Issue Date: 9/10/2015
Issue Time: 9:20 AM

NO FLOOD THREAT IS FORECAST.

A stark contrast of two forecasts will exist across Colorado today, split down the middle along the Front Range and Southeast Mountains. Locations west of the line will see temperatures a few degrees warmer than yesterday underneath mostly sunny skies. One exception to the dry rule will be the eastern San Juan Mountains, where an isolated shower/weak thunderstorm will attempt to overcome the otherwise unfavorable environment.

Along and east of the Front Range and Southeast Mountains, a cool front lurks and will pass through the state through this evening, entering NM by midnight. As the front pushes through, a few isolated thunderstorms will be possible across the Northeast Plains, Palmer Ridge, and Southeast Plains. Behind the front, upslope flow will develop, bringing in low clouds, showers, and a couple of weak thunderstorms, with best chances across the Urban Corridor, Palmer Ridge, and western portions of the Southeast Plains/Northeast Plains/Raton Ridge. Generally light rain will result from activity today/tonight as moisture will have to rebound from morning values in the 25th percentile at Boulder and Grand Junction (see IPW graph above). For more information on timing and rain rates, please see the zone-specific discussions below. Otherwise, the primary effect of the cool front will be high temperatures a few degrees cooler than yesterday.

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

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

Mostly sunny early, with clouds increasing during the late afternoon/evening and through the overnight hours as the front moves through and upslope flow develops behind it. Isolated-to-scattered showers and weak thunderstorms are expected, beginning during the mid-afternoon and continuing through the overnight hours. No flood threat is forecast, as rain rates will be generally light, moderate at best. Max rain rates are as follows:

Front Range, Urban Corridor, Palmer Ridge, and Northeast Plains: 0.4-0.8 inches/hour
Southeast Plains and Raton Ridge: 0.5-1.0 inches/hour
Southeast Mountains: 0.5-0.9 inches/hour

Timing will vary, so check out the breakdown:

Front Range: 8 PM – 4 AM
Urban Corridor: 8 PM – 6 AM
Northeast Plains: 3 PM – 8 AM
Palmer Ridge: 6 PM – 6 AM
Raton Ridge: 2 PM – 8 PM, redeveloping from Midnight – 5 AM
Southeast Plains: 4 PM – 8 AM
Southeast Mountains: 10 PM – 5 AM

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

Mostly sunny skies and warm temperatures will be the main story today, with highs climbing a few degrees above normal. Moisture associated with the cool front to the east will not be deep enough to bring an impact to these regions, and thus, dry and pleasant weather is expected. An isolated shower/weak thunderstorm will be possible, albeit a low chance, across the eastern San Juan Mountains today. Rain rates with any potential activity will be less than 0.25 inches/hour.

Timing: 1 PM – 7 PM

Issue Date: 9/9/2015
Issue Time: 10:15 AM

NO FLOOD THREAT IS FORECAST.

If you like sunny skies and warm temperatures today is the day for you. Stuck under northwest flow aloft, the air mass over Colorado has dried significantly, with the deep moisture plume suppressed to the south. One quick glance at the water vapor image below shows this drying clearly, with Colorado “between” the upper-low over central Canada and a building upper-level high over western Mexico. The dry air and mostly sunny skies will allow for temperatures to climb nicely through the afternoon, finishing off at, or just above, average for the date.

The only exception to the dry rule today will be over the preferred terrain of the San Juan Mountains, Southeast Mountains, and Raton Ridge. A bit of stubborn residual moisture will combine with daytime heating and orographic effects to force a couple isolated showers/weak thunderstorms. No significant activity is expected, and rain rates will be very low. Additionally, one or two isolated thunderstorms will be possible across the Southeast Plains, where a narrow corridor of instability will be present. The chances of development are low, though (15%).

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:

Mostly sunny and warm, with high temperatures climbing to, or just above, seasonal average. The Raton Ridge and Southeast Plains hold a slight chance for an isolated thunderstorm or two this afternoon/evening, but otherwise the regions will be quiet. Rain rates will be 0.4-0.7 inches/hour.

Timing: Noon – 8 PM

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

Mostly sunny skies with seasonal high temperatures will be the main story today for all regions, minus a few isolated showers/weak thunderstorms over the San Juan Mountains and Southeast Mountains. Rain rates will be low (0.15-0.3 inches/hour), and no significant activity is expected.

Timing: Noon – 8 PM

Issue Date: 9/8/2015
Issue Time: 8:57 AM

NO FLOOD THREAT IS FORECAST.

If you love September weather in Colorado, chances are good that you will love today’s forecast. Drier, subsident air will work in from the west behind a shortwave translating across the northern Rockies (black dashed line); this drier air will be responsible for the increase in sunshine and fewer showers/thunderstorms. As is typical with Colorado, however, there will be an opportunity for isolated-to-widely scattered showers/weak thunderstorms this afternoon and evening across the southern half of the state. Aside from that activity, though, today will overwhelmingly be marked by seasonable temperatures under partly-to-mostly sunny skies.

 

 

 

 

 

 

 

 

There are not any flash flooding concerns for today, as moisture is in fairly short supply. Pueblo has not received the effects of drying from the west just yet, but the IPW graph shows that the other three normal reporting stations (Grand Junction, Boulder, and Shriever AFB) have come under the drying influence. It is only a matter of time before Pueblo receives the same treatment. For more information regarding rain rates and timing, please check out 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, and Grand Valley:

Mostly sunny skies and seasonable temperatures will be the weather story today. Overnight, mostly clear skies will give way to cooler than average low temperatures for tomorrow morning.

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

North of I-70, partly-to-mostly sunny skies will be present, allowing temperatures to climb to seasonal averages across the area. To the south of I-70, isolated-to-widely scattered showers/weak thunderstorms will develop this afternoon and evening, coming to an end around, or just after, sunset. Rain rates will not be very high, maximizing at 0.2-0.4 inches/hour, with most rates less than 0.2 inches/hour.

Timing: Noon – 8 PM, with a lingering shower or two over the Southeast Mountains until midnight.

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

North of I-70, mostly sunny skies will prevail as the moisture/support sags further southeast as the day progresses. South of I-70, isolated-to-scattered showers/weak thunderstorms are expected this afternoon and evening, mainly across the Palmer Ridge, southern Urban Corridor, and western portions of the Southeast Plains/Raton Ridge. Further east, instability will be a bit higher so isolated thunderstorms cannot be ruled out, but chances are much lower than the aforementioned favored regions. Maximum rain rates are as follows:

Urban Corridor and Northeast Plains: 0.15-0.25 inches/hour
Palmer Ridge: 0.4-0.8 inches/hour
Southeast Plains and Raton Ridge: 0.8-1.2 inches/hour

Issue Date: 9/7/2015
Issue Time: 9:30 AM

NO FLOOD THREAT IS FORECAST.

Mother Nature did not get the memo that today is Labor Day, and she is working to bring isolated-to-scattered showers and thunderstorms to Colorado. Overall, activity will show a slight uptick from yesterday, but no flood threat is expected. The IPW graph gives a glimpse into why no flood threat is expected; precipitable water values are below an inch at the four normal reporting stations, and should not increase drastically through the afternoon/evening hours. All in all, these values will lend themselves to low/moderate rainfall rates when combined with the marginal instability for the following regions: Southwest Slope, San Juan Mountains, Northwest Slope, Northern Mountains, Front Range, Southeast Mountains, Grand Valley, San Luis Valley, Urban Corridor, and western portions of the Palmer Ridge/Northeast Plains/Southeast Plains/Raton Ridge.

The exception to the rules outlined above will be across far eastern Colorado, near the CO/KS border. In that area, a surface cool front will remain stalled/become diffuse through the afternoon hours, resulting in a pool of higher dewpoint values and greater instability. Rain rates will be higher there than any other point in the state, maximizing around 1.5-2.0 inches/hour. Easterly storm motions at about 15-20 knots will help limit the flood threat, and thus no flood threat is issued. Street/field ponding, especially in areas that have drainage issues, will be a concern under brief heavy rainfall. Other threats will be strong, gusty winds (45-55 mph), lightning, and small hail (up to 1 inch in diameter).

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:

Isolated-to-scattered showers and thunderstorms today and tonight, ending from west to east as drier air filters in amid westerly flow aloft. For most areas, max rain rates will be 0.25-0.5 inches/hour. Near the CO/KS border, however, maximum rain rates will be 1.5-2.0 inches/hour.

Timing: 2 PM – Midnight, with a few showers/weak thunderstorms continuing into the early morning hours across the Northeast Plains, Southeast Plains, and Palmer Ridge.

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

Isolated-to-scattered showers and weak thunderstorms are expected, with the greatest coverage across the higher terrain along and north of I-70. Westerly steering winds aloft will help push storms over adjacent valleys, but during the evening as drier air filters in, storms will become more anchored to the higher terrain. Rain rates will be low, generally 0.15-0.3 inches/hour, and maximizing around 0.4-0.6 inches/hour.

Timing: Current – 9 PM, with a couple isolated showers lingering into the early morning hours.