STP 08-30-2015: Abundant Sunshine with a Few Isolated Mountain Thunderstorms

Issue Date: Sunday, August 30th, 2015
Issue Time: 9:00 AM MDT

Summary:

Colorado could not have asked for a better Saturday as Mother Nature produced one of the best of the summer. Warm temperatures and abundant sunshine were the big story as dry air and high pressure laid across the state. A few isolated mountain thunderstorms developed with the heat of the day, but nothing of note resulted. Most rainfall totals were less than 0.05 inches, obviously well below the threshold for any flash flooding issues to result.

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Storm Total Precip Legend

FTB 08-29-2015: Mostly Sunny for Most with Isolated Mountain Thunderstorms

Issue Date: 8/29/2015
Issue Time: 9:35 AM

NO FLOOD THREAT IS FORECAST.

A great Saturday is in store for Colorado as most locations will stay mostly sunny and dry thanks to an upper-level ridge over the region. The ridge axis will shift east, so locations along and east of the I-25 corridor will see temperatures climb a few degrees over yesterday, and temperatures to the west will be fairly similar, perhaps a degree or two warmer, to yesterday’s readings. A few isolated thunderstorms over the mountains, mainly along and south of I-70, will be all the atmosphere can muster in this overall environment. Heavy rainfall and flash flooding is not expected with precipitable water values well below 1 inch at all four normal reporting stations (Boulder, Grand Junction, Pueblo, and Shriever AFB). For more details, including rain rates and timing, be sure and check out the Zone-Specific forecast discussions below.

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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.

Flood Threat Legend

Zone-Specific Forecasts

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

Sunny and warm, with highs ranging from the 80s to the 90s. Steering winds will be northerly again today, so mountain thunderstorms will remain mountain thunderstorms and no threat to adjacent lower elevations. A few more clouds will be present near the mountains compared to the abundant sunshine further east.

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

Mostly sunny becoming partly sunny during the afternoon as daytime heating and terrain play on the available moisture. Isolated-to-widely scattered thunderstorms will develop during the afternoon and evening hours, roughly along and south of I-70. The best coverage will occur across the Central Mountains and San Juan Mountains. The main threats will be gusty winds and lightning, with brief moderate rainfall. Rain rates will generally be 0.25-0.5 inches/hour, maximizing around 0.4-0.8 inches/hour.

Timing: Noon – 9 PM

STP 08-29-2015: High Pressure and Drier Air Brought About More Sunshine, Less Thunderstorms

Issue Date: Saturday, August 29th, 2015
Issue Time: 9:00 AM MDT

Summary:

Overall, yesterday was a fairly quiet day across the state, with isolated thunderstorms confined to mainly the higher terrain. Northerly flow aloft kept those storms over the mountains and foothills, leaving points along and east of the I-25 corridor dry. High temperatures were around average statewide; there just was not much to complain about with regards to yesterday’s weather.

No flash flooding was reported yesterday. Be sure and check the STP map below for a statewide overview on precipitation.

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Storm Total Precip Legend

FTB 08-28-2015: More Sunshine on the Way, Fewer Showers/Thunderstorms

Issue Date: 8/28/2015
Issue Time: 9:20 AM

NO FLOOD THREAT IS FORECAST.

Following behind yesterday’s disturbance/trough is a high pressure ridge that will build across the southwestern US today. The water vapor imagery below depicts the situation well, and I have annotated the image for clarity. With the building ridge will come decreasing moisture, though there will be enough remaining moisture for isolated thunderstorms mainly over the Continental Divide, San Juan Mountains, Southeast Mountains, and Front Range mountains/foothills. With northerly flow aloft expected, the adjacent Urban Corridor and western portions of the Southeast Plains should stay dry as storm motions will keep them from moving overhead.

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Further east over the Northeast Plains, Southeast Plains, Palmer Ridge, and Raton Ridge, a mostly sunny and dry day is expected, with temperatures climbing slightly above average for this date. An isolated thunderstorm may develop over the Cheyenne Ridge and Raton Ridge during the late afternoon/evening hours, but probability of occurrence is ~10%

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.

Flood Threat Legend

Zone-Specific Forecasts

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

Isolated showers and thunderstorms are expected, mainly over the Continental Divide, San Juan Mountains, Southeast Mountains, and Front Range mountains/foothills. With moisture decreasing, heavy rainfall is not expected, nor is flash flooding a threat. Maximum rain rates will be 0.5-0.9 inches/hour, with most rain rates a more modest 0.2-0.5 inches/hour.

Timing: Noon – 9 PM

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

Mostly sunny and dry for most areas, with only a slight chance (~10%) for a thunderstorm to develop over the Cheyenne Ridge and Raton Ridge. With northerly flow aloft, it will be very difficult for the Urban Corridor/western extents of the Southeast Plains to experience the common “thunderstorms drifting off the mountains.” A bit more cloud cover than other areas to the east will be about all the environment can muster.

Timing: 2 – 8 PM