Area forecast discussion
National Weather Service Missoula Montana
410 am MDT Wed may 22 2013
Discussion...while the forecast heavy rain and high elevation
snow is still on track for today through the end of the week, a
few changes to the forecast have been made, albeit small changes.
It seems that the cold air intrusion may not be as impactful as
previously forecast, although enough cold air will still be in
place to cause accumulating snowfall in the high terrain across
the northern rockies. Snowfall amounts continue to be a question,
as placement of precipitation and cold air will ultimately impact
who gets what, and where. There is good confidence that Glacier
National Park, the Whitefish Range, mission mountains, and the bob
Marshall wilderness should see the most snowfall, with the bulk of
this snow falling above 7000 feet. Lighter amounts are possible
between roughly 5000 feet and 7000 feet. Below 5000 feet, most all
locations will see rainfall throughout the day, with precip
continuing well into the day Thursday, and much of Friday as well
(especially across northwest montana). Those with plans to be outdoors,
especially if you are traveling to Glacier National Park, or over
lookout and Marias Pass, should prepare for inclement, rapidly
changing conditions.
Forecast models continue to shift both the path of the closed upper
level low pressure system circulation and the subsequent location
of the heaviest precipitation on Friday. The consensus of today's
model suite in comparison to the past two days of model data would
present the heaviest precipitation along the Continental Divide,
and perhaps even into northwest Montana Friday morning. Then on
Friday afternoon, a second wave rotating around the main upper
level low will help initiate showers and thunderstorms first
across central Idaho, spreading across western Montana into Friday
evening. Key impacts will likely be heavy rainfall and perhaps
some lightning associated with the strongest thunderstorms.
Saturday should be a rather nice day with temperatures warming to
near normal. However, there will be a continued threat for some
scattered afternoon showers. But then on Sunday, models bring in
yet another atmospheric disturbance to help produce more
widespread showers and some thunderstorms across the northern
rockies. The GFS depicts a slower timing with the passage of that
disturbance lasting into Monday as well. Beyond Monday, the
forecast becomes increasingly complex and highly volatile to
change. But the overall theme will be continued chances for
showers and thunderstorms, with temperatures no warmer than normal
and likely below normal throughout the week.
&&
Aviation...rain with embedded thunderstorms continue to stream
across central Idaho and across west central and northwest Montana this
morning. Precipitation will continue to fill in as the day
unfolds, with heavy rain affecting all terminals. This will cause
periodically lowered ceilings and visibility, with gusty winds
also increasing by this afternoon. By nightfall, High Mountain
terrain will begin to receive snowfall, especially across northwest
Montana. Mountains will become shrouded in thick cloud cover and
falling snow, with elevations below 5000 feet will receive rain,
or a rain/snow mix through Thursday morning.
&&
Mso watches/warnings/advisories...
Montana...none.
Idaho...none.
&&
$$
Allegretto/Dickerson
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