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Discussion: (For details on individual airsheds see table
below)
A slow moving upper level low pressure system will move
through the intermountain west over the weekend keeping cool conditions and
high humidity with light winds. For most areas this will create POOR to
MARGINAL dispersion through Sunday. Southeast ID will be the one exception with
a bit more southerly wind producing GOOD to EXCELLENT dispersion on Saturday
and MARGINAL to GOOD dispersion on Sunday.
Another weaker system passes over the area Monday into
Tuesday keeping conditions cool and unsettled. Dispersion does begin to improve
for southwest and central and eastern MT for MARGINAL to GOOD conditions but
much of the rest of the region will continue POOR to MARGINAL. Later next week
upper level high pressure moves into the Pacific Northwest with a cool
northwest flow aloft setting up over ID/MT. This pattern is likely to support
inversion formation over ID and western MT especially in areas where recent
moisture supports overnight fog formation.
Dan Borsum – Northern Rockies Predictive Services Meteorologist