Forecasting winter weather is a challenge - especially in this part of the country. We rarely have one type of precipitation.
In a day and age in which technology advances at a rapid pace, so does the demand for instant gratification.
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When do you start looking at potential?
Because of what I just wrote above, we start looking at patterns a week or more in advance of a potential storm.
At the same time, however, it is important that we don’t promise specifics. So many things can change when dealing with storms that haven’t even materialized.
As time goes on, you can start to look for consistency in the forecast modeling before getting into specific details closer to a storm’s arrival.
How can you apply this approach now?
We're currently applying this to a storm that is projected for Friday. It's in the 4-5 day time frame, so we are still looking for consistencies while beginning to monitor where different types of precipitation can form.
This storm materializes from three different sources. It's like if it took three animals to give birth to one pup.
How and where these three pieces of energy interact will determine what we see locally.
A sooner arrival farther to the south would yield more wintry weather (not just snow) north of I-40 Friday morning, while a later arrival farther north would favor us with more of a chilly rain than anything.
How can you tell which is more likely?
Even at this range, we use something called "ensembles."
A forecast model is essentially a supercomputer that attempts to simulate behaviors in the atmosphere.
An ensemble refers to a group of these supercomputers, each of which has a different variation. This allows us to assign a probability to a certain weather event happening.
For instance, we can look at the odds of 1" of snow happening Friday in our area. Based off the most recent ensembles, the odds are 10-20% from the Triangle northward.
That's higher than the 0-5% that was previously shown Monday.
So no, we're not sounding the alarm and suggesting that you deplete the grocery stores of their milk and bread inventory.
However, it's a trend we'll watch for in the days ahead.
Have questions about the weather and how it works?
Send me an email with the subject line 'Ask the Meteorologist:' to cmichaels@jshu.net.