Issue Date: Thursday, August 2nd, 2018
Issue Time: 09:00AM MDT

— A LOW flood threat has been issued for the Lake Christine burn scar

Similar to yesterday, another shortwave trough will make its way through the state from the northwest to the southeast around the top of the ridge. This feature is marked in the visible satellite imagery below (orange) and can also be spotted by the cloud deck over NE Utah/SE Wyoming. The ridge axis itself won’t move much today except for slight movement east. This means the increase in subtropical moisture won’t begin until tomorrow, and weak thunderstorms that are able to fire today will again produce more gusty winds than heavy rainfall.

The 12Z sounding shows a large spread between the temperature and dew point already over Grand Junction, but PW has increased to 0.82 inches. While this is about average, it has increased quite a bit over the last couple of day. This translates to a bit more measureable rainfall coverage this afternoon over the western, high terrains. At Denver, there only seems to be some shallow moisture, which is expect to mix out west to east throughout the day. The area of 50F dew points is to the east of the green line in the visible satellite imagery. Thus, not expecting many storms to survive in the adjacent eastern plains that move off the mountains this evening. However, there is still a slight chance for weak, high-based thunderstorms over El Paso, Elbert and Lincoln Counties thanks to increased convergence along the Palmer Ridge.

Minimal CAPE (convective available potential energy) this afternoon should produce weak thunderstorms/showers and low rainfall rates, but the passing of the shortwave will produce more coverage of storms over the higher terrains. Without a lot of atmospheric dynamics at play, storms will be more pulse-like this afternoon with a general movement to the southeast. Max 1-hour rain rates will again be under flood threat criteria, but there is a chance of a storm popping up over the Lake Christine fire. This fresh burn scar has proven to be susceptible to flash flooding and with rain rates in the area being just above 0.25 inches/hour, a Low flood threat has been issued. Elsewhere, flooding is not expected on Thursday.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

 

Zone-Specific Forecasts:

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

High clouds and haze continue today, which will help limit instability for afternoon showers and thunderstorms. With the passing shortwave, coverage should ramp up a bit over the mountains this afternoon, but rainfall should be mostly confined to the mountains. The exception is that a storm or two may survive along the Palmer Ridge. Max 1-hour rain rates up to 0.5 inches possible, but most storms will be in the 0.1-0.3 inch/hour range. The extra upper-level lift from the shortwave will help showers linger over the higher terrains into the night. Flooding is not expected.

Primetime: 2PM – 1AM

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

Haze and smoke will continue to limit visibility this afternoon. With the addition of some early high clouds, not much instability will be able to build for strong thunderstorms this afternoon. Expecting weak thunderstorms and showers over all the western mountain regions through early tomorrow morning. Max 1-hour rain rates up to 0.5 inches/hour are possible with 24-hour totals up to 0.7 inches further south over the San Juan Mountains. A Low flood threat has been issued for the Lake Christine Fire as it has shown to have flooding issues with rain rates in the 0.25 inch/hour range. Elsewhere, flooding is not expected.

Primetime: 2PM – 3AM

Issue Date: Wednesday, August 1st, 2018
Issue Time: 08:55AM MDT

— Flooding is NOT expected today

The upper-level high begins to shift a bit to the east and south today, which will shift the axis of the ridge eastward as well. This will allow some upper-level disturbances (marked in orange below) to move through the state and help increase the coverage of showers and thunderstorms this afternoon by increasing lift. Currently, the shortwave over Utah is helping produce some cloud cover over the northwest corner of the state. At this time there no observations of rainfall making it to the surface, so just a cool start to the day with temperatures in the 50Fs to low 60sF.

Precipitable Water (PW) at Grand Junction this morning was measured at 0.56 inches, so there has been a slight increase since yesterday though it is still well below normal for this time of year. With the early passing of the shortwave over the northwest corner, rather than at peak heating, showers and thunderstorms over the Central and Northern Mountains will likely be confined to the Divide this afternoon. Further south over the San Juan Mountains, showers and thunderstorms should have a bit better coverage this afternoon. However, the large dew point/temperature spread will produce more gusty winds than plentiful rainfall.

East of the Divide, the shortwave should be arriving just as thunderstorms are starting to pop over the higher terrains with the diurnal flow. This should help increase coverage of storms along the Front Range, Palmer Ridge and Southeast Mountains. The sounding this morning measured PW at 0.64 inches, which again is an increase from yesterday, but still not quite high enough to produce local, heavy rainfall. Storm motion will be to the SSE at around 15-20 mph, so this too, will limit heavy rainfall chances. To the east of the I-25 corridor over the Palmer Ridge and Southeast Plains, SE flow at the surface will pull in some higher dew points from the plains, so expecting rain rate intensities to increase a bit for storms that track into this area. However, rain rates are still expected to be below flood threat criteria, so flooding is not expect today. The main threats from the storms today will be dangerous lightning and gusty outflow winds. Hail is also possible under the stronger storms over the eastern plains.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

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

Mostly clear skies this morning will help increase instability as the sun begins to shine. By mid-afternoon the shortwave will arrive at peak heating, which is expected to increase coverage of thunderstorms over the higher terrains. As storms move off the mountains into the adjacent plains, lack of low-level moisture will have storms producing more gusty winds than heavy rainfall. As the storms track east of the I-25 corridor into the Palmer Ridge and Southeast Plains, rain rates are expected to increase some due to higher low-level moisture. The rain rates should remain below flood threat criteria, so flooding is not expected. Max 1-hour rain rates are as follows:

Front Range, Southeast Mountains, Urban Corridor, Northeast Plains: 0.25-0.6 inches/hour
Palmer Ridge, Raton Ridge, Southeast Plains: 0.75 – 1.0 inch/hour

Primetime: 1:30PM to 11PM

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

Cloudy start to the day for the northwest corner of the state. The early arrival of the shortwave, should keep measurable rainfall confined to the Divide this afternoon over the Northern and Central Mountains. Max 1-hour rain rates are expected to be under 0.15 inches with plentiful virga and light showers. Further south, thunderstorms should be confined to the southern ridgelines of the San Juan Mountains. Max 1-hour rain rates up to 0.3 inches/hour are possible. Once again, the HRRR shows a lot of near surface smoke over these regions, so expect limited visibility. Flooding is not expected today.

Primetime: 2PM to 6PM

Issue Date: Tuesday, July 31st, 2018
Issue Time: 08:00AM MDT

— Flooding is NOT expected today

Other than a few clouds over the Southeast and San Juan Mountains, the visible satellite imagery below shows clear skies this morning. The drying trend will continue today as northerly upper-level flow pulls in a very arid air mass from the north. Precipitable Water (PW) values at Grand Junction and Denver this morning have dropped to 0.5 inches and 0.46 inches, respectively. Normal for this time of year is closer to 0.8 inches. Thus, the dry atmosphere and rising pressure should eliminate the rainfall threat this afternoon over the higher terrains. Some residual moisture may be able to hold on over southern Colorado near the NM border, so the Southeast and San Juan Mountains may receive some light, high-based afternoon showers. Rain totals are expected to be under 0.15 inches. Flooding is not expected today.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

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

Mostly clear this morning with the exception of a few high clouds over the Southeast Mountains. Some isolated showers may be possible over the Southeast Mountains this afternoon, but max 1-hour rain rates will remain below 0.15 inches. Elsewhere, expect some cloud cover over the higher terrains this afternoon with more seasonal to a bit below average high temperatures. Flooding is not expected today.

Primetime: 2PM to 6PM

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

Abundant sunshine today with some scattered cloud cover over the higher terrains this afternoon. A few high based showers may be possible over the southern San Juan Mountains. Max 1-hr rain rates should remain under 0.15 inches. High temperatures in the lower valleys will be in the 90sF with higher elevations in the 70-80F range. The HRRR shows some near surface smoke over these regions through this evening, so expect limited visibility. Flooding is not expected today.

Primetime: 1PM to 6PM

Issue Date: Monday, July 30th, 2018
Issue Time: 08:25AM MDT

— Flooding is NOT expected today

Calm and cool start to the Monday morning after an active day of severe weather across the Northeast Plains on Sunday. Currently, there is a little bit of fog over the Southeast Mountains, but that will begin to breakup this morning as the sun begins to heat the surface. There are also a couple light showers over the far Southeast Plains, which will continue to work their way east by late morning. The mid-level high pressure will continue to sit southwest of Colorado over the Great Basin today, which will provide northerly flow aloft over Colorado. This will pull in dry air (marked in the water vapor imagery below) over the state and bring a break to the heavy rainfall threat this afternoon and evening.

There will be some residual moisture left over the Southern Front Range and Southeast Mountains, so expecting some showers and thunderstorms to pop over the higher terrains this afternoon. Coverage will decrease quite a bit when compared to the last few days and the majority of the rain should remain over the mountains. There is a slight chance for some showers and thunderstorms over the adjacent plains this afternoon, but storms are not expected to become severe or bring a heavy rainfall threat. Over western Colorado, the dry, northerly flow will almost completely nix the chances for rainfall today. The San Juan Mountains might get a few drops of rain, but measurable precipitation is not expected.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

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

Dry air will move into the state today from Wyoming. Some residual moisture will remain over the southern Front Range and Southeast Mountains, so some isolated rainfall is expected this afternoon over those regions. However, the dry mid-layer will limit rainfall rates. Max 1-hour rain rates up to 0.5 inches are possible though most storms will produce abundant virga and rain rates under 0.25 inches/hour. A couple storms could wander into the adjacent plains, but are not expected to become severe. Flooding is not expected today.

Primetime: 3PM to 8PM

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

The northerly flow aloft will also pull in dry air over western Colorado, which will suppress any chances for measureable rainfall this afternoon. Outside of a few scattered clouds over the Southwest Slope and San Juan Mountains it should be a clear day with temperatures near normal for this time of year. There may be a few drops of rain with the clouds over the San Juans, but the more likely scenario is that they bring some shade and relief to the afternoon heat. Flooding is not expected today.