Issue Date: 9/18/2015
Issue Time: 9:00 AM

NO FLOOD THREAT IS FORECAST.

The upper-level trough that kept scattered showers in the forecast for a few days will finally move east of the state today, ushering in a drier and more stable air mass across the state. Currently, the trough is crossing the Central/Northern Rockies and is responsible for the morning showers over the northeast Colorado. Those showers will diminish/exit the state in the next hour or two, bringing an end to precipitation chances across the Northeast Plains for this forecast period.

The only regions that hold any chance for isolated showers today will be across the peaks of the Central Mountains, Front Range, San Juan Mountains, and Southeast Mountains due to orographic effects working on residual moisture. Any showers will be very weak, producing less than 0.05 inches/hour rainfall rates. For the lower elevations, subsidence and cooler temperatures will be enough to suppress any activity. A dry day with breezy conditions is expected.

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

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

Mostly sunny and cooler today. Isolated, weak showers are possible this afternoon/evening across the Front Range, Central Mountains, Southeast Mountains, and San Juan Mountains regions. Sprinkles will be the main result, with rain rates less than 0.05 inches/hour. Otherwise, breezy conditions will be the most noticeable weather element.

Timing: 1 PM – 8 PM

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

Partly sunny north of I-70, mostly sunny south of I-70. Temperatures will return to seasonal temperatures today, representing a cool down from the past few days. As soon as the showers on the Northeast Plains end this morning, the rest of the day will be marked by dry, but breezy, conditions.

Issue Date: 9/17/2015
Issue Time: 9:03 AM

NO FLOOD THREAT IS FORECAST.

Colorado remains under the influence of west/southwest flow aloft, allowing moderate moisture to continue streaming across western Colorado. IPW is a bit above average of Grand Junction, but not enough to generate any heavy rain concerns. East of the mountains, IPW is around average; again, no concern for heavy rain indicated in the precipitable water values.

Isolated-to-scattered showers/thunderstorms are expected along the CO/WY border, with chances diminishing as you move southward. High Country regions of the Northwest Slope, Northern Mountains, Central Mountains, Grand Valley, northern extents of the Front Range will all see isolated-to-scattered activity today, while the Southeast Mountains, San Juan Mountains, Southwest Slope, and San Luis Valley remain mostly sunny and dry. East of the mountains, the northern portions of the Urban Corridor, and much of the Northeast Plains will hold the chance for isolated showers/thunderstorms during the afternoon/evening, but areas to the south will remain under mostly sunny skies. Fire danger will be high south of a line from Pueblo to Springfield, so please be extra cautious with, or avoid altogether, burning in those 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, jump below the map.

Zone-Specific Forecasts

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

Sunny and warm for most, with a few more clouds than the last couple of days due to upslope flow behind the weak cool front that passed through this morning. As stated above, the Northeast Plains and northern portions of the Urban Corridor will hold a chance for isolated showers/thunderstorms this afternoon and evening, with the best chances along the CO/WY border. Flash flooding is not a threat as maximum rain rates will be 0.7-1.0 inches/hour.

Timing: 2 PM – Midnight along the Urban Corridor, 4 PM – 5 AM for the Northeast Plains

Front Range, Northern Mountains, Northwest Slope, Central Mountains, and Grand Valley:

Isolated-to-scattered showers/weak thunderstorms expected, with less coverage than previous days. Activity is currently underway across the Grand Valley and Northwest Slope Regions, and will be moving into the Central Mountains and Northern Mountains in short order.

Heavy rain is not expected, and maximum rain rates will be 0.25 inches/hour or less.

Timing: Current – 5 AM

San Juan Mountains, Southwest Slope, Southeast Mountains, and San Luis Valley:

Mostly sunny and dry will be the main story today. The Southwest Slope will see more clouds than the other regions, but anything more than a sprinkle is not expected.

Issue Date: 9/16/2015
Issue Time: 9:05 AM

NO FLOOD THREAT IS FORECAST.

With the upper-level trough still slowly making its way onshore, west/southwesterly flow continues across the state. This will allow moisture to continue filtering into western Colorado, while dry, desert air streams into eastern Colorado. This difference in moisture will lead to a “tale of two forecasts,” if you will. The High Country, mainly along and west of the Continental Divide, will see another day of isolated-to-scattered showers with embedded weak thunderstorms. Meanwhile, eastern Colorado will experience mostly sunny and dry conditions once again, with Red Flag Warnings in place. Be sure and check with your local NWS office for more information on those dangerous fire conditions.

No flash flooding is expected, as heavy rain is not expected from any shower or thunderstorm activity. Precipitable water readings at Grand Junction show decent moisture available, but the ingredients to make best use of that water are just not in place. The best rainfall will fall across the Northwest Slope, Northern Mountains, Grand Valley, and western extents of the Central Mountains regions where the best instability will reside. For a look at timing and maximum rain rates, see the zone-specific 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

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

Isolated-to-scattered showers and embedded weak thunderstorms expected this afternoon and evening, with a few continuing overnight. The best coverage will be for areas along and west of the Continental Divide and north of I-70. Further south, less moisture will be available, so activity will be less and mainly confined to the higher terrain of the San Juan Mountain, Southwest Slope, and Grand Valley regions.

Maximum 1 hour rain rates will be low with 0.3-0.6 inches/hour being the best the atmosphere can dish out across the Northwest Slope, Northern Mountains, western portions of the Central Mountains, and Grand Valley regions. Otherwise, rain rates will remain less than 0.25 inches/hour. The Red Flag Warnings also include small portions of the Front Range, Central Mountains, and Southeast Mountains regions.

Timing: 11 AM – 11 AM. That is not a type. A few isolated-to-widely scattered showers will continue into tomorrow morning. Much like this morning.

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

Mostly sunny and climatologically hot, with Red Flag Warnings issued for portions of the Urban Corridor, Southeast Plains, Raton Ridge, and Palmer Ridge regions. Please, use extreme caution if you have to use outdoor flames today. No rainfall is expected.

Issue Date: 9/15/2015
Issue Time: 9:05 AM

NO FLOOD THREAT IS FORECAST.

A little bit of everything is expected today:

– Scattered showers continue over the High Country
– Fire danger increases for portions of the Palmer Divide, Urban Corridor, Central Mountains, Front Range, Southeast Plains, Raton Ridge, and Northeast Plains regions
– A couple of strong-to-severe storms are possible near the CO/KS border

The scattered showers/weak thunderstorms over the High Country today/tonight will be garden-variety, thanks to unfavorable timing of the shortwave moving across the state, lessening moisture, and cloud cover limiting instability. The downward trend is already evident for Grand Junction (green line) in the IPW graph above. The best rainfall will occur over the Northwest Slope, Grand Valley, and western extents of the Northern Mountains regions; even so, maximum rain rates will be 0.4-0.7 inches/hour, which is below flash flooding thresholds. Most of the activity will be confined to the along and west of the Continental Divide and north of I-70 where moisture will hang on the longest.

The fire danger cannot be oversold today as dry fuels, gusty winds, and low relative humidities will combine to create significant fire conditions for the regions listed above. Red Flag Warnings have been issued by the National Weather Service, so be sure and check with your local NWS office for more details. Please, avoid any outdoor burning in locations under the Red Flag Warning, and be especially careful disposing of cigarettes.

Finally, there will be a couple of isolated strong-to-severe storms develop along the CO/KS border, thanks to a developing dry line and passing shortwave disturbance. The near-surface environment will be dry, so the main threats will be strong outflow winds, dry lightning, and perhaps a bit of hail. Very little rainfall will occur.

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

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

Scattered showers/weak thunderstorms expected today through tonight as the upper-level longwave trough continues to advance across the western US. The best rainfall will occur across the Northwest Slope, Grand Valley, and western portions of the Northern Mountains where moisture will be best. No flash flooding is expected. Fire danger is high across portions of the Front Range and Central Mountains.

Rain rates will generally be light at less than 0.25 inches/hour. Any potential for rain rates greater than that will exist across the aforementioned regions, at 0.4-0.7 inches/hour.

Timing: 11 AM – 6 AM

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

Red Flag Warnings are in place, and a couple of isolated strong-to-severe storms are possible near the CO/KS border. These thunderstorms will be capable of producing damaging outflow winds, dry cloud-to-ground lightning, and hail.

Across the Urban Corridor, an isolated shower/weak thunderstorm moving overhead cannot be ruled out, but will result in only gusty outflow winds and some lightning; no rainfall is expected.

Timing: 2 PM – 9 PM