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Forecast

December 14, 2019/pm update

December 14, 2019

Summary: Light showers continue this afternoon over the Sierra Nevada and Kern County mountains.  Temperatures on the valley floor are running between 4 and 7 degrees cooler than 24 hours ago as a relatively colder air mass is invading central California.  Winds at most locations this afternoon are ranging between 10 and 20 MPH, even on the east side.  The second phase of the current change is coming in the form of an upper low moving through southern Oregon and northern California.  It will dive into Nevada by sunrise tomorrow.  Another round of showers will  move down the Sierra Nevada later tonight, however precipitation is not anticipated on the valley floor other than a slight chance along the foothills of the Sierra Nevada and the Tehachapi Mountains.  Doppler radar is also indicating winds between ground level and 4,000 feet above the valley floor are out of the northwest between 15 and 20 MPH.  This will cause uplope clouds to form against the Kern County mountains and the west facing slopes of the Sierra Nevada, especially in Tulare County so mostly cloudy conditions can be expected tonight into Sunday morning in portions of the southern and eastern flanks of the valley.

 

Skies will begin to clear Sunday afternoon as upper level high pressure begins to build in from the west.  As skies clear, and with relatively colder air in place, widespread low to mid 30s are expected Monday and Tuesday mornings with upper 20s possible in coldest locations.  More in the frost discussion below.

 

Fog will be patchy Monday morning then will become more widespread Tuesday morning as a temporary weak warm air inversion develops above the valley floor.  Models for the storm system which will move through Wednesday depict a rather fragmented system that’s weakening rapidly as it comes on shore.  Some models now indicate this system will be completely dry as it moves inland while others depict only light showers at best.  Another ridge of upper level high pressure will quickly build in from the eastern Pacific Thursday through Friday night.  areas of fog will no doubt become a challenge.

 

Models are still holding onto the idea of a significant trough of low pressure stretching from the Gulf  of Alaska to southern California between the 21st and the 24th.  Some models show possibly two systems moving through during this period.  Models also seem to be trending towards a cold low center developing over southern California Christmas Day and over the Desert Southwest a few days thereafter.  In the meantime, a ridge of upper level  high pressure will flank from southwest to northeast with a ridge extending into western Canada.  Theoretically, colder air would be driven into central California from the northeast.  So far, however, this is not a classic freeze situation but as no doubt modeling changes in the next few days, it would be wise to remain abreast.

 

Forecast: Partly to mostly cloudy tonight.  a slight chance of showers near the Sierra Nevada and the Tehachapi Mountain foothills later tonight and early Sunday.  Becoming partly cloudy Sunday afternoon but possibly remaining partly cloudy in southeastern Tulare County and Kern County into Monday morning.  mostly clear Monday afternoon through Tuesday with possible areas of fog and low clouds Tuesday morning.  increasing cloudiness later Tuesday night with a slight chance of light showers Wednesday. partly cloudy Wednesday night and Thursday morning with fog and low clouds possible Thursday morning.  mostly clear Thursday afternoon through Friday night.  increasing cloudiness Saturday.

 

Short Term:                                                                        

Madera 36/53/31/54 Reedley 38/54/31/54 Dinuba 37/53/31/53
Porterville 37/53/31/54 Lindsay 36/53/30/54 Delano 40/52/32/55
Bakersfield 43/52/38/56 Taft 42/52/41/56 Arvin 40/51/35/56
Lamont 38/53/32/54 Pixley 38/53/32/55 Tulare 37/52/31/53
Woodlake 38/52/31/54 Hanford 39/53/32/54 Orosi 37/53/30/53

 

Winds: Winds tonight will be mainly out of the northwest at 10 to 15 MPH for a time, diminishing to 5 to 10 MPH after midnight.  Winds Sunday will be mainly out of the northwest at 8 to 15 MPH, diminishing Sunday evening.  Winds Sunday night through Tuesday will be generally at or less than 6 MPH with periods of near calm conditions.

 

Rain:  There will be a slight chance of a few light showers later tonight and early Sunday near the foothills of the Sierra Nevada and the Tehachapi Mountains.  Otherwise, dry weather will prevail through Tuesday night.  most of the models for a system which will move through Wednesday show a fragmented looking system, so  only a minimal chance of a few light showers exists.  Dry weather will return Wednesday night and continue through at least Friday night.  models from late Saturday through Christmas Eve show a deep trough of low pressure from the Gulf of Alaska to southern California with possibly two winter storms moving through the trough and into central California.  The fact that this is more than a week away means that trying to time potential precipitation is impossible at this point.  Suffice it to say there will be a chance of rain from Saturday night through Christmas Eve.

 

Frost Discussion:  All locations will be above 32 degrees tonight.  temperatures this afternoon are running 4 to 7 degrees cooler than 24 hours ago as a colder air mass moves down the valley on the back of gusty northwesterly winds.  The colder sector of this storm is now moving into northern California and will dive into the Great Basin Sunday morning.  temperatures Monday and Tuesday mornings will dip into the low to mid 30s.  the coldest locations Monday morning will chill to 28 to 29 degrees and on Tuesday morning down to 27 to 29 for two to three hours before sunrise.  Most typical flat terrain will range from 30 to 34 degrees Monday morning and 29 to 34 Tuesday morning.  hillsides will remain slightly above freezing.

 

This appears to be just a two night affair as clouds begin to increase ahead of a weakening low pressure system which will move through central California Wednesday.  Thursday and Friday mornings could see mid to upper 30s again in coldest locations with areas of low clouds and fog no doubt forming.

 

Next weekend will see the beginning of an active pattern which will maintain above freezing conditions through the weekend and more than likely through Christmas Eve.  We still need to scrutinize the pattern from Christmas Day and for several days thereafter.  Some models are showing a cold low over southern California that would drift into the Desert Southwest as a ridge of high pressure over the Pacific ridges northward into the Pacific.  Fortunately, at this point the ridge is not shown in the polar reaches of Alaska or northern Canada, but it’s still more than worth watching.

 

Next report: Sunday morning/December 15