Category: High-latitude Blocking

Buckle In…

Updated 02.05.21 @ 7:18a

Where to begin?! Simply put, the pattern over the next 2 weeks is a winter weather lover’s dream setup. Does that mean central Indiana has to “cash in” on every event? Negative. In fact, by next weekend, we believe the Deep South will even get in on the wintry fun (outside of the higher elevations that have been doing quite well this year). That said, systems will be targeting our general area fast and furious and require us to remain on our toes. Given that a more prolonged period of cold is developing, we should be able to build a nice snowpack for outdoor winter enthusiasts over the next 7-14 days.

The setup is all thanks to a persistent negative to deeply negative AO and the associated high latitude blocking. The Pacific pattern is also changing to allow more meaningful cold (truly arctic air is getting involved in the pattern) into the East with staying power. We can thank the now negative EPO for that. That leads us to the PNA. A negative to even neutral PNA will continue to put resistance on the pattern and result in southern ridging at times. That’s especially true early on in this regime. That puts the Ohio Valley in the cross hairs of these systems. As the arctic air takes hold, I still believe eventually we’ll see a more suppressed storm track for a time but that likely doesn’t develop until late next week. Before that, we have multiple storms to track and a snowpack to build. 🙂

First up is an arctic wave that arrives Saturday evening. This is a system that should deposit 1” to 3” of snow, mainly from Indianapolis and points north (dusting up to 1” across the southern half of the state). This will be a fast moving system that will arrive around 5p across western parts of the state and will be out of here during the predawn hours Sunday.

Temperatures will crash Sunday morning into the single digits and highs will likely only climb into the middle teens. Good thing there’s a Super Bowl to focus on.

Additional upper level energy will result in light snow moving back in here Monday afternoon and night. With cold, arctic air in place, this system should be able to squeeze out an additional dusting to inch of snow (even as weak as it is).

That leads us to Tuesday night and Wednesday. A surface wave is expected to develop in the Ark-la-tex region and lift northeast. This will be a “juicier” event and result in widespread wintry precipitation across the state. Early thinking here is that across central and northern parts of the state, this will be mainly a snow event. Southern portions of the state may mix with sleet and/ or freezing rain. While we can’t throw out numbers this early, where it stays all snow, several inches seem likely.

If that’s not enough, more “fun and games” are dialed up with yet another system next Thursday and Friday. This, too, could be a meaningful winter event, locally, and will require close attention moving forward.

From a temperature perspective, it continues to look like a case of “delayed but not denied” on the topic of truly dangerous arctic air. As the pattern evolves and a snowpack is established, the concern here is that we’re looking at a period of severe cold (double digit below zero temperatures and wind chill values exceeding 20° below zero) by late next week/ next weekend.

More later today! Have a great Friday, friends!

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VIDEO: A Busy Winter Pattern Settles In…

Updated 02.03.21 @ 7:24p

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VIDEO: Pattern Drivers Starting To Align To Deliver More Sustained Cold As We Get Deeper Into Feb?

Updated 01.28.21 @ 6:30p

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VIDEO: Negative AO, Negative PNA Patterns Are Far From Boring…

Updated 01.26.21 @ 9:40p

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Evening VIDEO: “Active” Would Be An Understatement Into Early February…

Updated 01.25.21 @ 9:35p

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VIDEO: Detailed Breakdown Of Our Latest Thoughts Concerning Next Week…

Updated 01.21.21 @ 8:00a

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VIDEO: And The “Squeeze Play” Is On…

Updated 01.20.21 @ 7:45a

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Active Pattern Persists To Close January; Targeting Storm Dates…

Updated 01.19.21 @ 7:58a

Another upper level disturbance will push into Indiana this evening, providing a renewed shot of snow showers after dark, continuing into the overnight hours. Before we look at this and other storm dates of interest, I wanted to review the upcoming couple of weeks from a temperature and precipitation perspective.

While there weren’t a lot of changes overnight with respect to the ensemble guidance from Week 1 to Week 2, it’s fair to say the GEFS and EPS are trending in 2 separate directions- at least across the Ohio Valley into the Northeast Week 2. The theory here is that the differences come from the way the modeling handles the EPO and subsequent downstream ridge resistance. At any rate, confidence remains lower than normal in the 7-14 day period and it’ll likely take another 48-72 hours for things to become clearer during this time frame.

Week 1

GEFS Week 1 Upper air pattern
GEFS Week 1 Temperature Anomalies
GEFS Week 1 Precipitation Anomalies
EPS Week 1 Upper air pattern
EPS Week 1 Temperature Anomalies
EPS Week 1 Precipitation Anomalies

I would lean more on the European in the Week 1 timeframe (due to the precipitation pattern with forecasted trough/ ridge positions), though the solutions are similar, overall.

Week 2

GEFS Week 2 Upper air pattern
GEFS Week 2 Temperature Anomalies
GEFS Week 2 Precipitation Anomalies
EPS Week 2 Upper air pattern
EPS Week 2 Temperature Anomalies
EPS Week 2 Precipitation Anomalies

Despite the subtle differences, I would lean heavier towards the European solution again (retrograding eastern trough idea).

Storm dates of note include the following:

Jan. 24th-25th

Jan. 27th-28th

Jan. 31st-Feb. 1st

Expect continued wild run-to-run swings on the operational guidance as the data tries to understand the battle between the high latitude blocking (courtesy of the negative AO) and maturing negative PNA (will lead to southern ridging and more resistance as this gets established). These combined ingredients will lead to more of a question of wet vs. white, as opposed to a non-storm “event” that we’re dealing with Thursday-Friday. With the blocking in place, it’ll be tough to drive lows to the Great Lakes and we’ll need to watch for southward trends on guidance the closer we get to these potential storm dates of note above.

In the meantime, we have one more clipper system that will dive into the region this evening. This will offer up yet another round (the last in the series going back to last week) of snow showers after dark into early Wednesday (snow should be out of here by mid to late morning tomorrow). Snowfall accumulations across central Indiana can be expected to fall within the dusting to half inch range.

Permanent link to this article: https://indywx.com/2021/01/19/active-pattern-persists-to-close-january-targeting-storm-dates/

VIDEO: Short And Long Range Update As We Head Into (At Times) A Snowy Weekend And Get Set To Traverse The 2nd Half Of Jan/ Open Feb…

Updated 01.14.21 @ 6:52p

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1st Wintry “Jab” Blows Into Town This Weekend In What Should Be A Stormy Finish To January…

Updated 01.12.21 @ 8:08a

Finally we can breathe a sigh of relief as the seemingly unending low cloud deck erodes and gives way to increasing sunshine today. Along with a return of the sun will be a moderating trend in the temperature department. Expect highs in the low 40s today and mid 40s Wednesday and Thursday as a southwesterly flow develops ahead of Friday’s cold front.

The cold front, itself, will swing through central Indiana late Thursday night and early Friday morning. While we still think this will be a mostly dry FROPA (frontal passage), models are becoming more robust with a “bowling ball” of an upper level low pressure system over the weekend.

Note how the upper low becomes almost cut off from the primary steering flow for a time Saturday across the Great Lakes region. Additional “spokes of energy” (upper level disturbances) will pivot south of the primary cut off low across the Ohio Valley Friday night through Sunday afternoon. This will help lead to enhanced periods of snow and snow showers throughout the weekend.

We’re still not looking at heavy snowfall, but the rather persistent nature of light snow this weekend will accumulate to an inch or two for some communities along with a much colder air mass. After Friday evening, temperatures won’t make it above freezing again likely until Tuesday afternoon.

When we look at the bigger picture, this will likely go down as the first “jab” of more exciting weather to wrap up the month of January.

While still not overly cold (doesn’t have to be this time of year for wintry issues to arise), the pattern does look very, very active through the 2nd half of January and to open at least the 1st week of February. While the Greenland Block continues to mature, note the change in the Pacific. We may finally be able to get a negative EPO to develop to align with the negative AO and NAO.

If this does, indeed, transpire we should see a rather expansive snowpack get laid down across the country during the last week to 10 days of January. It would then be this time into early February to look for the possibility of more significant arctic air to spread out and cover more of the Lower 48 (after initially likely being bottled up in western Canada and the northern Rockies).

At the very least, times are becoming more interesting. It’ll be a fun ride through the rest of the month and to open February.

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