Issue Date: Thursday, August 3, 2017
Issue Time: 10:00AM MDT

— LOW/MODERATE flood threat for portions of the Front Range, Urban Corridor, Palmer Ridge, Central Mountains, Southeast Mountains, Southeast Plains, Raton Ridge

— LOW flood threat for the Southwest Slope, San Juan Mountains

A strong summer cold front passed through the northern portion of the state last night bringing some isolated thunderstorms and much cooler temperatures for today. There are ongoing scattered showers over the eastern plains and central mountains this morning that can be seen in the water vapor imagery below. The showers are located near the cold front and upper-level disturbance, and will continue to move to the SE and exit the state by early afternoon. The cold front helped usher in some low and mid-level moisture east of the Continental Divide. The Precipitable Water (PW) over 1 inch for this afternoon is marked in the map below.

Some of today’s storms will begin to form over the higher terrain midday, while the storms over the Central Mountains will move to the SE and exit the state by early afternoon. Coverage will be more numerous than the previous couple of days favoring the southern Front Range, Southeast Mountains and San Juan Mountains for the heavier precipitation. Storm motion will continue a bit faster to the SE, but the two rounds of precipitation over the SW mountains warrants a Low flood threat. As storms begin to move off the higher terrain, they will favor the higher terrain along the Palmer Divide and Raton Ridge where there will be little convective inhibition and higher instability. There will also be some shear today with the NW upper-level flow that could support a couple severe thunderstorms with 1 inch hail and gusty winds. Flood threats include mud flows, debris slides and small stream and road flooding especially near burn scars. The ongoing showers and associated cloud cover will limit coverage of heavy rainfall over the far eastern plains today. Mainly dry weather is expected over the northwest portion of Colorado.

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, Palmer Ridge, Northeast Plains, Southeast Mountains, Raton Ridge, Southeast Plains:

Partly cloudy early then turning more sunny through the day. Expecting scattered showers and thunderstorms to develop over the terrain around midday and last into the early evening hours. Highest coverage will be along the Front Range, Palmer Ridge, Southeast Mountains and Raton Ridge. Storms on the adjacent plains will favor the Palmer Ridge. Max 1-hour rainfall up to 1.8 inches (east) and 1.4 inches (west). A Moderate/Low flood threat has been issued for today.

Primetime: 1PM to 10PM

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

Ongoing showers continue over the Central Mountains as they move to the SE. Mostly sunny and pleasant today with the cooler temperatures over the NW portion of the state. Scattered thunderstorms expected throughout the afternoon over the San Juan Mountains with 24-hour totals up to 2 inches. Max 1-hour rainfall up to 0.5 inches (north) and 0.7 inches (south). A Low flood threat has been issued for the 24-hour totals.

Primetime: 10AM to 10PM

Issue Date: Wednesday, August 2nd, 2017
Issue Time: 10:30AM MDT

— Flooding is NOT expected today

After a brief pause in the action on Tuesday, more active weather is expected over the next 24-36 hours. However, for today, this is not expected to result in a flood threat. As shown in the visible satellite image, below, a weak surface low pressure is located in the northern Great Plains this morning. Associated with this feature is a modest strength mid-level disturbance, currently supporting mid-level clouds over central and western Nebraska. As this disturbance moves quickly to the south and east, it will graze mainly the northeast quadrant of Colorado. An increase in rainfall coverage and intensity is expected this afternoon and evening to the north and east of the Palmer Ridge. However, rain rates are expected to stay below flood threat thresholds.

Looking farther northwest, a 1032mb surface high pressure, very strong for this time of year, is developing to the lee of the southern Canadian Rockies. An accompanying strong surface cold front is expected to enter northeast Colorado later this evening. The main sensible impacts will be a secondary shot of shower and thunderstorm activity, and an increase in low-level moisture. However, with limited instability, relatively fast SSE steering winds and only a shallow easterly component of storm inflow, max rain rates with this activity are also expected to stay below flood threat levels.

Much cooler temperatures are expected tomorrow for northeast Colorado, with an increase in heavy rainfall across southeast Colorado where instability will be present. Mainly dry weather is expected to the west of the Continental Divide.

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, Palmer Ridge, Northeast Plains, Southeast Mountains, Raton Ridge, Southeast Plains:

Sunny early then turning partly cloudy with isolated to scattered showers and thunderstorms developing in the early afternoon, lasting into the early evening. Highest coverage will be along the Front Range and also towards the KS/NE borders. Max 1-hour rainfall up to 1.2 inches (east) and 0.7 inches (west). A secondary increase in precipitation is expected during the late evening as a cold front moves into Colorado. Max 1-hour rainfall up to 1.0 inches (east) and 0.7 inches (west) will be possible with this activity. Flooding is not expected today.

Primetime: 12PM to 2AM

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

Mostly sunny and pleasant today with isolated showers and weak thunderstorms over the higher terrain. However, scattered thunderstorms will be possible over the San Juans. Max 1-hour rainfall up to 0.3 inches (north) and 0.6 inches (south). Flooding is not expected today.

Primetime: 12PM to 8PM

 

Issue Date: Tuesday, August 1, 2017
Issue Time: 9:50AM MDT

— Flooding is NOT expected today

After a very long stretch of heavy rainfall somewhere across Colorado, we are in store for a break today. On a side note, we have issued a flood threat for the past 21 days in a row, which is the longest such stretch that we can remember!

The water vapor image, below, shows that an upper-level ridge, currently centered just west of Colorado, will intensify today. The implication for our weather will be subsidence and some modest drying. Precipitable water this morning range from 0.5 – 0.9 inches and will continue to drop a bit further. This will partially be offset by very wet soils that will evaporate into the boundary layer and keep moisture higher than it would otherwise be. Marginal instability will develop this afternoon in far eastern Colorado, and an isolated thunderstorm is possible. One or two of the storms could briefly turn severe (large hail is the main threat). However, flooding is not expected today.

With the recent string of rainfall in southeast Colorado, the Arkansas River and its tributaries remain elevated. The Purgatoire River is particularly high after a pronounced river crest formed late Sunday. This morning’s analysis suggests the river peaked earlier today in the “Action” level, and it is expected to stay below Minor flood stage.

Looking out further, a strong surface high pressure system is set to move into Colorado starting Wednesday afternoon. It will usher in a fall-like cool front that will briefly interrupt summer. High temperatures on Thursday could end up being as much as 20F below normal for parts of eastern Colorado.

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, Palmer Ridge, Northeast Plains, Southeast Mountains, Raton Ridge, Southeast Plains:

Sunny early then a partly cloudy with an isolated thunderstorm possible in the higher terrain as well as far eastern areas. Max 1-hour rainfall 0.4 inches (west) and 0.7 inches (east). For eastern areas, the strongest cells could briefly turn severe, with hail up to 1.25 inches possible. Flooding is not expected today.

Primetime: 1PM to 8PM

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

Mostly sunny and pleasant today with isolated to scattered showers and perhaps a weak thunderstorm possible especially across southern areas. Max 1-hour rainfall up to 0.4 inches. Flooding is not expected today.

Primetime: 12PM to 8PM

 

Issue Date: Monday, July 31th, 2017
Issue Time: 09:40AM MDT

— LOW flood threat for portions of Central Mountains, Front Range, Urban Corridor, Southeast Mountains, Raton Ridge

An elongated High pressure system is oriented from northern California to northern Texas today that will turn the mid-levels to a more northerly flow. This northerly flow will help pull in the drier air located over WY and NE that will lower Precipitable Water (PW) values across the northern portion of the state. PW over 1 inch is still forecasted for the areas east and south of the dotted green line. The soundings over Colorado this morning are both about 0.85 inches and have drying in the mid-levels. The high dew points over the eastern plains are expected to decrease some throughout the day, and gusty winds are expected with storms that form. There is a Low threat for flooding today, and the threat will be much more isolated than the prior couple days.

As storms begin to initiate over the higher terrain with the diurnal heating pattern just after noon, they are expected to favor the Central, San Juan and Southeast Mountains. PW over the SW corner of the state should be high enough to see 3-hour totals up to 1.5 inches over the San Juan Mountains. Over the eastern mountains, 1-hour rain rates up to 1 inch are possible. Over the immediate adjacent plains along the Palmer Ridge, 1-hour rain rates up to 1.1 inches and 3-hour totals up to 2 inches are possible. Heavy rainfall over the last couple days along the southern Front Range and Southeast Mountains has saturated soils. With 3-hour totals up to 1.25 inches, a Low threat has been posted and burn scars should be monitored closely. Threats include gusty winds, small stream flooding and debris slides. Storm motion will be more southerly today, so there will not be widespread rain over the eastern plains like the previous two days. Showers should come to an end soon after sunset this evening.

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, Palmer Ridge, Northeast Plains, Central Mountains, Southeast Mountains, Raton Ridge, Southeast Plains:

Sunny today with isolated showers over the mountains this afternoon. 1-hour rain rates up to 1 inch are possible with 1.1 inches over the Palmer Ridge area just adjacent to the mountains. 3-hour rates up to 1.25 inches over saturated soils warrant a Low flood threat. Threats include gusty winds, debris slides, small stream flooding. The threat should diminish by midnight.

Primetime: 1PM to 10PM

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

Sunny today with storms confined to the Southwest Slope and San Juan Mountains. 3-hour rainfall amounts up to 1.5 inches are possible.

Primetime: 1PM to 10PM