Tricky forecast Saturday afternoon-Saturday night

As explained in multiple blogs over the past couple weeks the computer model guidance is all over the road short-term and long-range.

The Atlanta National Weather Service Office (NWS) puts it well in their discussion:

The air is not going to be very cold, in fact on the mild side in the 40s and not falling below 32. The issue is dry air in place at precipitation onset, and air cools when rain falls into dry air, and there looks to be at least a weak “wedge” (CAD-cold air damming) developing.

Because of this the RAIN could mix with or change over for a time to snow/sleet SOMETIME between 2pm and 8pm near and North of I-20 but especially North of the top end perimeter. As things look now as I type this it looks like a nothing burger for most of us, some minor accumulation (for a brief time) possible IN SPOTS North of I-285 but mainly far North suburbs. (remember I don’t forecast for Rome, Athens or the mountains). No travel impact expected as of now for Metro Atlanta. All in all MORE RAIN THAN ANYTHING ELSE.

See the Low pressure system in the Gulf by early Saturday evening and the hint of the wedge in the surface pressure pattern of a Miller A-C type:

Multi model forecast surface pressure 7pm Saturday

APPROXIMATE rain/snow line forecast Saturday Black dashed line snow/sleet odds increase the farther north of line, more rain the farther south of line.

Forecast rain snow line dashed black line late Sat night R/S line forecast to move north with time

NAM MODEL SATURDAY PM:

NAM Model simulated radar Saturday PM Not all models show this

MULTI-MODEL BLEND PRECIP TYPE SIMULATED RADAR SATURDAY PM:

MUTLI MODEL PROBABILITY OF ACCUMULATION:

Multi model probability of significant accumulation

So at least for now, more rain than anything else for most of us and best chance for real snow/sleet accumulation is for the mountains.

Expect changes in forecast in future updates.

Follow me on Twitter @MellishMeterWSB.

Let me show you something I don’t remember ever seeing before in my 30+ years in Atlanta, two different forecast maps from the same NWS/NOAA but made by different people, shows the uncertainty: