The posts in this forum are NOT official forecast and should not be used as such. They are just the opinion of the poster and may or may not be backed by sound meteorological data. They are NOT endorsed by any professional institution or 
Let's take a look at what's happening. I'll look at Dallas, as that that seems to be where the battleground is. As you may remember, my main concern 3-4 days ago was that the GFS was predicting too much available moisture so far north (0.90"). As I said, typical West Gulf lows produce heaviest precip over coastal counties, not 200+ miles inland. Sure enough, the GFS dropped the prediction of such heavy precip in Dallas and now predicts a more reasonable 0.2 to 0.3". The NAM is in line with this precip prediction, by the way.
Over the past weekend, the models indicated that temps in the D-FW area would stabilize slightly below freezing at the surface, suggesting significant snow accumulations. However, recent runs (GFS & NAM) are forecasting surface temps 2-4 degrees warmer. Such temps would not be so conducive to accumulations, even if most of the precip falling is snow. Let's take a look at a current GFS sounding forecast for Dallas:
http://ready.arl.noaa.gov/readyout/1160 ... f_anim.gif
Note that the red line (temperature) is to the left of the freezing level (0 deg C diagonal line) the whole time, with the exception of a shallow layer of above-freezing temps right at the ground. It's very critical if the surface temp is 34 or 31. In past events, the models have tended to err on the warm side, so I think there's a good chance they're doing so again with this system. But that's no guarantee. It would just take a little more southward surge of the sub-freezing surface layer to put D-FW in an all snow and accumulating event.
Next comes the question of available moisture. I think the models may have a good handle on moisture. 0.2 to 0.4" of precip would suggest POSSIBLE snow accumulations up to 2-3 inches. That's if it's all snow and if surface temps are colder than forecast. At least one big "if" there.
Let's take a look at the latest meteograms. First the GFS:
Now the NAM:
There was some talk of dewpoints so low that surface temps may fall well below what was currently forecast by the D-FW NWS office. But dewpoints aren't that low. Once the precip starts, the dewpoints will rise quickly to the lower 30s.
So for the D-FW area to get 2-3" of snow, the surface temps will have to be a few degrees lower than forecast. This could happen if just a tad more cold air moves just a little farther south. It's going to be a close call. I suspect that the D-FW office isn't too far off with their forecast. Snow mixed with rain at times. Surface temps just a degree or two too warm to prevent accumulations on paved surfaces. Could see an inch or two accumulation on grassy and/or elevated surfaces. But it's a really close call and a hard one to make.
the 12z now will be VERY interesting... however will it be on shore when the nam comes out? i havent looked at the latest sat but i do know the nam should be out in just a little bit...
