#8 Postby David » Tue Dec 09, 2003 4:31 pm
Here's the responce to my email...
Hi, David! Thanks for the note and inquiry. Actually, the information process starts with a watch with is a longer term (24-60 hours) heads up/outlook that winter weather is possible over a wide area. After a watch, then the next product could be a warning, advisory or nothing, depending on what is expected. The watch is based on projected info from computer models that are run every 6 to 12 hours. They almost always show different scenarios as to what "may" happen, when and where. Forecasters at each NWS office review the models, know the biases, have discussions among offices and in offices, and then come to decision as to what may be the best approach at the time. Naturally, with as more info becomes available and as the storm begins to take shape, more definition and details can be firmed up. Also, model and forecaster biases can be smoothed out. We have certain national/regional criteria we must also work with with regard to some amounts etc. A winter weather advisory is snowfall under 6 inches, while a warning is over 6 inches in 8 hours.
In the case yesterday, a watch was issued for Shawnee county at 3AM for Tuesday and Tuesday night based on the potential threat of heavy snow, freezing rain and blowing/drifting snow. With later model runs during the day, the forecaster felt we would get more rain than snow, and that snow accumulations would be under 6 inches which is the minimum winter storm criteria. He also felt based on his experience and other indications that the other elements, freezing rain, blowing snow etc, would not be as significant, and thus a winter weather advisory would be the best approach. In contrast, the Wichita forecaster felt he would get more sleet and freezing rain that would justify a winter storm warning in his area...and at the same time, in the Kansas City area, the forecaster was not yet confident what would happen so far out, and wanted to keep a winter storm watch for the potential of severe winter weather.
Although it may appear things should be seamless, there is usually a sharp boundary and cutoff with winter storms and forecasters are trying to blend as best they can. Forecasts are also made for each county, and some counties are large with large variations in weather.
You may have watched channel 4 out of KC last evening and noticed "a doughnut" as the weathercaster referred to over northeast Kansas. This was a problem of his display as a winter weather advisory was posted for this area, and I am not sure why his display did not pick this up. I will check because it gave the impression something was missing.
I hope this answers your questions on winter weather. I would be most happy to have you visit the weather office for a tour, demonstration of our equipment and visit with some of the on duty forecasters. Just let me know and we will set up a time and date.
Thnaks again,
Mike Akulow
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