FTB 09-30-2020: Dry with Ample Sunshine to End the FTB Season

Issue Date: Wednesday, September 30th, 2020
Issue Time: 9:50AM MDT

This is the last scheduled Flood Threat Bulletin for the 2020 season. Once again, it has been a pleasure to serve you! The next Flood Threat Bulletin season begins on May 1, 2021.

— Flooding is NOT expected today

A very dry air mass has worked its way over the western US and Colorado under an impressive dual High pressure ridge (yellow/orange shades below). Under this set up, northwesterly flow aloft will continue with the core of the jet to our northeast. The jet may nose into the far Northeast Plains, so surface winds in the 15 to 20 mph range will be possible over the border counties.

A shallow cold front is currently moving through eastern Colorado, so more seasonable temperatures are expected over the lower, eastern elevations today. Surface winds in the 15 to 20 mph range are possible as the front passes through before it stalls out over the Palmer Ridge area. There is very little moisture return with this front, as shown by dew points increasing from ~25F to 35F. However, that will increase relative humidity values enough that critical fire weather conditions are not forecast. The lack of moisture return also means another day with precipitation chances close to zero. The northerly surface flow behind the front has transported smoke south over the Front Range and I-25 Corridor, so lower air quality is expected. With clear skies and ample sunshine, there is no flood threat issued.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

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

Breezy conditions are expected over the plains this morning and today as another cold front passes through. The front is rather shallow, so high temperatures will only be affected over the lower elevations to about the Palmer Ridge. Highs will be in the mid 70Fs to lower 80Fs, and temperatures over the eastern mountains will reach the mid 60Fs (north) and lower 70Fs (south). It will be too dry for any rainfall or clouds to develop with the upslope flow, so no flooding is forecast. Although skies will be clear, smoke from the fires will travel southwards and lower air quality. Ash is being reported across the I-25 corridor this morning.

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

Above average temperatures are forecast along with clear skies. High temperatures are forecast to reach 4F to 8F above normal. So, highs will reach into the 80Fs over the lower elevations with 70Fs for most of the mountain valleys. No rainfall is forecast with PW measured at 0.25 inches in the Grand Junction sounding this morning, which is a new daily record low value.

FTB 09-29-2020: Elevated Fire Conditions over the Plains with Temperatures Warming Statewide

Issue Date: Tuesday, September 29th, 2020
Issue Time: 9:10AM MDT

— Flooding is NOT expected today

Nearly clear conditions over the state this morning with a very dry air mass overhead, so extra radiational cooling occurred again last night. This caused freezing temperatures over the mountain valleys, Northwest Slope, San Luis Valley, and Southwest Slope, so it’s another cold start to the morning. Dew points across the state are below 30F, so it will be too dry for rainfall today. Additionally, it’s another day without much vertical lift. Overall, forecasting a beautiful fall day with nearly clear skies. Furthermore, temperatures will keep increasing until they are slightly above normal, and highs are already between 5 and 12F warmer than this time yesterday.


There’s also a downtick in fire weather conditions due to surface winds relaxing when compared to yesterday. This is because the majority of the jet is now to our east (purple). The clouds over the northeast corner of the state are being generated by this feature, but any rainfall is well to our northeast (orange “X”) in the left exit region of a jet streak. Surface flow is expected to turn northwesterly over the plains due to this upper disturbance (orange “X”) throughout the day. Winds will likely reach between 15 and 20 mph this afternoon over the northeast quadrant of the state. So, elevated fire conditions will be possible for a couple of hours due to relative humidity dropping into the teens.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

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

Highs will be on the upswing today with the ridge dominating the weather regime. Along the I-25 Corridor, highs will reach the upper 70Fs and low 80Fs, and 80Fs are forecast over the eastern plains. Over the mountains, high temperatures will jump back into the 60Fs and 70Fs. Increasing northwesterly flow over the lower elevations could push near surface smoke into the Urban Corridor, but at this time, it looks like only the northern Urban Corridor will be affected. Too dry for any rainfall, so the main weather concern will be the elevated fire conditions over the northeast quadrant of the state due to the proximity of the jet/trough. Gusts may reach 30 mph over the Northeast Plains for a couple hours this afternoon. Rainfall is not forecast.

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

It was a cold morning again for the valley locations, which includes the Southwest Slope today. Over the northern portion of these zones it’s already 5 to 10F warmer than yesterday, so highs will be trending upwards. Highs are expected to rebound into the 70Fs over the lower elevations and reach the 60Fs for most of the mountain towns. The very dry atmosphere means bluebird skies with a broken cloud cover possible over the Southwest Slope/San Juan Mountains this afternoon. Surface winds will remain light with the ridge overhead, which will reduce the fire danger.

FTB 09-28-2020: Sunshine will Help with Below Average Temperatures & Wind Continues

Issue Date: Monday, September 28th, 2020
Issue Time: 9:10AM MDT

— Flooding is NOT expected today

A highly amplified pattern has set up over the US bringing strong north and northwesterly flow aloft to the state. There’s a well-defined jet streak edging into Colorado, which is marked below. This feature will push eastward throughout the day as the High builds to our west. That means another day with windy conditions, and those winds are expected to expand into the eastern plains. Since there are much cooler temperatures behind the cold front that passed through yesterday, the elevated fire danger will be confined to the plains and northern Front Range near the ongoing fires where relative humidity values will become quite low.

There is some upper level cloud cover and likely a little fog/light rain over south, central Colorado to start the day. It is very dry elsewhere, and PW has dropped to 0.22 and 0.28 inches in Grand Junction and Denver, respectively. Additionally, increased subsidence will nearly nix rainfall chances. So outside of some very light showers in the area with cloud cover this morning, it should remain dry. Flooding is not forecast.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

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

Despite cooler temperatures, relative humidity will be quite low this afternoon. So, elevated fire danger is forecast for the eastern plains and northern Front Range for northerly winds in the 17 to 23 mph range (gusts up to 25-30 mph). Higher gusts will be possible along the Continental Divide this evening. Due to dryness and sinking motion behind the trough, rainfall is not forecast. If rainfall is generated in the area of cloud cover this morning, totals will remain below 0.08 inches. High temperatures are expected to be 10-15F below normal, so quite chilly but the increasing sunshine will help. Classic Colorado fall day is ahead.

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

It will be windy over these regions as well, although a bit more spotty than over eastern Colorado. Isolated gusts up to 25 mph will be possible with wind speeds in the 15 to 20 mph range over along the western border and near the Continental Divide. High temperatures will be 8 to 12F below normal (north) and 3-6F below normal (south). No rainfall is forecast due to increasing heights and very low moisture. A Freeze Watch is in place for the Central/Northern Mountains and portions of the Northwest Slope tonight. The SLV could also see freezing conditions early tomorrow morning, and frost is forecast for the lower Arkansas River valley.

 

FTB 09-27-2020: Scattered Showers Possible (East) as Another Cold Front Pushes South

Issue Date: Sunday, September 27th, 2020
Issue Time: 9:10AM MDT

— Flooding is NOT expected today

In the water vapor imagery below, the cold front that moved through last night can be seen in blue. The northerly wind shift during the evening hours made for some hazy conditions across the Urban Corridor/Front Range, but cleared out the near surface smoke over northwest Colorado and the eastern plains. Behind that front and with another incoming front, cooler high temperatures are expected today. Except over the southwest corner, where highs will be similar to yesterday.

Precipitation chances will increase slightly today as a strong shortwave (orange “X”) and associated front digs southward. This will increase north/northwesterly flow, and the tightening temperature gradient will produce a narrow band of light, scattered showers beginning by midday (north). As this band of scattered showers moves southward, expect most of the precipitation to fall over the lower elevations of eastern Colorado. Some isolated, light rain may occur over the foothills with a brief rain/snow mix possible over the northern Front Range. With PW measured at 0.65 inches in Denver this morning, relatively low dew points, and limited instability, the highest totals are forecast to be under 0.20 inches. So, flooding is not forecast.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. If there is a threat, hover over the threat areas for more details, and click on burn areas to learn more about them. For Zone-Specific forecasts, scroll below the threat map.

Zone-Specific Forecasts:

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

Much cooler high temperatures are expected today, and the Northeast Plains/Palmer Ridge/Urban Corridor will likely only reach into the mid 60Fs. 70Fs are forecast over the lower elevations south of the Palmer Ridge. Over the mountain valleys, highs will only reach into the 50F. Windy conditions are forecast over the mountains and plains as the front moves through and strengthens. Gusts up to 40 mph will be possible, but cooler temperatures and higher relative humidity values means there is no Red Flag Warning issued.

Best chance for measurable rainfall will be over the lower elevations as scattered showers move across the northern border. As this feature moves south and the front tightens, a narrower band of scattered showers is expected (Palmer Ridge). Generally, totals will be between 0.10 and 0.15 inches. A brief light rain/snow mix will be possible over the northern Front Range, and it looks like the Southeast Mountains may get some light rainfall accumulations this evening. Flooding is not forecast.

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

Windy conditions continue for these zones this afternoon, and the mountain zones could see gusts from the north up to 50 mph. The decreasing temperatures and slightly higher relative humidity values will limit the fire danger, so there is No Red Flag Warning issued. No precipitation is forecast west of the Continental Divide due to PW under 0.50 inches and a very dry surface layer. Scattered clouds will be likely today with overcast conditions forecast by tomorrow morning. Highs will be in the 50Fs and 60Fs, expect over the Grand Valley and Southwest Slope where highs will reach into the 70Fs.