This content was originally published by the Longmont Observer and is licensed under a Creative Commons license.
Forecast Discussion:
The warm air pushed our chilly Friday away on Saturday. It was up into the mid-80's F by afternoon Saturday (red arrow in Figure 1). Rosa is still headed north then northeast, our way, for later this week. You can see the pretty still intact structure of Rosa yesterday in Figure 2.
The upper air pattern from Saturday shows the west coast trough that is responsible for the future track of that storm (Figure 3). The surface forecast map for today shows a backdoor cold front has again slipped in from the northeast back to the front range. Today will only get up to the 70's F (Figure 4) because of it.
For tomorrow, as the moisture begins to pour into Arizona, the heat pushes east AGAIN - and we yo-yo back to the 80's F for a few (Monday-Wednesday) days (Figure 5).
The longer range forecast:
The future path of Rosa has it as a tropical depression up around Winslow, AZ on Day 5 (Figure 6). The comparison of various tropical models (Figure 7) still has one model bring the center of the remains of Rosa right over Longmont later in the week. Wow.
The GFS gives us a five day total of only up to 1/4th inch (Figure 8). The weatherunderground model gives us closer to an inch of rain over about 3 days at the end of the week. That would be wonderful.
Figure 9 is the same map, but for the entire southwest U.S. Much of Arizona gets 2 inches of rain with a few places up around 4 inches.
