Category: Forecast Models

Jan 15

Reviewing The Snowy Details…

After a brief thaw, winter’s set to return with authority in the days and weeks ahead.  In fact, the overall long range weather pattern looks colder and snowier than average into early February, at least.

A current look at the National Radar shows the next clipper system taking shape to our northwest this evening.

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A dive into the latest model data continues to highlight two distinct opportunities for accumulating snowfall in the days ahead.  The first comes Thursday into Friday while the second (potentially more robust) snow maker arrives Saturday afternoon and evening.  By the way, my hat’s off to the GFS for jumping on Saturday’s system well in advance of the other modeling.  Sometimes it’s easy to hammer the GFS, but it should be pointed out during the model’s shining moments, as well.

Back to the near-term… We think widespread snow overspreads central Indiana Thursday morning and continues through the majority of the day and on into Friday in varied intensity.  By the time all is said and done, 2-4″ of new snowfall will be likely across central Indiana, with some locally higher amounts possible.

Here’s a look at the latest HRRR simulated radar valid 10am Thursday. Some moderate to briefly heavy snow is possible late morning into the afternoon.

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Of interest, we note forecast models carrying a vigorous upper level disturbance across the state Thursday night/early Friday and this will help carry accumulating snow into Friday for some.

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We’ll note an intrusion of briefly drier air Friday afternoon into Saturday morning, but by this time all eyes will be focused on the next clipper system that promises to keep snow shovels and plows busy for parts of Indiana into the weekend.  We think snow overspreads the region from northwest to southeast Saturday afternoon and evening.  Steadiest snow falls Saturday night and could accumulate to the tune of a few inches by daybreak Sunday within the axis of best moisture.  Just to the north of the clipper’s track will be where you find the highest snow totals with Saturday’s system and the precise track of this clipper will be tough to iron out with any sort of certainty until Friday evening.  Stay tuned.  By the way, the snowy and cold events keep on keepin’ on in the longer range…

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Permanent link to this article: https://indywx.com/2014/01/15/reviewing-the-snowy-details/

Jan 15

Series Of Fast Moving Snow Makers…

A series of fast moving snow makers will make for busy times in the good ole forecast office in the days (and weeks) ahead.

Of course we’re dealing with scattered snow showers this morning, but this really isn’t a big deal as accumulations will be nothing more than a dusting for most communities.

Our next clipper system will deposit light snow and snow showers across the region Thursday and Friday.  Short-term, high resolution data, highlights the chance of some light accumulation Thursday into Friday- generally an inch or less for most.  Here’s a look at the latest simulated radar valid Thursday morning at 8am and Friday at 4am:

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We then look ahead towards Saturday when potentially the best shot of accumulating snow arrives.  The GFS has been leading the way on this system and now other forecast models are following it’s lead.  It’s important to note that these northwest flow systems can be over-achievers (as mentioned in previous posts) and the “fluff effect” can really kick into gear thanks to high snow ratios with the cold air.  We’ll continue to monitor this.  As of now, we think a few inches of snow is possible Saturday as this clipper moves through.  Stay tuned…

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Permanent link to this article: https://indywx.com/2014/01/15/series-of-fast-moving-snow-makers/

Jan 14

Challenging Northwest Flow…

We’ve made mention of this in the past and we bring this up again as the upcoming weather pattern is one that’s predictable in one sense, but very challenging in another.  We know it’s going to get colder, that we’re confident on.  That said, models will continue to struggle with the details of snow chances, associated with clipper systems diving southeast into the region.  Issues with timing and snowfall amounts are common in these patterns up until 24-48 hours prior to the event.

Case in point, let’s take this weekend. Three forecast models are handling snow chances differently in the Friday-Saturday period.  The European model and Canadian are jumping more on Friday snow (light accumulations), while the GFS is focused on Saturday snow (again, light accumulations)…

Which is the correct solution?  It’s a tough call at this point, but we’ll go with a blend of the three for now, focused on best accumulating snow chances (1-2″ variety) coming late Friday into Saturday morning.  That said, as mentioned above, it’s a tough call and this will require fine tuning as we move forward.  Make it a great day!

The European and Canadian forecast models are honing in on Friday for best chance of light accumulating snow:

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Meanwhile, the GFS is focused on Saturday for best snow chances:

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Permanent link to this article: https://indywx.com/2014/01/14/challenging-northwest-flow/

Jan 09

Bet On The Colder Look…

Sometimes in life there are things much more important than the weather and so has been the case the past few days. Moving forward, posts will be a bit erratic,…

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Permanent link to this article: https://indywx.com/2014/01/09/bet-on-the-colder-look/

Jan 04

Serious Winter Storm Takes Aim On Indiana

We awake this morning to most of the data very consistent with what we’ve been passing along to you over the past few days…a very serious winter storm is taking aim on Indiana and will result in a combination of significant weather events that ultimately may end up being something we’ll remember for quite some time…

Quick Bullet Points:

  • Snow develops early Saturday morning
  • Heaviest snow falls between 10a-5p
  • Wind increases through the day Sunday and gusts in excess of 30 MPH leading to white outs and severe blowing and drifting
  • Temperatures crash to 10-14 below zero Monday morning with wind chill values of 40 to 50 below zero.
  • Widespread snowfall of 5-9″ is likely across central Indiana, with a heavier band of 9-12″ including Indianapolis and running along and just north of the I-70 corridor on the south side north to include Vermillion to Adams counties on the north side.

This is a hazardous and severe winter weather event that will likely lead to road closures from the heavy snow and wind, as well as extremely dangerous conditions to spend anytime outdoors Sunday into early next week due to the cold.  The bitter wind chills will be capable of frostbite in less than 30 minutes to any exposed skin.

Latest model data shows consistency in precipitation amounts, or QPF. We’re showing you the GFS, Canadian, and European models below.  Please note that the numbers and maps below don’t show snowfall amounts, but show precipitation totals.  Bring in a 12-15:1 snowfall ratio with these numbers and you get the snowfall discussed above.  We’re leaning heavily on a Canadian/ European model blend as the GFS has been more erratic.

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Much more later this evening!

Permanent link to this article: https://indywx.com/2014/01/04/serious-winter-storm-takes-aim-on-indiana/

Jan 01

Triple Threat Of Dangerous Winter Weather Ahead…

You can always catch your latest 7-Day Video Forecast in the video player to the right of this post.

We continue to be very impressed with what’s ahead, winter weather-wise, for central Indiana over the course of the upcoming 10 days.  Simply put, what’s at stake is a 10-day period of winter weather that could rival the all time greats in terms of snowfall and cold.  It’ll certainly be interesting to watch things unfold in the days ahead.

Here are some quick-hitting bullet points of what we’re eyeing…

  • Accumulating snow late tonight-Thursday
  • Accumulating snow late Saturday night-Sunday
  • Coldest air since 1994 early next week
  • Dangerous cold and wind chill values to 40 degrees below zero

First things first and that’s tonight’s and Thursday’s snow event. We think snow becomes widespread across central Indiana prior to, or around, midnight.  The low pressure system that will aid in snow production across our region Thursday AM is organizing across the central Plains this evening and this will move east northeast with time between now and Thursday morning.

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Latest high-resolution simulated model data shows the snow increasing in coverage across central Indiana around midnight.

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We think the period of heaviest snow comes during the early to mid morning Thursday and will result in a horrible rush period on area roadways.  Accumulating snow ends by noon and is replaced with falling temperatures, gusty northwest winds resulting in blowing and drifting, and scattered lake-driven flurries.

All eyes will then shift to storm number two set to arrive late Saturday night into Sunday.  An arctic boundary will moves towards the region Saturday night and Sunday and help surface low pressure develop.  All of our medium range models (GFS, Canadian, European) are on board with a developing surface low in the Ark-la-tex region late Saturday night/ early Sunday morning and can be seen below.

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There are still some questions that we have in regards to the extreme snowfall forecasts off some computer models, and we’ll stick with our initial call made here last night of an additional 3-6″ of snow late Saturday night-Sunday for now.  We come up with that range based off an all model blend, including raw numbers, operational data, and ensembles.  An extremely strong arctic high pressure system will be plunging south and will limit how far north the heavy snow makes it.  That said, snowfall ratios and an initial impressive thermal gradient will lead to a heavy snow storm for some parts of the Ohio Valley region Sunday.  Stay tuned.

As early next week approaches (and I’m all settled in to enjoy what I hope to be Auburn’s second National Championship in 4 years), the coldest air since 1994 will be blowing into the region.  Downright dangerous wind chill values of 40 degrees below zero will be possible Monday into Tuesday and result in extremely dangerous conditions to be outdoors for any period of time.

Here’s a look at the latest wind chill idea:

plotterForecast lows of 15 to 20 degrees below zero will be likely early next week across central Indiana with afternoon highs struggling to make it to zero.

Prepare now for a significant triple threat punch of snow and cold in the days ahead. Stay tuned!

Permanent link to this article: https://indywx.com/2014/01/01/triple-threat-of-dangerous-winter-weather-ahead/

Jan 01

Things Progressing As Planned; Double Shot Of Snow Love…

It’s great to be back in the good ole weather office and craft a post about the upcoming weather pattern- a pattern that should be pointed out to be progressing along as planned.  Simply put, if you like winter weather, this is the pattern for you.

If you haven’t had a chance to read the posts from the past couple weeks, please be sure to do so as we laid the ground work as to why we were buying a cold, wintry pattern returning:

As we look ahead over the upcoming (7) days we’re tracking two accumulating snow opportunities and one big slug of downright bitter (and dangerously cold) air.

First things first and that’s the snow event ahead Wednesday night into Thursday.

We currently think snow overspreads central Indiana late Wednesday night into the wee morning hours Thursday.  Snowfall accumulations with system numero uno will likely be in the 2-4″ range for many neighborhoods across central Indiana.

The latest high-resolution NAM model shows the snow moving in and becoming moderate to briefly heavy during the wee morning hours Thursday:

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Heaviest snow with system #1 falls prior to noon Thursday with light snow and gusty winds lingering for the PM.

That said, we don’t have much down time as system #2 is set to arrive late Saturday night into the wee morning hours Sunday.  The weather situation is one that features an arctic boundary sinking south over the region Sunday morning with a wave of low pressure organizing along the middle Mississippi River Valley. The surface low is expected to move northeast Sunday and help spread precipitation into the greater Indianapolis and central Indiana region. With cold air in place, this precipitation is likely to fall in the form of snow.

While we have a couple of days to keep an eye on the Saturday night-Sunday time period, the likelihood of additional accumulating snow is growing with each and every model run.  The “ridiculously” early call on the Saturday night-Sunday time period, based on a variety of raw numbers, medium range models, and ensembles would suggest 3-6″ of additional snow is ahead during the aforementioned time period.  Again, we caution confidence ins’t as high as with system #1, due to the time period, but please be sure to stay tuned.

The GFS shows widespread snow falling across the region Sunday, with a favorable surface low track for accumulating snow across central Indiana:

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Following the second snow system, model data continues to suggest we have to deal with some downright dangerous air. In fact, this would be the coldest air in many a year across central Indiana and many other locations of the Mid West and even into the Deep South.  Forecast lows in the double digit below zero range are possible following the second snow maker and associated arctic front early next week….

Needless to say, I hope you like winter weather!

Permanent link to this article: https://indywx.com/2014/01/01/things-progressing-as-planned-double-shot-of-snow-love/

Dec 23

Impressive Cold Pattern Looming; Beware Of The Northwest Flow…

We continue to be very impressed with the cold pattern that’s looming.  Even before the warm up and thaw last week, we made mention that the seeds were being planted for a very cold close to December and open to 2014.  Latest data continues to back this idea up.  Additionally, in the longer term, there are some goings on that would suggest we better hunker down for a colder than average January.  While December will finished colder than average, a colder than average January can really hurt the pocket book as “average” temperatures are obviously even colder than December.

Today’s 12z ensembles are locking in on the pattern than can deliver one shot after the other of arctic air in the 8-10 day range.

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As for the snow, we still think we need to watch the models around the New Year for the threat of some southern stream energy interacting with the available cold air.  That said, even without the southern stream, one must remain abreast of the challenge that a northwest flow pattern can produce.

Forecast models have a difficult time handling clipper systems in these type of patterns until within 24-48 hours within an event.  Many times what appears to be a rather “harmless” clipper 4-7 days out can suddenly turn much more robust once the model catches onto the track and ability to literally squeeze out any and all available moisture from a cold air mass.  Furthermore, the “normal” 10:1 snow ratio, many like to use, doesn’t apply in the least to these type systems.  In cold environments you can easily get what’s called the “fluff effect” and snow ratios are more in the 20-30:1 range.  Needless to say, it’s a challenging pattern that will keep us on our toes over the coming couple of weeks.

To summarize, we’re extremely confident on a colder than average close to December and open to January.  We’ll have to monitor fast moving clipper systems that modeling will struggle with until right up to the event.  Finally, we’ll keep a close eye on the potential interaction of the southern stream and cold air around the New Year time period for the possibility of a storm of “more significance.” Stay tuned!

Permanent link to this article: https://indywx.com/2013/12/23/impressive-cold-pattern-looming-beware-of-the-northwest-flow/

Dec 20

Colder Than Normal Pattern Set To Return

Before we go into the cold pattern that is looming, our current forecast of severe flooding developing across central Indiana this weekend remains.  Our projected precipitation numbers remain in the 3-4″ range for most of central Indiana, but there will be some higher totals reported.  Combine that with the recent snow melt and the stage is set for potentially a severe and dangerous flooding event.

As we look ahead to the next weather “challenge,” it has to do with temperatures.  As we’ve talked about in previous posts, our weather pattern flipped to one that has been predominantly colder than normal back in the middle of October.  Despite a handful of days, cold has dominated the pattern.  Before our current thaw temperatures were averaging 5 degrees below normal for the month of December.  While the recent thaw is certain to reduce the anomalous cold, the last week of December could send us right back to readings much colder than average, helping put the exclamation point on the month as far as cold goes.

The latest 8-10 day ensemble plots showcase a very cold pattern to end December.  Cross polar flow gets involved, helping lead to some bitterly cold air around these parts.  We note excellent agreement between the GFS and European forecast models, helping to further increase our confidence in the cold pattern ahead.

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But it doesn’t stop there…  We note long range data suggesting this cold pattern continues well into January.

The latest European forecast ensembles showcase the cold continuing to reload into the first week of the month.  This is an impressively cold look, considering we’re still a couple weeks out and that these are a multitude of individual computer model runs averaged together to come up with this solution.

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As we watch the evolution of the cold pattern, it’s important to turn to the “goings-on” with the upper air pattern.  Note the reorganization of the polar vortex and, equally as important, the placement of the polar vortex.  For the purpose of giving you a couple of different viewpoints of the evolution of the pattern we’ve pasted a Northern Hemisphere and North America perspective.

Note how the polar vortex reorganizes itself and decides to set up shop over Hudson Bay and Baffin Island by early January.  This is significant in that it promotes multiple reinforcing shots of arctic air into the eastern half of the country and backs up what the data above would suggest in the cold pattern that appears to be looming as we move forward…

Sunday, December 22nd

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Friday, January 3rd

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What does all of this mean?  That the current “thaw” is very brief.  The seeds were being planted for a return of the cold pattern earlier this week and it all begins Sunday night.  As the data above would suggest, the arctic cold appears to reinforce itself as we go through time and an overall prolonged colder than normal pattern appears to be setting itself up.

Additionally, we’ll have to handle winter storm systems as they come (and they will), but the pattern is one that very well may promote fast-moving clipper systems moving southeast out of Canada.  While most of these clipper systems don’t drop tremendous snowfall totals, the more potent clippers can deposit several inches of snow and serve to “feed back” and turn what’s initially a cold, dry pattern into one that’s suddenly snowy.  We’ll keep an eye on that.  Furthermore, the southern stream may also decide to add a little “excitement” into our forecast late December or early January.

Needless to say, there’s a lot of weather to talk about in the days ahead…

Permanent link to this article: https://indywx.com/2013/12/20/colder-than-normal-pattern-set-to-return/

Dec 20

Model Data Not Backing Down On Flooding Rains Ahead

A scan over multiple computer models this morning shows that forecast models remain consistent of the idea of a weekend deluge across central Indiana.  Unfortunately, when combined with the snow melt, if even the numbers are half right, we’ll have to deal with significant flooding this weekend, especially Saturday afternoon through Sunday.

Here’s a look at the data.  We average multiple computer models together to come up with our precipitation forecasts (both rain and snow) that you see in our daily 7-Day Video Forecasts (available to the right of this post).

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Needless to say, when looking over all of the data above, we still feel confident in the forecast we have out…widespread 3-4″ rainfall with locally heavier totals.  Preparations should have already begun if you live, or work, in a flood prone area, but if not, please do so today.  The question remains not if we’ll see flooding, but how severe the flooding will be.

Permanent link to this article: https://indywx.com/2013/12/20/model-data-not-backing-down-on-flooding-rains-ahead/

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