Category: NAM Model

Feb 07

More Weekend Snow Talk…

We’re still dealing with some questions that will have to be sorted out for the weekend’s snow.  Latest high resolution data suggests we may see a couple of waves of accumulating snow cross the state this weekend.  Namely, we’re focused on late Saturday night into Sunday morning and again Sunday night into Monday morning.  Scattered snow showers will fall during the day Saturday, but shouldn’t be a big deal and won’t impact everyone.

It’s a tough and challenging pattern we’re in over the next 60 hours and forecast models will continue to struggle with handling upper level energy as it ejects off the Rockies and heads east.  While our initial idea of a more organized, robust, storm system won’t come to fruition, it’s certainly possible some central Indiana neighborhoods deal with a “few” inches of fresh snow by Monday morning.  It’ll be important to stay tuned to latest forecasts this weekend as what may seem to be a rather harmless inch, or so, of snow could pile up to the tune of 2″-5″ for some areas should latest high resolution model data, hot off the press, come to fruition.

Case in point, the latest high resolution NAM model, courtesy of Weatherbell Analytics, paints a couple of stripes of snow across central Indiana and seems to have a pretty good handle on the evolution of things over the next 48-60 hours.  It should be noted that not all model data suggests accumulating snow is ahead this weekend.  THAT SAID, many times, in similar weather patterns, the high resolution data performed better.  We’ll fine tune things and have a fresh updated 7-Day forecast available to you in the morning.  Make it a great night!

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Permanent link to this article: https://indywx.com/2014/02/07/more-weekend-snow-talk/

Feb 03

Here We Go Again…

Yet another winter storm is bearing down on the region and will promise a snowy time of things here Tuesday evening into Wednesday.

Surface low pressure will begin to organize over the lower Mississippi River Valley Tuesday morning and move northeast…eventually into PA before a secondary low takes over off the Northeast coast Wednesday.  We like our track of the storm below.

TueWedStormTrack

 

 

 

 

 

 

This will really be the first storm that’s tapped into Gulf of Mexico moisture since the major winter storm that pounded our area early last month.  Moisture will be plentiful with this system and, when combined with the cold air, will lead to significant snow accumulation for most of central Indiana, with significant ice accumulation expected downstate across southern sections of Indiana.

We think snow begins to develop across central Indiana as early as early to mid afternoon Tuesday, but the heaviest of the snow will fall Tuesday night into the wee morning hours Wednesday.  In fact, snowfall rates may approach 1″ per hour for a time Tuesday night, especially where the heavy snow bands set up.  Just exactly where do these heavy bands of snow develop?  It’s a very tough call, but thinking at this juncture would suggest mainly north of Indianapolis.  Additionally, latest data suggests a thundersnow report or two may occur tomorrow night within the heavy snow bands.  Snow will begin to taper from west to east Wednesday morning, but the open country will have to deal with some blowing and drifting through the day Wednesday as the low departs northeast.  We’ll then enjoy a dry and cold couple of days as arctic high pressure builds in before our next winter storm develops for the weekend…

We forecast widespread 4-8″ (localized 8″+ totals possible within convective heavy snow bands) of snow to accumulate by the time all is said and done across central Indiana and our call right now is for the greatest chance of those 8″ reports to fall within the highlighted zone below.

HVY Snow Totals 020414:020514

Quick Bullet Point Thoughts:

  • Snow develops towards 3-4pm Tuesday.
  • Heaviest snow falls Tuesday night into the wee morning hours Wednesday.
  • 4-8″ of snowfall expected across central Indiana, with heaviest totals from Indy’s northern suburbs and points north.  Locally heavier totals can be expected within the heavier convective snow bands.
  • Significant ice accumulation of 0.25″, or greater, possible down state
  • Placement of embedded heavy snow bands will have to be monitored closely Tuesday night and may be accompanied by thunder and lightning.
  • Snow begins to diminish Wednesday morning, but blowing and drifting continues through the day.

The dry slot, originally mentioned here Sunday, will likely impact southern and south-central Indiana late Tuesday night into Wednesday morning and will essentially shut off the accumulating snow threat south of I-70 during the wee morning hours Wednesday with some light freezing rain and/ or freezing drizzle glazing over the snow that falls.  Meanwhile, accumulating snow will begin to taper Wednesday morning north of I-70.  The latest high resolution NAM simulated radar, courtesy of Weatherbell Analytics, shows this well.

Dryslot1

Permanent link to this article: https://indywx.com/2014/02/03/here-we-go-again/

Jan 30

Complicated And Complex…

If you have travel plans across central Indiana Friday and Friday night, please make sure you leave plenty of time to get to your destination and prepare for a variety of precipitation types.  In fact, it’s entirely possible (depending on what time of day you’re traveling) that you have to deal with rain across south-central Indiana and snow by the time you arrive into the northern Indianapolis suburbs, complete with an icy mixture “in between.”

Digging through the weather playbook for Friday into Saturday:

A cold front is expected to move through the region Friday morning, allowing a wind shift out of the north to arrive into the city in the early to mid morning Friday. We’ll have to be in “nowcast” mode Friday to determine just exactly how far south the front makes it as this will go a long way into determining precipitation types across central Indiana.

Ultimately, a wave of low pressure will move along the front Saturday, which will help milder air push north and result in a changeover from a wintry mix to all rain during the majority of the day Saturday. In fact, there’s the chance portions of central Indiana may not have to deal with much, if any, precipitation through the majority of the day Saturday- especially south.  Before that, however, we’ll have to deal with a wide variety of wintry precipitation issues Friday and Friday night…  Warmer low level air will be drawn northward and overrun the colder air at the surface Friday and Friday night.  What will initially be a period of snow Friday will transition to an icy mixture of sleet and freezing rain Friday night and all rain Saturday.  That said, we note the milder push will be brief, and colder air will pour back into the region on gusty northwest winds Saturday night. This may result in a brief period of light snow Saturday night (not a big deal).

We think the latest high-resolution, short-term, NAM model (courtesy from the fine folks over at Weatherbell Analytics model suite) has a very good handle on accumulation ideas Friday and Saturday and is in best agreement with our analysis laid out above.  This is a look at forecast snow accumulation between now and Saturday night, but we also note there will be some light sleet and freezing rain accumulation on top of any snow that falls Friday. As far as that snow goes, we think a 1-2″ band is laid down from the city and points north, increasing further as you travel into north-central and northern Indiana.

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Permanent link to this article: https://indywx.com/2014/01/30/as-promised-complicated-and-complex/

Jan 22

Model Vs. Reality

An intense snow squall blew through central Indiana this evening, thankfully post-rush hour (what a horrendous situation we would’ve had on our hands had this snow burst arrived an hour…

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Permanent link to this article: https://indywx.com/2014/01/22/model-vs-reality/

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.

usa_None_anim

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.

500mb

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/

Dec 10

Snowy Pattern Continues…

Considering we’re only a third of the way through December, we’re certainly running “snowier” than normal at this very early stage in the game.  As we look ahead at the upcoming 10 days, or so, we see this snowier than normal pattern continuing with multiple systems to contend with over the course of the upcoming couple weeks.  Up next will be the threat of some light snow showers and flurries with reinforcing arctic air Wednesday PM.  Nothing significant is anticipated here on Wednesday, accumulation-wise, but snow showers will blow through the area Wednesday afternoon.  The latest high-resolution NAM shows this well.

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Then our attention turns to a developing winter storm for the weekend. We think clouds increase Friday and snow develops Friday night into early Saturday.  Here’s a look at the latest GFS forecast model, valid Friday night.

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Fast forward that to Saturday morning and snow grows heavier…

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The GFS suggests a weak surface low tracks into eastern Ohio with backlash snow showers and embedded squalls continuing here Saturday night into Sunday.

gfs_ptype_slp_east_20

 

 

 

 

 

 

It’s important to remember that we’re still a few days out from this event and I can guarantee you things will change as we go through the course of the upcoming few days that will require us to do some adjusting to our forecast Friday-Sunday.  That said, at this early stage in the game, unlike with our last storm, I’d favor areas from IND and points north as the place where heavier snow falls this go around.

Latest GFS ensembles suggest something similar to the operational run shown above with one low tracking into the eastern Ohio Valley as another coastal low develops.

f120

The European ensembles provide an “intriguing” look for an Ohio Valley winter weather event this weekend, as well.

Geopotential32at32500hPa_North32America_96

 

 

 

 

A couple of additional items to consider at this early juncture- this will be a fast moving winter storm so that will have an impact on snowfall accumulation.  Additionally, there’s also the chance enough warm air aloft advects (WAA or warm air advection) into the southern portions of the region to result in “mixing” issues (i.e. sleet and freezing rain).  In the primarily “snow zone” Friday night-Saturday (again, we’re currently targeting IND and points north for the snow zone) several inches of snow could accumulate.

Here’s an early look at what the latest mid-range forecast models are seeing in terms of potential accumulations with this event.  Top to bottom: ECMWF, GFS, and Canadian.  Stay tuned, we’ll have another update later!  Enjoy your day!

ECMWFGFScmc_snow_acc_east_24

Permanent link to this article: https://indywx.com/2013/12/10/snowy-pattern-continues/

Nov 20

Wednesday Evening Video Update: Rain Moving In; Arctic Blast This Weekend

http:/ Tonight’s Video Highlights: We talk rain and amounts for Thursday and Friday. The coldest air of the season and coldest November day in some 13 years is ahead! A…

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Permanent link to this article: https://indywx.com/2013/11/20/wednesday-evening-video-update-rain-moving-in-arctic-blast-this-weekend/

Oct 04

Monitoring Where The Heaviest Axis Of Rain Sets Up

Good Friday morning!  Overnight model data is in and we continue to look things over from a total rainfall perspective, as well as any severe weather threat that exists Saturday evening. As of now, we anticipate the best chance of any kind of severe thunderstorms to occur Saturday evening/ night and the biggest threat appears to be from a damaging wind standpoint.  The latest severe weather outlook from the trusted Storm Prediction Center (SPC) places central and western Indiana under a Slight Risk of severe weather Saturday.

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The 12z NAM is hot off the press and suggests the heaviest rainfall threat is mostly east of Indianapolis proper.  There’s the chance rainfall amounts approach 2″ across far eastern Indiana.  We’ll continue to analyze the data as it comes in this afternoon and have a complete update posted later today.

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Permanent link to this article: https://indywx.com/2013/10/04/monitoring-where-the-heaviest-axis-of-rain-sets-up/

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