In Brief:
Severe weather to our east Thursday, storms and prolonged rain for the weekend.
The Forecast Discussion:
We have one more warm day, Thursday, with moisture streaming into the state. We might see thunderstorms form in the foothills in the early afternoon (Figure 1). As they move east, they will tap into much deeper moisture and instability. With an approaching upper air low, (to the upper left of the state a day later in Figure 4) they will have the potential to become severe storms just east of I-25 (Figure 2). These storms may even produce isolated tornadoes out on the lains (Figure 3). The weekend will be covered in the Longer Range Forecast below.
The Longer Range Forecast:
Another, deeper, trough will approach the state for the weekend and cut-off, slowing a lot (Figure 4). It looks like healthy rain rates and snow in the mountain will remain in place from Friday afternoon through Sunday morning (Figure 1 and 5).
Weatherunderground (Figure 1) gives Longmont about 2 inches of liquid. The GFS (Figure 6) is much more bullish. It has a bullseye of 3.5+ rain from central Larimer County to Boulder County. Much of central and northeast Colorado gets 1-2 inches.
Figure 7 shows snowfall. It is very elevation dependent, picking up rapidly as you climb into the mountains (that is a strong cut-off line!). Places in RMNP may see a foot or two of snow while Estes Park only picks up a few slushy inches. Allenspark might see a foot or more.
We warm up again next week with thunderstorms returning mid-late week.
