When Big and Little Combine… (Feb 7-8, 2013 Snowstorm)

A progressing shortwave, similar to our recent clipper systems, will cut down from Canada Wednesday and merge/phase with a longwave trough moving across the continental U.S. This interaction will ensure moisture transport from the deep south into the Great Lakes region, amplifying precipitation amounts in the area. In this way, it is different than our previous shots of snow.

This is a good example of how tricky weather can be. This past weekend, the storm was little more than a trace-3″ disturbance, now it threatens to bring triple that amount to some locations of the state. Quite interesting to see models not show agreement, and then all of a sudden snap in line with each other. Euro had this solution previously, and the GFS/NAM had come into agreement by Tuesday morning. This actually falls near a date back in 2008 when much of mid-Michigan had a 1-2 punch of snowfall:

On February 6, 2008, a snowstorm hit most of Southeast Michigan. Widespread amounts ranged from 6 inches across central Livingston, Oakland and Macomb Counties to greater than 10 inches for all of the Flint (11.3 inches at Bishop Airport), Tri Cities (12.0 inches at Tri Cities Airport)and Thumb regions. Areas across the southern Saginaw River Valley were dumped with 16 to 18 inches of snow from southwest Saginaw to Birch Run to Vassar. -Detroit/Pontiac National Weather Service

Accumulation wise, central Michigan and lower Michigan look to be in the cross-hairs for persistent snow beginning Thursday morning and continuing through to Friday morning. There is some discrepancy between the GRR(Grand Rapids) and DTX(Detroit/Pontiac) forecast offices. as to what the heaviest snow amounts will be. My experience is that GRR likes to over estimate snow accumulations, and DTX likes to hold a conservative line on accumulations. Typically with winter storms, you get little pockets of the high accumulations, but they are not as widespread as the forecast covers. These higher amounts will also depend greatly on how consistent the early snowfall is. Therefore, I believe isolated areas across mid-Michigan will receive 9″ or 10″, but most locations across mid-Michigan will see 6-8″. Along the I-94 corridor, a good swath of 3-6″ seems like a good bet as they will get high intensity snowfall, but for a shorter duration. With warmer temperatures moving into the region, this snow will have a wetter characteristic compared to lighter dry snows this past week.

Grand Rapids NWS depiction for snow accumulations through Friday morning.dtx

Snow will begin to trickle in Thursday morning for central Michigan. Snow should then continue through the day, intensifying in the afternoon. Overnight, snow will be at the strongest. This leaves little time for morning commuters to have  a clear surface, and roads will likely be covered and treacherous  Further south in the state, the initial snow will not begin until the afternoon/evening on Thursday, thus lower amounts are expected. However, once the main portion of the system is over the region, heavy snows will be occurring  and accumulation rates will be high enough to cause transportation issues.

The Detroit forecast office has a great briefing of timing, expectations, and other facts about the storm available to view in a PDF document online here.

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Messy Midwest Thurs/Fri

Storm arriving onshore tonight will strengthen over the Plains Wednesday before slamming the Midwest with heavy snows.

Clues of our storm can be found on the west coast of the US. Note how the lime green height lines dip and form a sort of ‘U’ or ‘V’ shape. This forms our trough. Typically the center of low pressure will form a little south and east of the bottom of the trough, but this depends on what level of the atmosphere you are observing the trough in. Typically trough features are most recognizable in upper air maps (500-300mb), while the low is noted on surface maps lower in the atmosphere. Anyway, this trough will propagate east through the coming hours and our surface low will begin to take shape.

500mb look at the storm arriving on shore in southern California.

500mb look at the storm arriving on shore in southern California.

NWS has great confidence in where the heaviest snows will occur. Think they are on to something as models have been fairly consistent with the storm track. Typically for heavy snows, you want to be in that northwestern portion of the low circulation. This is where cold air is in place and moisture is fed up the warm conveyor belt into it. Here is a map showing current watches/warnings.

Watches and Warnings heading into the northern Great Lakes. Blue=Winter Storm Watches, Pink=Winter Storm Warnings, Red=Blizzard Warning

Watches and Warnings heading into the northern Great Lakes. Blue=Winter Storm Watches, Pink=Winter Storm Warnings, Red=Blizzard Warning

This coincides well with the modeled snow accumulations through the period. Below, the GFS’s latest shot at snowfall.

Snow totals (inches) by Saturday.

Snow totals (inches) by Saturday.

Winds will be nothing to sneeze at for this storm. This will likely be the main threat for southern Michigan. Warm southerly winds will be in place come Thursday morning before shifting as the low passes. Once the low has passed, winds will pick up and shift from the north. These winds will be cold and will coincide with wrap around moisture leading us to our chances at snow. Gusts to 45mph are not out of the question for Friday morning.

Wind gusts for Friday morning.

Wind gusts for Friday morning.

While lower Michigan is missing out on the brunt of this storm, should still be aware for the mentioned wind and any slick spots during the rain/snow transition. Rain will be the main precip type for many locations south of Grand Rapids and Saginaw.

 

This is December Right? Yes.

First of all, that’s 4 years down. Many more to go. No doubt the blog will morph and adapt along the way, but I enjoy sharing the weather I and everyone else encounters. Thanks for the support, interest, and kind words along the way! Lets keep this short, because we may have a surprise late this weekend/early next week.

Short and sweet, Monday may bring a decent amount of snow that we have missed for a whole year. I say this with better confidence as two major weather models have come into better agreement with a solution. The GFS has been showing a possible storm in the Great Lakes for the better part of 3 days, and the European ECMWF model has strengthened from it’s previous run.

Why does agreement matter? Each model is created with equations all about our atmosphere and earthly relationships. However, they are different and each have their own bias towards one type of weather or another. This is good for different scenarios and what-ifs. Comparing models and using forecaster sense is what nails down forecasts. If some models are coming into line with each other, it is reasonable to believe the weather may occur. So lets have a peek.

GFS continues to have the strongest storm. It has trended south, as the original path a few runs ago had a swath of snow north of Michigan. More recent trends have a swath of synoptic snow (the best type in my opinion, based off the development of a low pressure system) across SW, central, and northern Michigan.

The system looks to develop off a surging trough out of the northwest. This trough will dig very deep into the deep Southwest with an interesting ‘double dip’ looking vorticity layout (will need to look into that more!).  The trough continues to dig and eventually a low forms over the Texas Panhandle. While it may not be an authentic Panhandle Hook, moisture from the Gulf of Mexico will be tapped, and further fuel the system during a process called cyclogenesis, the strengthening/development of a Mid-Latitude Cyclone.

Where the storm center tracks will have a large effect on position of rain/snow and any precipitation at all. This also will change timing of the system. As of Wednesday night, the storm looks to track from north Texas into the Great Lakes region with a center over Northwest Ohio at 996mb, a fairly nice pressure for a system.

Capture

 

The storm does not enter the occluded phase until it is up into the far Northeast. This is where it looks to be the strongest, but potential snowfall looks very decent for our area. Analyzing this same run on the GFS, a line from Grand Rapids, to Mount Pleasant, to Bad Axe could end up with a 8+ inch event. This happens to also be riding the rain/snow line.

That is a very scary place to be. As well as near the dry slot. I’ll use a filled popcorn container as an analogy. You want as much popcorn as you can get for a long movie. So you, or the person behind the counter, try to fill it to the rim, and beyond. But if you put too much popcorn on top, it will all fall over and make a mess. This is similar in that the rain/snow line has strong moisture transport and cloud depth for very heavy precipitation. However  if you go too near this supply, latent heat from condensation and the general surging of warm air from the south will toss you overboard into liquid precip opposed to frozen precip.

That last paragraph is ultimately what sums up heavy snow to no snow for every event. These effects are often based on the small side of meteorology, and it is hard for models to predict. It is often proven taking a look at post storm snow accumulations. Perhaps that swath of heavy snow is smaller, or placed south/north of the forecasted position.

If this all turns out to be hype, I apologize. At least I got to dump a little weather ‘behind the scenes’ for you and want to do more of this (jet streaks perhaps?). A key rule of thumb is to wait for the storm to enter the landmass before making any huge calls. In this case, we still have a day or so before that happens.

Happy snow wishing!

Not Over ‘Till It’s Over

I keep bearing a face that grimaces every time we get a shot of warm air. “This is it guys.” “This is our last warm day.” “Enjoy that ice cream in the right environment.” “We aren’t going to see it for another 4 or 5 months!!”

Is that another strong trough I see upstream going to bring us some warm air for the weekend again? Alright. No complaints, but get it over with.

If early Fall temps keep teasing me like this, my winter self will start to get jealous. He is still upset by Winter 11-12′. He wants some revenge action.

Winter 12-13′ is really up in the air. One of usual players holding key cards come wintertime, is that El Nino and La Nina factor. An El Nino pattern was expected to be in place this year, but symptoms are lacking. While neither is expected to show up at this time, we will look for a ‘Equal Chance’ or neutral ENSO outlook. This was briefly discussed by the Grand Rapids NWS office as they previewed the Winter season:

The location of the polar jet stream shown in the diagram puts Southwest Lower Michigan near the boundary dividing cold polar air and the more temperate air that comes from the eastern Pacific. This suggests that cold spells and warm spells could be more extreme compared to the previous two winters. The winter of 2012/2013 could resemble the winters of 2004/2005 and 2008/2009, which often had two weeks of warmer than normal temperatures followed by two weeks of colder than normal conditions.

So that is something to look towards as we eventually get cooler.

I’m missing the white stuff. The closest I have seen so far is a bit of frozen ice pellets Sandy tossed our way. Biking around in it was fun for the first two minutes. Anything more and it felt like a bunch of people pinching your face.

My thoughts on Sandy were mixed.

It was no doubt a massive and historic storm. In the history of weather prediction, not one scenario fits it. Usually with a predictable storm, past storms can be analyzed and forecasts generated based on what happened. Sandy was loosely based around Hurricane Hazel of 1954. Hazel struck the East Coast much further south along the border of North/South Carolina, but it still offered a glimpse into front/hurricane interaction. Hazel similarities were first compared when Sandy was still developing in the Caribbean. Once Sandy moved further north, the guess was between the GFS and ECWFM models. GFS took Sandy out to sea, while the European model had the distinctive turn towards New Jersey.

We all know which path was correct. The National Hurricane Center did a great job in making the proper adjustment to model tracks, and had the landfall position nailed down to a 30 miles radius 4 or 5 days out. A great show for human and numerical weather prediction. I hope to further learn about this. (only so I can dominate everyone on the WxChallenge)

Weather in our neighborhood looks good. Those warm temperatures I was talking about are actually going to happen. While it may be a little dreary, temps will near 60 on Saturday, and may be comfortably there on Sunday. Sunday night will be wet, and temperatures will drop quite a bit as a strong cold front moves through. So much so, areas could see first white cover of the season (yes, snow).