Halloween morning will dawn with a cold rain. Coverage of rain will increase rather dramatically after midnight and continue through the morning rush before tapering off mid to late morning. An additional 0.50″ to 0.75″ will be common by the time this next round of rain moves out.
Rain will be widespread across central Indiana Halloween morning.
Colder air will begin to whip into central Indiana late morning into the early afternoon, accompanied by strong and gusty WNW winds. After a lull in the precipitation, snow flurries and scattered snow showers will develop across the area after lunch, potentially becoming a bit steadier (especially from Indianapolis and points north) during the 6p-8p time frame. Yes, trick-or-treaters (kids and adults alike) will need to be bundled up!
The first snowflakes of the season will fly Halloween afternoon-evening.
Snow will end rather abruptly between 9p and 10p and then the story will be the cold. By daybreak Friday, all of the region can expect to be in the middle 20s with wind chill values in the 10s.
A very cold open to our Friday is on deck.
With the MJO focused on rumbling into Phase 5 (and eventually 6), along with a deeply negative EPO and slightly positive PNA, it’d be wise to gear up for more “out of season” cold and potentially wintry conditions as we move through the 1st half of November…
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I. A cold front will slip through central Indiana this evening. After a high near 60 today, temperatures will be stuck in the 40s most of the day tomorrow. To add insult to injury, rain will overspread the state from the southwest late tonight into Wednesday morning.
There will be brief lull in the rain Wednesday evening before rain becomes widespread yet again early Halloween morning. All total, many central Indiana rain gauges can anticipate around 1″ of rainfall with this storm system.
II. Speaking of Halloween, it’ll be important to dress warmly when out and about trick-or-treating Thursday evening. Falling temperatures, increasingly gusty winds, and snow flurries/ scattered snow showers can be expected. How cold? Temperatures will be falling into the lower 30s Thursday evening with a gusty wind (around 30 MPH) resulting in wind chills in the upper 10s to middle 20s.
Precipitation will transition to light snow showers/ flurries Thursday PM.
Wind chills will fall into the upper 10s to middle 20s Thursday PM.
III. The first lake effect snow event of the fall will take place this weekend. Accumulating snow is expected in the snow belt regions- especially Saturday night. Otherwise, the first official freeze of the season can be expected for many across the Ohio Valley this weekend.
IV. Longer term, I’d get used to the cold, more wintry weather. The pattern continues to look much colder than average and active as we rumble through the early part of the month. (In case you didn’t see it last night, our November Outlook can be found here).
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I want to give a couple examples of significant conflicting signals- both short and long-term. The end result is a situation where long range, climate, and seasonal models are likely to have a very tough time not only in the medium to long range (2-4 week period), but thinking seasonally, as well (winter and next spring).
Short-term
To start, let’s look at the EPO. While strongly positive at present, both the EPS and GEFS pictured below take the EPO, or East Pacific Oscillation, negative in the coming couple of weeks.
A negative EPO pattern favors a trough across the eastern portion of the country, especially here in our neck of the woods, with western ridging.
All well and good, right? WRONG. The MJO, or Madden Julian Oscillation, is forecast to stall out into early October in Phase 1.
This time of year, Phase 1 argues strongly for eastern ridging and well above normal warmth while the western portion of the country can experience early wintry conditions.
Talk about contradiction! That’s what makes weather so fun and fascinating. Expect to be humbled often and to always learn! At various times of the year, select teleconnections can mean a lot more than other times of the year. For example, during the summer and fall, we lean heavily on the EPO, PNA, and MJO (if amplified). During the winter and spring, it’s important to take into account what the AO and NAO have to say. It’s important to know when to “pick and choose” when to use particular teleconnections… Furthermore, the various MJO phases (1-8) mean drastically different things at different times of the year. While lovers of chilly fall conditions have grown to hate an amplified Phase 1, they have to love it come winter (shown below). Just look at that difference!
Before jumping ahead to another example of “contradicting signals,” we’re confident the amplified MJO Phase 1 will carry the day through the short to medium range period. Note the strong agreement between the EPS and GEFS below with respect to temperature anomalies in the 6-10 day period.
With that said, there will be challenges within (the big difference as early as this weekend between the GFS and European operational data). A lot of that has to do with the “fight” between the EPO and MJO to take control.
As all of this unfolds across the East, the west will begin to cash in on early winter. Well below average cold and snowy conditions will begin to make headlines over the weekend into next week across not only the Rockies, but some of the low ground, as well. Should the MJO swing into Phase 2 (and I think it will towards mid-Oct), then watch out. We’ll be looking at a rather significant shift towards a much colder feel- and it’ll sting even more so with the late season heat over the better part of the next couple of weeks.
Flipping the page to winter (remember, our prelim. winter outlook will be posted later this week) and the contradiction continues. Upon looking at the current SST configuration, one could easily argue we’re talking about a La Nina winter unfolding ahead.
Meanwhile, the current SOI would suggest we’re in a moderate El Nino.
If you think this can’t wreck havoc even on the short-term forecast pattern, think again…
To close, while the conflicting data can create headaches at times, it’s more fascinating than ever trying to sift through the data and build our forecast(s). It’d be wise to expect more wild swings ahead- leave it to us to try and minimize the impacts of those swings in your day-to-day personal and professional lives. Accordingly, it’s also ultra-important to factor in additional items, such as solar and PDO into the equation for the upcoming winter.
Speaking of, without giving too much away, if I’m a winter weather fan (and I am), I wouldn’t worry in the least about the current warmth… 😉
