Friday, March 19, 2010

Winter Storm: Mar. 19/20 Update #4

Just a quick update with the 12z model runs...  Amazing to think I'm sitting with the sliding door wide open letting the great outdoor air in at the moment, give another 12 hours and we'll be nearing 32 degrees and snow!!

The 12z NAM stays consistent with the frontal passage across Kansas and Missouri during the overnight hours, however, has changed the trowel strength and maximums once again.  With a surface low path further south compared to previous runs the best area for significant snow will be over parts of Oklahoma into extreme southeast Kansas and perhaps into portions of southwest/western Missouri. The 12z GFS is similar with a surface low track through Arkansas just a little further southeast, thus the best trowal now located a little further southeast away from the Kansas City Metro. 

Will likely get the 'live' setup going late tonight after I arrive home from work, but may not turn it on until the early morning hours so that there is truly something to view besides a dark view of the ground.  Expect to see white ground by sunrise Saturday over Kansas City, with total accumulations of ~4" along and south of I70, with 2-4" for the areas north of I70.  An additional update is likely tonight ~11PM or shortly thereafter...

Winter Storm: Mar. 19/20 Update #3

The off-hour model runs (06z) last night kept some consistency, although they both once again depicted some areas seeing over 18" of snowfall in eastern Oklahoma.  No drastic changes nonetheless, and we have Winter Storm Watches now posted for large areas of northern Oklahoma, southern Kansas, and western Missouri. Areas currently under the Winter Storm Watch are expected to see at least 6" of snow through Saturday evening. This heaviest swath is fairly consistent with my wording last night of where the heaviest snowfall is likely to occur, south of I35/I335 and I70 in Kansas and then between I70 and I44 in western Missouri.

I work this afternoon, thus will not be able to update during the afternoon hours as the cold front begins to dive into the area and we finally start to find out how quickly the change-over from rain to snow will occur.  Current indications are that a few hours of rain in Kansas City before we see snow mixing in and a change over to all snow just after Midnight tonight. The heaviest snow will not likely come with this first band of frontal precipitation, but rather the trowal development that will occur on Saturday and likely skirt the southern portions of the Kansas City Metro.  Will post another update after the 12z runs are available and hopeful confirm the going forecast, but would expect to see at least 4-6" of snow for areas of Kansas City south of I70.  The heaviest snowfall totals still look to occur over portions of Oklahoma and Kansas, but the remaining areas under the Winter Storm Watch aren't going to escape without some hefty amounts as well.

Additional update expected ~11AM...

Winter Storm: Mar. 19/20 Update #2

Just a quick update to post two model images from tonight, both the NAM and GFS 00z snowfall forecasts courtesy of Earl Barker's Model Page.  The snow algorithm used here is a max-temp in profile, although not as high as an omega or Cobb algorithm output, it is still likely higher than what you will actually see. This will be due to melting that will initially occur with any snowfall (due to warm ground temperatures), but then also compaction as the snow is expected to be quite wet and heavy at times.  With that, the two images are below (NAM above, GFS below):




Thursday, March 18, 2010

The Madness Continues... Winter Storm: Mar. 19/20

In the NCAA Tournament there is still plenty of good games with a Tennessee vs San Diego State game going down to the wire, and a Texas vs Wake Forest game going into overtime.  This has been one of the best first days of the tournament that I can remember...

In other madness, there is very high confidence of a winter storm taking shape over parts of the Central/Southern Plains with the potential for 8"+ of localized snowfall and sustained winds of 25-35 mph and gusts of 45 mph. The question has been on the exact location of this heaviest band, which has been hindered not only by model differences but by run-to-run differences as well.  The latest NAM (00z) has continued its' idea of a frontal passage over Kansas and northwest Missouri Friday night continuing into central Missouri during the day on Saturday. As this front continues into central Missouri the upper low deepens dramatically over Oklahoma and into Arkansas while the surface low tracks over northern Arkansas and then into the Tennessee Valley by Sunday.  This sets up the trowal axis over parts of extreme eastern Kansas and into western Missouri with the potential for over 12" of snow!  The NAM has been the outlier and was widely discounted, but the latest solution is quite similar to the latest run (00z) of the GFS.  The difference lies within the trowal location, as the GFS has the precipitation wrapped tighter/closer to the surface low.  The difference is less than 100 miles between the two, but the question remains on the solution to the ECMWF which has been the preferred model as of late.  I do feel confident enough to indicate that the heaviest swath of snow is likely to fall between I70 and I44 in Missouri, back into areas of eastern Kansas south of I70 & I335/I35.

I have a few errands to do tomorrow morning, but will try and take a quick look at the 12z runs and make a quick update here.  I will likely have a live stream running locally by tomorrow evening with a view out into the yard...  Am still entertaining the possibility of a mobile live stream depending upon the location of the heaviest band of snow. 

March (Model) Madness

The NCAA tournament got underway with some great games in the first round, including a few upsets and a few other games that went down to the wire. I have a few brackets that are still looking pretty good through the afternoon/evening games. But, the true madness is that of the forecast models and their differing solutions regarding the upcoming storm system for the Central and Southern Plains this weekend.

As previously mentioned it appeared that we were beginning to trend towards a solution, however, we definitely didn't improve upon the agreement this afternoon. The ECMWF would appear to have the best run-to-run consistency compared to the GFS and NAM, and it also has the furthest south track with the initial shortwave and the eventual closed low over the Southern Plains. The 12z GFS run had similarities, but the 18z also came up with a differing solution in regards to the initial frontal band of precipitation. Thus far the NAM has been thrown to the side for the most part, especially after the 12z run indicated a foot or two possible across Kansas/Missouri.

The storm system is very complicated in itself, dealing with the timing of an initial frontal passage and then the closing of the low somewhere over Oklahoma/Texas. Add in the problem of warm vs cold air and its' timing and we are looking at a sharp gradient between over 1" of rain and upwards of 6" of snow. A lot of questions may not likely be answered until the event gets underway and you can watch the lower level winds and temperature profiles to determine how much and if any is going to fall over certain locations. It still would appear that an area of Kansas/Missouri will see a swath of 6"+ through the day on Saturday; and the heaviest may very well occur over eastern Oklahoma with potentially 12"+ possible. Tomorrow morning after viewing the 12z model runs I will hopefully feel confident enough to say where this heaviest swath is likely to occur...

An additional update is possible late tonight after the 00z model runs are completed (~11pm) otherwise a quick update tomorrow morning can be expected.

Weekend Snow Storm?!?

Models had continued their questionable outputs in regards to snowfall and transition of rain to snow over the Central Plains on Friday night and Saturday, but are once again coming into a trend towards a solution. This mornings' GFS and NAM both had a fairly similar solution in regards to snow amounts over Kansas/Missouri, but still having slightly different tracks in regards to speed and north/south variability in the surface low. The ECMWF has been fairly consistent in a solution for the past few runs, and via current NWS discussions it would appear that it has the slight edge in regards to forecasting value.

I'll have a better chance during the afternoon today to look at the various models and see what the 18z and early indications of the 00z models have to say.  An update later this evening/tonight will be likely...

Looks like we'll see the change from rain to snow during the overnight Friday, and there should be enough cold air spilling in that we keep the precipitation as snow even as we hit the daylight hours Saturday. A lot of questions regarding snowfall amounts not only because of the model variability, but the fact that we will have temperatures in the 60s and sunny skies for today and Friday and we'll see rain before the change which will allow the wet surfaces to melt the initial snow as well.  If we had cold ground and no initial rainfall we could easily be looking at 6-12" with even higher isolated amounts across portions of Kansas/Missouri. However, with the questions raised above it would appear that we will struggle to see anything higher than a 4-6" widespread swath.  Again, I'll update more later on this evening.

In regards to the weekend event, I'm entertaining the idea of setting up a live stream for the duration of the storm.  For the most part this would be at a stagnant location, but if requested by any local media sources could become a live mobile stream.

Tuesday, March 16, 2010

Where's the Sun?!?

We've been going the past several days with mornings' filled with low level clouds and high moisture values leading to sprinkles and mist. Today is no exception, and it looks to continue tomorrow morning as well.  Yesterday during the late afternoon hours we were able to see the sunshine in Kansas City as the low level stratus finally cleared out, but the clouds made their return during the overnight.

A disturbance is going to slide north to south across the Northern Plains today, and over along the Missouri/Kansas border overnight tonight arriving into the Southern Plains by Wednesday morning. This disturbance does not have much for dynamics, and even less in regards to moisture to use for precipitation. This means we'll mainly see the cloud cover continuing, with a few rounds of sprinkles or light showers across  western Iowa, and Western Missouri. This will be out of the area by Wednesday morning, and we should dry out and clear out by Wednesday evening.  The clear skies will continue into Thursday and through most of Friday before out next storm system will bring in the next round of clouds and definitely a round of heaviest precipitation for the Central Plains.

This storm system for Friday and into the weekend is something to keep an eye on, as of yesterday morning it was the operational GFS that was the outlier showing a decent storm system. However, several models by the afternoon hours were showing a trend towards the operational GFS solution and the last 4 runs of the operational GFS have all continued with a similar solution. The surprising and questionable solution at this point is the amounts of snowfall that is forecasted with the operational GFS on the cold side of the system. Just for humor, last nights 00z operational GFS showed a surface low tracking along southern Kansas/Missouri leading to a swath of snow across western and central Kansas, into northeast Kansas and into northwest Missouri. With ~18" of snow in Russell as the maximum, but a solid swath of 6-10" across the remainder of the locations named above. For the Kansas City Metro this meant a gradient of 1-8" from south-to-north across the metro area.  Now keep in mind that I am not saying that this is going to be correct, as there is a lot of questions regarding the track and amount of cold air that can influx into the region. Also the ground temperatures are going to be quite warm after seeing temperatures near the 60 degree mark on Friday, thus if snow did fall how much of it would melt trying to get the surface temperature down to the freezing mark.  I'll continue to update this week as we near this storm system, the first one of Spring that has the potential to give us snow!!

Wednesday, March 10, 2010

Thunderstorms to Snow?!?

Numerous clusters of thunderstorms continue across portions of the Central and Southern Plains tonight, with a continued risk of a few severe/tornadic storms through the early overnight. The tornadic threat today across much of the risk area in Kansas, Oklahoma and Missouri was hindered by shallow moisture layer. Which when subjected to continued mixing during the afternoon led to marginal dew points in the 40s for most areas, and even meager dew point depressions. With the addition of early showers and cloud cover to areas just ahead of the low pressure system, little instability, especially in the lower levels, was present to aid in the development of strong convection. Nonetheless convection was able to fire, especially just ahead of the scattered showers/sprinkles in extreme northeast Oklahoma into southwest Missouri during the evening. Marginally severe hail and some rotation was noted on the stronger cells, and although tornadoes were reported thus far no damage reports have been received.

This current storm system is sliding to the north and will become vertically stacked over Iowa. Leading to continued wrap-around moisture and thus ongoing scattered showers through the day on Friday. Cold air advection will also be present to the west and southwest of the vertically stacked low, thus conditions may become favorable for at least a wintery mix of precipitation during the overnight Thursday into Friday for parts of northern Kansas and Missouri. Areas including the Kansas City Metro may see a few hours of a rain/snow mix early Friday, although with current surface temperatures there will not likely be any accumulation. Areas of northeast Kansas, northwest Missouri and southeast Nebraska and adjacent areas of extreme southwest Iowa may not be quite as lucky with snowfall becoming heavy enough for accumulations at least on grassy surfaces. Models are having a hard time depicting the magnitude of cold air and its' association with any lift to aid in snowflake development, in addition to warm surface temperatures will lead to models likely overestimating the accumulated snowfall.

Temperatures a little below average through the weekend, but we'll at least start to dry off after a decent amount of spring rainfall. The other story to watch through the weekend will by the flooding on several rivers in the Northern and Central Plains. Making matters worse in a high number of ice jams that are also occurring thanks to rapid melting. These ice jams can create rapidly rising waters and are very hard to forecast, thus anyone in flood prone areas should pay close attention to water levels through the weekend and beyond.

Got to hear a few rumbles of thunder in Kansas City, nothing overly impressive but it was a nice sound to hear. Wait and see about a few snowflakes and then hopefully get back on track towards spring!!

Severe Weather - Mar. 10

Models continue to indicate the potential for severe weather across portions of the Central and Southern Plains for this afternoon, evening, and overnight.  A low pressure system currently ejecting onto the Plains will continue to trek east-northeast across Oklahoma and into the southeast corner of Kansas by 6pm this evening.  The low is then expected to move nearly northward as it gets ingested by the upper level system located over the northern Plains.  Moisture return is ongoing this morning ahead of the surface low pressure and will continue through this evening, however, dew point values along the surface warm front and near the surface low are likely to only reach near 50F.  Slightly higher dew points are possible further south along the dryline in eastern Oklahoma, however, surface temperatures are also expected to be higher resulting in similar LCL's across the region.

Sufficient surface based cape, at or above 1000 J/kg, will be present in the warm sector resulting in surface based convection around or just after 3pm near the surface low and southward along the dryline.  Additional convection along the warm front will also likely develop during the late afternoon and move northeast along the warm front and surface low track during the overnight. These storms along the warm front will likely be a broken line and/or linear clusters therefore the severe weather threat is lower.  However, an isolated large hail or damaging wind gusts cannot be ruled out with these storms which may move into the Kansas City area after 10pm.

The storms along the low pressure system and especially the dryline will be a slightly different story, with the ability for surface based storms to remain somewhat discrete.  Given strong low level shear and sufficient instability, storm type will likely be supercellular with the potential for very large hail and isolated tornadoes. The tornado threat may continue into the overnight across Arkansas where storms may be able to stay somewhat discrete, whereas further north storms will likely congeal and continue their potential for large hail and perhaps an isolated damaging wind gusts over southern Missouri.  Many storm chasers are heading out today, with the majority of targets being the southeast corner of Kansas or northeast Oklahoma.  As mentioned last night with my target area along Highway 169 at the Kansas/Oklahoma border; this hasn't appeared to change to much with this mornings' NAM.

I'll be in the office working this afternoon and evening, likely getting off just before our round of thunderstorms arrive in the Kansas City area. I'll be watching the storms initiate across the warm sector, however, no updates on the blog are expected until early tonight if at all. 

Tuesday, March 9, 2010

Severe Thunderstorm Potential - Mar. 9

A quick morning update on the potential for severe weather today as the surface low currently located over south-central Kansas will move northeastward and create the potential for severe weather this afternoon for areas of eastern Kansas and western Missouri.  The low pressure system has become vertically stacked overnight, creating a true cold-core thunderstorm setup over the Central Plains.

Moisture is still somewhat meager with dew points nearing 50 over much of the area this morning, while a few more degrees of moisture can be expected before this afternoon to bring dew points into the lower 50s the key for thunderstorm development today will likely be the instability.  Some instability will be present simply due to the steep lapse rates created by the vertically stacked low, however, we will likely need to see some sunshine over the area to give us better low-level instability.  Current satellite trends do not bode well for sunshine with a cluster of thunderstorms located just east of the surface low in Kansas, and its' associated cloud shield covering much of eastern Kansas under thick cumulus.  We'll have to watch trends to see if we can get a dry/clear slot to rotate around the low pressure system late this morning or early this afternoon to give us a chance, but currently conditions don't bode well for our thunderstorm risk.

If we are able to see a few hours of sunshine to enhance the low level instability then we could see an enhanced risk for low topped supercells.  This would create the potential for some brief cold air funnels and perhaps a quick cold core tornado or two given strong low level wind shear and vorticity present with the low pressure system.  This currently seems to be at rather low probability, thus not too excited on the potential.  Will try to update if anything changes this morning before I get into the office...