today's forecast
Dense cloud cover and cool outflow is limiting heating across all of Iowa and parts of eastern Nebraska. Strong high pressure north of the stationary front maintains steady northeast to east-northeast surface flow down to the Kansas-Nebraska border and throughout the southern tier of Iowa. Dewpoints in the lower to mid 60's are pooling along the boundary in extreme northern Kansas and working into southern Nebraska. At 15Z, a single station in southern Nebraska reported southerly winds.
Aloft, dry air around 850 mb domintated soundings from Kansas along with a substantial capping inversion. Omaha's sounding appears contaminated (any other opinions on this?) and DVN was apparently undergoing a thunderstorm when they launched. This hot, dry air above the surface will move into the target region and reinforce the already strong inversion.
In the midlevels, I analyzed a small disturbance currently over eastern CO and might have spotted the same on the vapor loop. This is weak if it's actually there, or it's possible I've analyzed the Rocky Mountains--LOL. If somebody with more upper air analysis experience for this area could weigh in, I'd appreciate it. However, I believe the 14Z RUC has picked up this disturbance and moves it into central Nebraska by 0Z, maybe too late to help. The good news upstairs is that Omaha's 500 mb temp is -14C, cooler than forecast by the models.
It would appear that strong convergence along the front should have some chance to break the cap. The next question is, if the storms fire very close to or on the boundary, how long before they become elevated hailers on the stable side? Quickly I would guess. The best chance for surface based convection would seem to be somewhat south of or well off the boundary (if we had another lifting mechanism for instance). The good news here is that the RUC depicts the intersection of a weak surface trough with the boundary around Omaha at 0Z. This creates a convergence area and a small 'warm sector' in which increasing flux convergence could challenge the cap. Whether the front will ever make Omaha is a different question. I have my doubts. As for the appearance of a weak surface trough sufficient to assist in convergence, who knows?
Winds aloft are forecast to remain weak over central Nebraska, suggesting HPs if we're lucky or multicell clusters with hail if we're not. An increasing low level jet this evening should support any storms that appear, and helicity values along the front remain formidable, so tornadoes can't be ruled out if surface-based storms form.
Overall a highly conditional setup. My instinct is to stay in Des Moines for a few hours to see things develop rather than burning pricey gasoline touring the thick overcast along I-80. If I had to pick a target right now, I'd say 50 miles either side of a line from Wilber, Nebraska to Red Oak, Iowa.
