FROSTY, WITHOUT THE SNOWMAN...
Here we are on the first full day of autumn and if there is one thing I can definitively say, today will have the look and feel of fall. Under high pressure early last night skies were clear and temperatures made a quick fall into the upper 40s to near 50. At daybreak, the ridge is east of us and winds are veering to the south, what's known as return flow. That combined with a weak upper air disturbance, has already generated warm advection clouds which continue to increase Friday morning. Eventually, the clouds will lead to some light showers or sprinkles this afternoon as the atmosphere attempts to saturate. While the rain won't amount to much (more on that in a moment), the impact of the clouds and evaporative cooling will hold temperatures well below normal Friday with highs in the upper 50s to low 60s.
Friday's projected highs on the 3K NAM
Early afternoon readings with considerable cloudiness will be 10-15 degrees below the norms. Fall-like for sure!
As far as rains is concerned, I just don't see much moisture or forcing for much in the way of precipitation late Friday and Friday night. More than anything it will be a nuisance when it arrives, just enough to makes things damp and dreary. Most guidance keeps amounts 1/10th of an inch or less. The EURO is the wettest model and I question its totals up to 2/10ths of an inch in a few spots, (that's worst case scenario). No matter what, rain totals will be light and some areas may see little if any rain at all. Here's what's suggested by various models.
The 3k NAM
The national model blend
The Weather Prediction Center
Any lingering showers should be out of the region early Saturday and by afternoon we are expecting the clouds to break for some periods of sunshine. Ahead of another disturbance diving into the upper Midwest this should get highs into the 70s and create a decent afternoon.
Sunday should be more of the same but perhaps a few degree cooler in the far north where upper 60s are possible, Otherwise lower 70s should do it which is very close to normal. Overall, not a bad weekend.
The weather next week, will be influenced by Fiona and what becomes of a yet to be named hurricane that approaches the southeast coast mid-week. Fiona is a beast, a true wind machine. It's on a bead that will take it into Nova Scotia Friday night as the strongest storm in Canadian history. Currently the lowest pressure ever measured was 940 millibars at St. Anthony, Newfoundland January 27, 1977. This storm is projected to be near 931 millibars when it strikes Friday night.
Winds over 100mph are estimated along with a storm surge of 6-8 feet, and more than 6 inches of rain.
Over the open ocean, wave heights may approach 80 feet, and there’s an outside chance that a few rogue waves could tower to near 100 feet. This will be a generational storm for Nova Scotia and Newfoundland with extreme impacts expected.
For us the impacts of Fiona will be its absorption into the 500mb long wave pattern. The energy at 500mb dumbbells' northwest which backs the flow and carves out a deep trough over the Great Lakes that looks like this.
You can watch the evolution of the trough in this animation as Fiona zips north of Nova Scotia and buckles the downstream flow and resultant trough over the Great Lakes. Fascinating to watch the interaction of energy!
This process draws colder air into the Midwest Monday night. By Wednesday morning scattered frost is possible in some parts of the area. Frost will be contingent on a night with clear skies and light winds which is depicted on some models, especially Wednesday morning. I don't see a hard freeze but we may be a bit frosty without the snowman.
Additionally, the new hurricane that threatens the southeast next week is expected to ride northeast along the eastern seaboard (you can see that energy coming into play at the end of the animation Tuesday). Depending on its track and intensity it may hold the trough through much of next week. That keeps us dry but potentially quite cool the majority of the week. The EURO indicates this for 5 day temperature departures Tuesday through Saturday.
That's the long and short of it for now. Have a stellar weekend and of course, roll weather...TS