Bill Schintler
EF4
Chase target:
30 miles NW of Aberdeen, SD
Timing:
Isolated storms will move into the target area by 7 PM CDT.
Storm mode:
Elevated and high-based storms will initiate over the Black Hills area after 3 PM, and later move and expand eastward into the deeper moisture through the early evening hours. Storms will remain isolated in nature until after dark, and a few supercell storms will be capable of large hail along with impressive storm structure. A bust during the daylight hours is a possibility.
Synopsis:
Strong ULVL ridging is in place throughout the Plains and Upper-Midwest while WV imagery indicated a number of embedded impulses over MT and WY. Nearly dry-adiabatic mid-level lapse rates were indicated on the UNR, RIW, and SLC soundings; while at the SFC dewpoints of 60F through a 50mb deep moist layer were pooling along a WF in SD.
Discussion:
A SFC boundary with developing low-pressure in CNTRL SD should provide the focus for isolated late-afternoon convection. Differential advection of a highly unstable airmass will take place as steep lapse rates approach from the west while SFC moisture continues to stream NWRD. The details of the upper-level forcing are not obvious at this time, however it appears that localized lift in association with the right-entrance region of a 45kt H5 jet translating through ND may aid in overcoming strong capping from a 12C H7 thermal ridge nosing into the region. Early in evolution, storms will be high-based as a result of dewpoint spreads on the order of 25F. Early in the evening, a short window of time may exist where BL temperatures cool and cloud bases lower, perhaps with the assistance of some storm-scale modification, while storms are still SFC-based. Later in the evening, a strengthening LLJ will result in an evolution into a small MCS that will track into WRN MN. The GFS continues to produce little in the way of QPF for tomorrow’s WX, however it also produces no precipitation for the elevated convection developing over NERN SD ATTM while other models (NAM, NGM) continue to advertise a small MCS after 06Z today.
- bill
30 miles NW of Aberdeen, SD
Timing:
Isolated storms will move into the target area by 7 PM CDT.
Storm mode:
Elevated and high-based storms will initiate over the Black Hills area after 3 PM, and later move and expand eastward into the deeper moisture through the early evening hours. Storms will remain isolated in nature until after dark, and a few supercell storms will be capable of large hail along with impressive storm structure. A bust during the daylight hours is a possibility.
Synopsis:
Strong ULVL ridging is in place throughout the Plains and Upper-Midwest while WV imagery indicated a number of embedded impulses over MT and WY. Nearly dry-adiabatic mid-level lapse rates were indicated on the UNR, RIW, and SLC soundings; while at the SFC dewpoints of 60F through a 50mb deep moist layer were pooling along a WF in SD.
Discussion:
A SFC boundary with developing low-pressure in CNTRL SD should provide the focus for isolated late-afternoon convection. Differential advection of a highly unstable airmass will take place as steep lapse rates approach from the west while SFC moisture continues to stream NWRD. The details of the upper-level forcing are not obvious at this time, however it appears that localized lift in association with the right-entrance region of a 45kt H5 jet translating through ND may aid in overcoming strong capping from a 12C H7 thermal ridge nosing into the region. Early in evolution, storms will be high-based as a result of dewpoint spreads on the order of 25F. Early in the evening, a short window of time may exist where BL temperatures cool and cloud bases lower, perhaps with the assistance of some storm-scale modification, while storms are still SFC-based. Later in the evening, a strengthening LLJ will result in an evolution into a small MCS that will track into WRN MN. The GFS continues to produce little in the way of QPF for tomorrow’s WX, however it also produces no precipitation for the elevated convection developing over NERN SD ATTM while other models (NAM, NGM) continue to advertise a small MCS after 06Z today.
- bill
