Issue Date: 5/19/2015
Issue Time: 10:36 AM
A MODERATE FLOOD THREAT HAS BEEN ISSUED FOR THE CACHE LA POUDRE NEAR GREELEY, SOUTH PLATTE RIVER FROM HENDERSON TO JULESBURG, AND THE ARKANSAS RIVER FROM AVONDALE TO LA JUNTA. A LOW FLOOD THREAT HAS BEEN ISSUED FOR PORTIONS OF THE FRONT RANGE, URBAN CORRIDOR, PALMER RIDGE, RATON RIDGE, AND SOUTHEAST PLAINS.
Last night/this morning’s rain and snow continues to taper off from southwest to northeast, bringing the widespread precipitation to an end. Don’t let this break after this morning’s action fool you, because another round of isolated-to-scattered showers and thunderstorms are in store (again). This new round of action will start around lunchtime as another disturbance rotates around the upper-level low (marked by the red “L” in the water vapor imagery below). Due to the cool air in place, thanks in large part to this morning’s rain, widespread heavy rain is not expected. Instead, most rain rates will generally be light, in the 0.25-0.5 inch/hour range. However, a few stronger storms will develop over southern portions of the Urban Corridor, Palmer Ridge, Southeast Plains, and Raton Ridge, producing rain rates in the 0.5-1.2 inches/hour range. For this reason, and the amount of rain received this morning, those locations have been put under a low flood threat for this forecast period.
Over the higher country, snow levels will be around 10,000 feet, with lower elevations receiving rain. Isolated-to-widely scattered showers are expected to increase in coverage around 11 AM, and last throughout most of the day, before diminishing after sunset. A few showers will linger over the Northwest Slope, Northern Mountains, and northern portions of the Front Range until midnight. Mid-level ridging will begin to build in overnight, meaning a more peaceful nighttime is in store across the state.
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 (south of Castle Rock), Palmer Ridge, Raton Ridge, and Southeast Plains:
This morning’s rain continues to taper off/push to the north-northeast, but the next round of isolated-to-scattered showers and thunderstorms will begin to develop between 11 AM and Noon. The strongest storms will produce rain rates of 0.5-1.2 inches/hour, but most rainfall will be in the 0.25-0.5 inches/hour range. The likeliest location for strong thunderstorms will be over the Raton Ridge and Southeast Plains, but moderate-to-heavy rain cannot be ruled out for the Urban Corridor and Palmer Ridge due to upslope surface winds.
Timing: 11 AM – 9 PM
Urban Corridor (north of, and including, Castle Rock), Front Range and Northeast Plains:
The precipitation shield currently across the region continues to push northward and out of the state, but a few showers continue to persist across Boulder, northern Jefferson, and Larimer Counties thanks to upslope surface flow. For this reason, a low a flood threat has been issued for portions of the Urban Corridor and Front Range where this upslope precipitation is occurring and will continue through the early afternoon.
The next round of isolated-to-widely scattered showers will begin to develop between 11 AM and Noon behind the exiting precipitation shield. Maximum rain rates will be in the 0.2-0.45 inch/hour range. Activity will diminish quickly after sunset.
Northern Mountains, Northwest Slope, Grand Valley, Central Mountains, San Juan Mountains, Southeast Mountains, San Luis Valley, and Southwest Slope:
Isolated-to-widely scattered showers are ongoing across the region, mainly over the higher terrain. An uptick in activity will occur between 11 AM and Noon, developing over the higher elevations and then drifting over valleys with time. Snow levels will be around 10,000 feet, with rain occurring below 10,000 feet. Rain rates will generally be light, in the 0.2-0.4 inches/hour range. Activity will diminish quickly after sunset, with only a few light rain/snow showers continuing over higher terrain in northern areas until midnight.
