Late December through early January is a critical time period where most folks (even those maybe not normally interested in the weather) are glued in on the forecast. For some, they’re rooting for a white Christmas, while others are preparing for holiday travel to see loved ones. The idea here of a transitional pattern remains and this should promote active weather during the holidays this year.
Understanding things can change with respect to timing from this distance (in some cases 2+ weeks out), these are the dates we’re targeting for storm impacts across central Indiana:
- Dec. 20-21
- Dec. 24-25
- Dec. 27
- Dec. 30-31
Before we talk specifics, it’s important to look at some of the pattern drivers. Some of these drivers include teleconnections such as the NAO, AO, PNA, and MJO.
Forecast indices with respect to the AO, NAO, and PNA are expected to be more or less neutral through the late month period. This is what the respective teleconnection “state” would result in the temperature department across the country.
Arctic Oscillation
North Atlantic Oscillation
Pacific North American Pattern
The basis of our late-December forecast is built from the MJO, or Madden-Julian Oscillation. We note the MJO is expected to rumble through Phase 4 before heading into Phase 5 around Christmas. Phase 4 (image 2 below) is a warm phase and correlates well to what the week ahead will provide. However, Phase 5 (image 3 below) is a colder phase and could “up the ante” for the potential of wintry weather around Christmas.
If the MJO amplitude remains, it’ll roll into Phase 6 to close the month and open January. Here’s how that would correlate in the temperature department:
The upcoming week will run milder than normal- lining up perfectly with MJO Phase 4.
The first of our targeted holiday storm systems will come at the tail end of the warm Phase 4 and will likely deliver a wind-whipped rain in here as early as Wednesday night and Thursday morning. However, as the storm pulls northeast along the Ohio River, it’ll deepen on its journey into the eastern Great Lakes region. This will help pull colder air into the region, likely resulting in rain transitioning to snow Friday. Given the path of the storm, this doesn’t favor some sort of prolonged backlash snow event, but it could be enough to result in accumulating snow across eastern Ohio Valley sections and downwind of the snow belt regions of northern IN, OH, and MI.
The pattern, as a whole, appears to be one of transition to close the month and open January and it’s not really until we get to mid-January where we think all of the drivers “align” to create more of a lock and hold cold pattern. With that said, a stormy late December pattern can present problems, even in the midst of relatively mild times. We’ll be here to dissect the storms as they come throughout the holiday season…
The early spring “fling” has lulled many into believing winter’s finished. While the worst of the winter is certainly behind us, we continue to think a dose of “reality” awaits as we progress through the better part of the first half of March. To be more specific, we feel the period March 6th through the 20th will offer up below average temperatures and an active pattern- capable of producing wintry threats.
Sure enough, modeling is going to the pattern that will produce below normal temperatures (doesn’t appear to be anything particularly frigid, but colder than average, nonetheless) through mid-month.
With blocking in place, an undercutting jet will serve to deliver an active storm track.
Keeping in mind March winter events need multiple items to come together to create impactful situations, it’s also important not to simply “buy in” to the idea that just because it’s been warm lately that winter is finished. March can be a wild month, as long-time Hoosiers are aware. The pattern we’re heading into over the next 10-14 days is one that’s been void most of the winter (high latitude blocking in place) and can serve as the player needed to flip a “nuisance” variety late-winter event to one that’s much more significant. We’ll need to remain on guard for the potential of one or two “more significant” wintry events as we move through the first couple weeks of the month.
The end result is one that should promote colder than average times over the next couple weeks, overall, along with an active storm track. With blocking in place, the potential of one or two more significant late-winter events are on the table, and we’ll have to fine tune specifics as the individual storms come. While confidence is high that someone within the Ohio Valley region is likely to still deal with a big-hitter event, there’s no way to get specific until the individual players are on the field. Thereafter, the pattern should begin to transition to one more conducive for “stick and hold” spring conditions during the latter portion of the month.
II. We’re hopeful for much needed sunshine Sunday as we’ll be in between storm systems, however any sun that we see won’t last long.
While this is an unseasonably warm pattern (we forecast highs of 50°, or above, 5 out of 7 of the upcoming days, and at least 2 60°+ days), it’s one that will likely result in periods of heavy rain not only next week, but in waves over the upcoming 10 days.
Widespread 10-day rainfall numbers of 3″ to 4″ will be likely in this setup, including locally heavier amounts of 5″ to 6″ in spots. Certainly, if you live near waterways we suggest having a plan in place as it’s not a matter of if, but when flooding takes place in spots across the region with such a setup.
III. We’ll turn briefly colder to close the work week. A couple of light snow showers are possible Friday morning and a wave of low pressure will “try” to push moisture into the cold air Saturday. As of now, we remain unimpressed with the prospect of impactful wintry weather Saturday, but have included the potential of wet snow in our Saturday forecast. Precipitation appears to be very light. Nonetheless, we’ll continue to keep an eye on things.
IV. The pattern continues to scream and warm and wet next week as a big ole southeast ridge remains in place. This will direct the steering current into the TN and OH Valley regions and multiple waves of rain, occasionally heavy, will result beginning early next week and continuing into the middle and latter portions of the week. Widespread 2″ to 3″ totals with locally heavier amounts seems to be a good bet next week.
V. We note data continues to suggest a colder period looms as we close out the month of February and head into March. Note how the GEFS and EPS continues to tank the Arctic Oscillation (AO). Winter’s not over, not by a long shot…
The GEFS might be a bit quick on dropping the arctic hammer, but the consistency of the model is impressive. Meanwhile, the European (even it’s ensemble data) has been much less consistent and has really been struggling the past couple of winters, overall, as a whole.
Let’s also keep in mind that the initial cold onslaught is coming in the face of the MJO still rumbling through the warm phases. We note the European is consistently having to correct towards a more “amped up” MJO- swinging into the cold phases as we approach mid-month. And it’s mid-February that continues to have us concerned for the potential of truly nasty, severe cold.
As for snow, it’ll come in this pattern. Again, don’t get caught up in the operational output, but understand that the pattern over the upcoming 7-10 days favors numerous fast-moving snow systems. While most of these will be light, we’ll have to keep a close eye on things as the potential exists for one of these waves to spin up a moderate event.
Despite the milder air over the past week, January, as a whole, is still running 4° below average at Indianapolis- a byproduct of just how frigid the first half of the month was.
While the January thaw has been nice, times are changing and winter sure seems to be reloading for a very active second half.
Once we get a snowpack laid down, arctic highs oozing southeast will likely lead to bitterly cold air. Recall our expectation for this pattern to yield at least (1) night of double-digit below zero lows, but it’s more towards mid-month that we think the severe cold takes hold.
The Madden-Julian Oscillation (MJO) is forecast to rotate into the colder phase 8 as we rumble from early to mid February. Given the amplitude of the MJO, it should continue to rumble right through the cold phases of 1,2, and 3.
All of these moving pieces that lead up to extended periods of cold, wintry conditions are part of a bigger outcome low solar, easterly QBO winters deal up. What we should experience with this setup is a 6-7 week period of wintry conditions, including times of severe cold. It appears to be a snowier version of what we went through late-December through mid-January. Hang in there, spring will come…eventually.
When we look ahead, the shelf life of this warmth is certainly limited. The GEFS showcases this shift in the pattern from a warm open to the month towards a much colder pattern very nicely. The GEFS has other model support, as well.
This is the type of dramatic shift in the overall pattern that not only threatens to “lock in” a colder than average regime, but potentially lead to plenty of wintry mischief to boot, and just in time for the holiday season.
To summarize, while unseasonably quiet and mild conditions will rule in the short-term, Mother Nature sure seems to have an attitude of making up for “lost time” in the medium to longer range. This is the type pattern that we’ll have to monitor the potential of some sort of leader-follower scenario as the transition from warm to cold takes place, and given the blocky nature of the pattern, it sure seems like we’re heading into a busy time of things from a wintry perspective mid and late month.
Such a pattern illustrated above, per the European ensemble (image 1) and the GFS ensemble (image 2), would help drill a tongue of unseasonably cold air through the northern Plains, into the Mid West, and across the East.
We’ve been discussing early snow cover across Canada and the northern tier for weeks and how models would have to “correct” colder as they realize the air masses traveling over the snowpack won’t be able to modify as they normally would without that snowpack. The differences between this November and last are startling and show how the early snowpack is beginning to “feedback” on itself leading to early-season cold air.
2017 snowpack and temperatures anomalies through the first week of November:
Given the overall look to the pattern downstream, I anticipate the cold will continue to “press” and eventually overwhelm the pattern east as we progress through the second half of the month.