FTB 05-15-2018: Heavy Rainfall with Afternoon Thunderstorms

Issue Date: Tuesday May 15, 2018
Issue Time: 10:15AM MDT

LOW flood threat for Front Range, Urban Corridor, Northeast Plains, Palmer Ridge, Southeast Plains, Raton Ridge

The low pressure that has been sitting over Nevada this past week finally begins to break down throughout the day. This will release extra energy to help support hail producing thunderstorms again today. A moisture axis is marked on the water vapor imagery below. This shows the threat for rainfall will again be confined to the eastern portion of the state, especially along the Palmer Ridge and southern Urban Corridor due to convergence from moist southerly/southeasterly flow. Also marked are the high clouds over the Southeast Plains from the rainfall overnight. These clouds will limit upslope convection along the Southeast Mountains and Raton Ridge until stronger heating occurs this afternoon. It will also keep the heavy rainfall south over Las Animas and Baca Counties.

As mentioned, the threat for copious amounts of nickel to quarter-sized hail continues today with the thunderstorm that form along a line of convergence in the Urban Corridor and Palmer Ridge. This is due to freezing levels being just above 6,000 feet. Larger hail may occur as the storms move into the eastern plains, but will not be as large as yesterday (baseballs) due to limited shear. Also important to the forecast today are slower steering winds. Together these factors increase the flooding and heavy rainfall potential, so a Low flood threat has been issued for the Front Range, Urban Corridor, Palmer Ridge and Northeast Plains. Threats include small stream flooding, road flooding and field ponding.

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, Southeast Plains, Raton Ridge, Southeast Mountains:

The strongest storms are expected to form in the early afternoon along the southern Urban Corridor and Palmer Ridge and grow into a large MCS as they move east into the plains. Later in the day, storms are also expected to form along the Southeast Mountains and Raton Ridge. A few storms might also sneak into the Northeast Plains from the Cheyenne Ridge, so the Low threat has been extended into this area. Max 1-hour rain rates to the north are 1.25 inches/hour. South and along the Palmer Ridge max 1-hour rain rates up to 1.75 inches are possible. A Low threat has been issued with small stream flooding, road flooding and field ponding likely.

Primetime: 12PM to Midnight

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

Best chance for showers today along the Central Mountains, but dry air from the southwest flow will limit rainfall totals to trace amounts. Temperatures will be a few degrees warmer than the past couple of days. Some cumulus are likely over the higher terrains and Northwest Slope. Flooding is not expected today.

Primetime: 1PM to 9PM