Understanding the NWS Winter Products

As some of you know, Winter Weather watches and warnings are issued differently than springtime severe weather alerts are issued. In the wintertime, all watches, warnings and advisories are issued by local National Weather Service offices. In the Spring, all watches are issued by the Storm Prediction Center, and warnings are issued by local NWS offices. Our local office is the National Weather Service in Louisville, and they cover all of the counties surrounding BG.

This is the homepage of the National Weather Service Office in Louisville.

Similarly to springtime products, there are certain criteria that must be met to issue a watch, warning or advisory in wintertime. There are many of these, their colors are all different, and different locations in the country have different criteria. This is a go-to post to use when trying to decipher NWS products this wintertime, and what preparations/actions you may want to make in light of them.

The Basics

Winter Storm Watch: The NWS in Louisville issues a Winter Storm Watch when:

The storm is 24-48 hours away; may be issued earlier if the storm is a high confidence storm
Medium confidence in significant snow (>4″ in 12 hours), ice (>.25″) or sleet accumulations are expected
Denoted by a dark blue color

A Winter Storm Watch basically indicates that there is a pretty decent chance that the area is gonna see a disruptive or significant winter storm within the next 2-3 day timespan. It does not guarantee a significant snow/sleet/freezing rain event. It does, however, provide initial warning.

That blue color is the Winter Storm Watch. h/t WOLC Blog

How to respond: This is largely dependent on the amount of wintry precipitation expected. Be prepared for school delays or closings, delayed time to work and messy road conditions. Take care of any additional grocery shopping needed before the night before the storm. Don’t wait. We all know how that ends.

Winter Storm Warning: The NWS in Louisville issues a Winter Storm Warning when:

Confidence is high that:
- Snowfall will exceed 4″ in 12 hours, and 6″ in 24 hours
- A combination of sleet, snow and freezing rain will cause dangerous travel conditions
- A combination of snow and sleet that averages ~4″ or more
The storm is 24 hours or less away

The warning is denoted by a pink color on the map. The warning just states that confidence is high that significant winter weather event will impact the region within 24-36 hours. It can be issued for strictly snow, sleet or a combination of snow, sleet and freezing rain.

How to respond: This is the final preparation stage. This is the final, “Hey, a significant storm is getting ready to hit” warning. You should anticipate school closures, at least some business closures, delays on the way to work and messy roads in general. Expect the stores to be out of milk and bread within 4-6 hours of a Winter Storm Warning being issued. Go during the Winter Storm Watch phase.

Winter Weather Advisory: The National Weather Service in Louisville issues a Winter Weather Advisory when:

Confidence is high that:
- Snowfall will accumulations will be 1″-4″ in 12 hours
- Sleet accumulations will be minimal
- A combination of snow/sleet/freezing rain accumulations will be less than 4″
The storm is 24-36 hours away

This is denoted by a light purple color on the map. The advisory is issued mainly as an alert to travelers. This is issued for wintry precip. accumulations that shouldn’t be significant, but they will likely be impactful. Confidence is usually high in this occurring, but it can be used in low confidence scenarios. These would include events that the precip type isn’t quite known, and snow may be hampered by that. If that issue is cleared up, and one of the precip types looks to dominate, then the advisory may be upgraded to a warning.

That color is the circle is the color for the winter weather advisory. h/t Lexington Herald Leader

How to respond: It depends on the scenario that unfolds. Travel times will likely be impacted negatively, but businesses aren’t likely to close. School will probably still be closed, because, you know, that is how that goes! Stores largely won’t be impacted, even though the outcome may be similar. If it starts snowing heavily, there may be a quick rush to the store. That would be an issue.

The Extras

Freezing Rain Advisory: The National Weather Service in Louisville issues a Freezing Rain Advisory when:

Confidence is high that:
- Freezing rain accumulations won’t exceed 0.25″ for a storm total
- Freezing drizzle is expected
The storm is 12-18 hours out

The advisory is denoted by some really, really weird color of pink that is different than the one for a Winter Storm Warning. A Freezing Rain advisory is fairly rare, but they’re issued and they have their place. They play the part of a Winter Weather Advisory, but only when the forecaster anticipates the event to be all freezing rain.

How to respond: Stay. Off. The. Roads. Just don’t do it. Stay late at the office, pick the kids up early, etc. Freezing rain is not something to mess with, especially when temperatures are in the 20s. Roads get slick really quickly, and accidents are more likely.

Ice Storm Warning: The National Weather Service in Louisville issues an Ice Storm Warning when:

Confidence is high that:
- Freezing rain accumulations will be greater than 0.25″ for a storm total
The storm is 24-36 hours out

The advisory is denoted by a much more discernible color of purple. It looks much scarier, and thus, is effective. Ice storms are bad. It is about as bad as it gets with winter weather. You do not want an ice storm, and luckily, they are rare and difficult to get. Confidence being placed at high is rather relative because it is a borderline thing a lot of the time. Unless significant snowfall is expected as well, if >0.25″ of ice is forecast, expect an ice storm warning.

How to respond: Avoid every bit of travel you can. For your own sake, avoid it. Roads become dangerous very quickly, especially if there is an initial round of snow or sleet to coat the roads. Get some salt at Home Depot or Lowes to make sure you can get your mail without breaking a bone in a fall. Additionally, be prepared for power outages. Ice is very heavy when it weighs on tree branches and powerlines. Once accumulation reaches 0.5″ of ice, power outages become likely.

Blizzard Warning: The National Weather Service in Louisville issues an Blizzard Warning when:

Confidence is high that:
- Snow will either be on the ground or falling with sustained winds of 35 mph or greater
- That blowing snow/falling snow must result in visibilities less that 1/4 mile for 3 hours or more
The storm is 24-30 hours out

This is the rarest of the Winter Weather products here in south-central Kentucky. In fact, the last time one was issued was back 2012 by the National Weather Service Louisville, and that didn’t even include south-central Kentucky!

The days since an individual NWS office has issued a Blizzard warning. h/t Iowa Mesonet

There is the potential that BG hasn’t even been in a Blizzard Warning ever. Who knows. Blizzard warnings are shown in red on the map, and stand out pretty well.

How to respond: Avoid all travel at all costs. Sincerely. This is second only to ice storms in terms of danger. The combination of cold air, heavy snowfall, low visibilities and strong winds can create life-threatening conditions for people who get stuck in the crosshairs. Getting groceries/supplies? The same rules apply here as they do a Winter Storm Warning/Watch. Don’t wait until the last minute to do so.