December 15, 2020
Summary: California remains on the eastern flank of weak high pressure off shore with a northwesterly flow aloft. This flow will continue through Wednesday night. the fog formed in various areas of the valley this morning and has yet to clear in some areas of northern Kings and Tulare Counties up through Merced County. The southern one-third of the valley is basically fog free this afternoon.
The main challenge tonight will be overnight lows and the possible development of dense fog as the night wears on. Dew points in roughly the southern one-third of the valley are in the mid to uppuer 30s while from roughly Visalia northward, dewpoints are generally in the low to mid 40s. Fog will more than likely rapidly form later this evening up the center of the valley then by sunrise fan out towards the foothills on both sides of the valley, possibly even moving into Kern County. How this may affect temperatures tonight is discussed below in the frost discussion. Wednesday’s highs will also be determined by when fog burns off at any given location.
Higher clouds will begin to increase by later Wednesday afternoon. The next system that will be barreling through the valley Thursday doesn’t appear very impressive. Even so, as the cold front marches down the valley, it’s possible a few light showers could make it down to even Kern County. The low and its associated cold front will move into the interior west Thursday night and Friday.
The northwest push of air wrapping around the low will again generate upslope clouds against the valley facing slopes of the Tehachapi and the west facing slopes of the sierra Nevada, so skies in the southern and eastern sectors of the valley may not clear out until midday Friday.
A zone of high pressure over the eastern Pacific will begin to push inland Friday. This high will dominate the pattern through at least the middle of next week. The storm track will generally run from west to east into British Columbia and the Pacific Northwest. With additional moisture expected from Thursday’s storm, and with a dome of warm subsiding air creating a warm air Inversion, the stage may be set for our first multi-day fog regime of the season. That’s when the fog lifts into a gray overcast with only limited afternoon clearing and the foothills and coastal areas enjoy mild dry weather with bright blue skies.
Forecast: Mostly clear skies tonight with areas of fog developing after midnight, possibly becoming widespread, especially up the center of the valley north of KernCounty. Areas of low clouds and fog Wednesday morning with increasing higher clouds Wednesday afternoon. Increasing cloudiness Wednesday night. Light showers will spread down the valley Thursday. Mostly cloudy Thursday night and Friday morning. clearing Friday afternoon. Mostly clear Friday night through Tuesday, however expect extensive fog and low clouds nights and mornings, possibly persisting through the day in some areas.
Short Term:
| Madera 28/54/41/57 | Reedley 28/55/41/58 | Dinuba 27/56/40/57 | |
| Porterville 29/56/41/58 | Lindsay 27/56/40/57 | Delano 29/57/41/58 | |
| Bakersfield 35/59/43/58 | Taft 42/58/47/57 | Arvin 32/58/42/57 | |
| Lamont 32/57/42/58 | Pixley 28/56/41/57 | Tulare 27/55/40/56 | |
| Woodlake 29/55/41/57 | Hanford 29/58/41/57 | Orosi 27/56/40/57 | |
Winds: Winds will be light to near calm tonight and no more than 10 MPH Wednesday. Winds late Wednesday night and Thursday will begin to increase out of the northwest at 8 to 15 MPH with possible local gusts to 25 MPH along the west side north of Kern County. Winds will decrease Thursday night with light winds returning Friday.
Rain: A weak and fast moving trough of low pressure and its associated cold front will sweep down the valley Thursday. Light showers are likely north of Kern County and there’s even a chance of light showers In Kern County. Rainfall amounts from this system will range from .10 to .25 in Madera County and eastern Fresno County, possibly a tenth or two from Visalia northward and generally .10 or less in southern Kings and Tulare Counties with trace amounts to a few hundredths in Kern County. In all likelihood, this will be our last chance at rain for quite some time as a blocking ridge of high pressure sets up shop off shore and extends inland over California into the Great Basin while storm after storm batters the Pacific Northwest and British Columbia. It’s possible we may remain dry through the Christmas holidays, but we’ll see.
Frost: Tonight will see the age old forecast challenge of fog and frost. As of 2:00pm, there were still clouds up the center of the valley from Tulare County up through Merced County. The southern one-third of the valley had abundant sunshine and blue skies. Dew points over most of the southern one-third of the valley were running in the mid to upper 30s while from Visalia northward, dewpoints were n the low to mid 40s.
In fog free areas north of Kern County tonight, unprotected frost pockets could dip down to 25 to 26 with typical flat terrain locations ranging from 27 to 32. With a warm air inversion above, fog will rapidly form, especially after midnight and will be fairly widespread after sunrise. If the fog layer is high enough, temperatures will be held into the low to mid 30s. Where skies remain relatively clear, upper 20s and lower 30s are likely with hillsides remaining above freezing.
The inversion tonight will be decent with temperatures at 34 feet anywhere from 4 to 8 degrees warmer at most locations.
Thursday and Friday mornings will be above freezing due to unsettled conditions and clouds. Saturday and well into next week, any morning with clear skies would potentially drop into the lower 30s. my gut feeling, however, is that we may be headed into our first multi-day fog regime, mostly from Sunday and beyond.
The flow aloft will be generally out o the west during this period with very mild air above the valley floor.
I just took a quick look at some of the modeling information for Christmas day through New Year’s. Some of these models are trending towards a massive high moving over the eastern Pacific and the western U.S. The ridge juts far into northern Canada while potentially a bitterly cold air mass rockets through the Rockies and into the Midwest. Of course, this is all preliminary, but we do want to make sure that this air mass remains far enough to the east to leave the valley comfortable.
Lows Tonight:
| Terra Bella
28 |
Porterville
28 |
Ivanhoe
27 |
Woodlake
28 |
| Strathmore
28 |
McFarland
27 |
Ducor
29 |
Tea Pot Dome
28 |
| Lindsay
27 |
Exeter
28 |
Famoso
27 |
Madera
28 |
| Belridge
27 |
Delano
29 |
North Bakersfield
29 |
Orosi
28 |
| Orange Cove
29 |
Lindcove
28 |
Lindcove Hillside
Af |
Sanger River Bottom
26 |
| Root Creek
27 |
Venice Hill
28 |
Rosedale
29 |
Jasmine
29 |
| Arvin
32 |
Lamont
32 |
Plainview
29 |
Mettler
32 |
| Edison
32 |
Maricopa
28 |
Holland Creek
31 |
Tivy Valley
28 |
| Kite Road South
31 |
Kite Road North
28 |
AF=Above Freezing
Next update: December 16/am