October Preview: Frost & freeze tonight; Growing signs of early snowfall this fall?

Freeze warnings out for much of northern & central Minnesota tonight

20s in International Falls, Ely, Brainerd Duluth & Hibbing

Frost likely even in metro suburbs Tuesday morning

39 at MSP Airport Tuesday morning?

Source: Twin Cities NWS

Kinder & gentler: Much milder next week

Scattered snow showers possible in northern & central Minnesota tonight & Tuesday

Growing fall snow indicators for Minnesota this year?

Source: Twin Cities NWS

The real deal:

Enough for beach & summer babble this week.

The season's strongest cold front delivers the first frost & freeze for many Minnesota & Wisconsin locations tonight.

With Monday morning temps already in the 30s in northern Minnesota, this air mass is plenty cold enough to deliver sub-freezing temps for several hours up north tonight.

Source: Duluth NWS

Frost in the metro suburbs?

I'd bank on it in the north & east metro suburbs tonight...and even south & west of the metro by Tuesday morning. The inner core of the metro (inside the I-494/694 ring) will likely escape frost tonight...but even MSP Airport could dip to near 39 by around 7 am Tuesday.

Source: NOAA

Kinder & gentler by midweek:

The weather will mellow over Minnesota by Wednesday as highs return to the 60s statewide, with a stray 70 not out of the question.

The milder spell will be short...as a second punch of colder air sags south Friday into the weekend.

There will likely be another frost/freeze and high may not climb out of the 50s Friday & Saturday.

At this point, it looks like we may get an extended spell of mild sunny weather next week. The 70s could return.

Growing indicators of possible early season snowfall in Minnesota this year?

Say what?

Yes, we're transitioning into an "El Nino" phase this winter...and the odds overall favor another milder than average winter in Minnesota.

That said there are some growing indications that early snowfall is a possibility for parts of Minnesota this fall.

1) "High Amplitude" Jet Stream pattern:

After taking a long summer vacation in northern Canada, the jet stream has returns to Minnesota. Today's cold front is the result of a large dip or "trough" in the "polar front" jet stream.

Large north to south undulations in the jet stream have evolved lately over the northern hemisphere. This "high amplitude" pattern looks to become "progressive" ...meaning it will deliver shots of cold air south into Minnesota like this week...followed by much warmer spells like the one I'm seeing for next week.

Source: NOAA/NCEP

If the cold (sub-freezing) air dips in the jet "phase" with moisture at times this fall...we could see an early shot of accumulating snow in parts of Minnesota.

2) Hudson Bay Vortex: Setting the table?

This week's upper air pattern...and family of cool fronts is brought to you by the "Hudson Bay Vortex."

Source: NOAA/NCEP

This swirling pool of unseasonably cold air is dealing cold shots south into Minnesota this week.

If the Hudson Bay Low becomes a frequent feature this fall...it may keep enough cold air coming south to change potential rain systems to snowy "Clippers" in parts of Minnesota.

3) Above average early Siberian snow cover:

One emerging and "sexy" predictor in forecasting winter weather in the USA is tracking early snow cover in Siberia.

Source: NOAA

Above average fall snow cover in Siberia can be an indicator of colder than average weather in the USA.

Last fall snow cover ran below climatology in Siberia. Today, snow cover is running above climatology in Siberia and northwest Canada's Yukon Territory.

Source: Riugers Global Snow Lab

This has the potential to chill air masses, and shift the jet stream to deliver colder air into the USA at times this fall.

4) El Nino transition:

The backdrop of the developing El Nino this winter suggest milder weather overall. But as we transition into El Nino this year...it's worth remembering that 1991 was also a developing El Nino year.

Source: NOAA/CPC

I'm not saying we're going to see another early season blizzard like the infamous "Halloween Mega-Storm"...but it's worth noting that big snows have happened in a developing El Nino year.

As we say in the weather biz....stay tuned!

PH