Issue Date: 7/20/2015
Issue Time: 10:07 AM
A MODERATE FLOOD THREAT IS ISSUED FOR PORTIONS OF THE RATON RIDGE AND SOUTHEAST PLAINS.
A LOW FLOOD THREAT IS ISSUED FOR PORTIONS OF THE CENTRAL MOUNTAINS, SAN JUAN MOUNTAINS, SOUTHWEST SLOPE, FRONT RANGE, SOUTHEAST MOUNTAINS, RATON RIDGE, AND SOUTHEAST PLAINS.
Colorado remains under the influence of mid-level subtropical moisture as the high pressure ridge remains in a favorable position over the south-central US. For locations experiencing greater surface moisture the result is higher precipitable water values. Low-level moisture decreases, on average, from south to north, and this is easily seen in the IPW graph below; Pueblo currently sits at 1.2 inches, Colorado Springs and Grand Junction between 0.8 and 1.0 inch, and Boulder around 0.6 inches. This deeper moisture is important when it comes to today’s thunderstorm chances and subsequent flood threat.
The mountains will experience the best coverage of showers and thunderstorms today, especially along and south of I-70, as orographic influences combine with daytime heating and make use of the subtropical moisture available. Locally heavy rainfall will be possible, but storm motions will help limit the flood threat somewhat. An influx of moisture from the southwest will occur overnight, likely keeping showers and a thunderstorm or two around through tomorrow morning.
For areas east of the mountains, the probability of thunderstorms decreases from west to east. The Urban Corridor and Palmer Ridge will hold the chance for isolated weak thunderstorms this afternoon and evening, but they will rely on outflow boundaries from mountain convection to develop. The Northeast Plains will stay dry, except for a stray weak shower/thunderstorm near the Urban Corridor, as the environment will stay capped due to weak subsidence, warm mid-level temperatures and drying low-levels. The most active locations east of the mountains will be the Raton Ridge and southern extents of the Southeast Plains, thanks to more available moisture and the presence of a weak surface boundary that will stall near the CO/NM border. Scattered thunderstorms will be likely across the Raton Ridge near the interface with the Southeast Mountains, with more isolated activity across the remainder of the Raton Ridge and the Southeast Plains.
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, jump below the map.
Zone-Specific Forecasts
Urban Corridor, Palmer Ridge, and Northeast Plains:
Mostly sunny and warm will be the main story today, with only a couple isolated, weak showers/thunderstorms possible this afternoon and evening, with the best relative chance across the Urban Corridor. Flooding issues are not expected as storm motions and low-to-moderate rain rates will not be enough to warrant concern. Maximum rain rates will be 0.4-1.0 inches/hour.
Timing: 1 PM – 9 PM, with one or two showers/thunderstorms possible through 1 AM thanks to outflow boundaries from mountain convection.
Southeast Plains and Raton Ridge:
Mostly sunny and dry for most, with scattered showers and thunderstorms south of Highway 50, near the interface with the Southeast Mountains, becoming more isolated to the east. Maximum rain rates will be 1.2-2.0 inches/hour.
Timing: 1 PM – Midnight, with a few scattered showers/thunderstorms continuing into tomorrow morning as moisture increases from the southwest with the arrival of the next disturbance.
Front Range, Northern Mountains, Northwest Slope, Grand Valley, Central Mountains, Southeast Mountains, San Luis Valley, Southwest Slope, and San Juan Mountains:
Partly sunny with temperatures slightly below average will be the name of the game today as isolated showers and weak thunderstorms are expected north of I-70, becoming scattered/more numerous south of I-70. The further south, the deeper the moisture will be, and thus, the higher the maximum rain rates. Let’s break it down:
Northern Mountains, Northwest Slope, and Grand Valley: 0.4-0.8 inches/hour
Central Mountains and Front Range: 0.6-1.1 inches/hour
San Juan Mountains, Southwest Slope, San Juan Valley, and Southeast Mountains: 0.8-1.4 inches/hour
Timing: 11 AM – 8 PM, with ongoing showers and thunderstorms expected into tomorrow morning for southern zones (Southwest Slope, San Juan Mountains, and San Luis Valley) as moisture increases from the south/southwest with the arrival of the next disturbance.
