Area Forecast Discussion
Issued by NWS Missoula, MT

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FXUS65 KMSO 052050

Area Forecast Discussion
National Weather Service Missoula MT
250 PM MDT TUE MAY 5 2015

.DISCUSSION...Thunderstorms have begun to form this afternoon
across southwest Montana (Butte/Blackfoot/Pintlar areas) into
Lemhi County in Idaho. A few of these storms could become strong,
with the main threat being gusty winds, brief heavy rain and of
course lightning. Thunderstorms are expected to generally come to
an end this evening. The rest of central Idaho and western Montana
is not expected to see much activity in terms of showers and
thunderstorms although breezy northwest winds are anticipated
through the early evening.

Areas that clear out tonight could see a rather chilly start
(low 30s) Wednesday morning, due to a dry airmass making its way
into the area. With regards to the low pressure system we`ve been
watching over the past couple days, forecast models continue to
dig this feature further south and west into northern California.
This more southern track is expected to shift the focus for
precipitation into southwest Montana and Lemhi County in Idaho for
late Wednesday through Thursday. These areas will see cooler
temperatures, precipitation and maybe even a brief period of snow
over high mountain passes such as Homestake and Lost Trail Pass.
There is potential that the track of this weather system will
continue to drag energy even further south with time, so we will
continue to monitor.

For locations in the rest of central Idaho (Clearwater and Idaho
Counties) and locations generally north of Interstate 90 in
western Montana: This system will likely result in little to no
precipitation through Thursday. Seasonable temperatures are
expected however there is potential for some gusty northeast to
east winds to develop during this time frame, which could cause
choppy conditions on area lakes.

Forecast models are showing a potential weak wave diving south out
of Canada on Friday, which could bring some increased shower
activity across the region. There is also the potential for gusty
north to east winds on Friday which may impact area lakes as well.
By the weekend, there is potential for a drier ridge pattern to
influence the region which could limit precipitation activity and
bring a warmer temperature trend.


.AVIATION...Showers and thunderstorms have developed this
afternoon, generally along and southeast of a line from KGTF to
K3DU to KSMN. The main threat with thunderstorms will be gusty and
erratic winds, lightning and brief heavy rain. KBTM and KSMN may
be briefly affected by these thunderstorms through 06/0300z. The
rest of western Montana and central Idaho can expect generally
breezy northwest winds, with gusts up to near 25kts possible.
Winds are expected to decrease after 06/0300z.



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