704
FXUS65 KMSO 172037
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
237 PM MDT Mon Jun 17 2024

.DISCUSSION...Depending on intensity of showers, snow levels have
been fluctuating from 5500 to 4500 feet with any snow that
accumulates melting off as precipitation ends. This afternoon the
low pressure will continue its movement to the east. As this
happens northwesterly flow develops and precipitation becomes
convective in nature. Although there will be little to no surface
heating to power convection, this a very cold trough producing
strong lapse rates in the upper atmosphere. Expectations for
afternoon showers have a small chance for lightning, but in
general expect intense showers of rain or graupel. Above 4000
feet, these showers will translate into snow showers capable of
an inch plus per hour. After sunset if intense showers continue,
snow will be possible between 3000 and 4000 feet.

All in all, the impacts remain the same: Backcountry travel will be
very difficult. Snow on trees could cause breaking branches and
power outages are possible. Hypothermia is also a risk for those
unprepared for the cold and raw conditions.

Models continue to show another disturbance digging south out of
Canada Tuesday morning. This will provide a focus for snow showers
across northwest Montana, particularly in the Glacier Park
region.

Gardeners beware of frost potential on Wednesday morning in
valley locations that see partial clearing. Currently, models
show this clearing from the Mission Valley southward into Lemhi
County. Please stay tuned for the latest low temperature forecast
as sensitive plants may need to be covered.

Model ensembles agree (nearly 100%) on a warming trend for the
rest of the week with scattered afternoon showers each day.
Daytime temperatures peak on Sunday about 15 degrees above normal
(upper 80s western Montana valleys, low/mid 90s for north-central
Idaho).

&&

.AVIATION...Baroclinicity driven stratiform precipitation associated
with the upper level low passing over the region has all but
ended and the Northern Rockies have entered into the backside,
convective region of the storm system. Unseasonably cold
temperatures throughout all levels of the atmosphere are driving
some intense showers which will bring the threats for isolated
thunderstorms and rapidly reduced visibility. These conditions
will be possible at all airfields but more favored at KMSO, KBTM,
KHRF, and KSMN into this evening. A secondary shortwave trough
will slide SE across NW Montana very early Tuesday morning
resulting in an uptick of showers for NW and WC Montana, including
airfields KGPI, KMSO, KBTM. KHRF will remain on the fringe for
shower threat and could even receive enough clearing to allow some
patchy fog to form. The atmosphere Tuesday afternoon will remain
unstable across the entire Northern Rockies and thus widespread
showers with isolated thunderstorms will again be possible and
could affect all airfields.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Winter Storm Warning until 6 AM MDT Tuesday for
     Bitterroot/Sapphire Mountains...Butte/Blackfoot Region...
     Potomac/Seeley Lake Region.

     Winter Weather Advisory until 9 AM MDT Tuesday for West Glacier
     Region.

ID...Winter Storm Warning until 5 AM PDT Tuesday for Southern
     Clearwater Mountains.

     Winter Weather Advisory until 2 PM MDT this afternoon for
     Eastern Lemhi County...Western Lemhi County.

&&

$$