FTB 09-26-2017: Lull In Between Systems

Issue Date: Tuesday, September 26, 2017
Issue Time: 10:40AM MDT

— Flooding is NOT expected today

As shown in the water vapor image, below, Colorado currently lies between two strong disturbances embedded in the larger-scale western North American upper-level trough. Over the northern Great Plains, we can see the current position of the system that affected our weather over the past 72 hours. That system is now a memory, though its footprint still remains across eastern Colorado in the form of a patchy low-level cloud deck. With subsiding flow in its wake, Precipitable Water (PW) values are bottoming out, with readings of only 0.47 and 0.30 inches at Denver and Grand Junction, respectively. However, just to our east, Dodge City, KS, has a PW of 1.00 inch, implying that this moisture has just barely been pushed east of our state.

Looking farther southwest, we see the makings of the next active weather producer. It is currently a shortwave with an axis roughly along the UT/NV border. As this feature “digs” south-southeast over the next 24 hours, it will cut-off from the main flow: a guaranteed headache for meteorologists! By the end of the day, we will begin to see some low and mid-level moisture return into southern Colorado. With only patchy clouds this morning, sunshine is expected to increase statewide (especially east of the Continental Divide). We expect some instability to be generated in the southern third of the state. Scattered showers and a few weak thunderstorms will be possible over the San Juans, San Luis Valley, Southeast Mountains and Raton Ridge. However, rainfall rates are expected to remain below flood threat intensity. Thus, flooding is not expected today.

Looking further ahead, the cut-off low will likely produce a period of very active weather for our state beginning tomorrow. Please check out the Flood Threat Outlook for a detailed overview of what we can expect, and stay tuned to daily Bulletins for updates on heavy rainfall and flooding chances. Remember that although we are in late September, the ingredients on the weather map suggest a continued possibility of heavy rainfall in the coming days.

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:

Southeast Mountains, Raton Ridge, Southeast Plains, San Juan Mountains, San Luis Valley:

Patchy early low clouds, then sunshine returning by early afternoon. Isolated to scattered showers and weak thunderstorms will develop by mid-afternoon especially over higher terrain. Max 1-hour rainfall up to 0.4 inches with max 3-hour rainfall up to 0.7 inches. Activity could persist into the overnight hours, especially along the NM border. Flooding is not expected today.

Primetime: 2PM to 1AM

Front Range, Urban Corridor, Palmer Ridge, Northeast Plains, Northwest Slope, Grand Valley, Southwest Slope, Northern Mountains, Central Mountains:

Mostly sunny this morning (though with some patchy low clouds east of the Cont. Divide) and turning warmer this afternoon. An isolated shower or weak thunderstorm is possible during the afternoon hours in the southern Front Range and Central Mountains. Max 1-hour rainfall up to 0.25 inches. Flooding is not expected today.

Primetime: 2PM to 7PM