FTB 05-26-2020: Scattered Storms are Forecast for Northwest Colorado with High Temperatures Increasing Statewide

Issue Date: Tuesday, May 26th, 2020
Issue Time: 9:10AM MDT

— Flooding is NOT expected today

The axis of the trough will be to our east today, which can be seen by the cloud cover over the Midwest and Great Plains in the visible satellite imagery below. This will place Colorado under north/northwest flow, which will allow the small disturbance over Utah/Idaho to reach the northwest corner of the state by early this evening. PW was measured at 0.34 inches this morning in Grand Junction, so even with moisture slightly increasing as the shortwave arrives, storms that pop over the higher terrains of the Northwest Slope, Northern Mountains and Central Mountains are expected to be high-based. This will limit the total accumulation and cause gusty outflow winds; thus, there is no flood threat issued. Across the rest of the state, subsidence will occur behind the trough as the ridge begins to build northward, so rainfall is not expected.

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:

Northwest Slope, Northern Mountains, Central Mountains, Front Range, & Southeast Mountains:

Best chance for storms today will be over the northwest corner of the state favoring the high terrains for development. Coverage will be spotty due to the mediocre moisture available and more virga/wind is forecast than rainfall. A couple weak storms could also form along the Continental Divide as the shortwave passes overheard, but not more than a few sprinkles and cloud cover are anticipated. Max 1-hour rain rates up to 0.10 inches are possible, and flooding is not forecast.

Primetime: 4:30PM to 10:30PM

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

Temperatures will be on the rise today with highs forecast in the high 70Fs over the Urban Corridor and low 80Fs for the eastern Plains. It will be mostly clear with some light cloud cover this afternoon over the Urban Corridor. There may be some heavier cloud cover along the Kansas and Nebraska border from the trough, which will help keep temperatures a little cooler than they should be.

Grand Valley, Southwest Slope, San Juan Mountains, & San Luis Valley:

High temperatures will also be increasing in these regions as the ridge begins to build. Highs for the lower elevations are expected to reach high 70Fs to low 80Fs in the valleys. For the mountain towns, 60Fs are forecast. Surface winds may pick up to around 15 mph this afternoon over southern Colorado, but they shouldn’t be widespread enough or last long enough to reach critical fire weather conditions.

FTB 05-25-2020: Drier than Yesterday with a Few Scattered Showers/Storms

Issue Date: 5/25/2020
Issue Time: 8:35 AM

— Flooding is NOT expected today

The upper-level trough that brought yesterday’s showers and storms is still meandering its way slowly across the state, with the trough axis highlighted in the image below. The trough is far enough east that the best forcing for storms will be over Kansas and Nebraska, so we will be dealing with drier conditions for Memorial Day. However, the cooler air aloft brought by the trough will result in some instability and allow for the development of a few scattered showers/thunderstorms this afternoon and evening mainly over the higher terrain of the Front Range, Southeast Mountains, Northern Mountains, and Central Mountains. A couple storms will drift over the adjacent lower elevations of the I-25 corridor. Activity will diminish during the late evening hours, coming to an end shortly after sunset.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. 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, Urban Corridor, Palmer Ridge, Northeast Plains, Southeast Plains, and Raton Ridge:

Drier than yesterday, but the cooler air aloft brought by the trough will allow for instability to increase in the sunshine, resulting in isolated-to-scattered showers/thunderstorms over the Front Range and Southeast Mountains. This activity will drift with time over adjacent lower elevations, however lacking low-level moisture will not allow them to sustain themselves for long. Any rainfall that occurs will be on the lighter side, especially east of the foothills where low-level moisture has been scoured out the most. Rain rates will generally be less than 0.2 inches/hour everywhere.

Timing: 11 AM – 10 PM

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

A few isolated showers/storms are expected over the higher terrain, mainly along the Continental Divide, during the afternoon and evening. Any rainfall will be light, with rain rates less than 0.2 inches/hour. Otherwise, much of the area will be mostly sunny and drier, with high temperatures a few degrees warmer than yesterday.

Timing: 11 AM – 9 PM

FTB 05-24-2020: A Day of Active Weather Statewide As Welcome Precipitation Arrives

Issue Date: Sunday, May 24th, 2020
Issue Time: 9:45AM MDT

— A LOW flood threat has been issued for parts of the Northeast Plains and Palmer Ridge

A cold front moved south across Colorado late on Saturday, leaving a shield of low and mid-level clouds across central and eastern parts of the state this morning. Light rain and higher-elevation snow showers were seen on radar and in surface observations mainly north of I-70 this morning. Just to our west, a large trough was noted on water vapor imagery (see below). This will support widespread shower and thunderstorm activity for most everyone except the southwest part of Colorado this afternoon and evening. Although the atmosphere’s dynamics are supportive of precipitation today, the combination of limited heating and marginal moisture will fortunately put a cap on rainfall rates for most areas. High temperatures will be anywhere from 5-15F below normal. Precipitable water (PW) values across the state this morning ranged from 0.50-0.70 in. east of the Continental Divide to well below 0.50 inches over western areas.

Over the higher terrain, rain and snow showers will pick up in intensity this afternoon, but will stay well below flood threat levels. Farther east, showers will turn into thunderstorms as more instability is encountered. The “sweet spot” today looks to be just southeast of Denver metro and over the Palmer Ridge. Latest trends in high-resolution model output are slowing the initiation of storm activity by several hours. This will allow instability to get higher than previously expected, with CAPE in the 600-1,000 J/kg range possible. Furthermore, low-level winds are expected to attain a more easterly component in response to the incoming trough, with a deep layer of upslope flow possible for a 2-3 hour period this afternoon. Despite relatively low PW, dynamics will make up for this and support isolated heavy rainfall during the afternoon hours. A Low flood threat has been posted for parts of the region. Several rounds of heavy rainfall are possible before storms organize into a rapidly moving cluster, limiting rainfall rates later into the evening.

In the Southeast Plains, there will be more sunshine and slightly higher moisture today, with CAPE values up to 1,200 J/kg and PW in the 0.70-0.80 range for this afternoon. Scattered storms are expected this afternoon that will have the potential to produce large hail, up to 1.5 inches in diameter, and gusty downdraft winds up to 55 mph. Brief heavy rainfall is possible with these storms, but flooding is not expected. Later into the evening hours, light to moderate rainfall is expected as the trough progresses eastward over the area.

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:

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

Mostly cloudy this morning with showers increasing in coverage and intensity and gradually turning into thunderstorms this afternoon. Max 1-hour rainfall up to 1.1 inches possible over a localized area southeast of Denver metro. Max 3-hour rainfall up to 1.7 inches possible. A Low flood threat has been posted for parts of the region for a brief period of time this afternoon. Hail up to 1 inch and gusty winds are possible with the strongest storms. Primetime for the flood threat is 2-5 PM.
Rainfall will persist into the evening hours, but will be below flood threat thresholds.

Southeast Plains:

Partly cloudy this morning, then scattered showers and thunderstorms likely this afternoon. The strongest storms could produce hail up to 1.75 inches and gusty winds. Max 1-hour rainfall up to 0.9 inches for western areas and 1.4 inches for eastern areas. However, flooding is not expected due to relatively fast storm motion. Storms will transition into showers during the evening and early overnight hours.

Northern Mountains, Northwest Slope, San Juan Mountains, Central Mountains:

Rain and snow showers picking up in intensity and coverage during the afternoon hours. Max 1-hour rainfall up to 0.5 inches possible. Snow level will range from 8,500 – 10,000 feet. Flooding is not expected today, but travelers should be cautious of slick roads in the higher elevations. Overall, up to 2 inches of welcome precipitation is possible today.

Grand Valley, Southwest Slope, San Luis Valley:

Mostly sunny then partly cloud with isolated to scattered showers this afternoon. Gusty winds are again possible today, leading to a Red Flag Warning for the San Luis Valley. Fortunately, cool temperatures will mitigate the fire threat. Flooding is not expected today.

FTB 05-23-2020: Critical Fire Weather Expands & Isolated Storms are Forecast for the Northeast Plains

Issue Date: Saturday, May 23rd, 2020
Issue Time: 9:05AM MDT

Flooding is NOT expected today

The base of the trough is just to our west this morning and will slowly migrate eastward. This will increase southwest flow and place the jet stream directly over the state. Higher wind speeds are forecast to mix down to the surface by noon causing winds to increase into the 15 to 25 mph range with gusts between 35 to 45 mph. Very dry air is still indicated over New Mexico and Arizona by the lack of cloud cover in the visible satellite image below, so this will cause Red Flag Warning conditions for the majority of the state (mostly lower elevations) as relative humidity values are expected to drop into the teens and single digits.

Over the far northwest corner of the state, southeast surface winds will keep higher moisture in place as a surface low develops near the Palmer Ridge. This will be the best shot for measurable precipitation this afternoon; first along the dry line and then along the cold front later this evening. Brief, strong winds and large hail will be the main threats for the severe thunderstorms that form along the dry line. Over the mountains, except some scattered storm development over the Central and Northern Mountains as a second surge of cold air moves in associated with the upper level Low. More virga and gusty winds are expected than measurable rainfall for this region. Rainfall will not meet flood threat criteria today, so 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:

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

Cooler temperatures are forecast for the Northwest Slope today due to the cold front that moved through yesterday evening. With a second surge of cold air forecast tonight, there is a Freeze Watch in place for the Yampa River Basin. Today, scattered storm activity is forecast for the Central/Northern Mountains and Front Range with the best chance of accumulation along and west of the Divide. Max 1-hour rain rates up to 0.20 inches will be possible with lots of virga and gusty outflow winds.

Back east, max 1-hour rain rates along the dry line could reach 1.25 inches with dew points in the 50Fs. Large hail and strong outflow winds will be the main threats, but coverage will be too small in area to create any flood threat. Along and just behind the cold front that moves through overnight, max 1-hour rain rates up to 0.75 inches will be possible.

Primetime: 2PM to 1AM

Grand Valley, Southwest Slope, San Juan Mountains, Southeast Mountains, Raton Ridge, San Luis Valley, & Southeast Plains:

A Red Flag Warning has been issued from noon today until sundown tonight for the lower elevations, so be sure to tune into your local NWS office for the latest. Southwest winds will pick up into the 15 to 25 mph range with gusts up to 40 mph possible. Be sure to use caution with any open flames and avoid burning. Rainfall chances increase tomorrow east of the Continental Divide behind the cold front with wet snow forecast for the high elevations as the snow line drops overnight. Cooler temperatures and light surface winds should also decrease the critical fire conditions west of the Divide.