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Live Blog (April 12-13, 2020)

NOTE: Entries are in reverse chronological order. This page does not automatically update.

  • 4/13/20 3:50 PM
    Winds continue drifting westward, shutting down lake-effect snow production. We’ve had no measurable snow since 12 PM. Humidity has dropped to around 65%. This should spell the end of our snow storm. I see that the National Weather Service has pulled down the Winter Storm Warning that was supposed to last through tomorrow morning. Gusty winds should subside over time, especially after sunset. But do mind the lakeshore flood warning and stay clear of Lake Superior as it takes some time to settle down after winds abate. Anyway, that ought to do it for our live blog. Again, our storm total was 17.2″ as measured 1 block north of the Jacobetti Veteran’s Home near downtown Marquette.
  • 4/13/20 2:45 PM
    Some light flakes continue to fly but nothing significant. The focus now is on the wind. Even as the trough of low pressure crosses into Quebec, it continues to deepen, drawing air from areas of higher pressure, such as Marquette, toward it. How big is this system? Well, it has 5 frontal boundaries extending from it, including 2 cold fronts stretching down into the Gulf of Mexico!
  • 4/13/20 1:15 PM
    After declining for about 4 hours, winds have kicked back up in the last hour as the surface low exits the region. Gusts nearing 35 mph have been observed here. Snowfall has tapered off to light snow showers as winds have turned solidly to the northwest.
  • 4/13/20 12:20 PM
    Light snowfall. Latest measurement (10 AM – 12 PM): 2.1″. Event total: 17.2″
  • 4/13/20 10:00 AM
    Moderate snowfall. Visibility 1/4 – 1/2 mile. Snowfall measurement (7 AM – 10 AM): 1.2″. Event total: 15.1″
  • 4/13/20 9:30 AM
    Some lake-enhanced snowfall could set up soon, lasting at least into the early afternoon hours. Conditions are somewhat marginal, so not expecting too much additional if the lake gets involved. Knock on wood because this is spring in the U.P. and Mother Nature likes to take a shot at us this time of year. Currently less than 1/4 mile visibility due to blowing snow.
  • 4/13/20 8:55 AM
    Looks like we’ve bottomed out in surface pressure. Our gauge recorded 998.7 mb (29.49″) MSLP at ~ 7 AM EDT. The center of the low is located near Sault Saint Marie. It should slowly march NE into Quebec this afternoon. We should be nearing the top of the mountain in terms of winds within the next hour or two (if we haven’t arrived already).
  • 4/13/20 8:25 AM
    Moderate snowfall continues. Visibility is generally 1/4 – 1/2 mile but localized blowing snow creates near whiteout conditions at times. Gusty northerly winds (30-35 mph gusts) continue to buffet the city.
  • 4/13/20 7:30 AM
    Winds continue to ramp up over the last several hours. The peak wind gust measured so far here is 34 mph but 40 mph does not seem not out of reach by later this morning. Fortunately, the moderate to strong winds throughout this storm have kept power lines free of snow.
  • 4/13/20 7:00 AM
    Moderate snowfall. 1/4 – 1/2 mile visibility. Snowfall measurement (9 PM – 7 AM): 8.2″. Event total: 13.9″
  • 4/12/20 9:00 PM
    Moderate snowfall. 1/4 – 1/2 mile visibility. Snowfall measurement (6 – 9 PM): 3.6″. Event total: 5.7″
  • 4/12/20 7:45 PM
    Heavy snowfall continues. Visibility between 1/8th – 1/4 mile. Next snowfall measurement at approximately 9 PM.
  • 4/12/20 6:05 PM
    Visibility has dropped to approximately 1/8 mile due to heavy snowfall. 2.1″ measured so far.
  • 4/12/20 5:30 PM
    Snow is beginning to stick to roadways too now. Visibility is just over 1/4 mile.
  • 4/12/20 4:05 PM
    Snow is beginning to stick to grassy areas around our property now. Cement is wet but free of snow.
  • 4/12/20 3:25 PM
    Initial snowfall this afternoon has been melting on contact due to the relatively warm ground, but temperatures have been falling over the past couple hours.
  • 4/12/20 9:00 AM
    Expect the snow to start flying by mid afternoon. Heaviest snowfall after 8 PM. Winds should stay light to moderate until daybreak Monday.  Winds will build after that point reaching a peak in the afternoon. Blizzard-like conditions are likely as it will be snowing all day Monday. As per usual, I will report periodic measurements & observations here throughout the event. Keep checking back.

Freezing Drizzle AND Snow?

You may wonder, “How can it snow & drizzle at the same time?”

Short answer: when clouds aren’t cold enough to produce snow (exclusively or at all) drizzle can form.

Longer answer: If the air is sufficiently cold and wet, only snowfall is possible. But when precipitating cloud top temperatures are above -10° C (14° F) but still below freezing, the ice nucleation process requires help. Unstable, rising air can induce the formation of snowfall. Failing that, with only slightly below freezing temperatures, snow crystallization needs smoke, dust, pollution or any other tiny airborne surface upon which to bond. Otherwise precipitation can fall as drizzle/mist.

Why today? We’ve had a shallow layer of moist, sub-freezing air (< 5,000 ft) “capped” by warmer, drier air above since Sunday evening (1/26/20). Cloud tops have been just below -10° C. The moist air from sublimating snow/ice and weak low pressure has combined with onshore, upslope winds to induce some lift in the lower atmosphere. This, along with whatever particulates were aloft, produced snowfall. The remaining moisture has fallen as drizzle which froze upon contact depending on the surface composition. Most surfaces weren’t cold enough to allow much, if any, ice accumulation. A light glaze has been observed in places around our property — just enough to increase stopping distances on untreated pavement.

Normally this time of year clouds are much colder. But we have been running well above normal throughout the atmosphere recently. That’s why we’ve had several wet snow events in December & January.

Revising Alert Policy

I normally don’t allow “Winter Weather Advisories” (WWA) to post on the City page (home page), because too often those end with unremarkable snow totals here. Also, people tune out after a certain point if they are constantly barraged with alerts, which can happen during the winter here.  When you see an alert posted on our main page, you can generally place confidence in its importance and relevance to the city.  Note that the detailed forecast will always specify accumulating precipitation within the next couple days regardless of alert status.

When I saw the Winter Weather Advisory hoisted on Friday (1/17/20), I decided to post it. I could see that just the front-end of the incoming storm was forecast to deliver 4-7″ in about 12 hours. I could also see that conditions were right for a decent amount of lake effect over the following 24 hours.  The $64,000 question, as always, was “how much?”

Continue reading “Revising Alert Policy”

Live Blog (January 18-20, 2020)

  • 1/20 08:00 AM:
    Skies are finally clear. The moon is up in the SE sky. Snowfall has ceased! Picked up an additional 0.2″ overnight to bring our final storm total to 11.3″.
  • 1/19 10:15 PM:
    The dry air that was supposed to enter the area by midday never happened. Instead, we’ve seen a steady stream of light, lake-effect snow. 0.4″ has fallen today and continues falling at this hour. This brings our storm total to 11.1″.
  • 1/19 2:50 PM:
    Light, intermittent snow showers continue coming in off Lake Superior, but, so far, it hasn’t been accumulating. The weekend storm total remains 10.7″ since Friday night (1/17). If you’re thinking of waiting until the holiday tomorrow to clear snow, that’s not a bad plan. Winds will be lighter, and the sun should come out.
  • 1/19 11:00 AM:
    Only a trace of additional snow since 7:30 AM. Snowfall is now intermittent with peaks of blue skies and sunshine. Looks like the storm is finally wrapping up.
  • 1/19 10:00 AM:
    Seeing some localized blowing snow. Gusts have been around 20 mph this morning.
  • 1/19 7:45 AM:
    2.4″ of fresh snow fell between 11:15 PM last night and 7:30 AM. Storm total is now up to 10.7″. Light to moderate snowfall continues this morning. Snow should end by noon but winds will remain brisk.
  • 1/18 11:30 PM:
    Another 1″ of snow has fallen in the last 3 hours bringing our storm total to 8.3″. Models show another 1″ mostly falling before daybreak. Wouldn’t be surprised if that turns into 2+” by 8 AM.
  • 1/18 8:20 PM:
    We picked up 1.3″ of additional snowfall from 2 PM to 8 PM. Event total so far: 7.3″. Meanwhile, lake-effect snow showers are underway and should intensify as the night wears on. I’ll take one more measurement before midnight.
  • 1/18 4:40 PM:
    Pressure is now rising. Winds directions are wobbling from north to northwest. Winds should stabilize to northerly eventually. There may be a bit of a lull for a few hours while lake-effect snowfall conditions optimize (faster winds, cooler temps, etc). Next snow measurement: 8 PM.
  • 1/18 2:15 PM:
    Additional 0.6″ measured at 2:00 PM bringing storm total to 6.0″. Expecting pressure to bottom out in the next couple hours. Winds will turn to the north and increase in speed as lake-effect snow commences. Could see heavy snowfall again this evening and/or overnight.
  • 1/18 12:10 PM:
    Snuck outside at noon for a preliminary measurement following heavy snowfall. Recorded an additional 3.7″ since 8 AM. That brings the storm total to 5.4″.
  • 1/18 10:35 AM:
    A heavy band of snowfall has dropped visibility to 1/4 mile. Meanwhile, wind speeds have been trending down all morning. Expect a directional change this afternoon. That’s when Lake Superior starts to get involved.
  • 1/18 8:00 AM:
    1.7″ measured since snow started flying last night. It’s fairly lightweight & shouldn’t be too difficult to shovel. I’ll take another measurement at 2 PM.