True to form for poorly organized systems undergoing a transition, the models did not come into solid agreement until it was too late. Right up til the end they did some swerving and swapping of positions on amounts and locations.
The 0Z GFS run yesterday showed 0.5-1 inch amounts, the 0Z NAM showed 0.5-2 inch amounts. However, that was output coming in after the event was underway.
Model performance based on the final primary cycle run PRIOR to the onset of the event, 12Z the morning data while the sun was still out, here's the run down estimates from the main models:
GFS 2.5, NAM 1, JMA 2.5, UK 2, ECMWF 1, Canadian 3
And the Cook Method using tropospheric warming, potential vorticity and net vertical displacement which I use as a short-term check against the models forecasted 4.5 inches with 12Z data and 4 with 00Z.
All in all not too shabby given how difficult it is to measure snowfall when melting occurs, since whats left on the ground can vary so much from what falls from the sky, and what falls from the clouds is all the science tries to figure out, since we're weather forecasters not road forecasters. The models did not suggest a max in the Athens areas but rather a min in that direction and I wrongly agreed. But for the Atlanta Metro the high and low amounts were fairly evenly distributed equally in all directions which is what I expected. Although for a while I thought there would be some preference toward areas NW, SW and South of the perimeter.
It's good performance regionally since the models did so poorly in states to our west like OK, AR, TX, (6-12 and isolated 24) MS (2-6 inches). Even in AL amounts were in the 1-5 inch range with most 2-4. The problem of course was the greater than normal (particularly in consecutive days and right up to the end) flip flopping. The models all stunk in this regard and in trying to properly place where the heaviest snow would fall.
When you see those huge amounts come in from a system to our west that is heading east it's hard not to panic and just extrapolate those numbers here. Trusting the science can be hard, but even the models are not supposed to be off by 6-12 inches. So sometimes you just forge ahead and hold your breath.
NWS official reports: (scroll down to bottom for a map)
Public Information Statement
NOUS42 KFFC 101622
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE PEACHTREE CITY GA
1120 AM EST THU FEB 10 2011
...SNOWFALL AMOUNTS ACROSS NORTH AND CENTRAL GEORGIA LAST NIGHT
AND THIS MORNING...
A FAST MOVING UPPER-LEVEL DISTURBANCE COMBINED WITH MODIFIED ARCTIC
AIR TO BRING SNOW TO MUCH OF NORTH AND CENTRAL GEORGIA FROM LAST
NIGHT THROUGH EARLY THIS MORNING. THE FOLLOWING IS A SUMMARY OF
AVERAGE SNOWFALL AMOUNTS ACROSS EACH COUNTY.
COUNTY SNOW AMOUNT REMARKS