Issue Date: 9/17/2016
Issue Time: 9:05 AM

A LOW FLOOD THREAT IS FORECAST FOR PORTIONS OF THE SOUTHEAST PLAINS AND RATON RIDGE.

Roughly speaking, if you split the state with a southwest-to-northeast oriented line from Alamosa to Sterling, you could break down the forecast fairly well. To the west of the line, the forecast is for mainly dry conditions, aside from a few isolated showers over/near the higher terrain of the Front Range/Continental Divide/San Juan Mountains. On the other hand, along/east of the line will feature scattered strong-to-severe thunderstorms, capable of large hail, damaging winds, and even an isolated tornado or two. Specifically, this includes portions of the following regions: Northeast Plains, Palmer Ridge, Southeast Plains, Raton Ridge, and Southeast Mountains.

Even with the strong-to-severe thunderstorms expected, the flood threat remains low-end. This is due to a combination of expected storm motions and marginal moisture profiles (inverted-V). Better moisture is expected to be transported in from the southeast and into the Southeast Plains and Raton Ridge regions, thus the issuance of the low flood threat in those regions. For more details on timing and expected rain rates, please see the zone-specific forecast 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

Northeast Plains, Urban Corridor, Palmer Ridge, Southeast Plains, and Raton Ridge:

Scattered showers/thunderstorms are expected across the Raton Ridge, Southeast Plains, Palmer Ridge, and eastern portions of the Northeast Plains. A few will be strong/severe, producing large hail, strong winds, and perhaps an isolated tornado or two. Elsewhere, including the Urban Corridor, dry conditions will prevail, minus an isolated shower or two near the higher terrain. Maximum rain rates will be as follows:

Urban Corridor: 0.1-0.2 inches/hour
Palmer Ridge: 0.2-0.5 inches/hour
Northeast Plains: 0.8-1.2 inches/hour
Southeast Plains and Raton Ridge: 1.0-1.5 inches/hour

Timing: Noon – 10 PM

Front Range and Southeast Mountains:

Isolated showers over the Front Range and isolated thunderstorms over the Southeast Mountains are expected this afternoon and evening. The best moisture will sit to the southeast of these areas, so heavy rain is not a threat. Maximum rain rates will be 0.1-0.2 inches/hour over the Front Range and 0.4-0.6 inches/hour over the Southeast Mountains. The majority of the regions will remain dry today.

Timing: Noon – 7 PM

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

Mostly sunny and dry conditions will be the name of the weather game today across these regions. A few clouds will develop over the higher terrain, producing a few streaks of virga across the sky, and perhaps a light sprinkle or two along the Continental Divide and San Juan Mountains, but nothing more.

Issue Date: Friday, September 16th, 2016
Issue Time: 9:55AM MDT

— Flooding is NOT expected today

As shown below, today’s Precipitable Water values continue to show a slight decrease compared to 24-hours ago. Moisture recovery is not expected today, and with such little moisture, there will be no flood threat. A few isolated storms are likely to develop over the higher terrain of the Palmer and Raton Ridges as some meager instability will be found there. However, little if any rainfall will make it to the ground. Otherwise, Coloradoans can expect a very pleasant fall Friday.

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.

Issue Date: Thursday, September 15th, 2016
Issue Time: 9:30PM MDT

— Flooding is NOT expected today

Today’s precipitable water (PW) chart, shown below for several Colorado stations, shows everything one needs to know about today’s heavy rainfall chances. PW has sharply fallen over the past 24 hours and is not expected to recover today. Thus, despite the presence of an upper-level trough to the west, the odds of heavy rainfall are slim to non-existent. Instead, we expect gusty winds and scattered showers with perhaps a thunderstorm mixed in especially over eastern areas.

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.

Issue Date: Wednesday, September 14th, 2016
Issue Time: 10:30AM MDT

— LOW flood threat for Northeast Plains, Southeast Plains, Palmer Ridge and Raton Ridge

The cut-off trough of low-pressure is centered over the northern Great Basin this morning, as can be seen in the water vapor image below. The disturbance is being supported by several jet streaks with winds approaching 100 mph aloft. Moisture is marginal overall with precipitable water (PW) values in the 0.6 to 0.8 inch range, except up to 1.0 inch along the Kansas border. Expect PWs to stay steady overall, though additional moistening is possible in the far east regions. Much like yesterday, an expansive low and mid-level cloud deck is seen this morning across the eastern third of CO. This will inhibit solar insolation and keep temperatures suppressed into the 60s for areas near the Kansas border. Low-level flow this morning is from the S/SSE and this is expected to intensify through the day. Such a flow will result in upslope flow on the southern faces of the Cheyenne and Palmer Ridges, which is where today’s heavy rainfall threat will be. Although isolated heavy rainfall will be possible, it will be mitigated by relatively fast storm motion, shallow moist layer and limited instability. Nonetheless, a Low flood threat is warranted for parts of eastern Colorado as even short-term heavy rainfall could lead to isolated flash flooding, and field flooding. Elsewhere, light to moderate rainfall amounts of up to 0.5 inches (through tomorrow morning) will be the norm.

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.