Persistent cold-air pool forecast valid Tuesday 01/22/2019

Tuesday, January 22, 20194 pm

Weather Synopsis:

Persistent cold-air pool forecast valid Tuesday 01/22/2019 4:00 pm MST 

This will be updated every 2-3 days except before and during major PCAPS (will be updated daily).

Summary: A major  storm system brought widespread snow  accumulations to Utah Valley ranging from 4-16 inches. Thus, a significant snowpack is in place to support intense inversions.

 To view snowfall accumulations see https://www.cocorahs.org/Maps/ViewMap.aspx?state=usa

However, a series of weak weather systems progressing around a high pressure system off the West US coast will keep temperatures aloft from warming much through Saturday.  Thereafter, cold-air pool conditions may become established starting Sunday but it is too far out to have much confidence in the forecasts. The 3-5 day forecast is also unusually uncertain. If the high pressure over the west coast shifts east more than currently forecast, a persistent cold-air pool could form later this week. Stay tuned for updates.

Wednesday 23 January:

Mostly cloudy flurries possible.

High 36 F Low 22 F

Thursday  24 January:

Mostly cloudy.Chance of snow Wed. night into Thurs morning.
High 37 F Low 27 F

GFS Forecast Model showing light snow and short-wave trough
impacting Northern Utah Thursday morning.

Friday  25 January:

Mostly cloudy slight chance of snow.

High 36 F Low 24 F.
  
GFS Forecast Model showing light snow and short-wave trough
impacting Northern Utah Friday night.

Saturday 26 January: 
 
Mostly sunny, cool.

High 37 F Low 24 F.

 
Sunday 27 January:

GFS Forecast Model showing high pressure ridge building over Utah on Sunday.

 
Mostly sunny, cool.

High  37 F Low 25 F.

Monday 28 January

Mostly cloudy chance of light snow.

High  36 F Low Monday night 20 F.

Friday, January 18, 2019 noon.

Weather Synopsis:

Persistent cold-air pool forecast valid Friday 01/18/2019 12:00 noon MST 

This will be updated every other day unless during major PCAPS (will be updated daily).

Summary: A major  storm system brought heavy rain and snow to Utah is winding down on Friday. Weak high pressure will result in brief cloud-topped cold-air pool/inversion through the weekend, with only minor impacts to Valley air quality. A major snowstorm is looking more likely for Monday. This could set the stage for a large high pressure system over the Western US with snow on the ground in northern Utah Valleys, potentially leading to a major persistent cold-air pool episode beginning around Saturday 26 January if current model forecasts hold. Stay tuned. 

Saturday 20 January:

Mostly cloudy with sprinkles or flurries possible in the morning. Weak cold-air pool in place in the cloud-topped inversion. PM2.5 concentrations between 5-10 micrograms/m3.

High 42 F Low 33 F

NAM model sounding showing the deep cloudy inversion layer between the surface and mountaintop (700 mb):

Sunday  21 January:

Partly cloudy. Weak cold-air pool in place.
PM2.5 concentrations between 8-14 micrograms/m3.

High 45 F Low 33 F

Monday 22 January:

Cloudy, 70% chance of snow. Significant accumulations possible.

High 35 F Low 21 F.
 

Tuesday 23 January: 
Mostly cloudy, cold.

High 30 F Low Saturday night 24 F.

 
Wednesday 24 January:
Mostly cloudy chance of light snow.

High  37 F Low Sunday night 25 F.

Thursday 25 January

Mostly cloudy chance of light snow.

High  38 F Low Monday night 24 F.

Tuesday, January 15, 2019

Weather Synopsis:

Persistent cold-air pool forecast valid Tuesday 01/15/2019 7:00 pm MST 

This will be updated every other day unless conditions warrant.

Summary: A weak storm system will clean out the remaining pollution Wednesday. A windy and wet pattern will ensue through Thursday night with several feet of snow in area mountains as a a strong Pacific storm system traverses the Western US. An inch or two of snow is possible in the Valleys Thursday night into Friday morning. A short 60-hr cold-air pool episode is forecast Friday afternoon through Sunday night followed by a cold front and mix-out to clean conditions late Sunday night or Monday morning. PM2.5 Pollution levels will stay below the NAAQS on Saturday and Sunday. Cool, clean northwest flow will follow into Monday and Tuesday. 

Wednesday 16 January:

Remaining pollution from last episode will be mixing out by mid-afternoon. 70% chance of rain and snow mix.  Winds 5-10 kts from south.

High 40 F Low Wednesday night 37 F

 

Thursday  17 January:

Clean air in Utah Valleys. Rain likely (90% chance), heavy at times. Too warm for Valley snow accumulation in the Salt Lake Valley until late Thursday night with 1 inches possible toward dawn Friday. Winds 5-10 kts from south.

High 46 F Low Thursday night 33 F

Friday 18 January:

Clean air in Utah Valleys. Snowshowers likely (70% chance). 1-2 inches possible.  

High 37 F Low Friday night 30 F.

Saturday 19 January: 

Weak pollution episode begins with cold-air pool conditions being established.

High 37 F Low Saturday night 26 F.

Forecast model inversion sounding late morning Saturday showing descending mountaintop subsidence inversion associated with progressive short-wave trough:

Sunday 20 January: 

Weak pollution episode continues through Sunday night. PM2.5 levels likely to remain below NAAQS. 

High  40 F Low Sunday night 29 F.

Forecast model inversion sounding in the morning Sunday showing the mountaintop subsidence inversion has descended and the low-level inversion has strengthened:

Monday 21 January


At this time (weather models could change) another cold front will end the short weekend episode with a chance of snow. Stay tuned.

High  38 F Low Monday night 25 F.

Jordan Narrows Transport Study Cold Air Pool Forecast 12 January 2019

High pressure aloft centered over the northern Rockies will remain 

the dominant weather feature early next week, resulting in a 

strengthening cold-air pool through Tuesday. A series of 

weather disturbances will finally return to the area toward 

the middle of the week and scour out the Valley pollution.

The PM2.5 levels across the SLV have remained nearly constant 

the last few days(~30 micrograms/m3) as rain, fog, and low 

clouds have increase vertical mixing and diluted the pollution 

trapped in the Valleys of Northern Utah.

A strengthening inversion with and marginal to poor air quality 

will remain the norm through Monday. Tuesday through Wedsday the 

inversions will likely mix out and air quality will dramatically

improve.

More detailed forecasts to follow starting Monday 14 December.

Jordan Narrows Transport Study Cold Air Pool Forecast 10 January 2019

High pressure aloft will strengthen to the west of Utah Friday, 

then shift east into the northern Great Basin for the weekend. This will result 

in a prolonged period of inversion conditions through at least Monday in

the valleys of northern Utah. 

Pollution levels are currently ~30 mg/m3. Expect particulate pollution

to increase ~5 mg/m3 per day on average in the Salt Lake Valley through Monday. 

This means several days exceeding the National Ambient Air Quality Standard 

are likely Friday - Monday.  

Fog and clouds within the cold-air pool will become increasingly likely 

as the inversion strengthens this weekend.

More detailed 7-day forecasts will start on 15 January.  

Jordan Narrow Exchange Forecasts January 8th 2019

Daily cold-air pool forecast valid Tuesday 1/08/2019 10:00  PM MST

 

Poor air quality is expected through next weekend as a weak inversion strengthens. More detailed forecasts will start with the beginning of the UDEQ Jordan Narrows Transport Study on 15 January 2019.

Forecast sounding showing inversion on Friday 11 January.

UWFPS 2017 daily cold-air pool forecast valid Thursday 2/16/2017 10:00  AM MST

 

The weak inversion episode that began Sunday night has mostly mixed out in the Salt Lake Valley but PM2.5 levels around 30 micrograms continues in the Cache Valley. Clean air across the region should be observed by Friday. Periods of stormy weather and no air quality concerns expected from this Friday February 17th through about Saturday February 25th.

This will be the last forecast issued for the UWFPS winter study period. Congratulations everyone on a great field study. Enjoy spring!