Thursday, 11:55 a.m.
With each passing run of the models, the idea of a storm to open up next week becomes more certain. There are still some significant differences on the models, and those differences are spread out over a number of different scenarios, but most all agree that a feature that is essentially still well out in the Pacific will come ashore into California Saturday, then reorganize over the southern Plains and northwest Gulf of Mexico Sunday night to become the next headache downstream.
Those differences on the models are quite intriguing. There is the idea of multiple waves along an arctic cold front, which seems to be something the models have in common. They also suggest the eventual storm will end up following this arctic boundary Sunday night and Monday into Monday night, regardless of where that boundary may ultimately be. Some models are faster than others, while some are much farther north with the warm air in the end than others. In the end, though, the message is more or less the same - there will be a storm on Monday and into Monday night (NOT this weekend) impacting the mid-Atlantic and Northeast. This storm WILL have a bearing on the weather Sunday and Sunday night from the central and southern Plains to the Ohio Valley, as well as portions of the Tennessee Valley and the Mississippi Valley.
The feature in question is still out over the Pacific this morning:
By the end of the day tomorrow, the upper-level low will be off the central California coast, as shown here by the 12z Feb. 27 GFS 500mb forecast:
After just getting hit with heavy rain over the past 24 hours, this storm promises to bring even more rain to the state, pretty much stem to stern. Even southern California will get a good, much-needed drink of water tomorrow into tomorrow night, with a few showers lingering into Saturday.
As the storm rolls inland, it will seemingly fall apart or lose its identity, all the while bringing rain and mountain snows through Nevada into Utah and Arizona, eventually spilling over into New Mexico and Colorado. Even as this is going on, there are two other features of note to point out on the maps, and I'll show you the Saturday evening 700mb forecast of heights and moisture:
The first of these two features to look at is the lobe of moisture streaking across the Northeast. There won't be a lot of precipitation with it, just plenty of clouds and some light snow and flurries, most of which will fall north of I-70 in the Ohio Valley and the Pennsylvania Turnpike in Pennsylvania. South of there, look for a nice warmup Saturday, with a mild day also in store for Virginia and points south on Sunday with no snow cover and the arctic air long gone. That disturbance, though, WILL pull a cold front swiftly through the Great Lakes and Northeast, and by Sunday morning it will lay down across the Ohio Valley and mid-Atlantic states. Look at the 12z Sunday morning GFS 850mb forecast:
The other feature of note on the image above is the lobe of moisture dropping into the northern Rockies. That's going to generate snow, and plenty of it, across Montana down into Wyoming then out into South Dakota and Nebraska. Some of that moisture will then be pulled farther east, almost like taffy, across the Mississippi Valley into the Ohio Valley to merge with the frontal boundary in place, all as the southern branch feature comes out of the southern Rockies and out into the southern Plains later in the weekend.
I should also point out that what follows this latter feature into the northern Rockies and northern Plains will be an insanely cold air mass! It will be pushed into place by a 1045mb high, and this air mass would probably set records in January! Therefore, I would have to believe it will shatter records for early March in these areas later this weekend and early next week. And beware. A significant chunk of that very same hyperborean air mass is coming through the Plains and across the Mississippi Valley into the Ohio Valley and the East behind the storm.
Now, with the upper-level trough swinging across the Mississippi Valley early Monday, the storm will then cross the lower Mississippi into the Tennessee valley and head east-northeastward from there. The arctic boundary to the north may be the limiting line concerning how far north the storm gets. Right now, it still looks as if areas south of I-70 in Ohio to southwestern Pennsylvania can see mixed precipitation, while areas to the north get mostly or all snow. And across Pennsylvania, the PA Turnpike will likely be close to that dividing line, one that should stay south of New York City and all of New England. Here's the 12z GFS 48-hour QPF forecast from 6z Sunday to 6z Tuesday:
Where it is all snow, with at least 10:1 ratios, that's pushing a foot of snow in parts of central Ohio and into the heart of Pennsylvania and New Jersey out onto Long Island. Chances are if the arctic air is in play north of that boundary, the ratios are going to be higher, which, given that much QPF, would translate into more than a foot rather easily.
Again, that's just the GFS scenario. The 12z NAM is considerably farther north with the warm air. The European, though, is also offering a warmer solution, bringing the 850mb freezing line pretty much up to I-80 to New York City and the southern New England coast. The 12z Canadian model is similar into Sunday night then pulls the cold air southward and elongates the storm, bringing more snow to the table into Kentucky and West Virginia as well as northern Virginia, parts of Maryland and Delaware.
So, as you can see, we can be certain of a storm Sunday and Sunday night from the central and southern Plains to the Mississippi Valley, spreading into the Ohio Valley, and on Monday in the mid-Atlantic and at least southern New England. It has the potential to be the biggest snowstorm of the season in some areas, and I should mention severe weather is likely to be a part of this storm in the lower Mississippi Valley into parts of Tennessee and Mississippi. And it will be followed by another bitterly cold air mass.
Spring is 21 days away. Tick. Tick. Tick.
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