Forecasters: Mike Skipper (NWS) Llyle Barker (NWS/STEPS)
Today:
Slightly drier surface air advecting in behind reinforcing shot of colder air has led to clearing across northern portion of the STEPS domain by 15Z. DEN and LBF soundings from 12Z keep fairly deep moisture with pooling in immediate wake of boundary. Return flow has already developed along urban corridor of front range. The challenge today revolves around impact on instability of drier air near surface versus better insolation and possible slightly colder air advecting in from northwest. Mid-level winds are progged to remain 30-40 kts by 00Z with SSE flow in the boundary layer approaching 15-20 kts. This combination should provide sufficient shear for isolated supercells.
We expect thunderstorms to initiate between Denver and Limon this afternoon then move east reaching near the STEPS domain's western edge around 4 PM. They should weaken as they move into the more stable air over the central and eastern portions of the domain. However, once again today there may be targetable supercell storms on the western edge of the domain during the late afternoon.
Day 2:
Return flow and good North-South boundary continues to be progged by 12Z ETA across western domain by 18Z and is forecast to move to near the Kansas/Colorado border by 00Z. Cool front that moved through last night is also progged to return to the domain as a warm front from the south by midday. Shear (0-6km) increases to 55-60kts by 00Z in the northern portion of the domain. CAPE forecasts are progged by usually dry ETA at 1500-1700 J/Kg just east of boundary by 18Z. At this time, Thursday looks like a good day for potentially targetable supercells near the center of the STEPS domain.
Day 3:
ETA suggests that North-South boundary from Day 2 pushes east of domain with slightly cooler and drier air in wake. However, stronger shortwave evident on last nights aviation may provide more mid-level forcing. Shear remains high with good NW flow at 500 mb and south flow redeveloping at surface by 00Z.
| VARIABLE | Day 1: 1-4 pm | Day 1: 4-9 pm | Day 2 | Day 3 |
|---|---|---|---|---|
| Convective Potential |
1.5 | 2.5 | 2.5 | 2 |
| Storm Type | 1.5 | 1.5 | 2 | 2 |
| Triggering | 0.5 | 0.5 | 2 | 1 |
| Intuition | -0.5 | 0 | 1 | 0 |
| Total | 3 | 4.5 | 7.5 | 5 |
| SYSTEM | STATUS |
|---|---|
| Ops Center | Operational. |
| CHILL | Operational. |
| S-Pol | Operational. |
| LMA | Operational. |
| MGLASS | Operational. Prior to any soundings today, there are 38 remaining sondes. |
| T-28 | Operational. |
| Storm ballooning | Operational, but will target only +CG or hail-producing storms because of limited numbers (8 remaining, with the possibility of refurbishing a few more) of EFMs. |
| Mobile mesonet | Three (or four?) vehicles are available. |
| Storm chase van | Operational as the primary precipitation verification vehicle. |
| YRFS | Operational. |
| NWS | Operational. |
There is considerable uncertainty in the forecast for today, but the situation warrants standingby for all facilities. Radars and nowcast support will start at 12:30 PM local. Balloon crew will start receiving updates at 1:00 PM. Mesonet (possibility of four vehicles) will leave for Limon, CO at noon. The T-28 to standby by for possible late afternoon, early evening flight. We will plan for 18 and 21Z sondes at Seibert and Limon.
No storms occurred in our area and operations were called down at 3PM. 18Z sondes were taken in Seibert and Limon.