FTB 05-31-2016: Scattered Heavy Rainfall Likely In The Southeast Plains

Issue Date: Tuesday, May 31st, 2016
Issue Time: 10:40AM MDT

— A LOW flood threat has been issued for the Urban Corridor, Palmer Ridge, Southeast Plains and Southeast Mountains

This morning’s water vapor image, below, shows many players across the Rocky Mountain states and the central US. Of particular important is the surface low-pressure system located over North Dakota. This is associated with an attendant trough that extends southward into central Colorado. Also associated with this low is a moist cool front that has entered Colorado from the northeast. Meanwhile, a cut-off low continues to drift along in southern Arizona. This feature looks like it is less and less likely to impact our state.

wv_markup

With the above features in mind, we considered the following factors for assessing today’s flood threat:

  • Moisture levels continue to be fairly limited for heavy rainfall with Precipitable Water (PW) values running close to seasonal normal in the 0.5 – 0.7 inch range east of the Divide and lower to the west; PW is expected to stay steady or increase, especially in the Southeast Plains as a weak low-pressure circulation may develop over Southeast Colorado later today. PW’s may reach 1.0-1.2 inches from about La Junta southeastward.
  • The cool front has increased moisture content, but also brought in a stable layer above the surface. Thus, instability will be focused immediately south of the cool front boundary. Roughly along and south of the Palmer Ridge.
  • Dynamics are neutral to slightly favorable for heavy rainfall. The presence of the trough will provide weak positive vorticity advection east of the Divide. However, most of the fuel for heavy rainfall will likely be provided by solar heating.
  • Storm steering winds will be 25mph+ today and storm training is not expected. It will likely be a “one-and-done” type day with heavy rainfall potential. The only exception is in the far southeast portion of the state where a nocturnal low-level jet may continue to fuel storm activity after sunset.
  • Dry air entrainment is expected over southern parts of the Raton Ridge which will likely limit rainfall rates.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below (hover over threat areas for more details). For Zone-Specific forecasts, scroll below the map.
FTB_20160531

Zone-Specific Forecasts:

Front Range, Urban Corridor, Northeast Plains, Palmer Ridge, Southeast Plains, Southeast Mountains, Raton Ridge:
Partly sunny early with scattered to widespread showers and thunderstorms developing by early afternoon and lasting into the late evening and early overnight hours in the far southeast. Maximum 1 hour rainfall rates are shown below:

Front Range/Urban Corridor/Northeast Plains: 1.3 inches per hour
Palmer Ridge/Southeast Plains/Southeast Mountains/Raton Ridge: 1.9 inches per hour

Primetime: 1pm to 8pm in northern sections and 1pm to midnight in the Southeast Plains

A Low flood threat has been issued for isolated field and roadway flooding. Mud flows and debris slides are possible over steeper terrain, including fire scar areas.

Central Mountains, Northern Mountains, San Juan Mountains, San Luis Valley, Grand Valley, Northwest Slope, Southwest Slope:
Mostly sunny early then turning partly cloudy. An isolated showers and perhaps a weak thunderstorm is possible over the higher terrain, with dry conditions elsewhere. Max hourly rain rates up to 0.2 inches. Gusty winds up to 50 mph will be possible under the thunderstorm updrafts. Flooding is not expected today.