MISSOULA — The warmer weather weather is on the way, but what a cold weekend and start to the work week we've had!
After record-breaking snowfall amounts this weekend, we switched to record cold temperatures.
We knew this weekend’s temps would most likely break records, but we didn’t expect that one spot, Potomac, would be the COLDEST spot for Sunday morning in the lower 48 AND the coldest place in the lower 48 this early in the season with temps registering at -29°F.
So why did things cool down so much more than we expected?
Well the first reason was that we already had the arctic air mass over us. That obviously kept things cooler than average to set a base of colder temps in our area this weekend.
But we also had clear skies.
Any typical day of the year (meaning warm or cold front-free, etc) , a cloudless night will be cooler than a cloudy night.
Clouds act like a blanket to our upper atmosphere and the incoming solar radiation we’ve receive or absorb during the day turns to outgoing solar radiation at night. When clouds are learnt this outgoing radiation is prevented from escaping.
So as we were Arctic AND cloud-free skies were above, things were going to get cold anyway.
Now, what we also have to factor in (which isn’t something we typically factor in this time of year is a large blanket of snow on the ground).
Snow is highly reflective. This is called albedo. Since snow has a high albedo, the incoming solar radiation wasn’t absorbed as effectively because the snow reflected it before absorption could begin.
On top of this, sunshine does help melt a little snow even when temperatures are below freezing. Melting is a cooling process.
We had very cold daytime lows because of these factors.
At night snow is also effective at admitting what little radiation was absorbed.
Dry was also a big part of this post-winter storm.
Dry air and calm conditions also helps the process of sublimation at night (solid to gas). This is also a cooling process which cools the surrounding atmosphere even more.
The combination of these factors are what causes such low nighttime temperatures this weekend!
Temperatures will slowly warm through the week.
Highs Tuesday return to the mid to upper 30s.
Highs Wednesday through Friday warm to the mid to upper 40s.
The 50s return by the weekend.
The average temperatures this time of year are in the low 50s for valleys.
By the end of this upcoming weekend, we could finally see temperatures return to above-average, and highs look to jump to the upper 50s and low 60s!