Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 220156 AAA
AFDMSO

Area Forecast Discussion...UPDATED
National Weather Service Missoula MT
755 PM MDT TUE OCT 21 2014

.UPDATE...Cancelled the winter weather advisories.


&&

.DISCUSSION...Due to precipitation ending and subsequent impacts
diminishing, the winter weather advisories have been cancelled.
Some lingering light snow showers may still plague mountain passes
through the rest of this evening, but the impacts have lessened
enough to warrant the cancellation of headlines.

&&

.PREV DISCUSSION... /ISSUED /

.DISCUSSION...A lot of rain has fallen across the area today, with
many locations reporting over 0.3 inches of rain in the last 24
hours, with many mountain stations reporting over half an inch of
new liquid. Snow was also observed at elevations above 6000 feet
south of Missoula.

As this system exits the area tonight, scattered low clouds and
patchy fog will develop across the northern Rockies due to the
ample moisture left behind. High pressure centered over Southwest
Montana and Lemhi county Idaho will drive light southerly winds
over much of western Montana tonight, keeping the fog patchy and
limited to areas sheltered from southerly winds. Also, much less
rain fell over northwest Montana, so fog is less likely there. In
central Montana, the southerly winds will be stronger preventing
fog from forming in the Grangeville and Orofino or on the Camas
Prairie.

On Wednesday high pressure will intensify as a ridge builds over
the area. This will continue to drive southerly winds and allow
temperatures to rise to above normal readings again. A strong jet
stream with very moist flow will move across the Pacific
Northwest, just glancing the northwest corner of northwest Montana
ahead of the next system, mainly affecting Troy before more
moisture from this system starts to move into western Montana
Thursday.

The Thursday system is forecast to bring rain and high elevation
snow showers, with breezy southwest winds across much of the area.
Showers with possible thunder is forecast for southwest MT and
central ID along the Bitterroot Mountains. The cool and wet
pattern will continue through the weekend and into early next
week. Some showers could produce heavier precipitation with a
colder airmass late Sunday into Monday, resulting in snow levels
dropping to the mid slopes around 4500ft.

&&

.AVIATION...The weather system that brought gusty winds, rain &
snow and scattered thunderstorms to the area will be moving into
central Montana by 22/0300Z causing shower activity to wane. Mountain
obscuration will continue through tonight due to westerly flow
keeping upslope showers in place. There will be somewhat drier air
moving in aloft after 22/0800z which could help improve ceilings
especially across central Idaho and areas west of the Continental
Divide. Considering all the rainfall that fell and some clearing
tonight, the chance for fog exists. There may be too much of a
southerly breeze to form widespread fog from KGPI to KBTM, but
confidence is higher that KSMN could see better development
overnight tonight. VFR conditions are expected to develop on
Wednesday at all the terminals. With increasing flow aloft, there
could be weak to moderate mountain wave activity across the
Continental Divide especially towards the Canadian Border on
Wednesday.

&&

.MSO WATCHES/WARNINGS/ADVISORIES...
MT...None.
ID...None.
&&

$$




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