Tale of two Octobers, anatomy of a snow shower ‘microclimate’

Talk about Jekyll and Hyde.

October has presented two completely different personalities to Minnesotans this year.  The first 12 days of the month greeted us with abundant sunshine a warm late summer hangover and temps that ran a good 10 to 15 degrees above average on several days.

The past 10 days? Not so much. Temps crashed on October 13th and have not cracked 60 degrees in the metro since then. I’m not a big fan of the overused ‘ugh’…so how about just plain ‘yuck’ to describe our rapid descent into November like weather in mid-October.

What ever happened to normal in Minnesota anyway? Here’s a look at how October has unfolded into two vastly different temperature regimes so far.

Image: Twin Cities NWS

Our November preview continues through tomorrow. We’re stuck in a pesky northwest air flow aloft, and life on the north side of the jet stream this time of year means persistent stratus, chilly northwest breezes and occasional snow and sleet showers. Here’s an hour by hour look at fairly flatline temps and generally gray weather through Thursday.

Image: Weatherspark

Moderation Friday

Those of us in search of milder weather may enjoy Friday. A southwest breeze will blow in some milder air,and we should see more sunshine. Here’s a look at temps and weather as we head into the all important weekend.

Image: Weatherspark

Long range forecast: Mostly cooler than average?

Looking ahead the next 14 days, all signs point to continued below average temps for most for the next 2 weeks. Here’s the GFS 16-day temp outlook as we head into early November. No 60s in sight.

Image: NOAA via IPS Meteostar

NOAA’s Climate Prediction Center agrees and keeps a cooler than average temperature bull’s eye over the central US.

Image: NOAA CPC

The overall jet stream pattern favors cooler than average temps into early November.

Sleet on fading hostas near Brainerd Tuesday. Image: Paul Huttner/MPR News

Anatomy of a sleet shower microclimate

The chilly northwest flow has brought us our share of renegade, often localized snow and sleet showers this week. It’s been a great study in microclimates driving through the highly localized snow and sleet bursts this week.

Image: Paul Huttner/MPRNews

Driving near Brainerd and St. Cloud Tuesday, I observed rapid temperature differences as my car thermometer dipped from 41 degrees  to 34 degrees under a raging snow/sleet shower in under a mile.

The chilly air under these sleet bursts is the result of downdrafts that pull down cooler air from hundreds or thousands of feet aloft as the sheer weight of the descending sleet/snow yanks colder air down to the surface as it falls.

Here’s a general look at how the circulation in rain/hail/sleet shafts can drag downdrafts and locally coder air to the surface from NOAA.

Image: NOAA

The result can be rapid temperature fluctuations as the showers move through.

These small sleet bursts give new meaning to the phrase “all weather is local.”