FTB 06-18-2018: Heavy Rain and Severe Weather for Northeast Colorado

Issue Date: Monday, June 18, 2018
Issue Time: 09:55AM MDT

— A LOW flood threat has been issued for portions of the Northeast Plains, Urban Corridor and Front Range

The water vapor imagery below shows that most of the moisture associated with Bud has moved through the state and is replaced by dry southwest flow. The burn scars over the San Juan Mountains, along with much of western Colorado is now under the influence of the dry slot, which should put an end of the heavy rainfall chances. The sounding at Grand Junction this morning shows PW values have dropped to 0.58 inches. Today and tomorrow the upper low over Idaho will continue its slow eastward migration. Today, the jet streak will move over the northwest corner of Colorado and mix down strong winds to the surface. Wind gust this afternoon are expected to be in the 30-40mph range, which with dry air, returns critical fire weather. A Red Flag Warning has been issued through 8PM tonight for the lower elevations of this region.

In eastern Colorado, a surface cyclone is expected to develop over the eastern plains, which will help create severe weather for the Northeast Plains this afternoon. Threats include large hail, strong winds and the possibility of some isolated tornadoes. For the Southeastern Plains, the dry southwesterly flow will limit moisture for afternoon showers and thunderstorms. However, some dew points in the 30Fs near the Palmer Ridge may allow for a few scattered storms. With decent storm motion and direction in this area paired with lower dew points, heavy rainfall is not forecast.

Over the Northeast Plains, southeasterly to eastern flow will return low level moisture with dew points reaching the mid 50sF (west) and 60s (east). Storms are expected to fire over the Palmer Ridge and Front Range this afternoon. As they move east into the high dew points heavy local rainfall is likely. Later this evening a southwest to northeast band of showers sets up overnight near the I-76 corridor. With high low level moisture, local heavy rainfall is likely. A Low flood threat has been posted for this afternoon into early tomorrow morning. Threats include street and small stream flooding over the Urban Corridor and field ponding/street flooding near low roads over the eastern plains.

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.

Flood Threat Legend

 

Zone-Specific Forecasts:

Palmer Ridge, Front Range, Urban Corridor, Northeast Plains:

High moisture returns to the Urban Corridor and Northeast Plains today. Initial set of thunderstorms this afternoon will have access to favorable severe weather parameters and high moisture. Threats include large hail, gusty winds, an isolated tornado and heavy rainfall. Max 1-hr rain rates up to 1.7 inches/hour are possible. Overnight a band of showers sets up near the I-76 corridor, which will allow for high rainfall accumulations. Max 1-hour rain rates up to 1.25 inches/hour are possible with local totals up to 2.25 inches by tomorrow morning. A Low flood threat has been issued for street flooding, field ponding and local stream flooding.

Primetime: 2PM – 5AM

Southeast Plains, Raton Ridge, Southeast Mountains:

Dry air will limit precipitation chances this afternoon. Expect isolated high clouds with limited rainfall over this area. An isolated storm may be possible over the Southeast Plain, but max 1-hour rain rates will be under flood thresholds. Over the Southeast Mountains, 1-hour rain rates up to 0.25 inches/hour are possible.

Primetime: 1PM –8PM

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

Southwest flow will pull in dry air to the area. Paired with increasing wind speeds over northwestern Colorado, a Red Flag Warning is in effect through this evening for the lower elevations. Clear skies are expected over the region with temperatures closer to average for this time of year. There is no flood threat today.