chance is certainly there.
I’m continuing to watch the possible pattern beginning Wednesday of next week. Models show a vigorous winter storm developing over the Rockies and the eastern Great Basin while a strong ridge of high pressure builds north/northeast into western Canada. This could potentially create a north to possibly even northeast flow over California, possibly pumping colder and drier air into the region. Some models are already indicating this cold air will invade the deserts of southern California, but so far the valley appears unscathed. Let’s keep our fingers crossed that we can get a good night’s sleep Christmas Eve.
Forecast: Scattered light showers this morning. mostly to partly cloudy this afternoon into Friday morning. Clearing later Friday. Mostly clear Friday night through Wednesday with increasing amounts of night and morning fog and low clouds, possibly persisting through the day in some areas. Partly cloudy Wednesday night and Christmas Eve.
Short Term:
| Madera 57/34/55/29/57 | Reedley 58/34/55/28/56 | Dinuba 57/34/54/28/56 |
| Porterville 58/36/55/29/57 | Lindsay 57/34/55/27/56 | Delano 58/37/55/29/57 |
| Bakersfield 56/41/56/35/58 | Taft 58/45/56/44/59 | Arvin 55/41/56/33/58 |
| Lamont 56/40/56/33/59 | Pixley 57/34/55/29/57 | Tulare 56/34/54/28/56 |
| Woodlake 57/34/55/28/57 | Hanford 57/35/55/29/57 | Orosi 57/34/55/27/56 |
Seven Day Forecast:
| Sunday
AM fog/partial clearing 30/54 |
Monday
AM fog/partial clearing 33/54 |
Tuesday
AM fog/partial clearing 34/53 |
Wednesday
AM fog/PM sun 31/55 |
Christmas Eve
Patchy fog/partly cloudy 30/55 |
Two Week Outlook: December 24 through December 30: 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 mainly out of the southeast for a time this morning. From late morning through this evening, winds will be mainly out of the northwest at 8 to 15 MPH with gusts possibly as high as 25 MPH north of Kern County and mainly along the west side. Winds later tonight through Sunday will be generally at or less than 5 MPH during the night and early morning hours with extended periods of near calm conditions and variable to no more than 10 MPH during the late morning and afternoon hours.
Rain Discussion: Light showers are currently moving through the valley. Only very light amounts have been recorded so far. As of 6:30, Madera had recorded .02, Fresno .04, and Visalia just .01. So far, just trace amounts have been tallied in the south valley.
Showers will end from northwest to southeast from late morning through the afternoon. Dry weather will begin tonight with the possible exception of near the base of the Tehachapi where upsloping could squeeze out some light drizzle. Friday will begin a prolonged period of dry weather, at least a week and possibly ten days.
Frost Discussion: All locations will be above 32 degrees tonight. it’s possible that, where skies clear and winds die off, that a few river bottom and similar locations could dip down to 30 to 32, mainly from Fresno County north and towards the center and west side of the valley. I’m anticipating upslope clouds to regenerate against the valley facing slopes of the Tehachapi and the southern Sierra Nevada, especially in Tulare County.
The air mass moving in behind today’s cold front is fairly cold, but also pretty typical for mid December. Beginning Saturday morning and lasting through the middle of next week, in areas that see clear skies and calm winds, lows in unprotected river bottom and similar locations could dip down to 26 to 27 with most flat land locations between 28 and 31 with Kern County in the low to mid 30s.
Of course, the wild cardi n all this will be fog formation. With a warm air inversion building over the valley floor, fog should become widespread, possibly locking into a full fledged fog regime where it lifts into a low overcast with only partial afternoon clearing. If this occurs, we would revert back to chilly days but above freezing conditions overnight. So, we’ll just approach this day by day.
I’m still very closely watching the pattern beginning next Wednesday. models are still trending towards a vigorous winter storm developing over the Rockies and into the Great Basin while a large high pressure system drives north/northeast into northwest Canada. This could potentially turn the winds aloft out of the north to possibly northeast.
By Christmas Eve, a very strong surface high will build over the Great Basin, generating a strong off shore flow. Some models are already projecting cold dry air spreading down the Owens Valley and into the desert regions of southern California. So far, this air is projected to stay just to our east, courtesy of the Sierra Nevada. If this potential air mass does get in here, we could face a freeze around Christmas. I’m certainly not calling for that at this time, but do want you to be aware.
Air Quality Expectations: The San Joaquin Valley Air Pollution Control District has issued the following warning(s) for December 17, 2020:
Today’s air quality is listed as The air quality for the entire 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: Mid to upper 40s. Kern, mid to upper 40s.
Actual Humidity Range Yesterday: Delano, 92%/50% Porterville, NA
Percentage of Sunshine Today/Tomorrow: Visalia: Today: 30%, tomorrow 70%. Bakersfield: Today: 10% Tomorrow: 50%
ET Rates Over the Past Seven Days: Stratford .37, Parlier .27, Blackwell Corners .NA, Arvin .37, Orange Cove .26, Porterville .NA, Delano .32. 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: 48.6 +3.5
Precipitation: Seasonal total for Fresno, 1.07, or -1.40, Month to Date: .79, or +.02
Precipitation for Bakersfield, Season, .40, +or- -1.01 Month to date .01, or -.46
Water year season is from October 1st through September.
Chilling Hours November 1st through February 28: Orange Cove, 351, Parlier, 431, Arvin, 346, Belridge, 410, Shafter, 377, Stratford, 403, Delano, 439, Porterville, 482
Hours at 45 or below 45. Courtesy UC Davis
Sunrise: 7:06 am Sunset: 4:45 pm Hours of Daylight: 9:39
Yesterday’s Weather
MCE : Merced 153 : DH1600 / 56 / 33 / 0.00 /
MAE : Madera 253 : DH1600 / 58 / 33 / 0.00 /
FAT : Fresno Airport 333 : DH1600 / 58 / 37 / 0.00 /
HJO : Hanford Airport 242 : DH1600 / 57 / 31 / 0.00 /
NLC : Lemoore Naval AS 234 : DH1600 / 58 / 30 / 0.00 /
BFL : Bakersfield Airport 496 : DH1600 / 58 / 34 / 0.00 /
VIS : Visalia Airport 292 : DH1600 / 58 / 33 / 0.00 /
ATEC1 : Avenal 787 : DH1600 / 60 / M / 0.00 /
PTV : Porterville Airport 442 : DH1600 / 60 / 33 / 0.00 /
LOSC1 : Los Banos 120 : DH1600 / 55 / 34 / 0.00 /
Rainfall: 24hr W.Y. % Last Y. % Ave. Year ave.
STOCKTON 0.00 1.38 39 4.05 114 3.55 14.06
MODESTO 0.00 1.20 40 2.79 94 2.97 13.11
MERCED 0.00 1.91 74 M M 2.57 12.50
MADERA 0.00 0.55 20 M M 2.73 12.02
FRESNO 0.00 1.07 43 M M 2.47 11.50
HANFORD 0.00 0.49 25 M M 1.99 10.10
BAKERSFIELD 0.00 0.40 28 M M 1.41 6.47
BISHOP 0.00 0.01 1 1.06 93 1.14 5.18
SALINAS 0.00 0.66 23 4.12 143 2.88 12.83
PASO ROBLES 0.00 0.30 12 4.70 187 2.52 12.78
SANTA MARIA 0.00 0.30 10 2.68 93 2.88 13.95
Next report: December 17/pm