September weather, winter predictions discussed with SEFC Forecaster

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September's weather report is out from Castlegar's Southeast Fire Centre but no new temperature or precipitation records were set this time around.

Last month 95% of total rain fell during a three day period starting on the 23rd.

Weather Forecaster Jesse Ellis explains why that isn't uncommon for this time of year:

He says we’re entering a time of year where we see weather patterns called atmospheric rivers or, pineapple express, which are stalled streams of pacific moisture with a really long fetch meaning moisture above is relatively narrow and remaining stalled for an extended period of time.

The 4th saw the highest temperature at 34.2 degrees and the mean monthly temperature was 16.8 degrees compared to the average 14.7 degrees for September.

Ellis says some of the lower temperatures were caused by wildfire smoke-shading which as a result sees less rising air over our terrain and less up-slope and up-valley winds.

Overall smoke-shading sees lower temperatures, higher humidly and lower winds.


If you're already hearing that BC is in for a more severe winter than normal this year, Ellis says it isn’t necessarily that simple and even he doesn’t know what we’re in for.

He explains that there is one extremely influential factor for severe winter weather in the West Kootenays: Artic Outbreaks.

Our region is right on the borderline of these features so very small environmental changes impact the big picture.

Ellis says whether these extremely cold and intense air masses skirt east of The Rockies or on this side and impact BC’s interior and down into The Kootenays is a very small difference when looking at the larger global-scale pattern.

He says a particularly harsh and snowy winter can see maybe four or five Artic Outbreaks, while less severe seasons might only see one or two.

Ellis relates it to forecasting lightning patterns in the summer, adding you need to monitor a pattern 10, five and even three days in advance to see what outcomes it can support.

He says computers are getting better at long-range forecasts but these surface-based air masses are still difficult to pin down seven or 10 days in advance.