Lake Wind Advisory 9, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
343 AM MDT FRI AUG 21 2015

...Critical Fire Weather Conditions Today...

...Light Snow Likely Late Tonight Above 6500ft in Glacier
NP...Great Bear Wilderness & Bob Marshall Wilderness...

.DISCUSSION...A very strong cold front is still on track to pass
across the Northern Rockies this afternoon, producing very strong
and gusty winds which will undoubtedly wreak havoc on many area
wildfires. And while the frontal passage across central Idaho and
SW Montana still appears to be largely void of precipitation, the
same cannot be said for much of NW Montana where widespread
measurable rain is likely. The greatest confidence in where the
heaviest amounts occur falls along the Canadian border and near
the Continental Divide, though the convective nature of these
storms may produce locally heavier totals in other areas of NW
Montana.

Late this evening a second, 'back door' cold front will descend
out of Canada and push across western Montana during the night.
Although this will result in gusty conditions persisting after
sunset, the wind speeds will pale in comparison to those observed
earlier in the day. However this back door front will present a
rather stark directional shift to the north or even northeast.
This front will also steadily lower the snow level with locations
along the Continental Divide above 6500ft seeing perhaps as much
as an inch of snow by Saturday morning.

Saturday still looks like a really nice day across the region
with the cooler atmosphere steadily drying under northerly flow
aloft. This should help keep much of the smoke at bay and the
clear, drying atmosphere on Saturday night still has a chance to
support some frost in NW Montana Sunday morning. However this will
all be very short lived with hot, dry conditions returning later
in the day on Sunday afternoon.

Next week still appears to start off with building high pressure
and a return to above normal temperatures. The one standout change
to the extended forecast is agreement that high pressure will
begin to weaken on Wednesday which may allow temperatures to warm
to some of the highest readings of the week. Southwesterly flow
throughout the week is a good flow pattern to have weak
disturbances and increased moisture into north central Idaho and
western Montana. So, early in the week there will be mainly a
slight chance for showers but better chances are in the forecast
each day from Wednesday through the weekend.

&&

.AVIATION....Wildfires throughout Idaho and western Montana remain
active with widespread decreased visibilities currently occurring
and likely to remain through the day. Winds will increase through
this morning as a cold front approaches the region. Widespread
gusty winds can be expected in all of north central Idaho and
western Montana by this afternoon with sustained winds of around
30 knots and gusts near 40 knots into the evening. The main trough
with this weather system will move through northwest Montana this
evening with lowering clouds, showers, and thunderstorms mainly
north of I-90 and between 22/0000z-22/0600z. Northeasterly winds
will also expand through northwest Montana during the evening with
terrain to become obscured by clouds and precipitation. Snow
levels this evening and tonight will also be low for this time of
the year with snow levels as low as 6000 feet MSL.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...RED FLAG WARNING from 11 AM this morning to 9 PM MDT this
     evening East Lolo...Flathead/Glacier Park...Kootenai...
     Salish and Kootenai Reservation...West Lolo.

     RED FLAG WARNING from 11 AM this morning to 9 PM MDT this
     evening Bitterroot...Deerlodge/West Beaverhead...East
     Beaverhead.

ID...RED FLAG WARNING from 10 AM this morning to 8 PM PDT this
     evening Clearwater/Nez perce...Palouse/Hells Canyon.

&&