We’ve already been dealing with winter weather this week, so I suppose the time is right to unleash my Winter Outlook! This outlook focuses on the three-month period known as “meteorological winter” (December, January, February). I will say this: The upcoming season has potential to be snowier than the previous two. I’ll get into the reasons why in just a moment.
First, as I always do, I want to briefly look back at last winter and how my outlook leading up to it fared. It wasn’t exactly spot on, but boy was it close!
Here are some excerpts taken straight from LAST November’s post for the ’17-’18 season:
TOTAL SNOWFALL: (7-10” – slightly below normal to near normal)
Actual season snow total: 11”, but that includes 2.3” in March and even 0.3” from that freak April snow, both of which occurred after “meteorological winter”. Take away those late season snows and you wind up 8.4”…right smack dab in the middle of that 7-10” range. Total snow is by far the toughest part of the Outlook to predict. That’s a win in my book.
CHANCES OF SEEING AT LEAST ONE ICING EVENT OF A TENTH OF AN INCH OR GREATER: 40%
This did verify, as we had some icing just prior to significant snow on Jan. 12th, 2018.
CHANCES OF SEEING AT LEAST ONE SIGNIFICANT SEVERE WEATHER EVENT BETWEEN DEC. 1ST AND FEB. 28TH: 70% (high probability given our history with La Niña winters – always be ready!)
Give that one another “check”. Recall we had a severe weather outbreak that featured several tornadoes in the region on Feb. 24th. Sadly, one of those turned fatal in southern Logan County.
PRECIPITATION: Above normal (pretty high confidence here)
That also came to pass, although February was the main reason. That’s when we saw a whopping 8.59” of rain. December and January actually wound up being quite a bit drier than normal. But I was correct on the overall idea.
I was also correct last season on the call that we’d have more cold and snow to contend with in March (although I sure didn’t think it would go so far into April!). And the coldest part of last season did indeed fall between mid-December and mid-January. I upped the ante for White Christmas chance to 25% (higher than the normal 10%) last year, and while that didn’t officially come to pass, we DID see flakes on Christmas Eve night. Speaking of flakes, I said that most of the season’s snow would come from two systems. Sure enough, 8.2” fell in January, all of it coming from two pretty big snow makers around mid-month (one on the 12th, the other on the 15th).
As a forecaster, when I’m wrong, I’ll be the first to admit it. I’ve eaten some slices of humble pie in my 17 years of doing this. But last year’s Outlook verified about as well as a forecaster could possibly ask.
OVERALL GRADE FOR LAST YEAR’S OUTLOOK: A-
Enough about last year. Now, on to this season’s outlook and the players on the field.
**HERE IS WHERE THE TALK GETS TECHNICAL. IF YOU WISH TO SKIP THIS PORTION, SCROLL DOWN THE PAGE TO FIND “WINTER OUTLOOK”**
- EL Niño: Unlike the past two seasons where “La Niña” played a role, it’s “El Niño” that will have an influence this go round. With “La Niña”, we saw cooling of the waters near the equator in the Central Pacific Ocean. But with “El Niño”, those same waters of the Pacific run warmer than normal by at least one-half degree Celsius.
Why is this warming a big deal? Well, it has an effect on the position of the jets stream’s southern branch, the “subtropical jet”. The subtropical jet tends to dip near Hawaii, riding eastward into the Desert SW and southern U.S. For the Ohio Valley, this jet branch is usually not as active in El Niño seasons as we often see it in La Nina years, but that is NOT to say we won’t see any decent-sized storm systems at all. Remember the Winter of ’14-’15 and how snowy it was, especially February into early March? That was an El Niño season.
The strength of an El Niño is a big factor, too. Winters such as 1982-’83 and more recently, 2015-’16 featured strong, “Super” El Niños where central Pacific waters ran close to 2 degrees above normal. This resulted in a lot of mild air overwhelming much of the lower 48 at times (aka “the blow torch effect”). Winter ’15-’16 turned out to be one of Bowling Green’s warmest ever. BUT…in the few occasions where it was cold, we had BIG snows, including that blockbuster on Jan. 22, 2016 that dumped over a foot of snow for many! Sometimes all it takes is that ONE system.
This time, however, I think we’re looking at a weak to low-end moderate El Niño. That’s based on the latest observed Pacific surface water temps and forecast trends. The graph below shows a surge of warmth that happened going into October. This had me concerned that El Niño could be stronger than was predicted, but that warming appears to have leveled off of late. A rather weak El Niño usually doesn’t overwhelm the patterns for North America, something that allows the polar jet to dive southward more frequently to deliver cold shots to Kentucky. If you like snow, that’s a good thing.
- PNA/NOA/AO: These are the “wild cards” when it comes to winter forecasting. Unlike the indices mentioned above that deal more directly with sea surface temps, these refer to the movement (a.k.a. oscillations) of semi-permanent pressure systems in the North Pacific, North Atlantic, and Arctic, respectively. Those movements can be highly variable. Unlike predicting El Niño or La Niña, there’s very little skill in predicting the behavior of the PNA, NAO, or AO much beyond two weeks out.
To put in simply, if a negative PNA is coupled with a positive NAO and AO, then we’re typically mild to warm in Kentucky. If the PNA goes positive AND the NAO and AO go negative, that’s when bitter cold, arctic air has a better chance of plunging south into our region. Combine that with an active subtropical jet and you increase the chance for accumulating snows.
- SNOW COVER: Here’s something to consider: Look how far south the snow pack is across the central Plains and Ohio Valley. That’s something we haven’t seen since November 2014. We all remember what the following season was like. Not saying it will be a repeat, mind you. Just pointing out the similarity.
ANALOG YEARS: To look ahead, sometimes we have to look back. I’m looking at winter seasons with an El Niño setup along with oceanic temperatures and other patterns that best match the upcoming season. My research led me to these (that season’s total snowfall in parentheses):
Winter 1979-’80 (14”)
Winter 2002-’03 (12”)
Winter 2009-’10 (16”)
None of those three featured extreme, out-of-the-ordinary cold, but all of them brought their fair share of snow, especially for Bowling Green standards. Winter ’79-’80, which came on the heels of three BRUTAL seasons in the late ‘70s, followed a year of record rainfall for BG (60”+). 2018 has also been far wetter than normal for us. 2009 was also pretty damp leading up to the winter season. Winter ’02-’03 had frequent moderate snowfall events of the 2-4” variety during January and February. It’s also worth noting that our coldest temps weren’t felt until the latter half of meteorological winter (late January into February). In fact, our biggest winter storm in 1980 mentioned didn’t happen until March 1st (5” for Bowling Green).
Other El Niño seasons given *some* consideration but not to the extent as those listed above include:
Winter 1969-’70 (16”)
Winter 1977-’78 (37”)
Winter 1994-’95 (2.5”)
Winter 2014-’15 (24”)
Of those, only one was a snow “dud” (’94-’95) with much of that season being mild. The odds of this upcoming winter coming anywhere close to ’77-’78 or even ’14-’15 – one of coldest and snowiest seasons since the 70s – are very slim. But hey, there are no guarantees in this business!
For perspective, here are some stats to keep in mind as we head into this season. On average, Bowling Green sees about 9” of snow for a winter season.
Here are some stats, along with some extremes.
First, the obligatory disclaimers: This is NOT an official First Alert forecast; it’s simply my own “outlook” for the upcoming season. As with any outlook, there’s always bust potential with any aspect of it. That’s especially true for the snowfall forecast.
DECEMBER: Here’s where we’ve underachieved in the snowfall department over the past decade or so. We haven’t had more than a few tenths of an inch of measurable snowfall in this month since the beginning of this decade (2010). It seems most Decembers in El Nino years have featured a lot of temperature variability vs. January or February. I can see a flip back to some milder conditions for a time after our chilly November. But there will be some cold air on occasion, too. I see a fairly active storm track continuing into next month. So White Christmas dreamers, don’t lose all hope!
FORECAST TEMP FOR DECEMBER: 1-3° above normal
FORECAST SNOW FOR DECEMBER: Less than 2”
FORECAST PRECIP FOR DECEMBER: Slightly above normal
JANUARY: Unlike last season when January started bitterly cold, I believe it starts milder this go round. However, the latter half of the month is historically the coldest part for our area. The analog years listed above all featured some very cold, snowy times near January’s end. I think this January follows suit.
FORECAST TEMP FOR JANUARY: 1° above to 1° below normal
FORECAST SNOW FOR JANUARY: 3-6”
FORECAST PRECIP FOR JANUARY: Slightly above normal
FEBRUARY: It’s funny how the each of the past two Februarys have ranked among the warmest ever for Bowling Green! On the flip side of the coin was February 2015, which was one of the coldest ever for us. I’m not sure if this one will feature the kind of brutal cold and heavy snow that Feb. 2015 did, but I’ll be shocked if we see a repeat of the warmth of the last two. All signs point to more frequent cold shots for the eastern U.S. during the latter part of this season, with potential for more snow than in the past couple of Februarys.
FORECAST TEMP FOR FEBRUARY: 2-4° below normal
FORECAST SNOW FOR FEBRUARY: 4-7”
FORECAST PRECIP FOR FEBRUARY: Slightly below normal
So here’s the season outlook in a nutshell:
If that 12-16″ snowfall forecast verifies, it would be 3-7″ above normal for BG.
Some other ideas/thoughts:
–We’ll have a couple of shots at getting in on “big ticket items” (i.e. storms that could dump more than 4” of snow)
–We may get in on more minor to moderate snowfall events of the 3” or less variety than last season
–Cold and mild temps tend to come in more extended “spells” in El Niño seasons with temperature swings less “crazy” than in La Nina years, such as last season
–Banking on a more-active-than-usual subtropical jet for an El Niño season, therefore keeping precip near normal overall
–Coldest period likely to be later this time (very end of January through mid-February)
–One more late season snow in early March not out of the question, but believe Winter breaks for Spring much earlier this time vs. last season
–Threat of large-scale severe outbreak within next three months not as great as last year, but can never completely rule out at least one significant cold season severe event
–Chance for a White Christmas: 10% (dropping it back to near climatological odds this time)
There you have it. As always, no matter what Mother Nature dishes out, we’ve got you covered on-air, on-line, on the WBKO Weather App, and on Alexa devices this upcoming season. Now, let’s see how it all shakes out!
Thanks for reading.