textproduct: Missoula

DISCUSSION

KEY MESSAGES:

-Slow warming trend with lingering showers, especially during the afternoon and evening.

Northwesterly flow will persist over the Northern Rockies through mid-week. This flow pattern is conducive to shower activity especially during the afternoon and early evening hours. The instability during the afternoon could be efficient enough to support isolated thunderstorms. A few very subtle disturbances embedded in the flow will keep some showers lingering throughout the overnight hours, mainly across northwest Montana each night. Temperatures will be slowly warming each day, but night-time lows will be still dropping around freezing in most valley locations. The exception being the deep valleys of Idaho and Clearwater counties, where temperatures should be in the upper 30s to low 40s at night. This slow warming trend will cause snow levels to slowly rise over the next couple of days. Snow impacts are expected to be fairly localized mainly impacting the mountain passes at times along the Continental Divide and occurring during the overnight into early morning hours.

A ridge of high pressure slides over the region by Thursday causing a warming and drying trend for the Northern Rockies. Temperatures are expected to climb above seasonal averages by Thursday. A weak disturbance on Friday is expected to slide along the Canadian border causing increased clouds and a few light showers, but temperatures are expected to remain above normal.

The consensus of the long term models have a low pressure system sliding southward along the west coast this weekend then move into the Great Basin area by the first part of next week. The exact path of this transition is still uncertain, but the majority (75%) have the system having a relatively minimal impact to the Northern Rockies other than increased shower activity.Temperatures appear to remain warm for this time of year keeping high snow levels.

AVIATION

Northwesterly flow will persist over the region for the next 24 to 48 hours. Shower activity will increase this afternoon into early evening. The majority of the shower activity will be mainly confined to the higher terrain, but all terminals have the potential of vicinity showers throughout the period. A weak disturbance is expected to move through northwest this evening into the overnight hours which has the potential to cause some showers to pass over KGPI. The precipitation type associated with these showers appear to be snow, which will cause a reduction in ceilings and visibility for a period of time.

MSO WATCHES/WARNINGS/ADVISORIES

MT...None. ID...None.