Monday, 11:30 A.M.
While it was balmy over the eastern half of the country this weekend, it was anything but in the West. Temperatures dropped into the 20s and 30s below zero in some of the deeper valleys in the Rockies, and that was the case again this morning. I saw one location in Colorado (Craig) at 35 below at one point early this morning where the sky was clear and there was no wind. Here's the morning minimum chart:
The pattern right now is one that favors extreme. It's what you call a very meridional flow, or one that has a lot of strong north and south undulations in the jet stream. Here's the early morning analysis:
The strong ridge over Florida helped pushed temperatures to record levels in the Sunshine State yesterday, and there's every reason to believe a few more records could go this week before a cold front finally comes through later in the week. By the same token, the ridge off the West Coast is becoming almost as impressive. One manifestation of that strong ridge is the soaking rains on the northwest side of it -- in south-central Alaska, of all places! The combination of rain and melting snow is causing some flooding in the region, virtually unheard of at this time of the year as temperatures have reached the 40s in many areas.
In between these two is the deep trough over the Rockies. That trough brought some very cold air southward throughout the West this weekend, resulting in temperatures averaging 15 degrees below normal from interior California to Arizona, and 30 below average in Denver.
This week the cold in the West will fade as the ridge offshore expands inland over the next couple of days. What cold remains in the southern and eastern Rockies will end up more over the southern Plains as the last upper-level trough coming from the Southwest moves across Texas, and pulls the colder air along with it.
At the same time, a strong push of arctic air will head east-southeastward across Canada behind a cold front. Here's the latest (12z) NAM surface snap shot for Wednesday night:
The packing of those dashed blue lines means the air will get quite a bit colder on the cold side of that front over a relatively short distance. Looking at it another way, the 5,000 foot temperature forecast for Thursday morning is impressively cold, though look where the bulk of it is aimed:
That piece of arctic air will aim for Quebec, with some of it bleeding southward into the Upper Lakes, upstate New York, and northern New England, but not a lot farther south.
What is waiting in the wings this weekend and early next week, though, could be much more impressive. Take a look at the Canadian model 850 mb temperature forecast for Sunday evening:
To give you an idea of just how cold that is, the dividing line between the dark green and light blue areas is the projected freezing level, forecast at this point to be over Atlanta to Dallas. The lightest purple area that encompasses northern and western Wisconsin, northern Iowa, Minnesota, and eastern North Dakota on north, is at least 30 degrees below zero C. That's just brutal. And that appears likely to come down through the Midwest and Mississippi Valley south and east late this weekend and into next week. It could easily result in a sub-zero day in Chicago early next week, and maybe Detroit as well. That's a virtual lock in most of Wisconsin and Minnesota, and could linger for a couple of days, as it looks now.
This cold may take an extra day or two to reach the East Coast, but it's coming next week.
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.