Friday, 11:45 a.m.
Mild air is moving across the Mississippi Valley into the Ohio and Tennessee valleys this afternoon, and it will make it all the way to the East Coast tomorrow as a warm front now stretching from central Virginia to Iowa lifts northeastward this afternoon and tonight. We have seen a weak, little disturbance moving along this boundary overnight and early this morning from the Midwest into the Ohio Valley, and that feature will fizzle this afternoon as it crosses the Appalachians from southeastern Ohio and southwestern Pennsylvania. Then the warmer air will move in for a brief period of time before the next cold front comes racing through from the northern Plains.
This very same cold front will race across the Northeast and mid-Atlantic states tomorrow. At 18z tomorrow, look at the 700mb moisture, which essentially will mark out the frontal boundary:
Much drier air will quickly follow the front, and most places downwind of the Appalachians in the mid-Atlantic states will get virtually no rain, just a nice day tomorrow in the middle of a cold pattern.
And the cold will waste no time in returning to the fold. For instance, when I came in this morning, it was above freezing in Grand Forks, N.D., with rain falling. It quickly changed back to snow as the surface wave passed, then the temperature began to fall. It is now in the upper teens with winds howling over 40 mph pushing snow all over the place. That sort of temperature change will be replayed this afternoon and tonight through the Dakotas and into the Midwest, though the change in the Ohio Valley won't be as sharp. The difference between today and tomorrow, however, will be quite significant.
Then there is the matter of that wave of low pressure I touched on yesterday. In a normal winter, as I opined yesterday, I would have leaned in the direction of the NAM, which trended northward at 12z and suggested snow would pile up for a time from parts of the Ohio Valley to the northern mid-Atlantic and southern New England. However, I also stated that the trends this winter have been pretty much the opposite - no northward trend with upcoming storms and that if anything the trend has been farther south.
Indeed, subsequent runs of the NAM model have joined the chorus of a southern tracked wave, one that might bring some clouds across the Ohio Valley and mid-Atlantic states, but any snow would be relatively minimal from parts of Kentucky to West Virginia and even central Virginia. To the north, just colder.
That sets the stage for a cold four-day stretch next week, with the highlight during that period the storm Tuesday and Tuesday night into Wednesday. If you look at the 12z NAM, check out the 84-hour 500mb forecast:
Note carefully the separation between the feature rolling through Missouri and the one entering North Dakota. The lead feature will help gather moisture from the Gulf of Mexico into the Southeast Monday night, and the farther north the precipitation begins to spread, the greater the chance of it being snow.
The model consensus is for the primary low to form off the Georgia and South Carolina coast late Monday night, which, quite frankly, is amazingly far south for this late in the season! However, given the strength and depth of the arctic air in place ahead of it, it's perfectly reasonable to expect. Then, as the storm moves northeastward over the comparatively warm waters of the Gulf Stream, and the second feature quickly approaches from the west-northwest, this storm should literally explode Tuesday afternoon and Tuesday night, tracking toward the Gulf of Maine Wednesday. Look at the 0z GFS forecast for 18z Wednesday:
That's about as nasty of a nor'easter as they come, and it will cause all kinds of disruptive problems along the way. The most obvious of those is the potential for snow, potentially crippling snows, from parts of North Carolina and Virginia to New England, depending on the track of the storm. There will also be the problem of power outages from strong winds, coastal flooding, beach erosion and the like. This has all the earmarks of a destructive storm, and my guess is that southeastern and eastern New England will bear the brunt of it when all is said and done.
The one 'good' side note from the storm is that after it blows by and reinforces the arctic air, it will all lift out to the northeast quickly. That means a quick snap back to normal by Friday and Saturday, if not above it, and the promise of a milder pattern to open up April!
One storm is finally exiting the Northeast this afternoon, only to be replaced by another, slow-moving for the middle and latter stages of next week.
As the pattern becomes more amplified this weekend and early next week, look for it to warm up from the interior west toward the Plains, while it trends cooler east of the Mississippi.
A storm in Indiana will produce heavy rain in the mid-Atlantic into New England over the next 48 hours, but most of the rest of the nation will have little active weather into the weekend.
A powerful storm in Illinois is being blocked from a rapid advance to the East, resulting in heavy rains ahead of it, but also little cooling for the mid-Atlantic and Northeast behind it.
A strengthening storm in the eastern Plains will generate a lot of severe weather and heavy rain through Wednesday all the way to the Eastern Seaboard.
A storm developing over the southern plains late Sunday and Sunday night will help generate severe thunderstorms and flooding downpours from the Eastern Plains to the Eastern Seaboard through Wednesday.