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Forecast

January 29, 2020/pm update

January 29, 2020

Summary: Much of the eastern half and southern sector of the valley remain under a low overcast as of 1:00pm.  The base of the overcast was at 3,300 feet over Bakersfield and Porterville and near 1,500 feet over Visalia and Fresno.  The far western portion of the valley is relatively clear with gusty northerly winds along the Interstate 5 corridor due to a low pressure system currently over Arizona.  These winds will die off this evening as upper level high pressure just off shore builds inland over the next 72 hours.  With building high pressure above the valley floor, a strengthening warm air inversion will develop.  Where skies clear this afternoon and evening, ground fog will develop overnight as dew points are running in the mid 40s this afternoon.  Temperatures through Saturday will be governed by fog coverage and how much clearing happens to occur during the afternoon hours.  On Friday and Saturday, where the sun is dominant, mid to upper 60s are likely with highs only in the low to mid 50s where the low overcast remains sealed in.

 

Models continue the trend of a major pattern change leading to colder weather beginning Sunday but more so Monday through Wednesday of next week.  A cold front will move through the valley Sunday night and Monday morning which will likely spread snow showers down the Sierra Nevada with even a minimal chance of light showers on the valley floor.  After the cold front  moves through, a deep and cold trough of low pressure will dig southward, stretching from the northwest territories of Canada all the way south into Arizona while a massive high over the eastern Pacific builds northward into Alaska.  This will result in a north/south flow right down the west coast Monday and Monday night and models are even indicating a north/northeast to south/southwest flow Tuesday and Wednesday.  the trajectory of this flow is completely overland and has the potential of driving modified arctic air into central California, leading to potential frost/freeze possibilities for at least Monday through Wednesday mornings.  More in the frost section below.

 

By Wednesday night or Thursday, the high over the eastern Pacific will begin to shift eastward, blocking the flow of modified arctic air for a warming trend.  Models look interesting, though, for weekend after next.  Another low is showing up on models stretching from the interior west to off shore California with a cold northeasterly flow wrapping around the western side of this system, potentially moving another cold air mass into California.  However, much can change between now and then as we’re talking a week and a half down the road.

 

Forecast: Remaining mostly cloudy along the eastern and southern flanks of the valley tonight and Thursday morning with possible areas of ground fog.  Becoming  mostly clear in  most areas Thursday afternoon.  Extensive fog and low overcast nights and mornings with afternoon sunshine Thursday night through Saturday night.  areas of low clouds and fog Sunday morning then higher clouds increasing during the afternoon.  Mostly cloudy, breezy, and cooler Sunday night and Monday morning with a small chance of light showers.  Mostly clear to occasionally partly cloudy Monday afternoon through Wednesday with cold nights and cool days.

 

Short Term:                                                                        

Madera 38/61/40/65 Reedley 37/61/41/66 Dinuba 39/61/41/65
Porterville 40/62/41/67 Lindsay 39/62/41/66 Delano 40/61/42/67
Bakersfield 44/62/44/68 Taft 43/61/43/68 Arvin 41/62/41/69
Lamont 41/61/43/68 Pixley 40/61/41/66 Tulare 39/61/41/65
Woodlake 40/62/41/66 Hanford 39/62/41/65 Orosi 39/62/41/65

 

Winds: Along the far west side, basically along the Interstate 5 corridor, expect gusty winds out of the north at 15 to 25 MPH through this evening.  Elsewhere, winds tonight through Saturday night will be generally at or less than 6 MPH with periods of near calm conditions.

 

Rain:  There will be a small chance of light showers Sunday night and Monday morning.  however, the bulk of the precipitation will spread down the Sierra Nevada with lowering snow levels. Otherwise, expect dry weather for the next week to ten days.

 

Frost Discussion:  Even though it ‘s cooler this afternoon, a low overcast remains over much of the valley as of 1:00pm. With dew points in the mid 40s, ground fog will rapidly form where skies happen to clear.  So, above freezing conditions can be expected tonight and on through Sunday morning.

 

Models have changed very little in depicting a major pattern change beginning Sunday.  A massive high will build far to the north into Alaska, covering the waters off the California coast northward almost to the Arctic Circle.  In the meantime, a trough of cold low pressure will stretch from the northwest territories of Canada southward to the Desert Southwest by midday Monday.  The flow aloft Sunday night and  Monday will become north to south right down the Pacific coast and into California.  There are some models that are showing winds aloft at a north/northeast angle to south/southwest Tuesday and Wednesday.  this is a completely overland trajectory.

 

Beginning Monday morning, when and if skies clear, lows in unprotected, low lying, wind sheltered areas could drop down to 26 to 28 degrees with general flatland terrain operations down to 28 to 32.  Cloud cover and wind conditions will be a large role Monday morning which could keep temperatures above their potential threshold.  On Tuesday and Wednesday mornings, the winds will have settled down and skies will potentially have cleared out, giving a higher risk, of a more general frost/freeze situation.  Models do show high pressure over the eastern Pacific building into California next Thursday through Saturday for what should modify temperatures.

Next report: January 30/morning