Georgia Skywarn

*** OUTDATED - See latest posts for updated information***

An Extreme Cold Watch is now in effect for all of Georgia from Saturday evening through early Sunday afternoon. Wind Chills - or feels like temperatures - of 5 degrees or below are expected. Take the time to protect people, pets, plants and pipes this weekend.

*** OUTDATED - See latest posts for updated information***

[ Thursday Afternoon Update ] A Winter Storm Watch is now in effect for parts of north and east Georgia from Friday evening through Sunday morning, where there is high confidence of snow accumulations of more than an inch. Any snow accumulations will produce slick roadways and impact travel.

An Ice Storm Warning has been extended to include the metro Altanta counties.

The warning will be in effect Saturday 1PM through Monday 10AM.

WHAT...Significant icing expected. Total ice accumulations between
a quarter of an inch and one inch are expected.

* WHERE...Portions of east central, north central, northeast, and
northwest Georgia.

* WHEN...From 1 PM Saturday to 10 AM EST Monday.

* IMPACTS...Expect power outages and tree damage due to the ice. Travel could be impossible. The hazardous conditions will impact the Monday morning commute.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Travel is strongly discouraged. If you must travel, keep an extra flashlight, food and water in your vehicle in case of an emergency.

Prepare for possible power outages. The latest road conditions for the state you are calling from can be obtained by calling 5 1 1

Winter Storm Watch has been issued for northern Georgia for late Friday-Monday morning.

Hazards: Heavy mixed precipitation possible. Total snow and sleet accumulations up to 4 inches and ice accumulations greater than one quarter inch possible.

Impacts: Expect power outages and tree damage due to the ice. Travel could be impossible. The hazardous conditions could impact the Monday morning commute.

Additional information: Based on forecasts and guidance models, this watch may be updated to include counties within the metro Atlanta area and further south.

Stay tuned for more information.

NWS>

A major winter storm and potential ice storm will move through the Eastern U.S. this weekend. Impacts are expected in north Georgia and now is the time to prepare! The forecast isn't as certain for central Georgia, but this is still a situation you should monitor closely

...SUMMARY...
A tornado outbreak is likely on Saturday across the central Gulf Coast States and Deep South into the Tennessee Valley. Numerous significant tornadoes, some of which should be long-track and potentially violent, are expected on Saturday afternoon and evening. The most dangerous tornado threat should begin across eastern Louisiana and Mississippi during the late morning to afternoon, spread across Alabama late day into the evening, and reach western parts of the Florida Panhandle and Georgia Saturday night.

...Central Gulf Coast/Deep South/TN Valley...
After collaboration with WFOs BMX/JAN/MOB, an upgrade to a level 5-HIGH risk appears warranted for the most likely corridor of potentially violent tornadoes, peaking tomorrow afternoon and evening. A broader level 4-MDT risk has been expanded somewhat eastward for the nocturnal significant tornado threat.

An intense mid-level jet, 100-110 kts at 500 mb, will eject through the basal portion of a broad southern Great Plains shortwave trough.

This will induce secondary cyclogenesis along an initially slow-moving baroclinic zone from the Ark-La-Tex to the central Great Lakes. Another day of air mass modification ahead of this wave will yield a pronounced plume of rich northwest Gulf moisture that should be pristine across southeast LA and southern MS through late morning. As mid-level height falls overspread the diurnally warming air mass, increasing convective development is expected along the deepening baroclinic zone, as well as residual outflows to its northeast in the TN Valley from prior late D1 convection.

Steep mid-level lapse rates atop the richly moist boundary layer will yield at least moderate MLCAPE from 1500-2500 J/kg across eastern LA into central MS. Vertically veering wind profiles with strong anvil-level divergence amid the favorable instability should support robust updrafts and intense supercells. Low-level shear will strengthen midday through the afternoon, yielding potential for a tornado outbreak.

The most probable convective corridor will be along the effective outflow boundary across central/northern parts of MS into north AL and south TN. Along and south of this will be the most favored corridor for long-tracked, discrete supercells. These will likely develop within north/south-oriented confluence bands as increasing large-scale ascent becomes coincident with the peak heating cycle.

A volatile combination of kinematic/thermodynamic parameters will support potential for long-track, EF3+ tornadoes. The overall spatial extent of this threat will be modulated by the degree of boundary-layer heating within the mid to upper 60s dew point plume, along with where exactly the large-scale outflow boundary sets up from late D1/early D2.

Significant tornado potential, along with very large hail and destructive damaging wind gusts, should persist into Saturday night.

Greater potential for a broken to linear band of thunderstorms is anticipated by this time, but wind profiles will still strongly favor supercells. As such, a mix of all three hazards may continue with sig severe hail potential favored south and sig severe wind favored north as the convective band spreads towards the southern Appalachians and the northeast Gulf Coast.

...OH Valley to central Great Lakes...
Forecast confidence remains low with regard to severe potential north of the TN Valley. Guidance continues to differ on the degree of diurnal destabilization in the wake of the D1 shortwave trough and deep cyclone tracking into northern Ontario. With increasingly widespread Mid/Deep South to TN Valley thunderstorms during the day Saturday, the northward extent of appreciable surface-based instability appears highly questionable within a predominately meridional deep-layer wind profile. Given the fast flow regime though, even weak convection late afternoon through Saturday night will pose some risk for locally strong gusts and a tornado.

The Winter Storm Warning will go into effect tomorrow morning at 7am and will be in effect until 7am Saturday morning.

WINTER STORM WATCH IN EFFECT FROM 7AM FRIDAY MORNING THROUGH 7AM SATURDAY
MORNING

* WHAT...A wintry mix of precipitation is possible. Snow and sleet accumulations in the mountains could average between three to six inches with locally higher amounts possible. Further south to the Interstate 20 corridor, a mixture of snow, sleet, freezing rain and rain is likely. Snow accumulations of two to four inches is possible with icing amounts around a tenth of an inch possible.

* WHERE...Portions of north central, northeast, northwest, and west
central Georgia.

* WHEN...From Friday morning through Saturday morning.

* IMPACTS...Plan on slippery road conditions, with travel likely becoming difficult. The hazardous conditions could impact the Friday commute and linger into Saturday morning. Bridges and overpasses could become icy even if temperatures remain slightly above freezing.

NWS Atlanta>

We've posted graphics the last two days that show the probability of 0.10" of ice accumulation (which, while it doesn't sound like a lot, would have adverse impacts on roads and power lines) and 1" of snow accumulation. Here is another way to visualize the forecast as it stands now.

Caveat❗️ Don't get too focused on where exactly the precipitation type transition areas are, as the forecast will undergo more fine-tuning over the next couple days as elements of this weather system become better resolved by models (especially high-resolution ones).

There is growing consensus among guidance models on the potential for over 1 inch of snow on Friday in parts of North GA. It is advisable to download the mPing app from the Apple or Google Play store at this time. The app allows for the tracking of weather conditions at your location and provides real-time data to local weather offices.

A further update on the potential winter storm later this week will be posted shortly.

NSSL Projects: mPING The NOAA National Severe Storms Laboratory is collecting public weather reports through a free app available for smart phones or mobile devices. The app is called 'mPING,' for Meteorological Phenomena Identification Near the Ground.