June 2, 2016

Team Duck's Forecast:

"Day 1 Synopsis: A decidedly unfriendly environment for severe thunderstorms is present over the southern CONUS today. There is mature surface low in the north central plains/southern Canada, while a trailing front extends southwestwards through IA, MO, OK and west through the TX panhandle into NM. The far southern part of this front is currently quasi stationary, but appears likely to become mobile southwards as convective overturning north of the frontal zone continues and becomes more pronounced during the day and the front is cold pool reinforced. A weak surface ridge is present over the northwestern high plains of CO, WY and MT. Heavy convective overturning over the past couple of days has resulted in a badly depreciated convective instability field, as repeated MCS development over South TX, northern Mexico has confined dew points above 70 to mostly the very far south CONUS. Significant outflow boundaries from yesterdays MCS in southern TX has also produced non-SE return flow, reducing available moisture, and CAPE northeast of the Big Bend region toward Del Rio to 1000-1500 J/kg. Overcast is present over north TX and the panhandle into NM, with only patches of broken cloud over the southern tier, which will likely limit insolation and thereby thermodynamic instability, in addition to a southward surging OFB. 500mb flow is expected to be relatively weak despite the subtropical jet, with DLS of ~30-35 knots over this area. Combined with the weak instability, this suggests a multicell storm environment non-conducive to any sort of sustained supercells. CAMs paint a similarly pessimistic picture, with convection struggling to remain discrete and MCS upscale growth again playing a large role.

A further concern with the potential target today is significant flooding. As we noted yesterday, flooding is already a problem in TX thanks to repeated rounds of large MCS type systems, and a flash flood watch extends over the entirety of the preferred forecast target on top of the existing heavy rainfall over the past three days. As the road network is already sparse, this suggests a potentially dangerous situation for chase operations in southern TX, and thus on this basis I would strongly advise considering not chasing this area, regardless of the forecast potential.

In light of this, my recommendation is for a travel day today to position northwards for Day 2 in the southern Dakotas/northeast NE. As this necessitates a ~12 hour drive assuming all things remain equal with todays forecast, we should position north today in either northern KS or southern NE. Some isolated convection is expected north of the frontal zone, particularly in western KS and CO, but shear is expected to be relatively anaemic. Nonetheless, there does appear to be some chance of a more sustained storm developing over far northeast CO associated with a DCVZ development and moving eastwards along the KS/NE border late this afternoon according to the 6Z NAM with reasonable updraft helicity, though moisture may be overestimated over that region. A similar signal however is not seen in the HRRR rendition for the same period, nor in RAP (both do not develop a lee low). "

Brindley helps a painted turtle across the highway under severe clear skies.

Team Duck's Summary:

"A pleasant morning greeted us in Norton, and we set off early through the sandhills of NE for our target of the day nearabouts Winner SD. CAPE was expected to amount to 1500-2500 j/kg associated with a moist axis extending from a warm frontal zone along the i90 corridor. Dew points were a limiting factor, with values in the upper 50s. Early observations in the Winner area appeared reasonably favourable when combined with a helical wind profile, however as the day progressed, initiation began to look increasingly less likely, suggesting that the CAMs were overestimating moisture and initiation potential. This was reflected by high cirrus skies, and a weak cumulus field, suggesting perhaps that the convective inhibition in the mid troposphere was too strong, or the trough too far west to provide a focal point. We did however enjoy a lovely afternoon at a park on the outskirts of Winner, watching people enjoy the summer pool and eating quite a collection of strawberries.

In light of the lack of convection, however, we decided to drive north to the interstate near Reliance, with hopes for initiation from the west. However, other than the predicted squall line in north-central SD moving in from the west, no further convection developed. The ongoing squall line north of the interstate was beginning to accelerate and move eastwards, with some interesting development on its southern tip. We repositioned further west for the scenario of a supercell or tail-end-charlie cell developing, however it became evident that the squall line was extremely high based, with marginal dew points and very little tornado potential. We called the chase, and progressed to our overnight destinations closer to the next day’s target in Minnesota."