FTB 09-25-2017: Below Average Temperatures Statewide with Rain East of the Continental Divide

Issue Date: Monday, September 25, 2017
Issue Time: 10:15 AM MDT

— Flooding is NOT expected today

Much cooler temperatures this morning with high temperatures expected to be 15-20F below normal. Overnight, some of the lower elevations over the Western Slope and San Luis Valley dipped below freezing. Still a lot of cloud cover over the eastern portion of the state, but the water vapor (wv) image below shows a decrease in the low level moisture statewide. This should give us a break from the heavy rainfall, although some rain is still expected east of the Continental Divide. Precipitable Water (PW) values at Denver and Grand Junction are 0.55 and 0.34 inches, respectively. Both have decreased a bit as the southwest flow aloft continues to advect drier air into the state. Today this southwest flow will get a bit more of a westerly component as the trough continues to move towards the northeast. Currently, the upper level low is located over Wyoming, and it is expected to pull north and reside over Montana/North Dakota by tomorrow morning.

The higher PW will also be east of Colorado today with the slow, eastward progression of the front. Another shortwave with upper level support from the jet stream is expected to move over the state. This will enhance vertical motion and help trigger showers over the eastern portion of the state. Northerly surface flow will get an easterly component this afternoon. Weak upslope flow and the associated showers are expected to be most numerous over the Front Range with more isolated showers over the Southeast Mountains. Some thunderstorms are also expected over the Northeast Plains this afternoon with the increased vertical motion. Due to decreased moisture over the western portion of the state, rainfall is only expected to be isolated and confined to the north where not as much drying has occurred. Again, expect higher elevations to see precipitation fall in the form of snow instead of rain. Tonight, showers are expected to end over the higher terrains around 11PM as subsidence behind the shortwave suppresses overnight shower and snow activity. There is no flooding expected today.

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:

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

Cloudy this morning with increasing showers and thunderstorms this afternoon. Heaviest accumulations in the mountains are expected to be over the Front Range. 24-hour precipitation totals up to 1 inch are possible with snow at the higher elevations. Showers and thunderstorms are also expected over the Northeast Plains this afternoon. 24-hour rain totals up to 0.8 inches are possible. Flooding is not expected today.

Primetime: 10AM to 11PM

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

Mostly sunny and cool with some clouds over the Northwest Slope. Dry air will limit shower activity to the north. Snow will likely fall at the higher elevations, but accumulations of both rain and snow are expected to be limited. 24-hour accumulations up to 0.25 inches are possible. Flooding is not expected today.

Primetime: 12PM to 8PM