Tuesday, 11:10 a.m.
The weather has already turned volatile across the central and southern Plains early this morning, and it will get worse over the next 24 hours before the weather quiets down later tomorrow night and Thursday with the passage of a cold front off the East Coast. Why has the weather turned so violent so far north in late January? Hopefully this graphic will set the table:
There are really two storms in play right now. One is crossing Wisconsin and heading over central Lake Superior. It is helping draw a record warm air mass northward through Illinois into extreme southern Wisconsin at this hour. The second storm is forming in central Oklahoma, and that will be the one to do most of the damage over the next 24 to 36 hours. The dew point temperatures south and east of that developing low are over 60. For this time of the year, that is really, really high, and with so much cold air amassing north of the border, it's really little wonder why the severe weather potential is so high for the rest of today and tonight and tomorrow.
The severe weather aspect of this storm is but one facet of many to the storm. Another, of course, is the record warmth surging northward ahead of it. Chicago broke their record for the date by sunrise, and even though it won't get much warmer during the day, it underscores how balmy this air mass is. Yesterday, Topeka set their all-time January record of 77, besting the old standard by 3 degrees. Rest assured that more records will tumble today and tomorrow from the southern Plains and Mississippi Valley all the way into the East.
Still another side of this storm is the heaviest of the precipitation. Granted, the NAM model tends to suffer from some degree of convective feedback, so its quantitative precipitation forecast (QPF) tends to be somewhat bloated. Still, you can get a sense of the rainfall potential with the storm by looking at the total precipitation being spit out by the model from its 7 a.m. initialization time through 7 a.m. Thursday:
The key isn't there, so the yellow areas are at least 2 inches being produced by the model over that 48-hour window, with a pocket of red over upstate New York at over 3 inches. Many areas shaded with the lightest blue and purple colors are projected to get at least 1 inch of rain.
There will be some snow, but it won't be a lot for most areas. Most of it will be limited to parts of Kansas tonight, spreading into southern and eastern Iowa later tonight and tomorrow morning (including northwestern Missouri), then cutting across southern and eastern Wisconsin and northern portions of Illinois tomorrow as the storm darts by and the colder air rushes in before the precipitation can cut off.
Finally, there is the bitter, arctic air. It will be every bit as cold across the Dakotas and Minnesota later tonight and tomorrow through Thursday, with Minneapolis in danger of having a second sub-zero day Thursday after doing it for the first time in over four years last Monday. This cold air will drill across the Great Lakes and Ohio Valley behind the cold front later tomorrow and tomorrow night, reaching the mid-Atlantic and New England coasts later Thursday and Thursday night.
As the cold air rushes downstream, it will move over ground that will be largely devoid of snow cover. It's all gone in the Ohio Valley, and the southern edge will retreat in Michigan in the next 24 hours. Most of what snowcover is left in Pennsylvania will disappear tomorrow, while the snow will easily diminish in southern New York state, if not largely go away there, too. Even in southern New England, the snow you picked up yesterday doesn't stand a chance tomorrow into tomorrow night as temperatures and dew points at least reach the 40s, and, in many cases, into the 50s.
So, as the cold air comes east, it should begin to lose a little of its bite. That doesn't mean it won't be dramatically colder by week's end in the East, but that the departures from normal won't be nearly as big as they will be in the Dakotas and Minnesota into Wisconsin and Iowa tomorrow and Thursday into Friday. And that may be something worth noting going into next week, as there are signs the cold may not be as bad going forward after this shot comes and goes later this week into this weekend.
One strong cold front moving through the Great Lakes and Ohio Valley this afternoon will be followed by another one to begin next week, and the recurving of a Typhoon in the western Pacific may enhance the cooling behind it.
A quick surge of heat and humidity is heading eastward today from the central and southern Plains. Behind it will come still another refreshing air mass later this week, while the West stays largely hot and dry.
Tropical Storm Arthur has formed in the Atlantic east of Florida and will likely graze eastern North Carolina Thursday night and early Friday before passing south and east of New England late Friday and Friday night.
An area of low pressure east of Florida is likely to develop in the next three days, and could become the first named storm of the year in time. It will delay the passage of a cold front off the East Coast until week's end, keeping the East very humid until Friday.
Wet weather has plagued the Midwest and northern Plains this month, and it's helping to keep temperatures down across much of the country from the northern Rockies to the mid-Atlantic states and New England. Look for this to persist into next week.
High humidity is in place across a large part of the country now, and it will remain that way through the weekend, helping to fuel showers and thunderstorms that can contain flooding downpours in some areas.