Monday, January 24, 2011

Yet another possibility of winter weather Tuesday night

It seems like every time we peek into the forecast, another potential winter weather scenario is shaping up.  This seems to the be the case again as yet another Gulf Coast low affects the region on Tuesday and early Wednesday.  This was the same type of system that brought the snow on January 9-10, though no two systems are alike in every respect. (That's the fun part of Meteorology!)

This morning's computer models are agreeing on the big picture, but not on the details, which produces two vastly different outcomes, as evidenced by the forecast comparison between two models below.  The GFS model on the left, predicts 3" of snow for the Memphis area by Wednesday morning, while the NAM model on the right, keeps the 1" snow just to our east and south.  Both of these models predict the surface low to travel along the Gulf coastline  at about the same time, though the upper-level systems and degree and timing of cold air aren't quite the same between them, thus the differing forecasts.

Model comparison of potential snowfall totals Tuesday night
It's my job to sort out the differences, determine which model (or combination of them) makes the most sense, and issue the MWN forecast.  Though I still have a couple of hours to look over the data and make my final decision before this afternoon's forecast is issued, I'm leaning towards the GFS timing and cold air solution right now, but not the GFS precipitation amounts, which I think are overdone.

Check out the MWN forecast later this afternoon for my ultimate decision, but at this point I'm thinking a changeover from rain to snow (with a brief period of sleet possible during transition) occurs during the evening hours (6-9pm) Tuesday with about a six hour window of light snow and about an inch on the ground by the time it ends.  Temperatures Wednesday morning will be below freezing, so another snow day is not out of the question (yes, I hear you parents groaning...).  I expect the NWS could issue Winter Weather Advisories later thisd afternoon and certainly I'll be monitoring each model run between now and tomorrow, posting updates as warranted.
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1 comment:

Jason H said...

Go GFS. NAM is behind 2-1 on storms here. NAM may tie it up on this one.