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Well, I issued a TOR for Rice County storm, but it should have been a SVR. Total User Error. Anyhow, it may end up working out. We were thinking that the original azimuthal shear was associated with the storm bowing out. However, in the past few volume scans that circ tightened up and became more distinct. It would make sense for a brief tornado to occur given that this storm is right along the boundary left from the morning MCS. -MRD
Cloud cover seems to be inhibiting convective initiation in FSD CWA. Looking toward OAX, CTC signature showing up over eastern Nebraska. CTC showing cooling rate of -24 degrees C/15 mins over Dodge/Cuming Counties in Nebraska. It also shows -19 degrees over Polk County NE at 2015z.
Reflectivity is increasing in the storms in these counties.
We have shifted to OAX and issued warning for Butler County. This storm was associated with the previous CTC signature over Polk County in Nebraska.
Tim/Steve
Quiet on the southwestern front at this hour…but we are starting to see a few echoes along the boundary. Latest OUNWRF wants to gen up a few storms along the boundary in the next hour or two…but then really gens up quite a bit of convection with a fairly large cold pool generating towards the 5 PM hour.
Not many signals being noted in the CTC or the CI products at this time, but we did get a CI 72 indication with a small tower going up on the boundary on the previous pass…will see if anything comes of it. Looking to the southwest upstream in the environmental flow, we note a few Cu towers going up at a faster rate and thinking this activity could move up into our area in the next 3 hours. See no reason why it won’t get going to the southwest given available instability.
NRE theta-e products showing a fairly unstable airmass over the area…and with near full insolation on the Cu field southeast of the boundary we expect initiation in the next 2 hours across the forecast area…
Garmon/Skov
Watching convection developing just past the FSD CWA line in Des Moines area as Cloud Top Cooling is showing a steady decrease in cloud top cooling rates from -8 degrees C/15 minutes over Pocahontas County IA at 1915z to -19 degrees C/15 minutes over Palo Alto County IA at 1932z.
Here is the KFSD reflectivity and enhanced echo top. Echo top was up to 37 kft on the storm in Pocahontas County IA at 1950z.
Update…this appears to be a false alarm as cell has continued to weaken and no cloud to ground lightning was indicated. Echo top reached 39kft before collapsing.
Tim/Steve
Thunderstorms are beginning to increase in coverage over the southwest portion of the MPX CWA. Modest increases in updraft strength and upper divergence coincided well 50 dbz reaching over 33kft. 60 dbz exceeded 22 kft. Felt hail was a certainty with the storm, as it rode near the warm front.
Missing the OUNWRF up here. The 17Z HRRR is out and has similar timing and location of initial convection as earlier runs over eastern NE around 20-21 UTC with more isolated storms over southern MN 21-22 UTC. Will we have to switch to OAX or DMX?
Line of storms over Dakota and Rice County has intensified with MESH increasing to 1.73 inches at 1925Z. At 1900Z, composite updraft increased to 17 while we saw an increase of upper divergence. Expect large hail although this storm is right along the instability gradient so we could start to see some wind problems soon as 1km 3dvar wind shows 25+ m/s. MRD/TY
Today, were are focused on the Upper Mississippi Valley for severe convective development. A potent, negatively-tilted shortwave trough is moving quickly across the north-central U.S. Strong deep-layer shear associated with the trough should combine with moderate (to strong) instability and deep moisture to produce severe convection, including supercells. It is uncertain, however, whether sufficient heating can occur in the wake of a late-morning mesoscale convective system across eastern Minnesota and western Wisconsin. If destabilization can occur in the vicinity of the residual outflow boundary, tornadoes will be possible.
A secondary area of interest is in south-central Nebraska, where the surface front curves to the southwest. In this area, the moisture is both deep and quality; the instability , strong to extreme; and the winds at the surface should back, augmenting — to some extent — the marginal wind shear. That said, severe hail and winds should be the primary threats.
We will start operations in the Minneapolis (MN), Sioux Falls (SD), and Hastings (NE) county warning areas, with an eye toward the Duluth (MN) CWA — should destabilization occur.
-G. Garfield, Week 5 Coordinator
– G. Garfield, Week 5 Coordinator
The storm moving out of SW Dallas county into NW Ellis county had some marginal increase in mesocyclone strength that may have been preceded by an increase in storm top divergence. Below are 3DVAR images from 0120 – 0135Z.
SNELSON/TY
