The cold front over NC-Kansas and SE Nebraska was monitored for further development. As expected, storms began to build SW-wards towards the KS boarder and CI products were effective in highlighting the area with highest probabilities for potential development along that boundary.

The event occurred over Clay and York counties (Nebraska). A series of images will be added to show the evolution:

Roughly 30 min before surface reflectivity at -10C isothermal level revealed first signs of development, the CI product highlighted both counties with 50-60 % probabilities. The cloud top cooling product showed values of -15 to -25K/15 min at 2315Z (not shown) and the first significant reflectivity signal (56 dbZ ) became visible at 2330 Z. At 00Z onwards a 63 dBz cell evolved out of that NE of York.

Helge

The area over E-Nebraska was monitored for initiation. The synthetic images did a pretty good job in timing of thunderstorm development. The real development occurred only slightly to the north to what the synthetic ones proposed. The model forecast however overestimated the development along the cold front over C/S Kansas, where warm mid-levels prevented DMC of developing until now (although showers finally try to form at 23Z onwards).

Helge

A report of quarter size hail came in around 2230 UTC, approximately where MRMS MESH estimated 1-1.25″ hail (lower left panel).

Between 2130 and 2145 Z another burst of the extensive smoke plume occurred, which was also captured by the CIMMS Cld Top Cooling product with values mainly below -5K/15 min.

Helge

Latest VIS imagery indicates a rapid increase in convection along slowly SE-ward progressing cold front, namely over Hodgeman, Ness and Rush counties. UAH-CI product already showed modest probabilities (50-60 %) for CI with no reflectivity yet present in local radar data.

Latest HRRR is a bit more optimistic with SW-ward zipping convection compared to OUN WRF. Still unsure if storms can initiate in that area with warm mid-level tongue partly covering the cold front/dry line. Strong shear now gradually moving in from the west, so increasing storm organization is likely in case of initiation.

Helge

At about 2130 UTC we decided to end operations over the Carolinas and move to the central Plains.  McKinney & Hirsh are working the Hastings CWA (GID) while Strassberg & Kleinsasser are covering the Omaha CWA (OAX).  Our to observers Helge & McCormick are checking out DDC (though concern over the cap in this region might move them to CO or Iowa).

Meanwhile the SPC issued a watch for the region as well…

-K. Calhoun

The top image is the MRMS estimate of the 60dbz echo top of a storm over Wilmington NC CWA, estimating the 60dbz echo top around 6500 ft at 2022 UTC on 5/23.  However, the bottom image is the corresponding KLTX 8.0 degree slice, indicating 60-62dbz to at least 29,000 ft.  At least in this instance, the MRMS 60dbz echo top algorithm did not perform well.