PARDON THE INTERRUPTION...
Indian summer weather in all its glory has been with us now for well over a week. The mild days and crisp nights, (along with the oncoming fall colors), have made for ideal early fall conditions. We haven't hit the end of the road yet but I can see the bend that will lead to a cool change later this week. Pardon the interruption!
Before that happens, temperatures will remain warm and conditions mainly dry through the day Thursday. Highs Tuesday through Thursday will remain in the range of 70-75 degrees which is a solid 5-7 degrees above the norms. One of the more notable aspects of Tuesday's weather will be the dry air. Relative humidity levels will only be in the 25-30 percent category in the afternoon.
PWAT's (available water vapor) are running around 4/10ths of an inch in many spots. That about half of what's typical.
Wednesday the ridging breaks down as a short wave streaks across the area. This may provide enough forcing for a few afternoon showers (especially in the south) but low level moisture is very deficient which means it will be tough to get raindrops down to the ground. Additional spotty showers or sprinkles are possible with a cold front Thursday. It's possible a spot or two between the two windows could pick up 1/10th of an inch but most areas will see little if any rain if current trends hold. Here's what models are suggesting for rain totals through Thursday.
The national model blend
For the NW half of my area the lack of rain is a growing concern. Wednesday will start in Dubuque as the 17th consecutive day with no measurable rain.
Going back to the 19th of September only 2 other years, 1897 and 1888 have had similar periods with no measurable rain.
From September 12th to October 3rd, just .03" was measured. That is the driest such period on record.
September 1 through October 3rd, just .60" was totaled in Dubuque, also a record low beating out 1974's .62".
I kid you not when I say it is bone dry up here. We really need a good soaking. That does not appear to be in the cards in any part of the Midwest the next week. Even worse, the blend of models shows essentially nothing in the coming 11 days ending October 15th. Not only is that problematic, its boring as heck!
That trend is evident in long range models as well with the EURO weeklies showing major deficits over the next 46 days ending November 18th. Lots of places in the central Midwest show deficiencies of 2-3 inches.
What's driving the dry weather is a persistent ridge of high pressure situated over the Pacific Northwest. The resultant NW flow steers moisture and storms away from the Midwest. The weeklies show a mean 30 day 500mb flow that look like this ending November 2nd. That ridge is still sticking its nose into the same general area. That should certainly lead to enhanced chances of below normal precipitation into mid-November.
Additionally, such a pattern at 500mb would also support below normal temperatures over the next 6 weeks. The 30 day temperature departures are showing that tendency over the central and east. What I would watch is the fact the EURO is notorious for not being able to see cold in the longer range. I think the potential is there for these 30 day departures to be colder than what the weeklies indicate, especially if the 500mb flow shown indeed verifies.
A couple of these potential cold snaps are showing up in the next 10 days. The first arrives Friday with a good chance of frost and freezing temperatures Saturday morning the 8th. That quickly moves out Sunday before the next surge October 14th which could bring some upper 20s if data holds. More on that in coming posts.
One last thing for you snow lovers. This is the EURO weekly snow output for the next 30 days. Somewhere between now and November 4th it shows snow accumulating to this level. Confidence on this is far lower that the temperature and precipitation trends I discussed earlier. Don't hold your breath!