FTB 09-10-2017: Uptick in Rainfall Coverage with Increase in Moisture

Issue Date: Sunday, September 10, 2017
Issue Time: 10:00 AM MDT

— Flooding is NOT expected today

The upper-level trough continues to sit off the west coast this morning. With the upper-level high pressure over northern Texas, more southwest and westerly flow will advect moisture into the state today. On the water vapor imagery below, you can see the increase in moisture over the western portion of the state. Precipitable Water (PW) values this morning in Grand Junction were measured at 1.02 inches and measured at 0.81 inches in Denver. With drying mid-levels, some of this moisture will mix out, but PW will be higher than climatology and PW yesterday. This should allow more numerous storms to form over the higher terrains this afternoon.

Diurnal flow will initiate showers and thunderstorms early this afternoon. Some extra mid-level energy from the trough will help enhance the upslope flow. Storms are expected to be more numerous over the western portion of the state than the last couple of days. Scattered showers are also expected over the Front Range and Southeast Mountains. Storm motion will be similar to yesterday with storms to the west having more of a northerly component, while storms to east will have more E/SE movement as they slowly move around the ridge. As storms move off the higher terrains to the east, they will favor the Cheyenne and Palmer Ridges. Storms will be elevated again today, which means more gusty winds and dangerous lightning than heavy rain. Some small hail may also be possible. Storm totals up to 0.7 inches are possible over the flash flood prone Flat Tops and Roan Plateau region, so stronger storms should be monitored closely. Most storms will end by 11PM with a few showers lingering over the higher terrains after midnight.

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.

Zone-Specific Forecasts:

Front Range, Urban Corridor, Northeast Plains, Palmer Ridge, Southeast Mountains, Raton Ridge, Southeast Plains:

Sunny this morning becoming partly cloudy this afternoon with thunderstorm development over the higher terrains. As storms move east, they should are expected to favor the Cheyenne and Palmer Ridges. Gusty winds, small hail and lightning will be the main threats today. Max 1-hr rain rates up to 0.8 inches (east) and 0.7 inches (west).  Flooding is not forecasted today.

Primetime: 1PM to 11PM

Northwest Slope, Grand Valley, Southwest Slope, Northern Mountains, San Luis Valley, Central Mountains, San Juan Mountains:

Partly cloudy this morning with cloud cover increasing this afternoon. More numerous coverage in showers and thunderstorms this afternoon with an increase in moisture and upper-level energy. Storms are expected to drift north throughout the day. Main threats are gusty winds, small hail and lightning. Max 1-hr rain rates up to 0.7 inches are possible. Stronger storms that form over the flood prone region of the Flat Tops and Roan Plateau should be monitored closely. Flooding is not expected today.

Primetime: 12PM to 11PM