ISSUED 05/04/2025 7:30 P.M. MDT/6:30 P.M. PDT

SHORT TERM (SUNDAY NIGHT THROUGH TUESDAY):

Weak shortwave that brought an abundance of cloud cover to the region on Sunday along with cooler temperatures lacked any instability, vertical motion or jet dynamics to produce any meaningful weather. The end result was simply an abundance of mid level cloudiness despite there being plenty of moisture around which again shows that moisture is not a primary ingredient to generate precipitation. Clouds will clear as the sun sets setting the stage for another chilly night with frost likely across most valleys in our region away from the larger lakes. Monday will see high temperatures return to a few degrees above early May averages and unfortunately the dry conditions as well but largely will be a fine and settled day. Upper level ridging will further establish itself as we move into Tuesday with a somewhat diffuse surface high sliding south just east of the Continental Divide. This may induce some light easterly winds but nothing noteworthy. Temperatures by Tuesday will once again be climbing almost 10 degrees above early May seasonal averages with a dry and stable atmosphere.

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY):

Upper level ridging will largely remain in place throughout much of this period although a weak shortwave will likely dent the ridge a touch on Thursday but other than a few clouds, slightly cooler but still above seasonal averages and perhaps an increase in west to southwesterly breezes not much can be expected from this feature. The ridge rapidly rebounds by Friday and Saturday with further amplification which will lead to some very warm temperatures, especially in our typically warmer Northwest Montana valleys where mid 80s are certainly possible for the first time this year! It is May however in the Northern Rockies and May is often one of the wetter months of the year so at some point this ridge is likely going to break down. Models are hinting that this may begin to occur by next Sunday so if you have plans for Mother’s Day it would be wise to pay attention to the forecast. For now have introduced “chance”wording across North Idaho for showers on Sunday and “slight chance” wording for Northwest Montana due to the uncertainty as to when the ridge axis will shift far enough east to allow for better lift and jet dynamics to help generate vertical motion and precipitation. Temperatures will likely cool a bit on Sunday but will still remain above seasonal averages for mid May. Looking out into fantasy land, which is never a good idea especially during the “swing seasons” of Spring and Autumn it does look like a more “May-like” pattern will return with cooler, unsettled conditions in the offing. Troughing in the Gulf of Alaska at this time of year is a fairly dominate force and the strengthening Continental ridge across the Desert Southwest helps to spin up a good jet across our region which tends to be in the battleground between the chilly upper level Gulf Low and the warm to hot upper level High to our south. Let’s hope the pattern does turn wetter and a bit cooler as we will be grateful for the unsettled conditions later on during the warmer and drier times of the year if they come to pass.

ISSUED 04/29/2025 9:05 P.M. MDT/8:05 P.M. PDT

SHORT TERM (TUESDAY NIGHT THROUGH THURSDAY):

Well as was anticipated our system on Tuesday brought the most significant rainfall and high elevation snows to North Idaho as well as Sanders County in Northwest Montana. Most locations in North Idaho saw between a half inch up to an inch of rainfall with a few inches of snow in the highest elevations. Bonner County saw the most precipitation in North Idaho with slower movement of the initial baroclinic band of steadier rain Tuesday morning followed by a couple of rounds of heavy showers and thunderstorms in the afternoon. Across Northwest Montana as expected most areas east of the Cabinet Mountains got shadowed out fairly well with the best rainfall amounts occurring with the late afternoon showers and thunderstorms that pushed in from North Idaho. Much of Sanders County was the big winner here with some rather heavy rains and frequent lightning continuing as of this writing on Tuesday evening. Much of Lincoln County did not see much in the way of rainfall at all at least east of the Cabinet Mountains thanks again to the shadowing effect of the mountains. Upper level ridging will build across the region overnight and persist for the rest of the workweek at least with rising heights and thickness values bringing a strong warming trend. While we will likely see some afternoon fair weather cumulus clouds each day the atmosphere will be stable so no showers or thunderstorms are anticipated. By Thursday a bit of a surface thermal trough will develop along the Continental Divide which should help create some better mixing in the afternoon to allow temperatures to climb more significantly with likely the warmest temperatures so far this Spring likely then. The warming will peak on Friday. Read below for more details.

LONG TERM (THURSDAY NIGHT THROUGH TUESDAY):

Friday will likely be the warmest day of 2025 across the entire region with many valley locations in Northwest Montana and perhaps parts of Boundary County in North Idaho seeing their first 80 degree reading of the year! This is a bit early but certainly not unheard of for our region. For those of you who are not ready for this summer-like warmth yet the good news is that by Saturday atmospheric heights and thickness values will begin to decline resulting in a lowering of temperatures as well and while still very warm and well above early May seasonal averages, will not be soaring into the 80s either. Still have doubts about the weekend weather pattern as the models are having some difficulty in resolving what the approaching upper level trough will do. Most models still want to split the system with the most significant piece of energy diving well south down into Central or Southern California with the northern branch fizzling out and limping through our region. Some models however are now showing some instability and lift with the weak northern branch passing through that would help trigger a few showers and possible thunder. Again as stated in the previous discussion this forecasters gut feeling is that the northern branch will largely weaken with mainly an increase in clouds and cooler temperatures with little in the way of precipitation but this could be wrong as well. Overall the weekend does not look like a washout at all and for the time being keep the outdoor plans in place. Better chances for perhaps more widespread wet weather returning to the Northern Rockies looks set to return sometime towards the middle to end of next week. May is often a much wetter month across our region than April and overall April was very dry so we will take the increased precipitation chances if they come to pass!

ISSUED 04/27/2025 7:40 P.M. MDT/6:40 P.M. PDT

SHORT TERM (SUNDAY NIGHT THROUGH TUESDAY):

Shortwave which helped to kick off Sunday afternoon and evenings showers and thunderstorms continues to swing out of the region taking the inverted surface trough with it as well. The inverted trough helped to increase low level surface convergence to create lift within the already unstable atmosphere to drive the showers and thunderstorms that did develop Sunday afternoon and evening. With the loss of daytime heating along with the eastward shift of the inverted trough and exiting shortwave the atmosphere will become stable overnight with showers quickly fading away. Models continue to hang on to some shallow instability on Monday afternoon mainly along the Coeur d’ Alene and Cabinet Mountains as well as the Whitefish Range so would not be surprised to see one or two light showers pop up in these areas although no thunderstorms are anticipated as the atmosphere will also be capped but a couple of light showers are certainly possible Monday afternoon over these mountain ranges. Further west the Selkirk Mountains in North Idaho will also see some buildups but subsidence ahead of the next incoming upper level trough will cap and likely prevent any showers from developing. Clouds will increase during the mid to late afternoon hours on Monday across North Idaho and into the evening hours across Northwest Montana as the next system begins to push inland. A steady band of mainly light to locally briefly moderate rain and high elevation snow will push across North Idaho and most of Northwest Montana Tuesday morning although across Northwest Montana many areas east of the Cabinet Mountains may actually get shadowed out pretty well but still could see some light amounts of rain and high elevation snow. The boundary producing the low level convergence will shift southeast out of the region by noon or so and will see another unstable atmosphere push into the region from the northwest with a redevelopment of scattered showers and isolated thunderstorms. This will likely be Northwest Montana’s best chance of receiving wetting rains greater than a tenth of an inch. Across North Idaho most locations will likely see between 0.15 and 0.50 inches of rainfall from this system although areas that see heavier afternoon showers and thunderstorms will see considerably more rainfall. Temperatures will be much cooler on Tuesday with the additional cloud cover and cooler atmosphere pushing in and high temperatures will be close to seasonal averages for late April or near 60 in the valleys. Snow levels will also lower down to near 5500 to 6000 feet so anticipated some light accumulations above around 6000 feet.

LONG TERM (TUESDAY NIGHT THROUGH SUNDAY):

Shortwave will quickly exit the region on Tuesday evening with strong positive height and thickness rises taking place as a robust early season upper level ridge will amplify across the region ahead of another deepening upper level trough in the Eastern Pacific. Yesterday it looked like this system may bring our region a decent shot of widespread beneficial precipitation but todays model runs are causing the system to dig southeast and take on a negative tilt again similar to the one that moved into California and Nevada the past couple of days. This in turn forces continued height and thickness rises across the Northern Rockies with warmer and drier conditions more likely now. Although the forecast for next weekend still has chances for showers and isolated thunderstorms along with cooler temperatures in it for now this forecasters gut feeling is that this next system will likely take a similar track as this weekends system did and would not be surprised if models trended warmer and drier for next weekend. These types of patterns typically repeat themselves unless a larger scale pattern shift takes place and early May is known for an overall weakness off the California coast which would tend to cause systems to dive southeast before lifting into our region from the southwest as they eject inland. The battle is becoming more intense during May as intense heating across the Desert Southwest promotes strengthening upper level ridging but the cold Eastern Pacific waters and weakening jet stream still allows for systems to drop into California where the greatest resistance to the ridge is located. We will see.