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Area forecast discussion 
National Weather Service Missoula Montana
412 am MDT Sat may 23 2015

Discussion...a disturbance moving in from the east will bring
scattered showers with isolated lightning strikes across western
Montana and north central Idaho today. The best area for
thunderstorm development looks to be over the terrain of Idaho
County this afternoon but an isolated rumble of thunder cannot be
ruled out for any showers this afternoon. Brief periods of
moderate rain will be possible along the I-90 corridor and north
central Idaho. Northwest Montana could see a few light showers
develop along the terrain near Glacier park, but overall dry
weather will persist through the weekend.

Sunday looks to be the driest day of the Memorial Day weekend with
seasonal temperatures and a few light showers along the terrain in
the afternoon.

Model guidance and ensembles seem to agree upon a closed low
pressure system from the northwest moving across the northern
rockies Monday through Friday. The presence of such a closed low
circulation this time of year tends to suggest decent
precipitation. The best opportunity of precipitation will be
Monday and Tuesday afternoons, when a weak cold front associated
with the low creates a Focal Point for showers and thunderstorms
to develop. Otherwise, convection will be the main mechanism for
precipitation. As with any convective event, there will be drastic
differences in precipitation totals from location to location. The
total of this precipitation may cause smaller streams to respond
by running more vigorously, however will have only a small effect
on mainstem rivers. The precipitation and cloud cover will warm
overnights and cool afternoons.

By next weekend, some long range models suggest that a warm ridge
of high pressure will develop over the inland Pacific northwest
and later move over the northern rockies. Model guidance suggests
that low level moisture will remain in-place through at least
early the following week, resembling something of a monsoon type,
daily afternoon convection type scenario.


Aviation...scattered showers will begin to develop around noon
today near kbtm, kmso, and ksmn. Main impacts with these showers
will be brief moderate rain, which could reduce ceilings and
obscure terrain especially at kbtm where shower activity looks to
be the greatest. Easterly winds are expected to increase at all
terminals this afternoon with wind gusts of 20-25 knots possible.


Mso watches/warnings/advisories...


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