This will cause the hot upper level ridge that has been centered further north along the British Columbia/Alberta border to be forced further south and sandwiched between the two on Wednesday and stretch along an east/west axis centered almost directly overhead. LONG TERM (TUESDAY NIGHT THROUGH SUNDAY):Ī very warm to hot airmass will develop across the region by late Tuesday into Wednesday as an upper level low that has been spinning off the British Columbia coastline shifts east while a new developing upper level low draws closer to Central/Southern California. This will become more of a factor in the extended forecast period across our region. At upper levels the main upper level ridge and positive height anomalies will remain anchored along the British Columbia/Alberta border with corresponding negative height anomalies remaining anchored across Central to Southern California, Nevada and Arizona. Temperatures will remain well above average and 10 to 15 degrees above early June seasonal averages which are in the upper 60s to mid 70s across valley locations with the warmer averages found across our Northwest Montana valleys. Winds will remain southwesterly on Monday afternoon feeding into the thermal low in Alberta but by Tuesday winds will shift and become light northeasterly as the thermal trough axis sets up along the Cascades of Washington and Oregon and a surface high slides down the east side of the Great Divide. One thermal or surface low will develop and slowly migrate further north and east into Alberta between Calgary and Edmonton while the main thermal trough axis will shift further south on Monday before reorganizing and shifting further west on Tuesday. A more stable airmass will be in place overnight into the day on Monday and Tuesday as the thermal trough looks to split and shift its location. This is exactly the same locations where we have seen showers and thunderstorms pop up Sunday afternoon. The axis of said thermal trough as of this writing on Sunday evening stretches from east of Waterton Lakes National Park in Alberta, southward to the eastern side of Flathead Lake then bends southwest towards I-90 and Lookout Pass and remains along the Idaho/Montana border further south.

At the surface the thermal trough has placed a role in helping to provide enough surface convergence and low level lift to aid in the development of isolated to widely scattered showers and thunderstorms over the past few days. The simple process of lift, vertical motion, instability and airmass modification is what is keeping the “moisture” in place and without any significant push from strong shortwave disturbances or frontal boundaries crossing the “moisture” will remain in place and fluctuate from day to day depending on any shortwaves that can increase instability and vertical motion through the atmospheric column thereby causing saturation and clouds and showers or thunderstorms to develop.

Contrary to what many “metoerologists are stating this moisture IS NOT being drawn northward from the Gulf of Mexico nor is it being “drawn up” from anywhere. Overall very warm and dry conditions have largely prevailed across North Idaho and Northwest Montana for the past week or so with only isolated showers and thunderstorms popping up across eastern reaches of Lincoln and Sanders County each afternoon due to the presence of the thermal trough anchored in that area along with shortwave disturbances rotating around an upper level low that is currently spinning north of the Great Salt Lake in Northern Utah. SHORT TERM (SUNDAY NIGHT THROUGH TUESDAY): In-Depth Weather Discussion for Northwest Montana/North Idaho/Northern Rockies

Mt spokane weather forecast