Bill Schintler
EF4
Chase Target for Friday, September 26
Chase target:
20 miles west of St. Cloud, MN.
Timing and storm mode:
Elevated storms will fire north of a Fargo to Duluth line during the morning hours. Hail will be the primary threat with these storms. Surface-based convection will develop further south between 4 and 5 PM CDT. A few supercells or embedded supercells will be likely.
Discussion:
A low-amplitude ULVL trough with embedded pieces of energy will shift east into the Upper Midwest on Day-2. Some uncertainty exists concerning timing and placement of H7-H5 mesoscale forcing mechanisms. It appears as though a lead wave will arrive in northwestern MN well before the timing of peak heating, while setting off a large area of elevated convection north of a Fargo to Duluth line. Subsidence will then overspread the area, and capping will be strong with warm mid-levels. Large-scale assent will approach from the Dakotas by late afternoon with a secondary wave while H7 temperatures cool several degrees. Omegas in excess of -10ub/s are noted. Surface-based convection should fire south of the elevated storm complex along a boundary or wind-shift line parallel to and 50 miles east of the main surface trough.
Limited instability will be available; however, it appears as though a narrow axis of 1500J/kg MLCAPE will develop along and southeast of the trough. This instability along with moderate shear parameters will set the stage for a few rotating storms. The area lies along the western periphery of a 35kt southwesterly LLJ, with SFC-3km SRH in excess of 200m2/s2. Deep-layer shear will increase to 40 kts as the H5 trough shifts to the southeast.
- bill
10:16 PM CDT, 09/25/08
Chase target:
20 miles west of St. Cloud, MN.
Timing and storm mode:
Elevated storms will fire north of a Fargo to Duluth line during the morning hours. Hail will be the primary threat with these storms. Surface-based convection will develop further south between 4 and 5 PM CDT. A few supercells or embedded supercells will be likely.
Discussion:
A low-amplitude ULVL trough with embedded pieces of energy will shift east into the Upper Midwest on Day-2. Some uncertainty exists concerning timing and placement of H7-H5 mesoscale forcing mechanisms. It appears as though a lead wave will arrive in northwestern MN well before the timing of peak heating, while setting off a large area of elevated convection north of a Fargo to Duluth line. Subsidence will then overspread the area, and capping will be strong with warm mid-levels. Large-scale assent will approach from the Dakotas by late afternoon with a secondary wave while H7 temperatures cool several degrees. Omegas in excess of -10ub/s are noted. Surface-based convection should fire south of the elevated storm complex along a boundary or wind-shift line parallel to and 50 miles east of the main surface trough.
Limited instability will be available; however, it appears as though a narrow axis of 1500J/kg MLCAPE will develop along and southeast of the trough. This instability along with moderate shear parameters will set the stage for a few rotating storms. The area lies along the western periphery of a 35kt southwesterly LLJ, with SFC-3km SRH in excess of 200m2/s2. Deep-layer shear will increase to 40 kts as the H5 trough shifts to the southeast.
- bill
10:16 PM CDT, 09/25/08
