Comprehensive Guide To School Closing & Delay Outlooks

West Michigan Weather has been creating School Closing Outlooks since the 2021-2022 school year. We began releasing these publicly in 2023. This means we have 5+ years of experience.

Our goal is that outlooks are issued by 7:00 PM on any day we think there is a chance that schools might be closed or delayed the next morning. Community supporters get early access to these outlooks by 5:00 PM. 

Each outlook has a map that visually indicates the chance (in %) for each school district within each different risk area on the map to be closed, delayed, or otherwise impacted (buses on paved roads only, or early dismissal), and an accompanying written forecast discussion outlining the risk and associated forecast considerations. We STRONGLY recommend reviewing this discussion to fully understand the Outlook and all of its variables.

We also issue extended range outlooks for our community supporters for the “Day 2” and “Day 3” periods. 

Administrative Note: Our goal is never to advise, suggest, or otherwise influence the decision-making process for school administrators, except in the most simple of terms, of making those individuals aware of potential hazards, as we do with any kind of weather event for our entire follower base. No AI is used in the creation of these forecasts; they are 100% human-generated and reviewed content created by our team of in-house forecasters.

Outlook areas are determined based on a number of factors, including, but not limited to:

• Weather threats, or what we call the “Threat Intensity Index.”

• Overall forecast confidence.

• The tendency of a particular school district to close or remain open. 

• The geography of the district and the infrastructure that the district and any surrounding municipalities may have.

• Messaging, warnings/alerts, and forecasting from the National Weather Service.

• Careful review of all relevant computer weather model data.

We evaluate and consider a total of 6 different threat categories and their intensity to create what we call the “Threat Intensity Index.” The 6 threats are:

• Snow

• Ice

• Wind

• Hazardous Temperatures

• Reduced Visibility & Air Quality (fog, smoke, freezing fog)

• Severe Weather

The cumulative value of these threats creates the overall "Threat Intensity Index."

Each of the criteria for each individual hazard's threat assessment lists the maximum possible risk that can be assigned based on that criterion. Lower risk can be assigned in certain situations at the forecaster's discretion, but will not be exceeded. 

The first, and perhaps the most obvious threat, when we talk about snow days, is, of course, snow! The Snow Threat Assessment includes considerations for all of the following:

• • New snow accumulations.

    • <3 inches = Minuscule Risk

    • 2 to 4 inches = Limited Risk

    • 3 to 6 inches = Medium Risk

    • 5 to 8 inches = Elevated Risk

    • 7 to 12 inches = Likely Risk

    • >12 inches = Extreme Risk

  • The rate of new snow accumulation. (How much in 1 hour).

    • >1 inch/hour between midnight and 5:00 AM = Medium Risk

    • >2 inch/hour between 2:00 AM and 5:00 AM = Elevated Risk

    • >1 inch/hour between 9:00 PM and 5:00 AM = Likely Risk

    • >2 inch/hour 9:00 PM and 5:00 AM = Extreme Risk

  • Power outages as a result of accumulating heavy/wet snow on trees and power lines.

    • Very isolated = Minuscule Risk

    • Isolated = Limited Risk

    • Widely scattered = Medium Risk

    • Scattered = Elevated Risk

    • Widespread = Likely Risk

    • Numerous = Extreme Risk

  • Post-storm roadway conditions, especially secondary roadways.

    • Isolated rural hazardous roadways = Buses On Paved Roads Only

    • Isolated secondary road issues = Minuscule Risk

    • Isolated primary road issues = Medium Risk

    • Scattered primary road issues = Elevated Risk

    • Widespread primary road issues = Likely Risk

    • Widespread impossible travel = Extreme Risk

  • Forecast afternoon weather conditions.

    • Isolated rural hazardous roadways = Minuscule Risk (early dismissals)

    • Isolated hazardous roadways = Limited Risk (early dismissals)

    • Scattered hazardous roadways = Medium Risk (early dismissals or closings)

    • Scattered dangerous roadways = Elevated Risk (early dismissals or closings)

    • Widespread dangerous roadways = Likely Risk (early dismissals or closings)

    • Widespread life-threatening travel = Extreme Risk (early dismissals or closings)

Ice must also be considered when we evaluate the threats to school closings and delays. Of the 6 threats, there are 2 that typically have the highest likelihood of causing delays and closings, and ice is definitely one of the two. The Ice Threat Assessment includes considerations for all of the following:

• New freezing rain, sleet, and freezing drizzle, and the resulting flat and radial ice accretion.

  • <0.10 inches = Limited Risk

  • 0.10 to 0.20 inches = Medium Risk

  • 0.20 to 0.30 inches = Elevated Risk

  • 0.30 to 0.40 inches = Likely Risk

  • 0.40+ inches = Extreme Risk

• Black ice and post-storm roadway conditions, especially secondary roadways.

  • Isolated secondary road issues = Limited Risk

  • Isolated primary road issues = Medium Risk

  • Scattered primary road issues = Elevated Risk

  • Widespread primary road issues = Likely Risk

  • Widespread impossible travel = Extreme Risk

• Power outages as a result of accreting ice on trees and power lines.

  • Very isolated = Limited Risk

  • Widely scattered = Medium Risk

  • Scattered = Elevated Risk

  • Widespread = Likely Risk

  • Numerous = Extreme Risk

• Flash-freeze events. (When stagnant melted snow/ice/slush or rain water freezes very quickly).

  • Minor rural flash freeze events = Limited Risk

  • Minor flash freeze events = Medium Risk

  • Moderate flash freeze events = Elevated Risk

We also evaluate wind when considering the risk for school closings and delays. Wind is typically one of our more minor concerns, at least at the lower end of this particular scale. The Wind Threat Assessment includes considerations for all of the following:

• Max wind gusts.

  • 40 MPH = Minuscule Risk

  • 45 MPH = Limited Risk

  • 55 MPH = Medium Risk

  • 65 MPH = Elevated Risk

  • >65 MPH = Likely Risk

• Drifting snow resulting in new or persisting snow drifts, especially over roadways.

  • 4 to 8 inch deep snow drifts = Minuscule Risk

  • 6 to 10 inch deep snow drifts = Limited Risk

  • 8 to 12 inch deep snow drifts = Medium Risk

  • 12 to 24 inch deep snow drifts = Elevated Risk

  • >24 inch deep snow drifts = Likely Risk

• Power outages caused by downed trees and power lines. 

  • Widely scattered = Minuscule Risk

  • Scattered = Medium risk

  • Widespread = Elevated Risk

  • Numerous = Likely Risk

• Blowing snow resulting in reduced visibility.

While arguably the simplest hazard to forecast, hazardous temperatures might be the most guaranteed way of seeing closings and delays, and we evaluate this very carefully as we create our Outlooks. The Hazardous Temperature Threat Assessment includes considerations for all of the following:

• When actual temperatures or heat indices are forecasted to be over 95°F.

  • 90°F to 95°F = Limited Risk

  • 95°F to 100°F = Medium Risk

  • 100°F to 105°F = Elevated Risk

  • 105°F to 110°F = Likely Risk

  • >110°F = Extreme Risk

• When actual temperatures or wind chills are forecasted to fall below -5°F.

  • -5°F to -10°F = Minuscule Risk

  • -10°F to -15°F = Limited Risk

  • -15°F to -20°F = Medium Risk

  • -20°F to -25°F = Elevated Risk

  • -25°F to -30°F = LIkely Risk

  • <-30°F = Extreme Risk

Reduced visibility also has the potential to cause school delays, and sometimes even closings, if we are talking about freezing fog potential. In extreme cases, smoke from regional wildfires can even result in reduced visibility and/or poor air quality. We evaluate all of these when creating Outlooks. Of the 6 threats, fog is often the number 1 cause of school delays each academic year. The Fog, Freezing Fog & Smoke Threat Assessment includes considerations for all of the following:

• Areal coverage and duration of fog or smoke. 

  • Scattered visibilities less than 1 mile = 10% Delays

• Areal coverage and duration of dense fog or smoke.

  • Isolated visibilities less than ¼ mile = 10% Delays

  • Scattered visibilities less than ¼ mile = 40% Delays

  • Widespread visibility less than ¼ mile persists after 9:00 AM = Minuscule Risk

• Ice accretion and reduced visibility caused by freezing fog. 

  • Isolated minor ice accretions and/or visibilities less than ¼ mile = 40% Delays

  • Scattered ice accretion and/or visibilities less than ¼ mile = Minuscule Risk

  • Widespread ice accretion and/or visibilities less than ¼ mile = Limited Risk

• Air quality reductions due to wildfire smoke. 

  • Air Quality Index values in the "Very Unhealthy" range = Limited Risk

  • Air Quality Index values in the "Hazardous" range = Elevated Risk

In rare cases, severe thunderstorm threats and the aftermath of those threats can cause schools to be closed, delayed, or dismiss students and staff early. Of the 6 threats, severe weather has the least amount of potential to cause closings and delays. The Severe Weather Threat Assessment includes considerations for all of the following:

• The NWS Storm Prediction Center Convective Outlooks

  • Level 3/5 "Enhanced" risk = Minuscule Risk

  • Level 4/5 "Moderate" risk = Limited Risk

  • Level 5/5 "High" risk = Likely Risk

• Post-storm power outage potential or existing power outages, and other severe storm-related damages.

  • Particularly isolated = Minuscule Risk

  • Isolated = Limited Risk

  • Scattered = Medium Risk

  • Widespread = Elevated Risk

  • Numerous = Likely Risk

The overall confidence that the team of forecasters here at West Michigan Weather has in any given weather event must be carefully considered when evaluating potential impacts to area school districts. We consider each of the following:

• Run-to-run consistency on models.

• Model vs. model agreement. 

• NWS forecast guidance.

• Our personal forecasting experience and beliefs. 

• The forecasted arrival time/start time of hazardous weather. 

• General ability to reliably forecast the specific event (e.g. fog or LE snow)

Higher overall confidence can maintain or sometimes increase the overall risk level. Lower overall confidence decreases the overall risk level.

The combination of the "Threat Intensity Index" and Forecast Confidence results in the overall risk level. There are 8 different risk levels.

1. >10% Delays (Green)

2. >40% Delays (Yellow)

3. Minuscule Risk (Cyan)

4. Limited Risk (Light Blue)

5. Medium Risk (Dark Blue)

6. Elevated Risk (Purple)

7. Likely Risk (Pink/Rose)

8. Extreme Risk (Magenta/Red)

All closure risk levels have other inherent risks. Any noted closing risk also means:

• At least a 40% chance for buses to run on “paved roads only” if they do not close. 

• At least a 40% chance for schools to be delayed if they do not close.

For this reason, we will never delineate delay risk levels on an outlook map that has a closing risk level.

In some rare cases, we may use closure risk levels to denote the chance for schools to dismiss students/staff early when threatening weather may hold off until later in the school day.