October 22, 2020
Summary: Upper level high pressure over California is slowly breaking down. There is a bulge in the jet stream in eastern Washington extending southeastward through the northern Rockies then into the northern Midwest. The main center of upper level high pressure is off the northern California coast with a weak upper low several hundred miles west of the southern California coast. As this cold trough over the Pacific Northwest and northern Rockies sinks further south, the high will continue to weaken. The main phase of autumn weather will begin over the weekend as a second trough of low pressure in western Canada dives southward, entering the northern Great Basin by Saturday evening. From there, it will dig southward into the Deseret Southwest Sunday and Monday.
Models this morning still show the main dynamics moving into the interior west just to the east of the Sierra Nevada. Even so, light showers are likely along the Sierra Nevada with snow spreading over the higher elevations.
The main cold front will likely be dry over the valley floor and will move through sometime Sunday, issuing in the coldest air mass since last spring. Temperatures Friday will dip into the upper 70s with mid 70s Saturday and mid to upper 60s Sunday and Monday. Strong upsloping due to a strong northerly flow will maintain heavy cloud cover over the south valley through at least midday Monday. On Monday, California will be sandwiched between a large upper high just off shore and a very cold trough of low pressure stretching from western Canada into Arizona and New Mexico. This squeeze play between these features will create a north to south flow over California, pumping in a much drier air mass.
Where skies clear and winds die off Tuesday morning, readings will chill well down into the 30s. it wouldn’t be a total shock to hear of a river bottom or two out there reaching the freezing mark.
The off shore high will slowly build inland after Tuesday for the beginning of a warming trend. Before that happens, however, a strong off shore flow at the surface will filter dry air onto the valley floor so even though highs will slowly be warming, overnight lows will continue to be chilly.
Forecast: Mostly clear through tonight. Mostly clear Friday and Friday night with occasional cloudiness. Partly cloudy Saturday. increasing cloudiness later Saturday night. mostly cloudy Sunday through Monday morning with a slight chance of sprinkles or isolated light showers. Clearing Monday afternoon but possibly remaining partly cloudy in Kern County into Tuesday morning. mostly clear Tuesday afternoon through Thursday.
Short Term:
Madera 84/50/77/47/76 | Reedley 83/49/79/47/75 | Dinuba 82/48/77/47/74 |
Porterville 84/50/78/48/76 | Lindsay 83/49/78/48/75 | Delano 84/52/78/49/77 |
Bakersfield 84/57/79/55/75 | Taft 83/59/78/55/75 | Arvin 84/54/78/51/74 |
Lamont 84/53/78/51/75 | Pixley 83/50/78/48/76 | Tulare 82/48/77/46/74 |
Woodlake 82/49/77/47/75 | Hanford 84/50/78/48/75 | Orosi 82/48/78/46/75 |
Seven Day Forecast:
Sunday
PM sprinkles 44/68 |
Monday
AM sprinkles 43/67 |
Tuesday
Mostly clear 36/73 |
Wednesday
Mostly clear 39/78 |
Thursday
Mostly clear 39/79 |
Two Week Outlook: October 29 through November 4: This model flips us back into more of an amplified pattern with high pressure over the west and a colder trough east of the Rockies. Therefore, rain appears unlikely during this period with a return to above average temperatures.
October: This model essentially depicts the entire lower 48 with above average temperatures over the next 30 days. The most pronounced temperature anomalies will be over the Desert Southwest. This model also suggests there will be an equal chance of above or below average precipitation.
October, November, December: This model reflects the influence of La Nina. It paints above average temperatures over much of the country, especially the Desert southwest, and to a lesser extent, central California. Drier than average conditions are anticipated over southern California while northern California could possibly luck out with near average rainfall. Above average precipitation is expected over the Pacific Northwest.
Winds Discussion: Winds through Friday night will be generally at or less than 12 MPH and variable in nature. Winds Saturday will be out of the west or northwest at 8 to 15 MPH with stronger gusts. Winds later Saturday night through Sunday evening will be out of the northwest at 10 to 20 MPH. Gusts to near 30 MPH are possible, mainly along the west side but locally elsewhere.
Rain Discussion: The chance of measurable rain later Sunday into early Monday still appears very slight over the valley floor. Light showers of rain or snow are possible over the Sierra Nevada with possibly some upslope precipitation over the Kern County mountains. Even so, I feel more comfortable keeping a slight chance of light sprinkles in the forecast for that time frame, but the chance of precipitation at any location is only about 10% to 15%. For Monday afternoon through next weekend, expect dry weather.
Air Quality Expectations: With the tremendous amount of smoke over the valley floor, the San Joaquin Valley Air Pollution Control District has issued the following warning(s) for October 22, 2020:
Today’s air quality is listed as moderate for Kings, Tulare, and Merced Counties. The air quality in Kern, Fresno, and Madera Counties is posted as unhealthy for sensitive groups.
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.
For more information on wildfires affecting the Valley’s air, visit: http://www.valleyair.org/wildfires
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 50s. Upper 40s to the lower 50s.
Actual Humidity Range Yesterday: Delano, 96%/30%, Porterville, 92%/26%
Percentage of Sunshine Today/Tomorrow: Visalia: Today: 100%, tomorrow 100%. Bakersfield: Today: 100% Tomorrow: 100%
ET Rates Over the Past Seven Days: Stratford 1.03, Parlier .88, Blackwell Corners .98, Arvin 1.11, Orange Cove .98, Porterville .79, Delano .88. Courtesy University of California *=estimate, NA=not available.
Seven Day Soil Temperatures: Stratford 69, Parlier 71, Blackwell NA, Arvin, 71, Orange Cove 75, Porterville 73, Delano 66
Record Temperatures: 92/35. Average Temperatures: 77/47
Heating Degree Days This Season: 0, -49
Courtesy of the NWS
Average Temperature for September So Far: 72.0 +6.5
Precipitation: Seasonal total for Fresno, .00, -.34 Month to Date: .00, -.34
Precipitation for Bakersfield, Season, .00, +or- -.15. Month to date .00, -.15
Water year season is from October 1st through September.
Chilling Hours November 1st through February 28: Orange Cove, Parlier, Arvin, Shafter, Stratford, Delano, Lindcove, Porterville
Hours at 45 or below 45.
Sunrise: 7:13 Sunset: 6:13 pm Hours of Daylight: 10:59
Yesterday’s Weather
MCE : Merced 153 : DH1700 / 88 / 51 / 0.00 /
MAE : Madera 253 : DH1700 / 86 / 51 / 0.00 /
FAT : Fresno Airport 333 : DH1700 / 86 / 60 / 0.00 /
HJO : Hanford Airport 242 : DH1700 / 87 / 51 / 0.00 /
NLC : Lemoore Naval AS 234 : DH1700 / 89 / 50 / 0.00 /
BFL : Bakersfield Airport 496 : DHM / 87 / 59 / 0.00 /
VIS : Visalia Airport 292 : DH1700 / 86 / 54 / 0.00 /
ATEC1 : Avenal 787 : DH1624 / 86 / 58 / 0.00 /
PTV : Porterville Airport 442 : DH1700 / 88 / 55 / 0.00 /
TFTC1 : Taft 759 : DHM / M / M / M /
LOSC1 : Los Banos 120 : DH1600 / 88 / 56 / 0.00 /
Rainfall: 24hr W.Y. % Last Y. % Ave. Year ave.
STOCKTON 0.00 0.00 0 0.00 0 0.43 14.06
MODESTO 0.00 0.00 0 0.00 0 0.38 13.11
MERCED 0.00 0.00 0 0.00 0 0.36 12.50
MADERA 0.00 0.00 0 0.00 0 0.39 12.02
FRESNO 0.00 0.00 0 0.00 0 0.34 11.50
HANFORD 0.00 0.00 0 0.00 0 0.23 10.10
BAKERSFIELD 0.00 0.00 0 0.00 0 0.15 6.47
BISHOP 0.00 0.00 0 0.00 0 0.18 5.18
SALINAS 0.00 T 0 0.00 0 0.33 12.83
PASO ROBLES 0.00 0.00 0 0.00 0 0.33 12.78
SANTA MARIA 0.00 0.00 0 0.00 0 0.30 13.95
Next report: October 22, 2020