“Surprise” Light Snow for Northern GA 1/15/15?

DISCLAIMER: The following is an unofficial forecast. Please refer to the NWS for any official statements regarding any potential frozen precipitation.

Good afternoon everyone.

Last week, I began closely monitoring a weak low pressure system for a chance at some frozen precipitation here in Northern Georgia. The longer-range models (GFS/EURO/CMC) all showed this threat to begin with then backed off. However, over the past couple days both the Euro and NAM (short range model) have breathed some life into the idea of some light frozen precip (in the form of light snow) falling late tomorrow afternoon. I’ve got the system broken down below.

TIMING: The latest run of the hi-res NAM has the very first bit of light precip breaking out as early as  3PM tomorrow. You can see the isolated, light blue returns showing up on the map below.

By 5PM it has widespread precipitation across the area.

and moves the last bit of the precip out by 8-9PM.

The Euro is extremely similar in it’s timing, while the GFS continues to show cloud cover and some light precip around the same timeframe.

SNOW OR NO? The biggest question here is: will any of this precip be snow? If the GFS is correct, then no, we have nothing to worry about. However, the Euro/NAM both work cold enough air in for some snow to fall, especially along and north of a Clayton->Cleveland->Dahlonega corridor. Outside of that area upper level temps will likely still be supportive of snow, but surface temps may not allow any precip to reach the ground without melting.

The NAM 850mb temps valid at 5PM tomorrow during the bulk of the precipitation. Areas in blue show upper level temps cold enough for snow.

I mentioned surface temps, and these are the surface temps valid for that same period.

As you can see there is a very sharp temperature gradient from Gainesville (at 42º) to the Blairsville/Blue Ridge area (33-34º). This would allow for any precip falling to reach the ground (and likely accumulate briefly) in the corridor I mentioned above. By the end of the event, temps will have fallen below freezing in the corridor mentioned above and into the 30’s for most everyone else, allowing any lingering precip to likely fall as light snow or flurries. The Euro is extremely similar though unfortunately those maps can’t legally be posted here.

Overall I have very low confidence in anything regarding this threat due to it’s nature and the model differences between the NAM and Euro vs the GFS (and SREFs, for what they are worth which probably isn’t much). However, I’ll be keeping an eye on things and I have a graphic below of my current thoughts from both a snow falling and snow accumulating standpoint.

snow1 snow2

As you can see, I currently anticipate this to be a primarily ridgeline and north event with just some token flakes south of the mountains.

I’ll be watching closely and keep you updated on the latest. ~TW

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