Category: GFS

More Thoughts On Our Next Winter Storm…

As we continue to draw ever closer to our next significant winter storm, we wanted to provide some of our latest thoughts.  This isn’t a post that will hash out snowfall accumulation ideas or precipitation types, but instead will provide details on our expected track and potential liquid equivalent precipitation amounts.  With so much hype and hoopla around this storm for the past couple weeks, lets just sit back and look at the “bigger” picture, as opposed to trying to sort out details that, quite frankly, are still too early to lay out with any certainty as I write this late Friday night

Here’s our (IndyWx.com) expected track of the low Tuesday afternoon to Wednesday afternoon.  We used a blend of the GFS, European, and Canadian operational model data, as well as the GFS and European ensemble data sets.  We think surface low pressure tracks out of northeastern Mississippi (Tuesday evening) through north-central Kentucky (Wednesday morning), and into Pennsylvania (Wednesday night) before a secondary low forms off the northeast coastline.

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This is an ideal track for a winter storm across central Indiana, but specifics such as strength and depth of the cold air, potential southern convection, and forward motion of the storm will have to be sorted out over the next day, or so.  Early indications are that while this storm will take a “good” track for winter weather lovers here across central Indiana, the speed in which the system will be moving may reduce snow and ice accumulations from what they otherwise could be.  That said…early raw numbers suggest .50″ to .80″ amounts (liquid equivalent) could fall in the Tuesday-Wednesday time frame which is significant.  Case in point, a standard 10:1 ratio that would suggest 5 to 8 inches of snow- assuming the form of precipitation fell as snow through the entire duration.  Again, that is far from a certainty at this point.

Ignoring items such as model snowfall forecasts and precipitation types, just looking at the expected track would suggest central Indiana is very much in the game for a potentially significant and disruptive winter storm Tuesday into Wednesday.  We’ll have to fine tune precise amounts and precipitation types in the next day or two.  Additionally, much colder air (below zero once again at night) may blow into the state behind this storm for mid and late week before we gear up for yet another winter weather maker heading into next weekend.  We still have a long way to go in this pattern…

Permanent link to this article: https://indywx.com/2014/02/02/more-thoughts-on-our-next-winter-storm/

Wintry Mix Issues Late Week/ Weekend

We’re going to enjoy another day of sunshine, but moderating temperatures (finally) will help being outdoors become a little more tolerable (we think we “warm” into the middle 20s today).  That said, another winter weather maker is brewing and will result in an active Friday-Sunday ahead.

A cold front will sink south Thursday night and could result in a little light snow (not a big deal).  As we move into Friday and Saturday, model data handles our sensible weather differently.  Precipitation type will be highly dependent upon exactly where the cold front stalls.  We want to show you the GFS as it depicts the variety of precipitation types. It should be important to note that the GFS, European, and Canadian, though different in their respected solutions this weekend, are close enough to go with a “blend” of all three models for our official forecast.

We think snow overspreads the region Friday morning and could deposit a quick couple inches across the metro area Friday. It’s as we get into Friday night and Saturday that we’ll note another (stronger) wave moving along the front. In response to this wave of low pressure, warmer air (both at the surface and aloft) will push north.  Exactly how far north is still up for debate as a battle will be established with push back being provided from an area of high pressure across the upper Mississippi River Valley. We feel as if south-central Indiana will get in on some mixing issues with sleet and perhaps a cold rain Friday night into Saturday.  Depending on how strong the wave of low pressure is will determine exactly how far north the rain line makes it.  For now, we think Indianapolis and northern suburbs remain in a wintry mix of snow, sleet, and possible freezing rain through the majority of the day Saturday.  That said, we do note this will warrant tight focus in the days ahead as any deviation from the track of the low or strength of the cold high to our north could greatly impact our weekend weather.1

 

 

 

 

 

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Finally, precipitation will begin to taper late Saturday night as the cold high to our north eventually wins out. It’s possible all of central Indiana deals with a quick pop of accumulating snow as precipitation ends Saturday night/ wee morning hours Sunday.

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We stress that this is still a highly changing weather situation and most likely will require some “fine tuning” as we move forward.  This morning we think heaviest snow (potentially approaching half a foot) falls across north-central Indiana, including Kokomo, Marion, and Lafayette.  A wintry mix of all precipitation types will fall south of there, including the Indianapolis metro.  South of I-70, we think rain will be the predominant precipitation type, with only a light accumulation of snow as precipitation ends.

As stated above, stay tuned…

Permanent link to this article: https://indywx.com/2014/01/29/wintry-mix-issues-late-week-weekend/

Big Fight Late Week Into The Weekend….

A major battle is taking shape between two of the more respected mid range forecast models for the late week period, including Super Bowl weekend.  The differences range from yet another wintry weekend, with a couple shots of accumulating snow to one that’s much milder and includes some rain.  Operational guidance today has remained consistent with what each particular model has been saying for the past 24-48 hours, adding further complexity to the upcoming late week period.  Usually we’d give a slight nudge towards the European output (warmer solution), but here in a bit we’ll tell you why we’re really not ready to hedge more towards one particular model over the other at this time frame.  Instead, we want to give it a couple more days and see which model “gives in” to the other.

Let’s dive into the European output first.

We note both models in relative good agreement on Thursday night into Friday as light snow overspreads the region (not a huge deal, but potentially enough to make for a slippery Friday morning commute).

As we move into Saturday the European tracks a developing surface low much further north than the GFS, resulting in a milder solution across central Indiana and a forecast that would produce a rain to snow solution Saturday as cold air quickly pours back into our region, with enough snow, perhaps, to produce a light accumulation Saturday night. However, it’s important to note, most European ensemble members are colder than the operational run and this is something we’ll need to continue to monitor.

As we head into early early next week, the European forecast model remains bullish on a potential major winter storm, with a favorable storm track for heavy amounts of wintry precipitation across central Indiana.  The time we’re eyeing for this next storm falls in the Monday night-Tuesday time period so we have plenty of time to monitor things and iron out the details…

Now, as we look at the GFS forecast model, we note a colder solution from start to finish.  We have to raise an eye brow here as the track record of the GFS in the mid range is one that has been known to be biased too “flat” and too cold in handling similar patterns.  Is that saying the GFS is wrong here?  Absolutely not…nobody knows that at this juncture.  It is saying we have to rely on experience and remember similar patterns of the past, including the way the model “corrected” itself with time as we drew closer to the particular event in most cases…

Nonetheless, similar to the European, the GFS delivers a round of accumulating snow Friday morning, but is flatter (colder) with the initial wave and also leads to quite the overrunning event through the Ohio Valley.  As a matter of fact, we deal with two rounds of accumulating snow…Friday morning into the early afternoon and again Saturday morning, associated with yet another wave of low pressure.

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Of interest, the GFS also sees the potential strong winter storm that could impact our neck of the woods early next week.  Needless to say, the surface map next Tuesday morning would have snow lovers smiling in a big way should this come to fruition…

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While we have many details to iron out late week and on into early next week, the overall weather pattern is one that we remain confident on and the results are cold and stormy (i.e. snowy) over the upcoming 10-14 day period.  As a matter of fact, long range teleconnections suggest we remain colder than normal and stormy through the majority of February. In short, there’s really no let up in sight from the overall cold and wintry time of things Hoosiers have grown oh so accustomed to this winter…

Permanent link to this article: https://indywx.com/2014/01/27/big-fight-late-week-into-the-weekend/

Quick Remark On Sunday.

We have enough to worry ourselves with tonight and again Friday night-Saturday, but many are wondering about what Sunday holds.  The consensus of operational model data today is for a north track Sunday, keeping most of the heavy snowfall across northern Indiana.  That said, is it the correct idea?  We’re not ready to buy the extreme north trend just yet…

While anything is possible, the northward trend in operational runs today has me scratching my head a bit given the overall pattern.  Current thinking here would suggest operational models  “correct” south with time over the next couple days, but time will tell.  The GFS ensembles help illustrate the wide variance with the track of Sunday’s snow storm (below).  While the track of the system is still up for debate, confidence is growing on amounts just north of the low’s track that approach half a foot Sunday.  Much more later!

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Permanent link to this article: https://indywx.com/2014/01/22/quick-remark-on-sunday/

Historic Snow Season Keeps Rolling Along…

The winter of 2013-2014 is off to a rip-roaring start and, as we’ve discussed in previous posts, the mid to long range data suggests we remain locked in an exceptionally cold and snowy pattern.  Officially, as of this evening, the Indianapolis National Weather Service has posted some impressive stats (the full report can be found here), including:

  • Through Jan. 21st, the 24.4″ of snow ranks as the 3rd snowiest January on record.
  • Through Jan. 21st, the season-to-date snowfall of 33.2″ ranks as the 2nd highest on record in the period Dec. 1st through Jan. 21st.
  • Through Jan. 21st, the season-to-date snowfall of 33.2″ ranks as the 8th snowiest on record for an entire winter season.

As we look ahead to the upcoming 7-10 day period, we note a continuation of arctic reinforcements- each which will be plenty capable of adding to the snowfall total.  Additionally, our cold air mass will only grow even more severe and bitter over time, including multiple days during the aforementioned period where central Indiana will go below zero.  Finally, there have been many questions concerning a potential big storm centered on early February.  I’m not sure where this rumor started, but it’s far too early to say with any sort of confidence any specifics around a possible big winter storm early February.  That said, as we’ll get into briefly below, the pattern does appear to be aligning itself in a way where a widespread winter storm is possible somewhere across the eastern half of the country.

Okay, okay, back to the near term…  Let’s start with tomorrow!  After a cold and dry start to the day, our next arctic front will blow into the region during the evening.  Arctic fronts are notorious for having bursts of heavy snow rates in a scattered fashion and this appears to be the case as the next arctic front moves through Wednesday evening.  We bracket the hours of 5p-8p for the possibility of heavy snow bursts racing through central Indiana.  While these won’t last long, they’ll likely be intense- capable of depositing a quick 1″-2″ of new snow on a gusty northwest wind within 30-60 minutes.  White-out conditions and extremely heavy snowfall rates will accompany the heavier bursts of snow.  Latest high-resolution model data shows the heavy snow bursts accompanying the arctic front tomorrow evening:

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Thursday will be mostly dry and frigid, but all eyes will then begin to turn to our next significant winter event Friday into Saturday.  The pressure gradient between high pressure across the Mississippi River Valley and the next approaching arctic front (and associated low pressure) will really being to kick up the wind across our region Friday.  We’re afraid we deal with another round of severe blowing and drifting snow Friday, especially Friday afternoon and night.  Areas most suspect to drifting and blowing snow will be central Indiana’s open country and may not be too different from the problems our region dealt with Sunday into Monday morning from blowing and drifting.

As we approach Friday night into Saturday, snow will overspread the region and will likely accumulate to the tune of a “few inches” during this time period.  Strong winds will remain, shifting from the west to the northwest and eventually north.  Open country will remain the prime place for continued severe blowing and drifting problems.

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Just as soon as Saturday’s snow systems exits stage right, we turn our attention to potentially another significant snow maker for the second half of the weekend.  Latest model data remains consistent on moving another potent clipper system into our region Sunday, including the GFS and Canadian forecast models.  We still have time to fine tune the precise track of the storm, but just north of the low’s track an additional 3-5″ type snow is possible Sunday.  Note the GFS and Euro in relative agreement on the track of the low, with the Canadian currently a touch further north. We’ll fine tune in the days ahead…  Experience with similar patterns from the past suggests central Indiana should brace for more accumulating snow Sunday.

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As for the brutal cold, we note multiple pushes of fresh arctic air behind each snow maker.  We currently target Thursday morning, Friday morning, Tuesday morning, next Wednesday morning, and next Friday morning as having the most likely shot at dipping below zero. The “coldest of the cold” likely means Tuesday morning takes the crown, with lows potentially dipping into the double-digit below zero range for central Indiana.  The European forecast model (below) even shows sub-zero temperatures making it as far south as the southern Appalachians.

As we look even longer term, there have been many questions centered on the potential of a big winter storm for early February.  Before we go any further, we want to stress it’s far too early to make any claim of certainty to the above.  That said, there are items we can pick up on to a least “raise an eyebrow” that something of significance may be brewing… Do we mean for anyone to take that verbatim and to the bank?  Absolutely not.

The European Weeklies suggest we need to keep an eye on the first week of February.  They show a potential phasing of the jet (where the northern and southern streams of the jet stream phase together- often times resulting in a big storm)… That said, we want to again stress this is far too early to be discussing with any sort of certainty.  Heh, the next week will keep us busy enough!

Keep the shovel handy!  Snow removal companies, thank you for your service and hard work…hopefully you have plenty of coffee on hand!

Permanent link to this article: https://indywx.com/2014/01/21/historic-snow-season-keeps-rolling-along/

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/

Cold, Snowy Pattern Reloading…

I sure hope you’ve taken time to get out and enjoy a couple of days of milder air (temperatures have run 10-12 degrees above seasonal levels the past couple days) and even some sunshine.  Given what I see coming down the road, the trend that looks to take a colder turn this week may really go into the tank week two.

Here’s an overview of the latest GFS and ECMWF ensemble data out at Days 8 through 10 (January 21st-23rd).  Both of these, more trusted, mid to long range computer models suggest a cold pattern locks itself into the East once again, and spells for colder than average temperatures and potentially a snowier than normal regime.

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We’ll now dive a little deeper into the forecast model vault, courtesy of the unbelievable Weatherbell Analytics model suite (can’t brag on that company enough).  We’re looking at the Northern Hemisphere Upper Air Pattern, courtesy of the European ensemble control run from this afternoon.

Note the mid week trough set to deliver a return of arctic air into the region.  That’s reinforced with a late week trough and renewed arctic air.  Both cold air masses will be capable of producing light accumulating snow across the area.

Per yesterday’s post, as we get into the early to middle portion of next week, we’ll have to keep a close eye on the potential of the southern and northern branches of the jet stream phasing, which would lead to a significant winter storm across some parts of the eastern half of the country (far too early for specifics or details).

We then note the Polar Vortex recharges itself and threatens to turn the last week to 10 days of January very cold.  How cold is yet to be determined, but I think it’s a safe bet sub-zero temperatures aren’t finished with our area just yet.

Intrusions of very cold arctic air will “pinwheel” around the Polar Vortex and likely lead to a bitterly cold end of January and open to February…

Permanent link to this article: https://indywx.com/2014/01/13/cold-snowy-pattern-reloading/

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/

Rare And Potentially Crippling Winter Storm Brewing…

Fresh on the heels of a significant winter storm that impacted central Indiana Wednesday night-Thursday, we’re eyeing our next winter storm and, quite frankly, it could be a memorable one.

We continue to keep a close eye on the pending winter storm Sunday and remain impressed with what we see.  A severe winter storm is brewing and may require blizzard watches and warnings before all is said and done as a combination of heavy snow, strong winds, and severe blowing and drifting promises to make travel difficult, if not impossible, for some areas Sunday.

Setting the stage:

A powerful arctic boundary will drift south towards Indiana Saturday night and Sunday morning.  As this takes place, low pressure will track off the lee of the Rockies and move east, northeast.  Model data continues to suggest this area of low pressure taps into some Gulf of Mexico moisture and really begins to deepen (strengthen) as it tracks into the central/ eastern Ohio Valley Sunday.  To the northwest of the low’s track, a deep blanket of fresh snow will fall.  As the winter storm departs, the coldest air since 1994 will pour into the region on a gusty northwest wind.  Temperatures will reach record territory, and downright dangerous levels, by Monday and Tuesday.

Last night we mentioned a couple of things going “for” and “against” a major winter storm here in central Indiana.  While there’s no doubt going to be a sharp “cut off” of heavy snow with this storm, this “cut off zone” is most likely well north and west of central Indiana.  Additionally, the impressive thermal gradient between the brutal arctic air mass to the north and the warmer air (relatively speaking) to the south and east will only add fuel to a deepening storm moving northeast into the Ohio Valley.  Finally, with arctic air pouring into the region, the “fluff effect” will be in full-go mode, meaning the northwest flank of the heavy precipitation is likely to have snow ratios of 15:1 as compared to the “normal” 10:1 ratio.  This will be very important to watch as the system develops and will most likely be the spot (far too early to pinpoint at this juncture) where snowfall amounts in excess of one foot will fall.

All of our medium range model data is in agreement on central Indiana receiving quite the blow from Old Man Winter Sunday.  Here’s a look at the latest GFS, European, and Canadian forecast models, valid Sunday afternoon:

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As you can see, there’s excellent agreement and this leads to a rather high confidence idea on a high-impact and rather rare severe winter storm set to impact Indiana.  Can we tell you with certainty exactly where the 12″+ band of snow will lie across the state?  Not at this time.  That said, we suggest preparing now for a rare and potentially crippling winter storm Sunday.  The combination of heavy snow, strong winds, historic cold, and severe blowing and drifting will make for an extremely dangerous situation Sunday, continuing into early next week.  Temperatures by Tuesday morning will approach 20 degrees below zero, with wind chill values plummeting to 40-50 degrees below zero Monday into Tuesday…

Permanent link to this article: https://indywx.com/2014/01/02/rare-and-potentially-crippling-winter-storm-brewing/

Major Storm Brewing This Weekend, But Details Are Murky…

During the late summer and early autumn months we were trying to look at the big picture and potential drivers in the overall weather pattern for the upcoming winter and openly admitted the challenges that were ahead.  Here we are now into the second half of December and a much colder and snowier-than-average month is a virtual lock at this point.  Furthermore, consider this has all taken place without the presence of a favorable NAO or PNA.  Sometimes you have to look for other drivers in a pattern- in this case, the EPO, as well as a growing early fall snow pack across the border to our north.  Additionally, we made mention of the likelihood of a southeast US ridge periodically making itself known through the winter of ’13-’14.  You can read all of our thoughts posted earlier this fall here, or by clicking the Thoughts On Winter ’13-’14 page above.

As we look ahead towards the upcoming wintry challenge, we’re confident of the overall pattern, but the sensible weather that’ll ensue is still up for great debate.  “Gut” tells me central Indiana will be looking at a rain to freezing rain scenario, but this is far from set in stone, and sometimes forecasters who go simply off their instinct can get burned.  The pattern is one that (once again) will feature a pressing arctic front against resistance from the southeast US ridge.  With this type of scenario, I would advise against looking at each and every individual operational model run, but instead invest time studying the ensembles- an average of several multiple model runs as opposed to just one operational model run.   I can guarantee a variety of wild solutions ahead in the days to come, based off the operational runs. (Heck, just the past 24 hours have been reason enough to have the dramamine on hand :-)).  That said, let’s take a look at the latest GFS and European ensembles, two models that we rely heavily on in the mid range weather pattern.

First, the GFS, valid Saturday through Monday.

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Now, here’s a look at the latest European ensembles (left), again valid Saturday-Monday.

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So what do all of these cool maps tell us?  Simply put, that “wintry mischief” is brewing for the weekend.  That much we know, but the details have to be ironed out.  It’s likely heavy snow and a significant ice storm looms for some of the Mid West and Ohio Valley for the upcoming weekend.  Is that Indianapolis or Chicago?  Perhaps in between?  It’s too early to know.  Additionally, in the “warmer” sector, heavy rains are likely to combine with an impressive early season snow pack for some to lead to flooding concerns.

A couple of additional items to note. Many times at this stage in the game (still 5+ days out) with this type of pattern, forecast models really struggle with handling low level cold air.  Cold air is very dense and, in this type of set up, can easily drain much further east and south than forecast at this juncture.  Additionally, sometimes the modeling can put too much “umph” into the associated surface wave that moves along the arctic front resulting in a further north track than what may actually occur when the event draws closer.  Just something to keep an eye on as we draw closer…

Needless to say, it’ll be particularly important to keep a close eye on the developing weekend forecast as we move forward.  It’s likely folks in the Ohio Valley region have to deal with significant precipitation amounts in the Saturday-Monday time period, including rain, freezing rain, and snow.

Permanent link to this article: https://indywx.com/2013/12/16/major-storm-brewing-this-weekend-but-details-are-murky/

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