FXUS65 KMSO 260940

Area Forecast Discussion
National Weather Service Missoula MT
340 AM MDT Mon Jun 26 2017

One more day of very warm temperatures is forecast for today as
the high pressure ridge axis shifts eastward and breaks down into
an active southwest flow. Abundant mid-level moisture will enter
the Northern Rockies late this afternoon/evening, allowing
widespread showers and thunderstorms to develop across north-
central Idaho and western Montana. Low-levels today will begin
with large dewpoint depressions, resulting in the threat of strong
gusty winds in addition to frequent lightning as thunderstorms
initiate. However, as low-levels begin to moisten throughout the
evening, bursts of heavy rainfall, hail, gusty winds, and
lightning will become concerns across the area. Some of these
thunderstorms could become severe due to winds and hail, so
weather awareness and designated shelters are encouraged
this evening.

Overnight and into Tuesday morning, showers and thunderstorms will
shift toward central Idaho and southwest Montana. Current hi-res
models are signaling a boundary to remain over Lemhi County and
southwest Montana throughout Tuesday afternoon. As the pattern
transitions into a more west-northwesterly flow aloft, winds will
become breezier and temperatures will be noticeably cooler for
Tuesday compared to Monday.

Seasonable temperatures and breezy winds under northwest flow
will persist Wednesday into the early weekend. Shower activity
will be common each day, especially over northwest Montana and the
Continental Divide. A brief drier and warm pattern may be
possible over the weekend into early next week.


Hot daytime temperatures are expected with high density altitude
concerns possible for the Northern Rockies. Increasing mid to high
level clouds are expected today as the upper level flow shifts
southwesterly, and widespread showers and thunderstorms will begin
to develop after 27/0000Z. Initial activity will bring strong,
erratic gusty winds, hail, and frequent lightning, which could
impact KSMN and KMSO after 27/0300Z. As low levels moisten tonight,
thunderstorms will bring additional threats of heavy rainfall
bursts and hail. KGPI and KBTM could see VCTS after 27/0600Z,
though forecast confidence is less certain for these sites.



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