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Chase forecast update for March 18, 2011
As is typical in the early season, models have drastically changed the outlook for the upcoming few days. They still haven't settled down enough to make a solid forecast, but I'll give my own take on what things look like as currently shown.
Saturday, Plains: Oklahoma's wind profile doesn't look too bad on Saturday afternoon, with both the NAM/WRF and GFS showing around 30-40 knots of westerly mid-levels, southerly to backed 850mb's and backed surface winds. The drawback is moisture and instability, which is shown being a limiting factor. Neither model is showing a surface low developing (thanks to the weaker flow aloft), which is resulting in no sharp dryline, warm front or triple point to focus on. The models do show storms developing and persisting on Saturday in western Oklahoma/southern Kansas, which will likely be elevated in nature. If the southern fringe of these storms can root in better moisture, a supercell or two isn't out of the question. It would probably be worth an expedition day if I lived there, but nothing to drive far for (if I still regularly drove to the Plains, that is).
Saturday, Midwest: A warm front seems to be trying to develop on Saturday night across the lower Midwest, with elevated storms out ahead of it during the overnight hours into Sunday morning. Possible lightning opportunities with this event.
Sunday, Plains: Wind profiles aloft are shown less favorable Sunday over the Plains. While westerly midlevel flow is still good over Kansas, veered 850mb winds are shown as a problem (Veered means out of the southwest - 850mb level winds in this direction reduce low-level shear and brings in dry low-level air, which affects the moisture depth/quality in the warm sector). Again, no good surface low to focus the typical target areas. Instability and moisture are much better this day, with a sharper dryline - but a cap is shown supressing daytime convection by both models.
Sunday, Midwest: Storms are shown on the increase along the warm front as it lifts northward across the region, though these appear to be mostly elevated in nature. Deep-layer winds would be favorable for supercells if a storm can root south of the front or along it, though instability is shown being weak. Again, early Sunday morning lightning looks to be the main play with this phase of the system, with no activity likely once the warm front has moved away to the north. The GFS shows a strong surface low deepening over Michigan by the end of the day, while the NAM/WRF doesn't show the feature. A strong low would likely drag a cold front southward toward the end of the day. Both models show light precip overnight into Monday morning, which would probably be associated with that feature.
Monday, Plains: This day is out of the NAM/WRF range, so we'll just look at the GFS. Upper flow is shown improving as an upper trough begins to move into the western Plains. The last NAM/WRF panel didn't show this feature as far east in the morning as the GFS. Deep-layer wind fields look nice. Moisture and instability look good, with a sharper dryline and warm front thanks to a surface low just getting started (cyclogenesis) in eastern Colorado. The main downside shown by the model is that a cap, like on Sunday, is shown as keeping storms from firing at all in the area of interest - which at this point would be the dryline bulge/triple point in central/western Kansas. The cap may not hold, however - and so this would be a better chase prospect in the event a storm or two can get going.
Monday, Midwest: A weak cold front is shown stalling around the St. Louis area on Monday, with light precip shown in the vicinity. This likely means a cloudy day with rain showers, and few if any storms. However, with the moisture, strong upper flow and the boundary, will have to watch if clouds can clear out and destabilize things in spots - which would increase the probability of something expedition-worthy.
Tuesday, Plains: A strong (60 knot) southwesterly jet streak finally plows into the Plains region on Tuesday. A surface low is shown spinning up in Kansas in response, but veered 850mb winds once again plague the setup. The cap is shown winning out yet again, with no storms in the areas of interest.
Tuesday, Midwest: The frontal boundary looks to stay mainly stalled out in the same general area as Monday, which again probably means clouds, rain and no notable storms. The not-so-impressive Kansas surface low is shown moving eastward into Missouri overnight, which could enhance the storm potential to the south of the boundary.
And that's about it! There isn't much of interest after this, until another trough shown impacting the Plains on Thursday. Some dryline storms might pop up in the Texas panhandle inside of a narrow warm sector. At this point it looks to be coming in too far south to bring any storm potential to the Midwest. However, this is simply too far away in time to really talk much about, so I'll just leave it at that. I will say that the Euro model and the GFS ensembles are hinting at a central US ridge taking hold by the end of next week, which would shut down storms in both the Plains and Midwest for an extended time. The good news is that this would mean warm temperatures, great for getting outside and doing something other than sitting in front of a computer looking at weather models!
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