Show Information for:
Monday 26 September
Discussion: Poor dispersion
conditions under strong upper ridging with slow to break valley inversions will
occur for most western airsheds today and tomorrow. Latest forecast modeling is
slowing down the progression of an upper trough, now scheduled in for Thursday
over ID and Western MT. So Wednesday will not see as much improvement as had
been expected earlier. On the other hand, the trough will also more slowly move
out, so a return to widespread poor dispersion for Idaho and Western MT airsheds
will not occur until next Sunday, and may be brief. As long range modeling is
indicating a more active fall pattern developing next week, with more upper
trough passages possible.
Today: POOR-MARGINAL dispersion will occur over
North ID and Western MT with the upper level ridging and strong valley
inversions. Light/variable surface winds. POOR dispersion will occur over
Central ID with light/variable surface winds. POOR-MARGINAL dispersion will
occur South ID and SW MT with light/variable winds. MARGINAL-GOOD dispersion
will occur in Central/Eastern MT with light E-SE surface winds Central and NW
surface winds Eastern.
Tuesday: POOR-MARGINAL dispersion will occur over
North ID and Western MT under strong upper ridging. Light/variable surface
winds. POOR-MARGINAL dispersion will occur over Central and South ID with
light/variable surface winds. MARGINAL dispersion will SW MT with light SW winds.
MARGINAL-GOOD dispersion will occur in Central/Eastern MT with light SE-S
surface winds.
Wednesday: POOR-MARGINAL dispersion will occur over North
ID and Western MT under strong upper ridging. Light S-SW surface winds.
POOR-MARGINAL dispersion will occur over Central and South ID with light S-SW
surface winds. MARGINAL dispersion will SW MT with light SW winds. POOR-MARGINAL
dispersion will occur in Central/Eastern MT with light/variable winds Central
and light SE-S surface winds Eastern.
Thursday: MARGINAL to GOOD dispersion North
ID and Western MT as upper trough passes. Westerly surface winds. Scattered
showers. MARGINAL-GOOD dispersion Central and Southern ID with W-NW surface
winds. GOOD-EXCELLENT dispersion Central and Eastern Montana with W-NW surface
winds, except SE-S far eastern.
Friday: MARGINAL-GOOD dispersion will occur over
ID and Western MT under circulation around upper low over Eastern MT. NE-N
surface winds. MARGINAL-GOOD dispersion will occur over Central and Southern ID
and SW MT with W-NW surface winds. GOOD dispersion will occur in
Central/Eastern MT with W-NW surface winds. Scattered showers.
Saturday: MARGINAL-GOOD dispersion will occur over ID
and Western and SW MT under northerly flow aloft. NE-E surface winds. POOR-MARGINAL
dispersion will occur over Central and Southern ID with light/variable surface
winds. GOOD dispersion will occur in Central/Eastern MT with NW-N surface
winds, scattered showers.
Sunday: POOR-MARGINAL dispersion will occur over
North ID and Western MT under upper ridging. Light/variable surface winds.
POOR-MARGINAL dispersion will occur over Central and South ID with light S-SW
surface winds. POOR dispersion will SW MT with light/variable winds. MARGINAL
dispersion will occur in Central/Eastern MT with light SE winds Central and
light NW-N surface winds Eastern.
Tuesday 27 September
Dispersion Forecast:
MONTANA
Northwest (AS 1, 2): POOR.
West Central (AS 3A, 3B, 4, 5, 6): POOR except
MARGINAL As 6.
Southwest (AS 7, 8A, 8B): POOR.
Central/Eastern (AS 9, 10): MARGINAL Central.
GOOD Eastern.
IDAHO:
North (AS 11): MARGINAL.
North Central (AS 12A, 12B, 13): MARGINAL.
West Central (AS 14, 15): POOR.
East Central (AS 16, 17): POOR.
Southeast (AS 18, 19, 20): POOR.
Southwest (AS 21, 22,
23, 24): MARGINAL.
Prepared by Dan Borsum/Michael Richmond NRCC Predictive Services Meteorologists