Issue Date: Tuesday, May 7th, 2019
Issue Time: 10:00AM MDT
— A LOW flood threat has been issued for portions of the Urban Corridor, Front Range and Northeast Plains
The low coming from southern CA has moved eastward and is currently over Arizona as seen in the water vapor imagery below. Throughout the day, expect the low to keep progressing eastward. This should bring continued favorable dynamics to the state for rainfall and thunderstorms in the mid and upper levels of the atmosphere. Earlier this morning, PW values at DIA were measured at 0.74 inches (which matches the record for this date, but is far from the May record of 1.14 inches). In comparison, the PW value over Grand Junction was at 0.3 inches; however there is some better moisture in the higher terrains near the Divide. Visible satellite shows heavy cloud cover and dense fog over the eastern portion of the state with cloud cover over the Central and Northern Mountains in western Colorado.
Expecting storm coverage to pick up early this afternoon over the higher terrains with the approaching trough. Storms will be most abundant near the Continental Divide over the northern portions of the high terrains (Central Mountains, Northern Mountains and northern Front Range). Over the Urban Corridor, a bit of instability is possible if low level clouds are able to clear. If this occurs, some thunderstorms with small hail are possible this afternoon/early evening as storms move off of the mountains. A quick 0.5 inches of rain is possible, and combined with small hail, this may cause some urban flooding issues. A Low flood threat has been issued for this reason. Storm movement to the NW at 15 to 20 knots shouldn’t cause many issues over the plains, though some field ponding is possible if multiple storms track over the same area. A cold front will drop through the state overnight, so expecting some light showers overnight.
A secondary set of storms forms as a wave passes through the southeast corner of the state. Expecting storms to fire over the Southeast Mountains and Raton Ridge this afternoon. Storm movement this afternoon will be NW at 15 to 20 knots, so not expecting major flooding issues over southeast Colorado. With more instability able to build over the plains, and upper level dynamics combining with low level moisture, another round of severe thunderstorms are likely. Hail up to 1.25 inches is possible along with gusts in the 60mph range for the stronger thunderstorms. Storms and rainfall will likely continue into the night as the upper level jet moves over the eastern plains, so there will be some decent accumulation by morning. As the cold front drops south overnight, there also may be an increase in light shower activity over the Southeast Mountains with the upslope flow.
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.
Zone-Specific Forecasts:
Front Range, Urban Corridor, Northeast Plains:
Expecting shower coverage to pick up this afternoon as the trough approaches from the west. Low level moisture, mid and upper level dynamics and a bit of clearing over the Urban Corridor may cause some thunderstorm activity this afternoon/early evening. A quick 0.5 inches of rain is possible, and paired with small hail, this may cause drainage issues. Threats for these storms include flooding and field ponding in poorly drained areas. 2-hr totals up to 1 inch may be possible with 1-hr rain rates up to 0.8 inches. Over the higher terrains, max 1-hr rain rates up to 0.6 inches are possible. Expecting some light showers to linger into tomorrow morning as a cold front drops through the state overnight. Temperatures should also begin to drop off today and tonight, which in turn will drop the snow level for tomorrow. A Low flood threat has been issued with a focus on the Urban Corridor.
Primetime: 2PM to 10PM
Southeast Mountains, Palmer Ridge, Raton Ridge, Southeast Plains:
Fog and low level clouds are being reported once again this morning with more dense fog near the mountains. Clearing is expected throughout the morning and with a shortwave moving across the southeast corner of the state this afternoon, storm coverage is also expected to pick up. Showers over the Southeast Mountains and Raton Ridge area are expected to begin by early afternoon. As these storms move into the eastern plains, they will encounter more favorable dynamics. That means another round of severe thunderstorms is possible over the far eastern plains. Max 1-hr rain rates up to 0.8 inches are possible with hail up to 1.25 inches and gusts around 60mph. With decent storm movement, flooding is not expected, although 24-hr totals up to 1 inch are possible as storms linger into the night with the passing cold front and support from the upper level jet. Some light showers are also possible along the Southeast Mountains overnight.
Primetime: 1PM to 5AM
Northwest Slope, Grand Valley, Southwest Slope, Northern Mountains, San Luis Valley, San Juan Mountains, Central Mountains:
Not quite as much moisture over the western portion of the lower elevations with a slot dry air (yellow) seen in the water vapor imagery. Some higher moisture still remains near the Continental Divide, which should allow for some midday precipitation with the approaching wave. Coverage should pick up over the Northern and Central Mountains by noon. With NW movement of the storms, not expecting much rainfall after sundown. Max 1-hr rain rates up to 0.2 inches are possible. A second set of storms moves into western Colorado by early tomorrow morning. With the cold front passing through, low level moisture return is expected, so light showers (and snow above 8-9K ft) are possible by tomorrow morning.
Primetime: 1PM to 8PM
