SPC MD 1046

MD 1046 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR FAR EASTERN NEBRASKA AND WESTERN/NORTHERN IOWA INTO SOUTHERN MINNESOTA

Mesoscale Discussion 1046
NWS Storm Prediction Center Norman OK
0819 PM CDT Sun Jun 28 2020

Areas affected...Far Eastern Nebraska and western/northern Iowa into
southern Minnesota

Concerning...Severe potential...Watch possible 

Valid 290119Z - 290315Z

Probability of Watch Issuance...40 percent

SUMMARY...Isolated severe thunderstorms could develop through
mid/late evening within a corridor from east/northeast Nebraska and
western/northwest Iowa into southern Minnesota. Although
considerable uncertainty exists regarding the magnitude/spatial
extent of the severe risk, convective trends are being closely
monitored.

DISCUSSION...Mid-level warming/subsidence has generally prevailed
across the region through peak heating and early evening in the wake
of an MCV across east-central Minnesota. Cumulus has begun to tower
particularly across northeast Nebraska into northwest Iowa, with a
modest increase in radar returns along with a couple of lightning
flashes, although the initial development across northwest Iowa has
recently diminished. The regional attempts at deeper convection are
likely related to an early evening increase of a southerly low-level
jet, whose axis extends into this region. Although there will
continue to be a modest nocturnal low-level jet increase with a
related increase in warm/moist advection, the extent of capping
remains a key uncertainty within an otherwise unstable environment.
Regarding this capping and the strength of the elevated mixed layer,
the 00Z Omaha observed sounding reflected about a 6.5C 12-hr
temperature increase around 700mb (13.6C) since this morning. 

If/where convection can become rooted/sustained this evening, ample
instability across the region could result in a severe risk.
Deep-layer shear will not be overly strong (mid-level winds
generally 20kt or less), but steep lapse rates and 4000+ J/kg MLCAPE
would conditionally include a severe risk, including the possibility
of a few initial supercells capable of severe hail.

..Guyer.. 06/29/2020

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...MPX...DMX...FSD...OAX...

LAT...LON   42669635 43609550 43899455 43589373 43469379 42839365
            42199382 41339488 41999644 42669635 

Read more

from SPC Forecast Products http://www.spc.noaa.gov/products/md/md1046.html