Wet weather will return Halloween, but we still believe the more concentrated rain will be “shoved” to our southeast as trick-or-treating begins in earnest across most central Indiana neighborhoods. Unfortunately,…
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October got off to a warm start, but unseasonably chilly conditions have dominated over the past couple of weeks. In fact, we’re on a stretch of (12) consecutive days below average after the summer-like start. The other common theme? Dry, dry, dry. Officially, IND is running close to 1″ below average through the first few weeks of the month. Changes loom- at least to some extent.
We notice the ensemble data (both the European and GFS) is painting a more active, wetter regime as we move through early November. Given the upper air pattern, we would tend to agree.
While confident on the return of wet conditions as we traverse the first week or two of November, data is struggling to get a handle on the PNA past the short-term. The PNA, or Pacific North American Pattern, teleconnection is one of our favorites this time of year to “key in” on the medium range pattern. While the NAO and AO get a lot of attention the deeper we get into the cold season, the PNA can be a tremendous tool during transition seasons. We note latest data is trending significantly more towards a positive PNA (compared to previous runs)- which is a colder signal.
To no surprise, data has trended chillier during today’s 12z update.
To close, bank on a return of the wet conditions as we move into the mighty month of November. From a temperature perspective, the forecast is much tougher for the first half of November. As things stand now, we continue to favor a relaxation of the anomalous chill overall, but can certainly see where “pops” of cold air can easily sweep in behind what should be an active storm track from the mid-south up into the Mid West and Ohio Valley. Stay tuned.
The short and medium range weather pattern will be highlighted by a colder than average regime, but one that’s also drier than normal.
The positive PNA will continue to support the mean trough position in the central and eastern portion of the country as we rumble into late October.
As we look ahead, there are growing indications a more significant storm may impact the general region as we get closer to Halloween. This is the next time frame we’re closely monitoring for the potential of an impactful storm system. Given the overall setup, we would be surprised if this particular storm didn’t present a wintry side, as well, but it’s simply too early to know the details from a couple of weeks out. Stay tuned.
The average date for the first frost and freeze in Indianapolis takes place on October 11th and 14th, respectively. Right on cue, the first frost of the season will take place for most central Indiana neighborhoods over the weekend. If you happen to miss out on the frosty conditions this week, reinforcing chilly air will descend on the region early next week.
We forecast (3) of the upcoming (7) nights to fall into the 30s. This is, obviously, a significant change from the extended summer like conditions we’ve been dealing with as of late. One primary driver behind the significantly cooler pattern has to do with the change in the PNA. The shift towards a positive PNA will result in the cooler air remaining in place with more staying power than the fleeting cool shots of a few weeks ago.
A series of cold fronts will sweep through the Ohio Valley over the upcoming couple of weeks and each will likely feature progressively cooler conditions.
With the positive PNA in place, it’s no surprise to see the mean trough setting up shop over the eastern portion of the country.
At the surface, we see the cool pattern taking hold into not only the short-term, but the 10-15 day range, as well.
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