Issue Date: 5/17/2016
Issue Time: 10:05 AM
A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE SAN JUAN MOUNTAINS, SOUTHWEST SLOPE, GRAND VALLEY, AND NORTHWEST SLOPE.
Another cool and unsettled day is in store for Colorado as the upper-level trough continues to sit across the western US. Two distinct upper-level low circulations are noted in the water vapor imagery (red “L), along with their expected movement today (red arrows). The placement of the circulations will continue to stream moisture (green arrow) from the south/southwest, keeping precipitable water values above average for the date. Additionally, diffluent flow/divergence aloft will provide broad scale support for scattered showers/thunderstorms, mainly over the High Country and the adjacent valleys. Thunderstorms will be capable of brief heavy rainfall and gusty winds, as well as heavy snowfall above 10,000 feet.
Upslope flow over eastern Colorado will keep isolated shower chances in place for the plains regions, with slightly more coverage over and near the foothills/Urban Corridor. Not much in the way of heavy rain is expected for areas east of the mountains as the atmosphere will simply be too stable. Expect precipitation to be more of a light shower/drizzle variety. For more information regarding timing/rain rates, please see the zone-specific discussions below.
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, Northeast Plains, Southeast Plains, Palmer Ridge, and Raton Ridge:
Another cool day is in store, with isolated-to-scattered precipitation expected. The atmosphere will remain mainly stable, keeping rain rates low. Maximum rain rates will be 0.1-0.3 inches/hour. Precipitation will be of the light shower/drizzle variety as upslope flow does the heavy lifting. Due to this, the best coverage of showers will be for areas adjacent/near the higher terrain.
Timing: Current – 9 PM, with isolated showers lingering into tomorrow morning
Front Range, Northern Mountains, Central Mountains, Southeast Mountains and San Luis Valley:
Scattered showers and weak thunderstorms expected today, resulting in mainly light rain and gusty winds. Maximum rain rates will vary:
Front Range and Southeast Mountains: 0.2-0.4 inches/hour
Northern Mountains and Central Mountains: 0.4-0.7 inches/hour
San Luis Valley: 0.5-0.8 inches/hour
Timing: 11 AM – 8 PM, with a few lingering showers into the early morning hours
Northwest Slope, Grand Valley, Southwest Slope, and San Juan Mountains:
Scattered showers and embedded thunderstorms expected. Rainfall from showers will be light, but thunderstorms will have the potential to produce brief, heavy rainfall at 1.0-1.4 inches/hour. The low-end low flood threat has been issued as a result of the potential for brief heavy rain to fall on top of saturated soil. The main concerns will be low-lying areas along streams/rivers and street ponding in poorly drained areas. Snow will fall above 10,000 feet, and may be heavy at times. Travel on mountain passes will see minimal impact, however, as roads will still be warm enough to melt the snow.
Timing: Isolated showers are ongoing, coverage of both showers and thunderstorms will increase through the afternoon/early evening. Activity will diminish after sunset, but expect isolated showers to continue into the early morning hours, mainly south of I-70.
