Area Forecast Discussion
Issued by NWS Missoula, MT
FXUS65 KMSO 112032
Area Forecast Discussion
National Weather Service Missoula MT
232 PM MDT Tue Mar 11 2014
Tonight through Wednesday Night...High pressure at both the
surface and aloft will provide a nice respite from has been a
very wet week. The stable, calm conditions will favor the
development of valley fog across much of north-central Idaho and
western Montana. Dense fog (visibility less than one-quarter mile)
is a real possibility after midnight tonight through Wednesday
morning across northwest Montana and western Idaho county,
including cities along the Clearwater river system. Dense Fog
Advisories have been issued to highlight these concerns.
Temperatures will be very close to normal values for this time of
year. However, locations where fog may linger into the afternoon
will likely see cooler temperatures, generally 5 to 10 degrees
below normal. There is a good potential for valley fog again
Wednesday night, but it is still uncertain whether or not there
will be enough dense fog to warrant another advisory.
Thursday...A weather disturbance moving through ridge pattern
does not appear to have much moisture associated with it. We will
see increased clouds, but any chance of precipitation will be
confined to the mountains of northwest Montana.
The next two impacts to the Northern Rockies will occur Friday
afternoon into Saturday, and then again on Monday.
The first of the aforementioned systems could bring snowfall back
to mountain passes, particularly Marias, Lookout, and Lolo passes
on Friday night through Saturday. Since snow has not been an
issue at passes for some time leading up to this, it will
certainly be a change in conditions to those traveling. Valleys
during this time frame will see rain, or a rain/snow mix.
A next, much more robust system is anticipated to affect the
region on Monday, bringing about potentially strong, gusty winds.
A tightening surface pressure gradient and a perfectly positioned
upper level jet stream could bring about strong gusts Monday
afternoon. The period of strong winds could be a quick one,
lasting through Monday night at the latest.
More details to come on this developing scenario.
Conditions will continue to improve this afternoon as a ridge of
high pressure builds into the Northern Rockies region from the
west. Unfortunately, the calm stable conditions will favor the
development of widespread valley fog, with some areas experiencing
dense fog after midnight tonight through Wednesday morning.
Northwest Montana and the Idaho Panhandle are the mostly likely to
see dense fog, reducing visibilities to less than one-quarter
mile. This would include KGPI and possibly KMSO. Fog and low
clouds will be dissipating again between 17Z-19Z Wednesday,
followed by VFR conditions through the remainder of the afternoon.
MT...DENSE FOG ADVISORY from 3 AM to Noon MDT Wednesday
Flathead/Mission Valleys...Kootenai/Cabinet Region...Lower
Clark Fork Region.
ID...DENSE FOG ADVISORY from 2 AM to 11 AM PDT Wednesday
Orofino/Grangeville Region...Southern Clearwater Mountains.
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