textproduct: Missoula

DISCUSSION

KEY MESSAGES:

- Scattered showers south of Highway 12 today.

- Significant closed low pressure moving through the region Wednesday through Friday bringing widespread snow and cooler temperatures.

The Northern Rockies will be under westerly flow today as temperatures warm to near seasonal averages. A plume of moisture will make its way up into north central Idaho, west central and southwest Montana by this afternoon causing showery conditions south of the mainly the Highway 12 corridor. The shower activity is expected to diminish after sunset this evening.

A significant low pressure system is still on track to impact the region Wednesday through Friday. The upper level flow will become southwesterly on Wednesday ahead of the system pushing in ample moisture causing widespread precipitation. Snow levels will rise to around 6000 feet during the onset of precipitation. Temperatures on Wednesday are expected to be around 5 degrees above normal for this time of year.

The cold front associated with the low pressure system is expected to move through the region on Thursday causing snow levels to lower to around 3000 feet by Thursday evening. The heaviest precipitation appears to be along the leading edge of the front Thursday morning. A TROWAL band of heavier precipitation appears to develop across northwest Montana by Thursday morning then this band shifts southward throughout the afternoon. As the low shifts eastward Thursday evening wrap around and upslope precipitation will be mainly focused along the Continental Divide. Then on Friday the upper level flow become northwesterly keeping snow showers lingering across the region. Most valley locations should anticipated experiencing snow by Thursday night, but accumulations will vary from a trace to several inches in the higher valley locations especially near the Continental Divide. The mountains are expected to receive a least a foot of new snow by Friday morning with some peaks getting up to 2 feet. The heavy, wet nature of the snow is likely to build up on trees, creating potential tree damage and power outages. Stay aware of forecast updates as we progress through the week. If you have plans to travel east over the Continental Divide later this week, plan ahead and make sure you pack supplies in the event you experience extensive delays over mountain passes.

The long term models are still showing a ridge of high pressure building over the region this weekend into the first part of next week causing a warming and drying trend.

AVIATION

Westerly flow will be over the region today. An increase in showers are expected today especially south of the Highway corridor mainly affecting KHRF, KBTM and KSMN. KMSO has a lower potential of being impacted by these showers. The shower activity is expected to diminish after sunset. These showers will caused lowered ceilings and the potential of reduced visibility under heavier precipitation.

MSO WATCHES/WARNINGS/ADVISORIES

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