FTB 08-14-2019: No Flood Threat, but Isolated Severe Thunderstorms are Forecast for the Northeast Plains

Issue Date: Wednesday, August 14th, 2019
Issue Time: 9:05AM MDT

Marked in the water vapor imagery below are the shortwaves in the area (orange X’s) as well as the direction of their movement today (black arrows). Exiting the state to the southeast is the shortwave that brought widespread, heavy rainfall to the eastern plains yesterday afternoon and overnight. There are still a few moderate showers over the far Southeast Plains associated with this feature as well as decent cloud cover over the southeast quadrant of the state in the wake of the rainfall. Northwest flow aloft is forecast continue today with less moisture and minimal to no mid-level energy moving through the state. With drier air mass in place (really dry above 400mb in the Denver and Grand Junction soundings), storms this afternoon over the mountains and adjacent plains should be fairly isolated. There is also a noticeable inversion in place around 400mb (Denver), which should keep rainfall out of the forecast for the Denver Metro area. As far as western Colorado, storm chances will again be confined to the eastern San Juan Mountains with only trace amounts of rain likely.

Looking for storms to fire under upslope flow around 2PM mainly over the southern Front Range and Southeast Mountains. As the high-based move off the higher terrains, they have a better chance of producing measurable rainfall over the adjacent plains, especially along the elevated terrains of the Palmer and Raton Ridges. It is likely that a storm or two fires over the Cheyenne Ridge/dry line that sets up moves through the Northeast Plains. A smaller ribbon of high CAPE and shear values over the area may produce a severe thunderstorm or two, although it’s important to note the threat for severe thunderstorms is over a much smaller area than yesterday. The severe storm or two will have the potential to produce large hail (around egg size), gusty winds and an isolated tornado. Storm motion is slightly faster than yesterday and moisture a little lower, so not expecting storms to reach flood threat criteria. All storms should exit the state by 11PM, and flooding is not forecast.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

Front Range, Southeast Mountains, Urban Corridor, Palmer Ridge, Raton Ridge, Northeast Plains, Southeast Plains:

Max 1-hour rain rates up to 0.2 inches will be possible over the adjacent plains with storms over the eastern mountains producing only trace amounts to no rainfall. Gusty winds will be the main threat with storms (west) today as they form and quickly dissipate. If storms make it to the southeast corner before falling apart, totals closer to 0.75 inches will be possible. The severe thunderstorms over the Northeast Plains will have max 1-hour rain rates closer to 0.9 inches with an isolated total around 1 inch possible. Once again, these storms may produce large hail, gusty winds and an isolated tornado or two. Flooding and overnight storms are not forecast. Cloud cover over the southeast quadrant of the state should knock down high temperatures a few degrees as well.

Primetime: 2PM to 11PM

Northwest Slope, Grand Valley, Southwest Slope, Northern Mountains, Central Mountains, San Juan Mountains, San Luis Valley:

Similar set up to yesterday with little change to high temperatures. Dry air continues to be entrained from the west, so storm chances will be limited to the eastern San Juan Mountains. These storms will likely only produce trace amounts of rainfall with a couple isolated totals up to 0.1 inches possible. Also expect some brief, gusty winds from the storms that do form. Cloud cover will also be similar to yesterday, so only minimal relief from the heat is forecast.

Primetime: 2PM to 8PM