Last week turned cold towards the end and this week gets considerably colder with the next clipper system dropping out of Canada and through the Great Lakes BUT modelling suggests an even colder air mass drops south towards the end of the month and that may bring some of the coldest temperatures in at least 20 years to some parts of the US.

First of all let’s take a look at this week and what we can expect.

The below GFS charts while showing cold NW winds blowing over the Great Lakes and producing downwind lake-effect snowfall, we also have a clipper-like system riding the southeast-bound trough and this is projected by the model to bring a swath of snow from North Dakota potentially all the way to the mountains of West Virginia

Here’s the 30 hr multi chart off the GFS.

Note the system riding the 0 line and diving out of the Dakotas en-route to the OH-TN valley.

By Tuesday the system intensifies and likely enhancing snowfall across Iowa and west-central Illinois as night falls along with the temperature.

By Friday the system is spreading precip, likely in the form sleet or wet snow across much of the Ohio Valley into the Appalachians. We could see 1-3 inches over the mountains of Pennsylvania, western Virginia, Maryland and West Virginia out of this.

Here’s the GFS snow chart by 48 hours and it shows a decent little swath from Alberta into the Ohio Valley. Notice the higher amounts over the same area the model increases the precip rate.

By 96 hours it takes the accumulating snow into the Appalachians. It looks overdone over the interior Northeast but that doesn’t mean we cannot get perhaps 6-12 inches locally in favoured spots downwind of the lakes.

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The cold air really intensifies once the system clears as does the skies and winds fall light with the first real cold high dropping into the Tennessee Valley.

Check out these projected lows according to the GFS Friday morning. It wouldn’t surprise me if we see low 20s in the North Carolina, Tennessee, even North Georgia Mountains, 30-32 in Atlanta while 20s reach northern Alabama with a hard freeze.

As mentioned in recent posts, the recurve of Wipha last week is part of the reason for the late week deep trough over the eastern side of North America. We of course are watching closely, powerful Typhoon Francisco which is poised to hit Japan in coming days. That system also recurves and will be part responsible for dropping another, potentially STRONGER/COLDER trough into eastern Canada and the US later next week.

Here’s the track from the JTWC

The trough which drops down over the Lower 48 appears to start off further west than this week’s but it’s stronger and could support some of the coldest late October temperatures in 10 to 20 years.

Check out the 204 hour surface chart off the GFS.

Note the unusually cold high which dives down the Plains on the backside of a storm system with the 522 line reaching the ON-MN border, 528 line drops into Nebraska while the 534 line gets all the way top the CO-NM line.

Check out the GFS 850mb temps by 204 hrs.

As a result, here’s the 8-14 day CPC temperatures which are now colder.

In other words next week looks to support a stronger, colder, further south but further west trough in response to the recurve of typhoon Francisco.

As for further down the road. Be sure to read yesterday’s USA Pre-Winter Forecast Briefing..

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Tags: October cold, US October arctic outbreak