469 
FXUS65 KMSO 302053
AFDMSO

Area Forecast Discussion
National Weather Service Missoula MT
153 PM MST Sat Nov 30 2019

.DISCUSSION...Plenty of sunshine is being felt across much of the
region after snow tapered off this morning. Webcams and road
reports reveal continuing snow and ice conditions in places. Watch
out for black ice this evening as the sun goes down. 

A brief ridge will move over us tonight allowing for some
radiational cooling with fresh snowcover in place. Some locations
could see temperatures plummet faster than forecast. It will be a
cold night as temperatures fall into the teens and single digits
for many locations. 

A southerly wind gradient will develop over north-central Idaho
later this evening and this will create strong gusty winds west 
and south of Grangeville. We've received reports of snow depths ranging
from 4 to 6 inches in that area and with the potential for winds 
to gust to 40 mph, we've issued a winter weather advisory for 
blowing and drifting snow. Expect low visibility down to one 
quarter mile at times on Highway 95 by Sunday morning. High 
profile vehicles will be susceptible to difficult crosswinds with
possible slick road conditions from the drifting snow.

An upper level wave will move across north-central Idaho into
northwest Montana on Sunday to bring light snow. Expect a trace up
to 2 inches in these areas of new snow. Our confidence is for the
areas in Clearwater County to see the higher amounts in that range
and lesser amounts in northwest Montana.

Next week, a ridge sets up across the region causing moist,
southwest flow. This is a good pattern for mountain snow showers
and above average temperatures. While the mountains should warm up
into the 20s and low 30s early next week, temperatures in the 
valleys is a little harder to forecast. The cold air currently 
pooled up in the valleys will slowly moderate, then break out 
suddenly, allowing temperatures in the afternoon to warm up into 
the 40s. Timing that breakout is tough to do, but seems likely to 
occur early next week. 

Late next week, models agree on a short-wave breaking down the 
ridge and setting up a nice mountain snow event. Having the 
warmer, moister air in place from southwest flow earlier in the 
week, will give the shortwave plenty of moisture to work with, 
and cause mountain snow as it moves in. Precipitation type in the
valleys will be a challenge with that system. 

&&

.AVIATION...Expecting clear skies tonight under a dry air mass,
causing very cold temperatures at area terminals with single 
digits to low teens expected. Some haze or mist is possible, but
is expected to be very limited in extent and shallow due to the 
drier moving into the region. Sunday morning cloud cover will 
start to increase again ahead of the next wave of light snow for 
the region, which is expected to start Sunday evening.


&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...Winter Weather Advisory from 10 PM this evening to 7 PM PST 
     Sunday Orofino/Grangeville Region.

&&

$$