textproduct: Columbia

WHAT HAS CHANGED

Cold Weather Advisory remains in effect for tonight. Updates for the long term forecast.

KEY MESSAGES

- 1) Cold Weather Advisory continues through 9a, with well-below normal temperatures continuing through the entire forecast period.

- 2) Another threat of winter weather is on the horizon, with guidance continuing to point towards a potentially impactful event over the weekend.

DISCUSSION

Key Message 1: Cold Weather Advisory continues through 9a, with well- below normal temperatures continuing through the entire forecast period.

Temperatures have cooled off so far this evening into the low to mid 20s across the forecast area. However, they are struggling to cool quite as fast as forecast as winds have stay between 5 and 10 mph so far this evening. Still expecting to see temps pretty easily fall into the mid teens to low 20s depending on your location, with cold weather advisory criteria easily hit through the early morning hours. Temps should begin coming up pretty quickly once the sun comes up and allow us to get well above criteria despite winds picking up through the day.

This is hardly the first cold night we will have this week. The synoptic scale pattern continues to favor well below normal temperatures through the entirety of this period. Teleconnections tell the story, with the coupling of a strongly positive PNA and strongly negative NAO combining to yield a pattern that results in cold across the eastern CONUS. This strong, persistent troughing will favor persistently cold high pressure sitting across the eastern two- thirds of the lower 48, with this airmass cold and dry through the end of this week. Guidance continues to indicate that it will be tough to see highs get out of the 40s for the foreseeable future, with overnight lows persistently in the 20s. Even though tonight looks like the coldest night until this weekend, pipes freezing will be a big threat given the persistently cold ground temperatures that we are going to end up seeing as the nights remain cold. Take steps to ensure that your pipes are protected by dripping faucets and keeping that water flowing.

Key Message 2: Another threat of winter weather is on the horizon, with guidance continuing to point towards a potentially impactful event over the weekend.

Physics based and AI guidance has trended towards a favorable setup for potential snowfall this weekend. Its done this fairly quickly over the last 4-6 model runs, showing a northern stream shortwave diving out of the Hudson Bay & phasing with a southern stream shortwave & rapidly amplifying over the TN Valley to our west. The Canadian & ECMWF suite of guidance (both physics-based and AI) were the first to trend in this direction & this has continued overnight. The GFS has trended towards this with the 00z run tonight, increasing the confidence in the possibility of snowfall this weekend across the forecast area. The forecast is slightly simpler than it was last weekend as thermal profiles look like they'll favor snow as the predominant p-type, though this could always change as we get closer to the event itself. The airmass associated with this is forecast to be straight up gelid, so overall snow would be favored. While confidence is increasing overall, this is a complex setup that will (as always) require several things to fall into place just right in order for us to see snowfall across the area. A slight difference in the placement of each individual part would yield a significant difference in our expected outcomes. AIFS and AIGFS guidance is very similar to one another on the 00z, with the AIFS showing a very consistent synoptic scale pattern run-to-run over the past 24h. I'd probably favor this guidance right now as it has been verifying well lately when compared to the physics-based guidance. It'll be interesting to see how this event pans out. It is uncommon to have a signal for widespread precip like this that also overlaps with an atmospheric profile cold enough to support all snow. Stay tuned!

AVIATION /06Z TUESDAY THROUGH SATURDAY/

VFR flight conditions continue through the TAF period with some gusty winds in the afternoon.

Clear skies expected through the TAF period. Northwesterly winds around 8-10 kts to begin the period decrease through the early morning hours. A few gusts remain possible over the first couple of hours. Winds shift to west southwesterly, increasing to around 10 kts with gusts between 15-20 kts expected for several hours after the 15z-16z timeframe. Winds diminish again for the overnight hours.

EXTENDED AVIATION OUTLOOK...Mainly SKC likely through early Friday, then impactful aviation weather becomes possible as a low pressure system likely moves somewhere near the region.

CAE WATCHES/WARNINGS/ADVISORIES

SC...Cold Weather Advisory until 10 AM EST this morning for SCZ016- 018-020>022-025>031-035-037-038-041-115-116-135>137. GA...Cold Weather Advisory until 10 AM EST this morning for GAZ040- 063>065-077.