December 15, 2019
Summary: Mostly clear skies are prevalent as of 1:00pm along the center and west side of the valley with partly cloudy skies in Tulare and Kern Counties. Surface winds towards the center and west side of the valley are currently averaging 10 to 15 MPH out of the northwest. Doppler radar out of Hanford depicts winds between 1,000 and 6,000 feet out of the north/northwest are averaging 15 to 25 MPH. obviously, colder air continues to invade the region. The freezing level above Vandenberg earlier today was just 5,100 feet. With mostly clear skies tonight, decent radiational cooling will commence, allowing many locations outside the urban areas to dip to at or below freezing both Monday and Tuesday mornings. More in the frost discussion below.
Yesterday’s system is now moving into the Rocky Mountain region. This is allowing surface high pressure to begin to develop above the Great Basin which will generate a moderate off shore flow Monday through Tuesday. In the meantime, at the mid and upper levels of the atmosphere, high pressure is building in from the west. There will be enough mixing tonight for fog to generally be patchy with a greater risk of more widespread fog Tuesday morning as a warm air inversion tries to set up.
Models for Wednesday continue to indicate a weak low will be just west of the Golden Gate. Only a few sprinkles at best are anticipated with this system, mainly from Fresno County north. This system will track into the Great Basin by Thursday morning, allowing the next ridge of high pressure aloft to build in from the eastern Pacific. The main challenge, especially for Friday and Saturday mornings, will be fog. Bottom line is this upcoming week will see temperatures that are pretty common for mid December with highs in the mid to upper 50s. overnight lows from Thursday through Saturday will generally range in the mid 30s to the lower 40s.
Medium range models this afternoon continue to indicate a major pattern change will occur this coming weekend as a significant trough of low pressure digs southward from the Gulf of Alaska all the way to southern California by early next week. A chance of rain and mountain snow will begin as early as Sunday with a chance of rain at any time from next Monday through Christmas Eve.
Models still show a sharp ridge of upper level high pressure building right along the Pacific coast behind this system on Christmas Day as a low develops over southern California or the Desert Southwest. This would create a north/south flow at the upper levels of the atmosphere which could pump very cold air into California. It’s not quite a classic freeze pattern, but it is a cold one and, as I’ve been emphasizing for several days now, I must restate to pay close attention to future reports as they come out.
Forecast: Mostly clear to partly cloudy this evening. Mostly clear later tonight with patchy fog developing after midnight. Mostly clear after patchy morning fog Monday. Partly cloudy Monday night. variable cloudiness Tuesday through Wednesday with a small chance of sprinkles Wednesday. partly cloudy Wednesday night. mostly clear to partly cloudy Thursday through Saturday with areas of night and morning fog and low clouds. Increasing cloudiness Saturday night leading to a chance of rain Sunday.
Short Term:
| Madera 30/54/31/55 | Reedley 31/54/30/56 | Dinuba 30/53/31/55 | |
| Porterville 31/55/32/57 | Lindsay 30/55/31/57 | Delano 32/56/32/57 | |
| Bakersfield 36/56/37/59 | Taft 38/56/40/60 | Arvin 32/57/32/60 | |
| Lamont 32/57/32/59 | Pixley 31/56/31/57 | Tulare 30/53/31/55 | |
| Woodlake 30/54/31/56 | Hanford 32/55/33/57 | Orosi 30/54/31/55 | |
Winds: Winds through the early evening hours will be out of the northwest at 10 to 15 MPH from Fresno County north and along the west side and from 5 to 10 MPH elsewhere. Winds tonight through Wednesday will be generally at or less than 6 MPH with periods of near calm conditions.
Rain: We’ll maintain a small risk of sprinkles or isolated light showers in the forecast for Wednesday as a weak low moves inland and essentially begins to fall apart. Otherwise, this week will be dry. Next week still appears to be a horse of a different color as a deep trough of low pressure digs southward out of the Gulf of Alaska and along the west coast. The first phase may show up as early as Sunday with an increasing chance of rain. There will be a chance of precipitation any given day Monday through Christmas Eve with potentially heavy snow in the mountains. Models still vary quite a bit for the last week in December ranging from dry conditions to possibly active from time to time. We’ll nail this down at a future date.
Frost Discussion: colder air continues to move down the valley. At the surface, winds have been out of the northwest at 10 to 15 MPH along the west side and from Fresno County north. Soundings above Hanford as of 1:00pm indicate winds between one and six thousand feet are averaging 10 to 15 MPH out of the north/northwest. This would favor the development of upslope clouds against the north facing slopes of the Tehachapi Mountains so it’s possible clouds could be a factor in Kern County and possibly southeastern Tulare County tonight. the other wild card, however, is the development of an off shore flow which could mix out the cloud cover during the course of the night. dew points as of 1:00pm were in the upper 30s to lower 40s all the way up and down the line, which are not critically low. With mostly clear skies tonight, coldest locations will drop down to 27 to 29 degrees in those typical cold spots. Locations that are generally flat will range between 29 and 34 with hillsides generally above freezing. The inversion tonight will be weak with temperatures at 34 feet ranging from 3 to 4 degrees warmer.
Similar conditions are likely Monday night and Tuesday morning. some models, however, are showing higher clouds developing after midnight Monday night. this could slow the radiational cooling process. We’ll study that more closely Monday.
Cloud cover should keep conditions above freezing Wednesday and Thursday mornings. Mid 30s to lower 40s appear likely Friday and Saturday mornings with the possibility of some of the colder spots dipping into the lower 30s.
Above freezing conditions are expected Sunday through Christmas Eve. Some models show a sharp north to south flow from the Yukon Territory right down the west coast and into California behind a low center over the Desert Southwest. This is typically quite a cold pattern and, in theory, could lead to a series of cold nights. It’s not quite a classic freeze pattern, but it’s close enough to be of some concern.
Lows Tonight:
| Terra Bella
31 |
Porterville
31 |
Ivanhoe
29 |
Woodlake
30 |
| Strathmore
30 |
Mcfarland
30 |
Ducor
32 |
Tea Pot Dome
31 |
| Lindsay
30 |
Exeter
29 |
Famoso
32 |
Madera
30 |
| Belridge
29 |
Delano
32 |
North Bakersfield
31 |
Orosi
29 |
| Orange Cove
30 |
Lindcove
29 |
Lindcove Hillside | Sanger River Bottom
27 |
| Root Creek
29 |
Venice Hill
30 |
Rosedale
32 |
Jasmine
31 |
| Arvin
32 |
Lamont
33 |
Plainview
30 |
Mettler
34 |
| Edison
32 |
Maricopa
34 |
Holland Creek
33 |
Tivy Valley
31 |
| Kite Road South
32 |
Kite Road North
29 |
AF=Above Freezing
Next report: Monday morning/December 16