Lake Wind Advisory 6, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
412 AM MDT Fri Oct 6 2017

...Breezy to Windy conditions Today and Saturday...

.DISCUSSION...Winds aloft will be steadily increasing today as an
upper level jet begins to drift southward over the Northern
Rockies. The atmosphere appears to become unstable enough this
afternoon to allow these stronger winds to mix to down to the
surface. Northwest Montana should experience the strongest winds
today with gusts to 20 to 30 mph will be fairly common. These
gusty winds will create choppy conditions on area lakes,
especially Flathead. A Lake Wind Advisory has been issued for
Flathead for this afternoon and evening. The largest waves are
anticipated across the northeastern quadrant of the lake.
Temperatures today will be warming to near normal readings for
most locations.

The gusty winds will persist in the higher terrain during the
overnight hours as the valleys stabilize after sunset. The
strongest winds will be along the Continental Divide. Due to the
weaker valley inversions, the strong upper level winds should mix
to the surface by late morning to early afternoon on Saturday. The
strongest winds appear to be draped over west central Montana down
into southwest Montana on Saturday. These locations should
anticipate winds gusts of 30 to 40 mph with localized regions
potentially experiencing gusts up to 50 mph. The areas of
greatest concern will be along the I-90 corridor from Deer Lodge
to Anaconda and the gaps along the Bitterroot and Mission mountain
ranges. Precipitation will be moving into northwest Montana early
Saturday morning as this upper level jet streak moves southward.
The showers shifts into Clearwater county and west central
Montana by Saturday afternoon. Precipitation will be mainly
confined to the higher terrain as the broader valleys will
experience downsloping effects due to the strong winds aloft.
Temperatures on Saturday appear to drop around 10 degrees compared
to today.

Snow levels will decrease across the Northern Rockies on Saturday
night, following the passage of a cold front. Widespread light
snow above 4000 feet may create hazardous winter driving
conditions for area mountain passes. Northerly flow aloft through
Sunday will make for a long-lasting light snow event for the high
terrain, however winds will be much lighter than Saturday daytime.

High pressure will diminish precipitation by Monday morning, with
warming and drying conditions present through at least Tuesday.
Patchy valley fog may develop Tuesday morning, as skies clear and
temperatures drop.

Unlike model runs a day ago, both GFS and Euro models are trending
colder and more active for middle and latter portion of next week.
Instead of a stable high pressure ridge for much of next week,
storm system will be moving near the Northern Rockies almost every
second day. No one storm system will bring long-lasting winter
weather conditions, however brief (overnight) periods of snow
covered mountain passes are possible, as well as elevated valley
winds, throughout much of next week.

&&

.AVIATION...Clear skies last night has allowed for the development
of patchy fog across the Northern Rockies. KGPI is currently being
impacted by the fog, then burn off by mid morning. KMSO and KSMN
have the potential of fog developing within the vicinity of the
terminals this morning. Upper level winds will be steadily
increasing today causing gusty westerly winds by this afternoon,
especially across northwest Montana including KGPI. The valley
winds will diminish after sunset, while the higher terrain
continue to experience strong westerly winds throughout the night.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...Lake Wind Advisory from 3 PM this afternoon to 9 PM MDT this
     evening for Flathead Lake in the Flathead/Mission Valleys.

ID...None.
&&