December 18, 2019
Summary: Our low pressure system has stalled just to the northwest of San Francisco this afternoon. Light precipitation continues to fall over northern California with even a few isolated sprinkles over the central and south valley, but nothing measurable has been reported. The air mass which has moved in aloft is colder. The freezing level over Vandenberg Air Force Base has dropped to 6,700 feet while the sounding over Oakland indicated a freezing level of 5,800 feet.
The next couple of nights will be chilly which is discussed in the frost section below.
By early Thursday, upper level high pressure will be building in from the west. California will be on the eastern side of the high Thursday through Friday, putting us in a relatively cold northwesterly flow aloft. Even so, with mostly clear skies, temperatures Thursday will range in the upper 50s to the low 60s with generally lower 60s Friday and possibly mid 60s in Kern County. Fog will more than likely be on the patchy side as dew points remain quite low because of the off shore flow of yesterday.
By late Friday night, some high clouds will become visible with increasing amounts of mid and high level clouds Saturday ahead of a trough of low pressure which will stretch from just west of British Columbia to off the central coast. The chance of rain will begin to increase Sunday. Models indicate the first of possibly three systems will move from north to south just off the California coast, spreading bands of showers inland Sunday through Monday with possibly a weaker system moving through Christmas Eve.
For now, Christmas Day appears dry and we may be between systems. Some models are showing a cold low dropping from north to south right through California. This system would have low snow levels and probably would only result in light amounts of precipitation. As of now, it looks like this system will take a north/south overland trajectory.
It appears we may be heading into a cold but dry pattern from next Friday through the end of the year. Models are showing a mammoth high building over the eastern Pacific into western Canada with a north/south flow aloft into California. This is not a classic freeze pattern, but it is one which could certainly result in a string of frost nights. Hopefully, we will record decent amounts of rain from this weekend through Christmas, resulting in a wet valley floor which is always a plus in moderating temperatures. We’ll simply approach this time frame day by day, tweaking the forecast as we go along.
Forecast: Partly cloudy tonight with patchy fog developing after midnight. Mostly clear Thursday through Friday night with areas of fog and low clouds possible Friday and Saturday mornings. Partly cloudy Saturday and Saturday night. increasing cloudiness Sunday with an increasing chance of rain, especially later in the day. Periods of rain Sunday night through Monday night with a good chance of showers Tuesday. A slight chance of showers Christmas Day then another shot at more shower activity Thursday.
Short Term:
| Madera 30/60/32/61 | Reedley 32/59/33/61 | Dinuba 30/58/32/60 | |
| Porterville 31/60/32/62 | Lindsay 30/60/32/62 | Delano 31/61/33/63 | |
| Bakersfield 37/61/40/65 | Taft 36/60/39/64 | Arvin 33/61/34/65 | |
| Lamont 33/60/34/64 | Pixley 31/60/33/62 | Tulare 31/58/32/60 | |
| Woodlake 31/59/32/60 | Hanford 33/59/34/61 | Orosi 31/58/32/61 | |
Winds: Winds will be generally at or less than 7 MPH with periods of near calm conditions through Friday night. winds Saturday will be out of the southeast at 8 to 15 MPH with stronger gusts possible towards evening.
Rain: Expect dry weather through Saturday night. the first of possibly three weather systems will spread showers over the valley Sunday into Monday then another Monday night through Christmas Eve with just possibly a dry day Christmas Day followed by a possible round of showers Thursday. Once this pattern sets up, it will be a cold one with relatively low snow levels, especially the deeper we progress into the week. These systems will have their origins over colder waters, so no pineapple connection is expected for healthy amounts of precipitation, just lighter amounts on any given day. Models do seem to be trending towards a dry pattern beginning next Friday and possibly lasting through the end of the year.
Frost Discussion: Dew points this afternoon remain pretty low. As of 1:00pm, the dew point at Madera was 23, Fresno 20, Visalia 31, porterville 32, and Bakersfield 29. Temperatures this afternoon have warmed into the mid to upper 50s and will hit 60 at the warmer locations, especially in Kern County. Tonight’s outcome will be determined in part by how much cloud cover remains over the valley floor. Relatively clear skies, especially after midnight, would allow radiational cooling to commence with the very coldest locations dipping down to 28 to 30 with most locations between 30 and 35. On Friday morning, temperatures should be similar even though daytime highs will be climbing a degree or two each day. By Saturday morning, we should begin to see high clouds increasing from the west which should slow down the radiational cooling process. If skies turn out to be relatively clear, then readings in the low 30s could be expected in the colder locations.
From Sunday through Tuesday of next week, above freezing conditions can be expected, however any relatively clear night sandwiched in there would see temperatures in the low 30s.
My main concern continues to be the period beginning a week from Friday as some, but not all, models are showing a mammoth high building over the eastern Pacific with a trough of low pressure over the Desert Southwest. This would result in a north to south flow right down the west coast. Fortunately, the flow at this point doesn’t appear to be originating in the bitterly cold air of northern Alaska or Canada, but further south. Even so, it would definitely be a cold pattern with a strong of frost nights likely, if this pattern does set up. Of course, this is still more than a week away. Nevertheless, that’s where my concerns lie at this point.
Lows Tonight:
| Terra Bella
31 |
Porterville
31 |
Ivanhoe
30 |
Woodlake
31 |
| Strathmore
31 |
Mcfarland
30 |
Ducor
32 |
Tea Pot Dome
31 |
| Lindsay
30 |
Exeter
30 |
Famoso
32 |
Madera
30 |
| Belridge
29 |
Delano
32 |
North Bakersfield
32 |
Orosi
30 |
| Orange Cove
30 |
Lindcove
30 |
Lindcove Hillside | Sanger River Bottom
28 |
| Root Creek
29 |
Venice Hill
30 |
Rosedale
33 |
Jasmine
32 |
| Arvin
33 |
Lamont
34 |
Plainview 30 | Mettler
Af |
| Edison
33 |
Maricopa
Af |
Holland Creek
34 |
Tivy Valley
31 |
| Kite Road South
33 |
Kite Road North
30 |
AF=Above Freezing
Next report: Thursday morning/December 19