Forecasters: Michael (NWS) and Gilmore (NSSL/CIMMS)
A strong gradient in surface moisture has set up across the STEPS domain this morning, with 30-40 kt SSW surface winds on the moist side of the gradient, east of Akron CO extending to west of Lamar, with light winds west of this zone in the drier air. An upper-level disturbance is also evident on the satellite picture over the southern Colorado mountains extending southward through New Mexico. This wave is forecast to proceed northeastward during the day, and serve as a primary trigger for convection this afternoon and evening. The moist-dry gradient will also tighten into a dry line during the day, and is expected to be located near the center of the STEPS domain by late afternoon or evening. High-based convection is forecast to develop on the western side of the dry line, with moderate-to- severe convective storms expected east of this feature. High surface winds are expected with any of these storms today. Cell motions will generally be towards the northeast between 25-35 kts.
The upper-level wave and associated surface front proceeds east of the STEPS domain by tomorrow, leading to cooler and drier conditions and less of a chance for convection.
Low-level moisture is forecast to return by late Sunday, increasing convective potential again.
| VARIABLE | Day 1: 1-4 pm | Day 1: 4-9 pm | Day 2 | Day 3 |
|---|---|---|---|---|
| Convective Potential |
2 | 2 | 1 | 2 |
| Storm Type | 1 | 1 | 2 | 2 |
| Triggering | 2 | 2 | 1 | 2 |
| Intuition | 0 | 1 | 0 | 0 |
| Total | 5 | 6 | 4 | 6 |
| SYSTEM | STATUS |
|---|---|
| Ops Center | Operational. |
| CHILL | Operational. |
| S-Pol | Operational. |
| LMA | Operational. |
| MGLASS | Operational. |
| T-28 | Operational. |
| Storm ballooning | Operational. |
| Mobile mesonet | Operational. |
| Storm chase van | Operational. |
| YRFS | Operational. |
| NWS | Operational. |
Radars will begin surveillance as of noon and mobile teams are on standby as of 1:00 pm in anticipation of convection over the STEPS domain by mid-afternoon extending through this evening.
All teams focussed on a multicellular line of storms which skirted the eastern CHILL-Spol dual-Doppler lobe and regions farther east. T28 penetrations were supported by mobile mesonet observations, 3 electric ballooning launches, and reasonable radar coverage. One cell late in the period at about 120 km from CHILL exhibited dominant positive CGs. One electric balloon penetrated the anvil of this cell. Ground teams reported up to 30 m/s surface winds with these cells, with pea-sized hail noted with the later positive CG storm. MGLASS soundings were taken at Goodland and Flagler at 18 Z, at Seibert at 21 and 00 Z, and east of Colby at 22:30 Z.