Thunderstorm Potential - Mar. 9

There are a handful of storm chasers that made the trek down into western Oklahoma and Texas today for a marginal severe weather setup.  Low-level wind shear is good in vicinity of the surface low, and while some cirrus has hindered full heating there does appear to at least be marginal instability for thunderstorms over the next few hours.  Marginal hail and perhaps a brief tornado would appear possible given the latest parameters on the SPC Mesoanalysis page.

Looking ahead to tomorrow this surface low will continue to move northeast, into south-central Kansas during the overnight and then across into northwest Missouri during the day tomorrow before moving into Iowa by tomorrow night. The low pressure system will continue to be vertically stacked, creating steep lapse rates and the potential for thunderstorms. Per the 12z NAM it would appear that during the early afternoon hours given diurnal heating that some surface instability and especially mixed layer instability would be present across parts of eastern Kansas and western Missouri.  Given marginal instability and strong low level vorticity given the proximity to vertically stacked low pressure system that a brief window of development for low-topped supercells would exist. Given cold temperatures aloft, marginal hail would be a threat; in addition to strong low level shear that would warrant the potential for a tornado or two as well.

An additional update is possible either late tonight or early tomorrow regarding any changes to the potential for severe weather for the Central Plains.  I work during the afternoon tomorrow, thus no chase activities are planned and blog updates are not expected.

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Ahhh... Sunshine!!

Another bright and sunshine filled day today, with surface winds becoming southerly in the afternoon to aid in our warming temperatures. Highs today were widely in the 50s for areas without snow cover, even well into the 40s for those on the southern portions of the snowpack. Areas further north across Iowa were still held into the 30s due to the large snow pack in their area, plus the surrounding. Nonetheless the warm air temperature and unabated sun did allow for melting which showed up as some dense fog during the morning hours. We'll look for another day of warming temperatures and clear skies for a majority of the Central Plains tomorrow, just ahead of a disturbance that will be developing in the lee of the Rockies.

This upper level system is a fairly compact, but strong system that will bring a good chance of rain and even isolated thunderstorms to portions of the central Plains. Latest model tracks have continued the trend of a cut-off low pressure system moving east/northeast from eastern Colorado into central Nebraska Friday night, then slowly meandering eastward across Iowa through Saturday night. This will lead to a good chance of rain showers for areas north of I70 in both Kansas and Missouri and as far north as the Dakota borders and central Minnesota. Most of this precipitation should fall as rain, however, as the upper level low continues to deepend and cool areas north of Highway 30 in northeast Nebraska and Iowa as well as adjacent areas of southeast South Dakota and southern Minnesota may be able to see some mixed precipitation and snowfall. The wintery precipitation will have its' best chance late Saturday through early Sunday with accumulations remaining minimal for most areas. Decent amounts of rain are possible for the remainder of the area, including those that have several inches of water frozen in their snowpacks. This will amount to some rapid rises in rivers over the weekend and may in turn cause flooding concerns for areas of Iowa and places downstream.

Many people are still watching the stronger system for early next week, with many eyes on it for the first severe weather event for the Plains states. Moisture return is weak thus far, but there is still several days of warming and moistening to go for many areas of the southern Plains. The latest GFS and its' ensembles have taken the further south track today with the center of the 500hPa low tracking along the Oklahoma/Kansas border into Arkansas on Tuesday. This is seemingly becoming the favorite solution of the models, at least until the disturbance comes ashore and the models actually get a good look at its' dynamics. Nonetheless, expect rain to dominate the forecast for the southern and central Plains for early next week. With the best chance of thunder coming for areas of Texas and Oklahoma, however areas of Kansas/Missouri can't rule out the thunder given intense lapse rates under the closed low aloft. One of the best highlights with this southern track is that there is really no cold air to be advected south, thus we'll keep temperatures near normal for most of next week. Could we be looking at a sign that spring may actually be arriving?!?

An additional update is possible tomorrow, however a 3-day weekend and continued warm weather will hopefully keep me busy with other things!

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Quiet Weather Continues...

Mainly sunny skies and slowly warming temperatures have been the story thus far this week. And this looks to continue through the remainder of the week given current forecasts. A disturbance is expected to develop in the lee of the Rockies on Friday, leaving areas of Kansas, Nebraska, and South Dakota with a chance of showers through the day on Friday. This low will push off into the Plains on Saturday, continuing the chance of showers for areas of Kansas, Missouri, and southern portions of Nebraska and Iowa. There will be enough cold air to see more wintery precipitation for areas of northern Nebraska and northern Iowa, along with adjacent areas of the Dakotas and Minnesota.

As this system exits to the Great Lakes, our next wave of energy will moving across the Rockies and likely resulting in a new low pressure along the front range in Colorado. With the previous low sliding well north compared to previous storms, ample southerly flow is expected across the southern and central Plains. This means warm temperatures and increasing moisture across much of the Plains. Temperatures may reach above normal levels for the first time in several months for areas of the central Plains, with 50s and 60s likely on Sunday and Monday. These above average temperatures may be short-lived as the low pressure will begin to enter the Plains and bring widespread precipitation chances. The timing and exact track of the surface low, along with the strength of the upper-level features continue to be in question. The latest GFS runs have actually began to decrease the intensity of the closed low aloft.  Nonetheless, discussion continues about the potential for the first good severe weather event for the Plains states which at this time would appear to occur over portions of western Texas/Oklahoma, and perhaps Kansas depending upon the surface low track. The talk also continues about the potential for a strong winter storm, with ample moisture if the low can bring down enough cold air we could see a strong deformation zone filled with snowfall across parts of the northern Plains. Given a forecasted strong pressure gradient, wind speeds would also be in the 20+ mph range and likely result in widespread blowing snow. Many questions remain for this storm system, and as mentioned previously is the main talk as we enjoy sunny skies and warm temperatures.

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Quiet Weather... For Now

Quiet weather continued through the weekend, with clear skies dominating the forecast. These clear skies allowed temperatures to moderate well over the weekend, with high temperatures into the 40s across the areas with little to no snow-pack and into the upper 20s and near 30 for those that do. The clear skies also gave way to cool overnight temperatures given ample variational cooling with the light winds. Conditions like this will continue for much of the week with a high pressure system centered over the Northern Plains.

A storm system will pass through the Southern Plains on Monday, and continue into the Gulf Coast on Tuesday. Behind this we will see a large scale ridge build into the Plains for midweek, allowing for another warm-up with temperatures likely reaching normal or perhaps even a few readings of above normal temperatures for Thursday/Friday! A quick wave will move across the Rockies on Friday and begin to flatten this ridge for the beginning of the weekend. This quick moving system will have enough energy that it may bring with it the chance of precipitation for areas of the Plains. At this time there is significant differences in the track and speed of the associated vorticity maximum and thus confidence is not very high to mention any areas or times for precipitation.

Behind this initial wave comes a system that has been well advertised by both the GFS and ECMWF for the past several days. A very strong upper level wave associated with great dynamics throughout its' lifetime as it crosses over the Plains and moves into the Great Lakes region. Details regarding position and exact timing are of course in question, given the near 60 hour difference in timing the GFS and ECMWF currently have. The track is a little more agreeable between the two models, given a low developing over the lee of the Rockies in Colorado and tracking eastward into KS/NE seems probable, with a quick ejection northwest into the Great Lakes region once reaching the Missouri River thanks to a strong jet maximum in the upper levels. This system has the potential to be one of the first severe weather producers given its' good dynamics and likely thermodynamics (50s for temperatures & dew points). Although the best bet would be a cold core situation close to the low pressure system. Other than the potential for severe weather, conditions to the northwest of the low center would likely endure blizzard conditions for at least a period of time. Moisture will be ample in addition to strong dynamics and deepening surface low, thus a strong deformation zone is likely. Given the tight pressure gradient, surface winds sustained above 30 mph would also appear likely with even higher gusts. Once again the exact location and timing are definite questions, but it does appear favorable for a significant storm system for the Plains in the March 8-11 time frame. Additional updates through the week will likely reference this storm for a majority of the discussion.

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Cold Air...

Just a short update tonight as the weather is extremely quiet for a majority of the Plains through the remainder of the week. Cold temperatures was the story this morning, with a record low set at St. Joseph, MO (-2) and a record low tied at Kansas City International (2). Single digits were prominent over much of the Northern Plains, with teens over the Central Plains this morning. Below zero lows were common, with teens below zero for areas of Iowa, Minnesota, and the Dakotas. The lows tonight won't be too much warmer, with many single digits and below zero readings expected.

Feb. 24 Morning Low Temperatures

Looking ahead through the rest of the week, we'll slowly begin to warm-up through the weekend, although temperatures will remain below normal to well below normal for many areas of the Plains. A storm system will intensify on Thursday over the southern Plains, leading to areas of snow for southern Kansas and Oklahoma. The low pressure system associated with the snowfall will quickly move southeast on Thursday night and Friday, leaving areas of the southern Plains and perhaps even the lower Mississippi Valley under a blanket of snow.

With all of the precipitation remaining south, we'll continue to see fairly clear skies. The sun is beginning to feel pretty warm though, which is hopefully a sign that if we can begin to get rid of some of the snow that is currently covering the Plains that we can at least begin to see normal temperatures! Next update is expected on Saturday for a look at next week!

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Feb. 21/22 Recap & A Look Ahead

The storm system this past weekend brought a mix of precipitation types to parts of the central Plains. Areas of flooding occurred and are ongoing due to substantial rainfall amounts across central Missouri this past weekend. An area from south-central Kansas into the Kansas City Metro saw ice accumulations of a few tenths to nearly a half-inch in a few isolated areas. Sleet was also a common precipitation type over the weekend, with several roadways in eastern Kansas and western Missouri becoming hazardous with slush accumulations of a half-inch or greater. And lastly there was snow, varying from around an inch on the south side of the Kansas City Metro and across I70 in Missouri to just an inch or so over parts of southern Iowa. In between however, a swath of 6-10 inches covered areas of northern Missouri with isolated amounts nearing 12 inches. Strong northwest winds allowed for blowing and drifting of the snow as well, creating large drifts in open areas and making travel impossible in some areas through the day on Sunday. To view all of the reports that came in from the region, check out the link posted below:

http://www.severeplains.com/snowfall_022210.html


To view other reports from the region, check your local NWS office homepage. The NWS in Kansas City has also provided a brief summary of the events that occurred in the metro area in regards to precipitation types. This includes a vertical cross-section image that shows the warm layer just above the surface that was responsible for the freezing rain over the southern metro area. The ongoing snow continues to make its' way into the record books, with a record daily snowfall at Kansas City International. With rounds of snowfall in Des Moines on Friday, they continued to increase their snow depth and continue to break records for the most consecutive and non-consecutive days with specific snow depth amounts. Plenty of other records are out there being broken as well, with plenty more likely to fall as the winter isn't about to give in to Spring.

Looking ahead for the remainder of the week, a cold front will sweep through the Plains tomorrow bringing with it the chance of flurries and some light snow mainly Iowa and eastern Missouri. Accumulations are expected to be little to none across the region due to limited moisture and meager lift along the boundary. The cold front passage will bring a reinforcement of cold air that will keep us well below normal for Wednesday and Thursday. Another storm system on Friday will bring the chance of precipitation to areas of the southern Plains, will have to watch and see how far north the precip chances can make it for Friday.

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Potential Winter Storm(s)

I decided on one more update before I head back to Iowa for the remainder of the week, seeing as with such nice weather today there was only the upcoming two storm systems to look forward too. Models are beginning to show some agreement, or at least a few models are coming to the same agreement with this mornings' and afternoon model runs. Essentially the confidence is building that we will see a rain/snow event mainly over areas of Kansas and Missouri for both Friday and Sunday.

Friday: Both the 12z and 18z NAM showed consistency in their solution, which had been the outlier when compared to other model runs yesterday. However, this morning the runs of both the Canadian GEM and European ECMWF trended to a stronger solution. Still not as strong as the operational NAM, but is something to think about in regards to the strength of the upper level wave that will be moving across the area on Friday. For this reason, expect precipitation amounts to be higher than the GFS, but not as strong as the NAM. The other large question will be regarding temperatures, as with a stronger solution should come better warm air advection just ahead of the trough. This would likely lead to a rain/snow mix near/along I70, with snowfall likely just north and all rain further south. This is shown fairly well in the NAM, with a tight gradient of no snow to heavy snow essentially focused over Kansas City and other areas along I70. The most likely scenario will have a true mix of rain and snow for the Kansas City area, with ~1" of a heavy wet snow likely across the area. Areas just north of the KC Metro may see up to 2" of snow, while just south may only see a dusting. This will be a tricky forecast, thus even any subtle changes in the track/strength of the system could drastically change the snowfall forecast.

Sunday: Models are beginning to creep towards a consensus in allowing the pacific wave to come onshore and across the Rockies without much inhibition by the emerging blocking pattern. This would lead to a stronger system, and with ample moisture available may lead to some significant snowfall amounts over some portion of the central Plains. This is another system that will feature a tight gradient of no snow to heavy snow, as the thermal gradient along the surface and lower levels will be quite dramatic. The 18z GFS left this gradient nearly along I70 in Missouri and along I35 in Kansas, with areas north seeing mainly snow (perhaps heavy at times) and areas south seeing mainly rain. That does leave a small area that will be along the transition line that would see a mix of rain/snow and perhaps even some sleet or freezing rain dependent upon localized thermal profiles. The 12z Canadian has a similar solution in regards to strength and only slightly slower in timing, location-wise it is approximately 50-100 miles further south than the GFS. The ECMWF has been the outlier in regards to timing and strength with this system, and continues to be so. However, it has trended a little faster and stronger in the latest 12z run thus increasing the likelihood that a solution similar to the GFS/GEM can be expected. With this in mind, it does appear likely that some portions of Kansas/Missouri will have the potential of significant snowfall for Sunday. The band of heaviest snow would appear to have the potential for greater than 8" of snowfall, with this band being quite narrow it is going to be difficult to forecast for at this time. However, expect forecasts from local sources to begin more discussion on this event as the weekend nears.

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Which System?!?

I decided to get one more post in before I head away on a trip back to Iowa for the Iowa State High School Wrestling Tournament. The reason for the update is mainly as a initial thoughts on what could be an interesting weather weekend for the central Plains states. Two waves are likely to travel across portions of the Plains and may bring the chance of precipitation, in both liquid and solid form. The best part about the upcoming forecast is that there really has not been a forecast model to get a good grip on a solution to this point. With the NAM favoring the initial wave, the GFS favoring the second wave, the ECMWF favoring the second but also being even slower, and the SREF ensembles which range anywhere from 0.00" to 0.97" for Kansas City Intl into this weekend. These are just subtle changes either, the 12z & 18z NAM today put out nearly 1"/hour rates of snowfall for Friday and Friday night leading to what the NAM believes is a foot of snow by Saturday at dawn for the Kansas City area! The GFS on the other hand, does not send out as much energy with the first wave and hence gives the Kansas City area a solid 0.00" of precipitation through Saturday morning.

The reason for the discrepancies is due to a wave of energy that will drop down into the Rockies late Thursday, and another wave that will drop southward from our arctic low. These two waves of energy would likely incur some phasing as they entered the Plains states on Friday, but the question that the models are trying to answer is how much energy from the 'southern' wave will actually eject out onto the Plains. The NAM of course has a majority of the wave coming out onto the Plains and thus forecasting a large amount of precipitation with it. The GFS on the other hand will keep most of the energy in the Rockies, providing little to no precipitation for the late week.

What happens with the initial wave will likely have large impacts on our second wave for Sunday/Monday. Looking at the ensemble members, you can judge that those which have this stronger system on Friday do not have as much energy shown with Sun/Mon and thus do not expect much of an impact with this system. With the ensemble members that do not expect much on Friday, have a much larger and significant system for the Sunday/Monday time frame. Essentially if a majority of our first wave is held back in the Rockies, it will contribute to the second wave that will be pushed out onto the Plains with the storm system entering the West Coast late Friday.

Although a good amount of time was spent looking at things today, it is still very hard to tell which model may have a better handle of this that far out. It would appear that it may be best to hedge towards the second event being the largest of the two, leading to some significant precipitation for Sunday/Monday across the central Plains. However, as mentioned it is pretty hard to make much of a justification for this. For now I will keep an eye on it as it may disrupt my travel plans for a return from Des Moines, but I won't likely see time to post any updates on the blog. For now keep an eye on what the various forecasters have to say, as it will be interesting to see who throws their hat out into prediction of the big storm as either Friday or Sunday/Monday.

The next update will likely not come until early next week, perhaps even after both storm systems have exited and there is a little downtime to post a recap of what occurred, or what didn't! In the meantime, enjoy a few days of quiet weather before we at least have a chance at adding to some snow totals across the Plains.

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Winter Storm: Feb. 14 Recap

Snowfall over the weekend held a few surprises, the biggest coming with a 'snow squall' in the Kansas City area that led to multiple pileups on interstates within the metro. These snow squalls were caused by strong lapse rates and elevated instability that was collocated with the best dendritic growth zone (-10 to -20C). This allowed for rapid snowfall associated with strong northwest winds, creating near-zero visibility for a short period (~15 minutes) across several areas near the Kansas City metro. For a little more background and a few graphics, check out the link below from Kansas City NWS and for a more meteorological review check out the blog post by Jon Davies:

Kansas City Valentine's Day Snow Squall

Jon Davies Snow Squall Blog Post


The heaviest bands of snowfall occurred across parts of eastern Nebraska, western/central Iowa and into northeast Missouri and other areas along the Mississippi River. The upper level low made its' turn east and allowed the heaviest snowfall to occur into parts of Illinois and Indiana. A few maps of the snowfall totals from this weekend are also posted below:

Omaha NWS Sunday Snowfall Image

St. Louis NWS Sunday-Monday Snowfall Image

Springfield NWS Regional Snowfall Map

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Winter Weather - Feb. 13/14

Snow ongoing over parts of northern Iowa, western Minnesota and the eastern Dakotas with some heavy snow reports even coming in at times. A few reports that have came in already include 4" in Sioux Falls, SD and 2.5" in Rock Rapids, IA. This snow will continue to expand through the overnight, and slowly make its' way southward as a surface low forms in association with the upper level low that has made its' way into the eastern Dakotas. No major changes in forecasted snow totals with a band of 3-5" and isolated 6" amounts still seeming likely from western/central Iowa south/southeast through central and eastern Missouri. The latest Kansas City NWS graphic shows a pretty good depiction of forecasted snow totals.

Beyond the snowfall, expect northwest winds to increase during the overnight and Sunday for the area. Leading to blowing and drifting snow and hazardous driving conditions for your Valentines' Day. Cold and breezy conditions will continue through Monday before we see the sun again and a slight warm-up through midweek.

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