Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Missoula Montana
412 am MDT Wednesday Sep 2 2015
..wet and cool tonight through the weekend...
Discussion...a cold front will sweep through western Montana and
central Idaho today, stalling across southwest Montana this
evening. The front will bring an increase in winds, especially
across southwest Montana where the frontal passage will interact
with daytime heating to help winds aloft mix to the surface.
Behind the front, forecast models continue to show a band of
precipitation developing tonight into Thursday across central
Idaho and western Montana. Most locations should see measurable
precipitation, with the heaviest precipitation oriented across
central Idaho and west central Montana. Behind the front on
Thursday, much cooler temperatures should be expected, especially
for locations that see steady precipitation.
Friday: the cold front will have stalled from northern Lemhi
County north and east towards Butte during the day.
Simultaneously, a strong south to north upper level jet will
provide a narrow region of strong lift and therefore bring the
best chance for precipitation. This focus for persistent rain
showers could exist from the southern Clearwater Mountains north
and east across the Bitterroot valley then north and east to
Glacier National Park during the day. One weather model solution
points to the possibility of colder temperatures due to upslope
mechanisms along the Continental Divide later in the day which
could drive snow levels down and enhance precipitation rates
especially affecting Essex to Marias Pass. With marginal
instability, there could be weak thunderstorm activity mainly from
Lemhi County to southwest Montana. With a northeast wind gradient
confined to northwest Montana, downsloping may be negating factor
in locations like Eureka to Kalispell from experiencing much
rainfall during the day. Also it appears Lincoln County south to
western Sanders County may also stay fairly dry during the day and
therefore warm up well into the 60s to perhaps near 70 degrees.
Saturday: the above normal chance for precipitation and cooler
temperatures continues as the trough tracks over the northern
rockies. Expect widespread rainfall, with some locations
experiencing moderate to heavy intensities at times. With high
pressure over southern Alberta nosing south along The Divide,
there will be a northeast wind gradient extending west into the
Flathead Valley. Despite lesser chance for rainfall in some of
these areas during the day due to downsloping affects,
precipitation chances increases once the trough begins to move towards
central Montana Saturday night. Normal high temperatures area-wide are
in the 70s, but highs may only reach the upper 50s to 60s. Those
visiting the area or expecting to Camp, should prepare for cold
and wet conditions this weekend.
Sunday: a slow drying trend will be felt across central Idaho
then across portions of western Montana during the day. There
still could be lingering showers from Lincoln County east to the
Flathead Valley and Glacier National Park. There is still
expected to be a fair amount of clouds and even areas of fog Sunday
night, but there could be areas that clear out enough to see
temperatures plummet down towards the freezing mark.
Drier weather is expected to return early next week, though
temperatures will be slow to warm.
Aviation...the advancement of a cold front across western
Montana and central Idaho will generate widespread gusty winds
along and ahead of the front today, lasting most of the day.
Stronger wind gusts of 30kts are possible at kbtm and ksmn
through 03/0300z. Showers will develop today across northwest
Montana, with a potential band of heavier precipitation expected
to develop tonight into Thursday. This band could cause lowered
ceilings, obscuring the higher terrain starting this evening in
central Idaho and into western Montana tonight. Kmso and kgpi are
the most likely locations to experience precipitation through
Montana...red flag warning from noon today to 9 PM MDT this evening
deerlodge/west Beaverhead...east Beaverhead.