UPDATED JAN 10 - 2:30P
Good Afternoon All!
So the NAM is trending the way the CMC was trending yesterday - warmer. Let's look at why the significant ice may not be as bad if the NAM solution is truth come Monday around 2AM.
This storm will still start out as ice/sleet for SE PA but will change to rain much faster than anticipated.
6AM Monday Morning:
If you recall, the most important factor in the type of precip would be dependent on the placement of the HP over the Upper MidWest. Well...look at where it is modeled to be....in North Dakota. That is too far north for the intense cold of that high to push our way. Again, the Northern Stream being modeled to be much slower than the Southern Stream.
Let's take a look at the winds at the 850mb level as well.
As I mentioned yesterday, because the HP is so far north, the winds are carring the warmer air up from the SW instead of the cold winds from the HP in the NW.
As always going to be the case, the temps at the 500mb level are quite warm which is why this was going to be an ice/sleet event in the first place:
All of this equals a start of sleet/ice but a quick change over to rain for SE PA. Anyone south of PA, will be rain the whole time.
NOW....this is all based on modeling. With how cold it has been with a +AO (its freaking cold outside today!!) and the way things have over performed lately, I am not so sold on the NAM solution right now. As some others have mentioned, it is very difficult to make decisions thus far this winter and with the crazy way the models are behaving. Things can certainly still change and there is still 36 hours before game time.
Hope y'all are having a great Saturday!
So all the models are on board for Monday. All are showing sleet/ice for SEPA and into SNJ. Where the strong HP over the plains ends up will largely determine what the precip type is for Monday AM and then into the afternoon and evening. We are at the point where we can start to consider the NAM as well.
The CMC has been showing the colder solution thus far but the 12Z GFS just came in a touch colder than the previous run.
AS an example of how different things can be based on the location of the HP in the upper MidWest, look at these two images from Hour 72 of the 12Z runs of the GFS and the CMC:
And then the CMC
Look at the direction of the winds and how in the GFS image you can see that the winds are delivering cold air from the HP and the winds in the CMC image are delivering warm air from the SouthWest. Look at the subtle difference in the location of the HP. We are talking a VERY subtle difference.