Airshed
Management
System

Monday, September 24 Discussion: Northwest flow aloft over the western airsheds between strong ridging off the Pacific coast and troughing over the Central US will persist through Thu. Best dispersion for the western airsheds will be today, then more limited each day thereafter as surface winds become lighter, and valley inversions stronger and harder to break. A pattern change to NE low-level flow over North ID and Western MT may occur Fri/Sat when a trough drops south from Canada. 

GOOD dispersion Today ID and Western MT under NW flow aloft with broad upper trough over the Dakotas. W-NW surface winds.  EXCELLENT dispersion Central/Eastern MT with NW surface winds. 

MARGINAL-GOOD dispersion Tuesday ID and Western MT under NW flow aloft with light W-NW surface winds. EXCELLENT dispersion Central/Eastern MT with NW surface winds. 

MARGINAL-GOOD dispersion Wednesday ID and Western MT under NW flow aloft with weak upper trough over the Dakotas. Light SW-W surface winds.  EXCELLENT dispersion Central/Eastern MT with NW surface winds. 

MARGINAL-GOOD dispersion Thursday ID and Western MT under NW flow aloft with weak upper trough over the Dakotas. Light SW-W surface winds.  GOOD-EXCELLENT dispersion Central/Eastern MT with SW-W surface winds Central MT and S-SE Eastern MT. 

MARGINAL-GOOD dispersion Friday ID and Western MT under NW flow aloft with weak upper trough dropping south from Canada. NE-E winds northern Panhandle and NW MT. SW-W surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE surface winds. Rain/snow. 

MARGINAL-GOOD dispersion Saturday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW-W surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

Tuesday 25 September Dispersion Forecast

MONTANA

Northwest (AS 1, 2): MARGINAL.

West Central (AS 3A, 3B, 4, 5, 6): MARGINAL. 

Southwest (AS 7, 8A, 8B): GOOD.

Central/Eastern (AS 9, 10): EXCELLENT. 

IDAHO:

North (AS 11): MARGINAL. 

North Central (AS 12A, 12B, 13): MARGINAL. 

West Central (AS 14, 15, 21): MARGINAL. 

East Central (AS 16, 17): MARGINAL.  

Northeast (AS 18, 19): MARGINAL. 

Southeast (AS 20): MARGINAL. 

Southwest (AS 21B, 22, 23, 24, 25): MARGINAL. 

Prepared by Michael Richmond, Meteorologist NRCC

Tuesday, September 25 Discussion: Dry northwest flow aloft will continue today through Thursday with light W-NW surface winds in the ID and Western MT airsheds. This will create strong valley inversions which will be slow to break each of those days, limiting dispersion. A NE low-level push of cool air from Canada looks to begin over North ID and Western MT Friday and persist into at least Sunday. This would improve dispersion in those areas. 

MARGINAL-GOOD dispersion Today ID and Western MT under NW flow aloft with light W-NW surface winds. EXCELLENT dispersion Central/Eastern MT with NW surface winds. 

MARGINAL-GOOD dispersion Wednesday ID and Western MT under NW flow aloft with weak upper trough over the Dakotas. Light SW-W surface winds.  EXCELLENT dispersion Central/Eastern MT with NW surface winds. 

MARGINAL-GOOD dispersion Thursday ID and Western MT under NW flow aloft with weak upper trough over the Dakotas. Light W-NW surface winds.  GOOD-EXCELLENT dispersion Central/Eastern MT with NW-NW surface winds. 

MARGINAL-GOOD dispersion Friday ID and Western MT under NW flow aloft with weak upper trough dropping south from Canada. NE-E winds northern Panhandle and northern half of Western MT. SW-W surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE surface winds. Rain/snow. 

MARGINAL-GOOD dispersion Saturday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

MARGINAL-GOOD dispersion Sunday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

Wednesday 26 September Dispersion Forecast

MONTANA

Northwest (AS 1, 2): MARGINAL.

West Central (AS 3A, 3B, 4, 5, 6): GOOD. 

Southwest (AS 7, 8A, 8B): GOOD.

Central/Eastern (AS 9, 10): EXCELLENT. 

IDAHO:

North (AS 11): MARGINAL. 

North Central (AS 12A, 12B, 13): MARGINAL. 

West Central (AS 14, 15, 21): MARGINAL. 

East Central (AS 16, 17): MARGINAL.  

Northeast (AS 18, 19): GOOD. 

Southeast (AS 20): MARGINAL. 

Southwest (AS 21B, 22, 23, 24, 25): MARGINAL. 

Prepared by Michael Richmond, Meteorologist NRCC

Wednesday, September 26 Discussion: 

MARGINAL-GOOD dispersion Today ID and Western MT under NW flow aloft with weak upper trough over the Dakotas. Light SW-W surface winds.  EXCELLENT dispersion Central/Eastern MT with NW surface winds. 

MARGINAL-GOOD dispersion Thursday ID and Western MT under NW flow aloft with weak upper trough over the Dakotas. Light W-NW surface winds.  GOOD-EXCELLENT dispersion Central/Eastern MT with NW-NW surface winds. 

MARGINAL-GOOD dispersion Friday ID and Western MT under NW flow aloft with weak upper trough dropping south from Canada. NE-E winds northern Panhandle and northern half of Western MT. SW-W surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE surface winds. Rain/snow. 

MARGINAL-GOOD dispersion Saturday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

MARGINAL-GOOD dispersion Sunday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

Thursday 27 September Dispersion Forecast

MONTANA

Northwest (AS 1, 2): MARGINAL.

West Central (AS 3A, 3B, 4, 5, 6): GOOD. 

Southwest (AS 7, 8A, 8B): GOOD.

Central/Eastern (AS 9, 10): EXCELLENT 9. GOOD 10. 

IDAHO:

North (AS 11): MARGINAL. 

North Central (AS 12A, 12B, 13): MARGINAL. 

West Central (AS 14, 15, 21): MARGINAL. 

East Central (AS 16, 17): MARGINAL.  

Northeast (AS 18, 19): GOOD. 

Southeast (AS 20): MARGINAL. 

Southwest (AS 21B, 22, 23, 24, 25): MARGINAL. 

Prepared by Michael Richmond, Meteorologist NRCC

MARGINAL-GOOD dispersion Thursday ID and Western MT under NW flow aloft with weak upper trough over the Dakotas. Light W-NW surface winds.  GOOD-EXCELLENT dispersion Central/Eastern MT with NW-NW surface winds. 

MARGINAL-GOOD dispersion Friday ID and Western MT under NW flow aloft with weak upper trough dropping south from Canada. NE-E winds northern Panhandle and northern half of Western MT. SW-W surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE surface winds. Rain/snow. 

MARGINAL-GOOD dispersion Saturday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

MARGINAL-GOOD dispersion Sunday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

Friday 28 September Dispersion Forecast

MONTANA

Northwest (AS 1, 2): GOOD. 

West Central (AS 3A, 3B, 4, 5, 6): GOOD. 

Southwest (AS 7, 8A, 8B): GOOD.

Central/Eastern (AS 9, 10): EXCELLENT. 

IDAHO:

North (AS 11): GOOD.

North Central (AS 12A, 12B, 13): GOOD 12A. MARGINAL 12B/13. 

West Central (AS 14, 15, 21): MARGINAL. 

East Central (AS 16, 17): MARGINAL.  

Northeast (AS 18, 19): GOOD. 

Southeast (AS 20): GOOD. 

Southwest (AS 21B, 22, 23, 24, 25): GOOD. 

Prepared by Michael Richmond, Meteorologist NRCC

MARGINAL-GOOD dispersion Friday ID and Western MT under NW flow aloft with weak upper trough dropping south from Canada. NE-E winds northern Panhandle and northern half of Western MT. SW-W surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE surface winds. Rain/snow. 

MARGINAL-GOOD dispersion Saturday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

MARGINAL-GOOD dispersion Sunday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

Saturday 29 September Dispersion Forecast

MONTANA

Northwest (AS 1, 2): GOOD. 

West Central (AS 3A, 3B, 4, 5, 6): GOOD. 

Southwest (AS 7, 8A, 8B): GOOD.

Central/Eastern (AS 9, 10): EXCELLENT. 

IDAHO:

North (AS 11): GOOD.

North Central (AS 12A, 12B, 13): GOOD 12A. MARGINAL 12B/13. 

West Central (AS 14, 15, 21): MARGINAL. 

East Central (AS 16, 17): MARGINAL.  

Northeast (AS 18, 19): GOOD. 

Southeast (AS 20): GOOD. 

Southwest (AS 21B, 22, 23, 24, 25): MARGINAL 21B, 22. GOOD 23/24/25. 

Prepared by Michael Richmond, Meteorologist NRCC

MARGINAL-GOOD dispersion Saturday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

MARGINAL-GOOD dispersion Sunday ID and Western MT under weak upper trough. NE-E winds northern Panhandle and Western MT. SW surface winds Central and S ID and SW MT. EXCELLENT dispersion Central/Eastern MT with NE-E surface winds. 

Sunday 30 September Dispersion Forecast

MONTANA

Northwest (AS 1, 2): GOOD. 

West Central (AS 3A, 3B, 4, 5, 6): GOOD. 

Southwest (AS 7, 8A, 8B): GOOD.

Central/Eastern (AS 9, 10): EXCELLENT. 

IDAHO:

North (AS 11): GOOD.

North Central (AS 12A, 12B, 13): GOOD 12A. MARGINAL 12B/13. 

West Central (AS 14, 15, 21): MARGINAL. 

East Central (AS 16, 17): MARGINAL.  

Northeast (AS 18, 19): GOOD. 

Southeast (AS 20): GOOD. 

Southwest (AS 21B, 22, 23, 24, 25): MARGINAL.   

Prepared by Michael Richmond, Meteorologist NRCC