Snow Cover In All 50 States

Winter Storm Inga brought snowfall all the way to the Gulf Coast this week. What is most intriguing is that this is not the first time this season that the Gulf Coast states (from Texas to Florida) have seen snow. As of Thursday morning, ALL 50 states have some portion of the state with snow cover.

If you’re wondering about Florida (as mentioned above) and Hawaii, yes, those states have snow, too. Snow and sleet fell and accumulated in parts of the Florida Panhandle, and the volcanic peak of Mauna Kea has snow too–which isn’t too rare during this time of the year. All 50 states having snow on the ground at the same time is rare because it is extremely difficult to get accumulating snow in Florida. The last time all 50 states had snow on the ground was in 2010 (February 12th); in fact, 53.7% of the lower-48 is snow covered.

Current Snow Cover Across Lower-48

Winter Storm Inga To Impact A Large Swath Of The United States

As an upper-level low pressure system digs southeastward towards the Great Lakes, a potent shortwave is going to continue digging southeastward across the Great Plains and Mississippi Valley tonight. An associated surface low is currently located in the Great Lakes region, and an Arctic cold front will continue sweeping southeastward. The positive-tilt (southwest to northeast orientation) of the trough has resulted in westerly/southwesterly flow across a deep layer of the atmosphere extending from the Southern Plains to the Mississippi Valley/Mid-south, Southeast, Tennessee/Ohio Valley, Mid-Atlantic, and Northeast. Despite a shortwave feature this past weekend ushering in colder and much drier air, the current pattern configuration has allowed/is allowing for some moistening of the atmosphere across most regions ahead of the Arctic front. Across most regions that are expecting to get snowfall tonight into tomorrow, this should allow for snow to begin reaching the ground sooner, although a decent amount of evaporation will still occur initially.

The unusual aspect of this setup, especially for southern locations that will be getting snow and/or ice, is the fact that there will be no generation of a surface low that will trek from southwest to northeast across the South. This is a scenario where enough lift will be generated along the Arctic front that snow will be able to fall at a decent clip, which is already occurring along a zone from southern Missouri/northern Arkansas to the Ohio Valley/Great Lakes region. That southwest to northeastward band of snow will continue moving/developing southeastward as favorable dynamics/lift sets up across additional regions (map included below). This upward motion will be further enhanced by a jet streak (a region of fast-moving air) that will be located to the right of the trough axis. When more air in the upper-levels of the atmosphere leaves than what is coming in, the atmosphere tries to compensate for that; thus, air begins to rise across that region. If there is enough moisture across that zone, it begins to condense and can produce precipitation.

The big concern with the air mass behind the front is how severely cold it is. As the drier and much colder air mass begins to intrude southeastward, any snowfall that initially melts on the roadways due to warmer temperatures today will result in major travel issues. Snow ratios will increase as the colder air seeps southward, so it will take less moisture to cause hazardous conditions. I’ve noticed that some meteorologists are drawing some comparisons to the event that unfolded in Birmingham and Atlanta in 2014, which resulted in people being stranded along roadways for hours, and honestly, it is a fair comparison.

winter storm inga snowfall map

We made some tweaks to our forecast since this morning. We upped the totals in our heaviest (purple) accumulation zones. Using a 10:1 snow to liquid equivalent ratio that is often shown on forecast model pages will not suffice with this setup; thus, this is why these totals are a bit higher than what you might be seeing on the model guidance. After much discussion, we went ahead and widened the 1-2 inch and 2-4 inch zones across the Carolinas and parts of eastern Georgia and included a zone of accumulations in southeastern Alabama and southwestern Georgia. We also specified ice accumulations across the zones that we foresee getting ice. Out of an over-abundance of caution, I suggest residents in regions, such as Atlanta, prepare for this event accordingly, despite our actual accumulations being on the low-side. Given that temperatures will rapidly drop behind the Arctic front, just a dusting to light accumulations could result in extremely hazardous traveling conditions. While a dusting/light accumulations may not be a concern in most cases, it actually will be in this scenario if they do occur.

Please be on our Facebook page tonight at 9:30 pm ET (8:30 pm CT) for a live Facebook discussion with Chris. You will be able to ask him any questions that you might have. In the meantime, we will continue to monitor this situation and will mention any necessary tweaks to the forecast in that video.

Winter Storm Hunter To Impact Parts Of The South, Ohio Valley, and Northeast

Winter Storm Hunter is taking shape tonight across parts of the county and will continue through Saturday. Rain will transition to freezing rain and sleet, followed by a changeover to snow for parts of the South, parts of the Tennessee Valley, the Ohio Valley, and parts of the Northeast. Accumulations are likely for millions and travel issues will likely arise. Here is the snowfall and ice forecast.

Southern Snow!

The latest numerical guidance is beginning to converge on a scenario that would produce snow for parts of the South, parts of the Tennessee Valley, and parts of the Ohio Valley late this week into the weekend. A upper-level trough will dig southeastward across the Southern Plains late on Thursday. As the trough begins to move out of the Southern Plains, it appears it will close off. This is supported by the European, the Canadian, and the NAM. The GFS actually does not close off the trough and is very fast with movement. This is the outlier, and many of the ensembles do not support the operational run. This will be tossed for now, and I will use the NAM and European as tools for this forecast. These two models appear to have a good handle on the evolution of the upper-level low.

Upper-Level Low (Friday Morning)

As the upper-level low develops south of the Ark-La-Tex vicinity, it will begin to deepen and wrap moisture around the northern and western side of the low by Friday. This is the cold side of the system, so precipitation will likely fall as sleet and snow in this area. This will place eastern Arkansas, northern Louisiana, northern Mississippi, and western Tennessee in a favorable area to see wintry precipitation. It is possible, depending on the location and track of the upper-level low, that wintry precipitation chances will extend into parts of Alabama and the rest of Tennessee by Saturday. Sleet, followed by snow is likely in the Ohio Valley by Saturday into Sunday.

Future Radar (Friday Evening)

Future Radar (Saturday Morning)

Looking at modeled forecast soundings, surface temperatures are initially marginal, and there will be an elevated (but thin) warm layer. This will likely cause a period of sleet. But dynamic cooling will eventually take place—leading to snow.

Accumulations are possible, but too hard to forecast at this point. Depending on the deepening of the upper-level low, and the track, it will have huge implications on snow amounts. The transition period will be important too. There are still too many uncertainties with the changeover from rain, to sleet, then to snow will occur. The deeper the low: the more snow. The faster the changeover: the more snow. These are variables that we cannot accurately forecast at this point. I will say, however, some guidance is hinting at a TROWAL developing. TROWALS are known for producing heavy precipitation. Wherever this feature sets up, if it does, some areas could see a surprise. I will have updates as needed.

Firsthand Weather’s Preliminary Forecast