Areal Flood Warning 4, NWS Missoula, MT

Area Forecast Discussion
National Weather Service Missoula MT
337 AM MDT Wed May 31 2017

.DISCUSSION...Another very warm day will occur over the Northern
Rockies today but changes are coming as the recent high pressure
shifts east and is replaced by southwesterly flow. An embedded
disturbance in this flow will set off scattered showers and
thunderstorms during the afternoon and evening hours. Conditions
are favorable for a few strong thunderstorms capable of damaging
winds and hail by late in the afternoon. Areas of showers and
isolated thunderstorms will continue tonight through Thursday
with a cold front passage. Noticeably cooler temperatures will
occur on Thursday behind the cold front with highs nearly 20
degrees cooler compared to Wednesday for west central Montana.
Cool and unsettled weather will continue on Friday.

Brief warm and dry conditions return by Saturday and daytime
temperatures will reach well above normal. This drier high
pressure will be short-lived, however. The upper level flow will
transition to southwesterly from an approaching low pressure
system, and moisture will feed into the area beginning Sunday
afternoon. Showers and thunderstorms will become more widespread
by Sunday evening into Monday, with a rapid temperature cool-down
by Monday. This closed low will stall over the northwestern U.S.,
keeping moisture over the Northern Rockies through at least
Tuesday. Emphasis of precipitation will be over western Montana
locations. This persistent shower pattern and increased snow melt
will promote concerns for rising river/stream levels through this
period.

&&

.AVIATION...High and mid level moisture will increase through the
day ahead of a disturbance that will initiate the ridge break
down. Scattered showers and thunderstorms are expected to develop
mid to late afternoon and push northward across the region. All
terminal sites stand a chance of thunderstorms but KMSO and KGPI
have the higher potential, generally after 31/2200z. Initially,
the lower levels of the atmosphere will be quite dry so showers
and storms will be capable of strong and gusty winds, along with
hail. Areas of showers and isolated thunderstorms will continue
tonight into Thursday ahead and along a cold front.

&&

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