Weather Service Report


838 
FXUS65 KMSO 222051 CCA
AFDMSO

Area Forecast Discussion...CORRECTED
National Weather Service Missoula MT
251 PM MDT FRI MAY 22 2015

.DISCUSSION...

Showers and thunderstorms have sprung up across southwest Montana
and north central Idaho this afternoon. Most showers and storms
will remain south of I-90 through this evening, keeping northwest
Montana dry. Because steering flow aloft is weak, storms remain
relatively locked to the terrain, but will move slowly to the
southwest over time. Lightning, gusty winds, and brief periods of
heavy rain will be the primary threats from these storms. Small
hail could fall from the strongest cells, with storms over the
Camas Prairie in Idaho having the best chance of reaching this
strength. Showers will diminish quickly after sunset.

On Saturday, a weak weather disturbance will move from NE to SW
across southwest Montana and Lemhi & Idaho county Idaho. This
could lead to additional light rain in many of the same places
that saw rain Friday. Temperatures will be a few degrees cooler
than Friday, but remain near seasonal values. Sunday looks like
the driest day of the Memorial Day weekend with more seasonal
temperatures.

Models are coming into better alignment regarding a moist low
pressure system shifting over the northern Rockies Monday,
Tuesday, and possibly Wednesday. Note, the majority of the models
within the ECMWF and GFS ensembles actually show the low pressure
system a bit further south and hanging around longer than the
operational runs. Bottom line...a wetter period, with widespread
showers and a few thunderstorms, appears in store for north
central Idaho and western Montana Monday, Tuesday and maybe
Wednesday.


&&

.AVIATION...
Showers and thunderstorms have formed this afternoon across the
area. The best areas for continued storms will be at terminals
along and south of I-90, namely, KSMN, KBTM, and KGIC. KMSO will
be at the northern border of this area of concern, so it too could
see a shower or two later in the afternoon. Winds could be gusty
to 15-20 kts near showers, but should be 10 kts or less otherwise.
Thunderstorms, showers, and winds look to diminish around
23/0300z. Rain showers are again possible tomorrow afternoon.


&&

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

$$

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Western Regional Climate Center, wrcc@dri.edu