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Forecast

January 31, 2020/pm update

January 31, 2020

Summary: We have about another 36 hours worth of mild, early February weather before winter returns with a vengeance.  Upper level high pressure along with its bubble of warm subsiding air will be almost right above central California Saturday, driving temperatures to near the 70 degree mark and possibly eclipsing that mark, especially over Kern County.  The high will quickly break down and be suppressed southwestward out over the ocean in response to a strong but moisture starved low pressure system moving down the North American continent from western Canada.

 

The center of the upper low will be almost right above north/central California by Sunday evening.  Ahead of the low will be a fast moving, but again, moisture starved, cold front which will spread light snow showers down the Sierra Nevada Sunday.  Behind the cold front, and as pressures rapidly fall over Nevada, will be strong, gusty, westerly winds throughout the valley from later Sunday morning into early Monday.  Wind gusts in excess of 40 MPH would not be a surprise in western Fresno and Kings Counties, especially Sunday afternoon and night.

 

Behind the front will be the arrival of a much colder air mass.  This air mass will have modified arctic air involved which will quickly drive dew points south Sunday night and Monday, setting the stage for what could potentially be a hard freeze Tuesday and Wednesday mornings.  This is discussed in detail below.

 

Temperatures Monday will struggle to reach the 50 degree mark, rising into the low 50s Tuesday and mid 50s Wednesday.  by Wednesday night and Thursday, upper level high pressure will begin to nudge in from the west with a warming atmosphere aloft.  This will be translated into considerably milder daytime temperatures with a slower recovery of overnight lows.  All this is being created by a large high over the eastern Pacific reaching into Alaska with that big cold trough over the interior west, creating a north to south pipeline of air down the west coast.  The origins of the air mass are in western Canada.  The typical moderating affect of the Pacific Ocean will simply not be there this time around as this air mass will be flowing southward over land.

 

Interestingly enough, for the third day in a row, models are showing a developing low possibly over northern California beginning a week from Sunday with a big high building northeastward into Alaska, possibly near the Arctic Circle.  This could lead us into a second cold weather episode beginning about a week from Monday.  This is by no means in concrete, however with a trend developing, it has piqued my interest.

 

Forecast: Mostly clear skies with one more mild afternoon through Saturday night.  variable cloudiness Sunday through Monday morning.  expect strong, gusty winds and much cooler conditions Sunday through Monday.  Mostly clear and cold Monday afternoon through Wednesday.  mostly clear Wednesday night through Friday with a slow warming trend.

 

Short Term:                                                                        

Madera 39/70/42/57 Reedley 39/71/42/57 Dinuba 38/70/42/56
Porterville 39/72/42/58 Lindsay 38/71/41/58 Delano 40/72/43/59
Bakersfield 44/73/45/59 Taft 46/71/46/58 Arvin 40/73/43/59
Lamont 42/73/44/58 Pixley 39/71/42/57 Tulare 38/70/41/56
Woodlake 38/70/41/57 Hanford 40/70/43/58 Orosi 38/70/41/57

 

Winds: Winds will be generally at or less than 6 MPH with periods of near calm conditions through Saturday night.  winds will begin to increase out of the northwest later Sunday morning at 15 to 30 MPH at times with gusts over 40 MPH possible in western Fresno and Kings Counties with local gusts to 35 MPH possible elsewhere.  Winds Sunday night and Monday morning will be out of the northwest at 10 to 20 MPH with stronger gusts, diminishing Monday afternoon.

 

Rain:  A rapidly moving but moisture starved cold front will move down the valley Sunday afternoon or evening.  It’s possible a few light showers may accompany the front, but most locations will remain dry.  The greatest risk for measurable rain may actually be over the valley portion of Kern County, especially areas closer to the base of the Tehachapi Mountains where strong upslope conditions will be evident.  Light snow showers will spread down the Sierra Nevada Sunday with light snow showers likely over the Kern County mountains late Sunday through Monday morning with snow down to 3,000-4,000 feet.  From Monday through all of next week, expect dry conditions.

 

Frost Discussion:  Models are marginally waffling up and down on potential cold temperatures for Monday through Wednesday mornings.  Models for Porterville for Tuesday morning range between 27 and 30 degrees. One model actually spits out a number of 28 degrees at Meadows Field for Tuesday morning, but that may be somewhat of an outlier.  For now, I see no reason to change the premise of widespread low to mid 30s Monday morning with coldest wind sheltered locations with clear skies possibly as low as 28 degrees.  Tuesday and Wednesday mornings have the potential for wind sheltered, low lying frost pockets down to 24 to 26 degrees with typical flat terrain locations generally ranging from 27 to 31.  Hillsides may actually be below freezing for a change Tuesday morning due to a weak inversion which will firm up Wednesday morning.  We could see temperatures below 32 degrees for as long as 8 to 10 hours in coldest locations and at or below 28 degrees for 4 to 6 hours.  For now, it appears Tuesday morning will be the most dangerous followed closely by Wednesday morning.

 

For this report, I won’t summarize the pattern which is well outlined in the summary above.  Beginning Wednesday night and Thursday, moderation will begin, especially during the day as upper level high pressure shifts eastward from the Pacific.  However, above freezing conditions may not occur until Friday morning, especially in colder locations.

 

I’m also watching the potential of another cold air mass expected to arrive about a week from this coming Monday as a cold low drops southward from western Canada possibly into northern California with a very cold northeast/southwest wraparound effect.  This could move in another bout of cold air into the valley.  That is then and this is now, so we’ll concentrate on the Monday through Wednesday event at this time.

Next report: February 1/morning