Wednesday, 11:45 a.m.
Weather changes are going to be slow the rest of the week through the weekend around the country. The main jet stream flow is pretty far to the north in most of the country, save for the trough in the West, as well as around the developing upper-level trough around the Northeast Friday and Saturday. That means weak winds aloft from the Rockies to the Appalachians, which, in turn, implies more subtle day-to-day changes in the weather.
Let's start first in the Northeast today, where the backdoor cold front continues making slow yet steady progress westward across New Jersey into extreme eastern Pennsylvania. It's over Delaware Bay and will soon inch across Delaware into Maryland and the Susquehanna Valley. Tonight, it will advance into northern Virginia and central Pennsylvania before running into the mountains, thus ending the westward expansion of the marine-cooled air. There won't be a lot of rain in most cases behind the front, basically little more than spotty drizzle or a touch of rain. However, it will be pretty cloudy, and that will keep temperatures down considerably from today's levels.
Another upper-level disturbance will come south-southeastward from Ontario tomorrow and tomorrow night. As it does, look for a northwest flow to develop quickly on Friday across the mid-Atlantic that will serve to wipe out the high humidity of recent days and also to allow clouds to break for some sunshine. An instability shower is bound to pop up as the upper levels of the atmosphere cool. Look at the projected 850mb temperatures for Friday evening:
As this morphs into an upper-level low Friday night into Saturday, and then a surface low develops well off the mid-Atlantic coast and south of New England, the heights will still be low across New England and the Hudson Valley down into the mid-Atlantic region, meaning an opportunity for a passing shower. Otherwise, it should be a nice day Saturday in most places around the Northeast and mid-Atlantic states back into the Great Lakes and Ohio Valley. Sunday will be nicer and a little warmer with full sunshine.
In contrast, the upper-level low currently wobbling around East Texas and Louisiana appears to about done with its eastward movement. Still, it is producing an inordinate amount of rain across Louisiana, and the prospects for flooding downpours remain high across Southeast Texas, Louisiana, Arkansas, Mississippi and the Florida Panhandle. This is the NAM model projection of total precipitation from 12z today through Saturday evening:
The remains of this feature will leech out over the weekend and early next week, but its 'ghost,' if you will, will help to keep a lid on daytime highs because of the high moisture content of the atmosphere and all of the water from the recent and expected rainfall.
You may also have noticed a second area of rather prolific rainfall, this one in the northern Plains. The bulk of this will come later Friday through Saturday and may linger into Sunday as an initial cold front makes it into the Dakotas but has a hard time leaving them. This is clearly borne out when you study the week-long precipitation anomaly forecast off the European model for this week:
What's interesting is that this area of wet weather is being forecast to expand next week from the northern Plains to the mid-Atlantic:
With all of the moisture lying in wait across the southern half of the country in a a typically warm, humid air mass for the beginning of June and still some cooler and drier air trying to push southward out of Canada, there will be a defined boundary between the two that will be quite active. One front comes in early next week, but really doesn't get past the Ohio Valley, though it will cool off the Great Lakes and New England yet again. A second front late in the week may make better progress to the south late in the week.
Those two images also tell a story of a lack of rain in the West, where the drought is destined to expand in the coming weeks now that the 'rainy' season is long in the rearview mirror. As next week grows along, the relatively comfortable weather through the end of this week and this weekend will gradually be replaced by some ridging that will gradually crank up the heat.
I'm off to Denver Friday to visit 850 KOA, as well as to run the SkirtSports Half Marathon on Sunday! I'll be back in the office briefly next Wednesday and Thursday before a long weekend in the Finger Lakes region the following weekend. The active spring and summer tour continues, with my sights still set on Challenge Penticton on Aug. 24, the site of what I hope to be a full Ironman for me!
The record warmth of recent days will be replaced by a much colder air mass following a cold front moving from the Ohio Valley to the East. Rain will change to snow in the higher ground of upstate New York and northern New England.
Nicole crossed Bermuda Thursday morning as a major hurricane. Two storms will blast the Northwest with high winds and heavy rains in the next 72 hours, forcing warmer air out into the nation's midsection.
Matthew is a dangerous hurricane bearing down on the east coast of Florida. While it ravages Florida and parts of the Southeast into the weekend, it will spare the Northeast of its fury.
Major Hurricane Matthew is now a significant threat to the entire Eastern Seaboard Thursday through the weekend with with potentially destructive winds and excessive rains.
Heavy rain will soak drought-stricken areas of the mid-Atlantic over the next couple of days. Focus will then shift to Matthew and its potential to impact the Eastern Seaboard with more heavy rain later next week.
Summer has ended astronomically, but from a meteorological standpoint, there's plenty more warm weather heading into October from the Plains to the East.