I try to identify a potential impacting storm sometime in the 7-10 day time period. I don't spend much time looking at model data and certainly not snowfall projections. I look at the 500mb chart indicating temperature patterns/fluctuations and storm track. The 500mb chart far out doesn't provide the detail that model data will as a storm system gets much closer.
I then alert you as to the potential. As we get to around 4-5 days out from a potential event, that is when I really start looking at model data. At around the day 3 time period, it becomes easier to start basing projections....start to nail down a time period.... much more is known at that point about available moisture....the details start to become more clear. Day 3 is when I am most likely to issue an early snowfall projection chart.
These charts often have a wide range of potential accumulation amounts (4"-8", 6"-12") covering a larger section of the state. At day 2, I can start to hone into specifics and narrow down the ranges some (at most, I like to give a 3" range). If confidence is high, I can issue a bullseye amount and potential area at this time. If confidence is average or lower, a bullseye amount won't likely come until the day before the event.
Snowfall projections:Snowfall projections are harder to nail than rainfall forecasts....and rainfall isn't particularly easy. With snowfall, you have a wide range between very wet snowfall and very dry snowfall. In a wet snow, liquid to snowfall ratios can run 6:1 or 8:1 - meaning 1" of liquid will produce 6 or 8 inches of snow. In a very dry snow, the ratio can be anywhere from 15 to 20:1 Again that would take that some 1" of liquid but instead produce 15 or 20 inches of snow. If projected ratios end up being a little off.... that will throw projections off as well.
Alberta Clippers are the most challenging to predict. Because these whip down from Canada....they don't have a lot of moisture, but they do bring down colder air. That can take a snow ratio very high. 0.25" moisture can dump 6" of snow.
Storm track is another key, critical piece. If a low pressure system tracks even 25-30 miles north or south of projection, that can turn a 4" prediction into 7" or sleet. Storms never travel in a straight line like what you see on TV. They do wobble. A little wobble is one thing - but anything over 25 miles can have a large impact on a forecast.
If you have a narrow temperature gradient, you can have a rain/mix/snow line over a single county. That makes for extreme frustration on my part! I do my absolute best to give you the most accurate information just as soon as I have confidence in an outcome. It does no good to give you information that changes every 12 or 24 hours. If you have a weather app and use it for other purposes besides current conditions, radar and satellite.....first, I recommend you stop doing that.....and second, this is why in the morning they throw out a potential of 6"-10" in the morning for 3-4 days into the future, then it changes to 2"-4" that afternoon.....then 4"-6" that evening. The apps take one single model run, without any human interaction, and call that a forecast.
Here is where you come in:
I post the most often and the most current updates on the Members Facebook Page. I post ALL bulletin information right there on that page. Check it often ahead of a winter storm. Check the Zone Forecast for your zone nightly.
Asking me for updates when a new update isn't necessary is pointless and takes my attention away from the important job of tracking storm potential for all our Paid Members. I WILL post anytime there is an update needed. When a question asked, it takes time away from me looking over data changes to answer the question, "could I see more snow than what you are showing?" I will answer that now. 90% of the time - you could see more, or you could see less than anybody's forecast is showing. (refer to all of the reasons why above).
A final thought:
There isn't a forecaster out there who enjoys seeing a forecast bust. With technology today, it is rare that by most people's standards a forecast truly "busts." I remember in my youth 35-40 years ago, going to bed expecting 6" of snow the next morning to wake up with nothing. I also remember the rare occasion that I woke up to a surprise 8" of snow when the snow never did change over to rain.
The most important thing I can wrap this up with.....always remember a snowfall projection is a RANGE. If your area is projected to see a 3"-6" snowfall, and you get 2.9" or 6.3" - that is a pretty accurate forecast. Every projection has a high end.....but it also has a low end. The same applies to rainfall projections.