The long-awaited cold front will finally reach the Atlanta metro tomorrow evening (Wednesday 11/12). At this time, it still appears that the front will move through the Atlanta area during the early-evening hours. After reaching the mid 60s on Wednesday, Atlanta will be 20 degrees colder on Thursday with highs only in the mid 40s.
Special Update (Wed 11/12 11:30 am): View my partial analysis indicating the observed position of the cold front at 11 am EST.
Location of the Front on Tuesday, November 11 (1:45 pm EST)
Here is my partial analysis at 1:45 pm EST today (Tuesday, November 11). At that time, the front was just entering western Mississippi.
Timing of the Front for Atlanta
This is my forecast position of the front at 7 pm EST tomorrow (Wednesday, November 12).
Forecast Specifics Through Sunday
- Wednesday: 65º (Cold front during the evening)
- Thursday: Mid 40s
- Thursday night: *FREEZE* 27º to 32º
- Friday: Lower 40s
- Friday night *FREEZE* 25º to 30º
- Saturday: Near 50º
- Saturday night: Increasing Clouds. Mid 30s
- Sunday: Rain likely. Rain may be heavy at times. High in the upper 30s.
Cold Rain on Sunday… No Snow.
I’ve received some questions about rumors of snow on Sunday. I do not expect any snow in Atlanta. I do expect a cold rain, with temperatures in the upper 30s to lower 40s. The mid-levels of the atmosphere will simply be too warm for snow, as it looks now. I illustrated the reasons why in the diagram below.
This is the vertical thermodynamic profile for Sunday, during which time I am forecasting a cold rain. The thermodynamic profile is plotted on a Skew-T diagram (used by meteorologists). The isotherms (temperature) are oriented diagonally with height. I have highlighted the 0°F isotherm and the 40°F isotherm. The solid red line represents temperature with height. The green line is the dew point. Where the two meet is where the air is nearly saturated (i.e., the cloud layer). In this layer, it will be well above freezing. The top of the warm (above-freezing) layer is progged to be around 8,000 feet, and extend all the way down to the surface. For snow to fall, the warm layer needs to be either very shallow, or non-existent.
Nevertheless, I do expect it to be a cold/raw day on Sunday. Interestingly enough, in this type of situation and with this type of airmass, the rain can begin as a period of sleet as the atmosphere cools via evaporative cooling. If this were to happen, the sleet would melt on impact and would quickly transition to rain as the atmosphere becomes saturated. At this time, I am not forecasting sleet, but don’t be surprised if you see a few ice pellets or hear a few dings on your window as the rain begins on Sunday.
More Cold Fronts On The Way
The front that will move through tomorrow is not the only cold front that I am watching. We are in an active pattern, highly amplified by extra-tropical cyclone Nuri. I expect a reinforcing surge of modified-Arctic air early next week. So, enjoy the mid-60s tomorrow, because the cold weather is here to stay for the next 5 to 7 days.
Update #1 (Wednesday, November 12, 2014)
This is my partial analysis on Wednesday, 11/12, at 11 am EST. The cold front is entering northwest Georgia, and will move across the Atlanta metro later today, as predicted. No changes in the forecast.