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The ETA model continues to show colder and drier weather for us, keeping the precipitation in the Gulf. That means cold and cloudy conditions Friday with maybe a flake or two of snow if you look hard enough. Nothing big at all. I continue to lean toward this solution because it's more likely historically and makes more sense.
The GFS is a different story. The 12Z run has INCREASED the amount of precipitation over us for Friday compared with the 00Z (6pm Tuesday) and 06Z (Midnight Wednesday) run. Also, atmospheric temperature profiles continue to support frozen precipitation for much of the area, and for many of us, this would mean snow.
On the GFS, it all starts Friday morning after 6am with some light precipitation area wide. This would probably mean flurries for the northshore and city, transitioning to sleet pellets and rain for areas south of the city. Temperatures may actually fall even more as the precip starts due to evaporative cooling.
The highest QPF (Quantified Precipitation Forecast) values on the GFS are occurring south of the lake as the day goes on and this is where most of the wintry precip would fall. The GFS is suggesting conditions cold enough aloft for snow north of a line from Houma to Lafitte to Delacroix. QPF values on the GFS model are significant enough to suggest that it could possibly stick from that line north to the city. The entire mess then transitions to all very light snow for the southshore by midnight Saturday with no precip being shown on the northshore. By Christmas morning, it's gone, and it's darn cold.
So, we have two models showing two different things. What's a meteorologist to do? Well, split the difference of course.
Right now our forecast is still calling for a chance of mixed precip for Friday and Friday night. I have the probability at 40%…higher than the 26% the ETA is showing and lower than the 68% chance the GFS is showing. OK, I am not exactly splitting it because I have a bias toward the ETA verifying. Note however, these numbers are much higher than the 20% the NWS in Slidell is putting on precip chances. They must be thinking the same thing.
The big problem here isn't so much the cold right now. It appears that will be sufficient for snow for most of us. The problem is, can we get any moisture to ride over the cold air? That will depend on the strength and track of the surface low. And I still question whether or not the surface low will even develop.
Don't expect our forecast to change much today, but I may decide to make some major changes tomorrow morning if I see fit. Time will tell. In the meantime, snow lovers keep your fingers crossed. I still think it's a long shot, but at least there's a shot. That's more than we can say most winters.
Now, onto the severe weather. We have seen heavy rains over coastal areas today with lighter rains over the city. I suspect most of the afternoon will be dry until late when a line of rain and storms moves through. This line of storms is now forming east of a Houston to west of Alexandria line. Expect this to arrive just in time for the evening rush hour. We will have a slight risk of severe weather with the main threat being strong winds and hail. There's also a chance of some brief street flooding, but nothing widespread. David will be here this afternoon and will have more on all of this.
Time for me to get ready for the noon broadcast.
John
John Gumm
Meteorologist
WWL-TV
1024 North Rampart Street
New Orleans, LA 70116
