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| Big Christmas storm remains likely across the eastern United States and into Canada | Big Christmas storm remains likely across the eastern United States and into Canada |
| (35 minutes later) | |
| A powerful storm is set to develop across the central and eastern United States on Christmas Eve. Impacts will linger through Christmas Day. | A powerful storm is set to develop across the central and eastern United States on Christmas Eve. Impacts will linger through Christmas Day. |
| Coming a few days after the official start of winter, the main story is less likely to be snow than big wind and areas of heavy rain. | Coming a few days after the official start of winter, the main story is less likely to be snow than big wind and areas of heavy rain. |
| The latest weather model runs, like the Global Forecast System (GFS) shown above, continue to portray a dance of weather systems that ultimately leads to development of a low pressure across the South by Tuesday night and into early Christmas Eve. The storm quickly intensifies and scoots north into the Midwest/Ohio Valley and Great Lakes through the remainder of Christmas Eve. From there, it’s off to Canada. | The latest weather model runs, like the Global Forecast System (GFS) shown above, continue to portray a dance of weather systems that ultimately leads to development of a low pressure across the South by Tuesday night and into early Christmas Eve. The storm quickly intensifies and scoots north into the Midwest/Ohio Valley and Great Lakes through the remainder of Christmas Eve. From there, it’s off to Canada. |
| Given temperatures running way above normal across much of the eastern United States (it could be the warmest Christmas eve in a long time for New England), the predominant precipitation type from this storm system is likely to be rain. Even up north of the border. | Given temperatures running way above normal across much of the eastern United States (it could be the warmest Christmas eve in a long time for New England), the predominant precipitation type from this storm system is likely to be rain. Even up north of the border. |
| Since the storm initially moves fairly rapidly, rain isn’t likely to last super long most spots, so flooding is not a big concern. But a large area generally east of the Mississippi and Missouri rivers to the East Coast can expect the risk of 0.5 to 1 inch of rain, or more. There’s also a chance of severe weather across the northern Gulf Coast states through Florida on Tuesday, and perhaps further to the east on Christmas Eve. | Since the storm initially moves fairly rapidly, rain isn’t likely to last super long most spots, so flooding is not a big concern. But a large area generally east of the Mississippi and Missouri rivers to the East Coast can expect the risk of 0.5 to 1 inch of rain, or more. There’s also a chance of severe weather across the northern Gulf Coast states through Florida on Tuesday, and perhaps further to the east on Christmas Eve. |
| As is common with a rapidly developing low pressure, winds are likely to whip over large expanses both Christmas Eve and Christmas Day. | As is common with a rapidly developing low pressure, winds are likely to whip over large expanses both Christmas Eve and Christmas Day. |
| On Christmas Eve, the strongest wind remains relatively close to the low, and could make travel hazardous, especially late in the day across particularly the Midwest and Ohio Valley. Other areas of strong winds are a good bet along the Gulf coast and eastern seaboard. | On Christmas Eve, the strongest wind remains relatively close to the low, and could make travel hazardous, especially late in the day across particularly the Midwest and Ohio Valley. Other areas of strong winds are a good bet along the Gulf coast and eastern seaboard. |
| The most widespread wind may actually come on Christmas Day as the strong low pressure system spins away through Canada. This can be seen on the map below which has sustained 25-35 mph winds from Michigan across to the Mid-Atlantic and then up the shoreline into New England around midday (don’t focus on the time too much though as it’s fluid). | |
| With sustained winds that high or higher, some damaging gusts may become a risk. | With sustained winds that high or higher, some damaging gusts may become a risk. |
| It is likely that snow will fall with this storm, the question remains how much due to rather limited cold air. | It is likely that snow will fall with this storm, the question remains how much due to rather limited cold air. |
| Weather models are generally bearish on the idea of a lot of snow, though places west and northwest of the low pressure center should see some. As an example, this morning’s GFS spit out around 4-8+ inches in parts of Illinois then toward Lake Michigan and up into Canada. The European model showed more modest amounts over the upper Midwest, with anything of consequence mainly north of the international border. Any snow that falls and sticks will do so among strong winds, so blowing snow would become a concern. | |
| Modest lake effect snow may impact spots in the wake of the storm as well, but it’s hard to narrow in on that just yet. | Modest lake effect snow may impact spots in the wake of the storm as well, but it’s hard to narrow in on that just yet. |
| Finally, will the storm “bomb” out? Still up in the air. It should be close. | Finally, will the storm “bomb” out? Still up in the air. It should be close. |
| GFS 00z 5-day forecast shows #Santabomb – rare land-based rapid intensifier 1000 mb - 975 mb in 24 hrs pic.twitter.com/IYmNZHEvr6— Ryan Maue (@RyanMaue) December 20, 2014 | GFS 00z 5-day forecast shows #Santabomb – rare land-based rapid intensifier 1000 mb - 975 mb in 24 hrs pic.twitter.com/IYmNZHEvr6— Ryan Maue (@RyanMaue) December 20, 2014 |
| GFS 00z 5-day forecast shows #Santabomb – rare land-based rapid intensifier 1000 mb - 975 mb in 24 hrs pic.twitter.com/IYmNZHEvr6 | GFS 00z 5-day forecast shows #Santabomb – rare land-based rapid intensifier 1000 mb - 975 mb in 24 hrs pic.twitter.com/IYmNZHEvr6 |
| Models have vacillated a bit on end strength of this system. | Models have vacillated a bit on end strength of this system. |
| The storm is sure to be quite intense, with almost unanimous agreement it will at least approach 980 millibars (mb), the general pressure equivalent of a category 1 hurricane. But the event could fall short of the 24mb in 24 hour drop required to classify as “bombogenesis.” Rapid strengthening like currently expected is nevertheless unusual over land. | The storm is sure to be quite intense, with almost unanimous agreement it will at least approach 980 millibars (mb), the general pressure equivalent of a category 1 hurricane. But the event could fall short of the 24mb in 24 hour drop required to classify as “bombogenesis.” Rapid strengthening like currently expected is nevertheless unusual over land. |
| Despite that scientific quibble, it’s sure to be an event that causes some headaches. Do prepare to plan accordingly, and keep in mind it could probably be a lot worse for holiday travel and activities, thanks to the expected lack of widespread snow. | Despite that scientific quibble, it’s sure to be an event that causes some headaches. Do prepare to plan accordingly, and keep in mind it could probably be a lot worse for holiday travel and activities, thanks to the expected lack of widespread snow. |