FTB 06-25-2016: Another Day of Rumbling Thunderstorms

Issue Date: 6/25/2016
Issue Time: 9:22 AM

A LOW FLOOD THREAT IS FORE FOR PORTIONS OF THE SOUTHEAST PLAINS, RATON RIDGE, PALMER RIDGE, FRONT RANGE, SOUTHEAST MOUNTAINS, AND URBAN CORRIDOR.

Current water vapor analysis shows the upper-level low/trough sliding across the northern Rockies/northern high plains, ridging over central US, and ridging building along the West Coast. Within this pattern, dry air is being transported into western/northwestern Colorado from the west/southwest, and mid-level moisture (green arrow) continues to be funneled into southern/eastern Colorado. Meanwhile, a cool front is shifting southward across the state today, later stalling over the I-70 corridor in the mountains and near Highway 50 across the lower elevations of eastern Colorado.

The plume of moisture and location of the cool front will do a good job delineating the areas expecting the majority of shower/thunderstorm activity during this period. Over the mountains, areas along and south of I-70 will see the bulk of activity, with coverage generally increasing from north to south and west to east. North of I-70 will remain mainly dry today, minus a shower or two over the Northern Mountains and northern extents of the Front Range.

WV_20160625

To the east, the Northeast Plains and portions of the Urban Corridor north of I-70 will see very little activity, with only an isolated thunderstorm or two possible near the higher terrain and along the Cheyenne Ridge. Brief periods of light-to-moderate rainfall are possible, but the main threats from any of this activity will be gusty winds and lightning. To the south of I-70, coverage will increase (just as moisture increases) from north to south. Scattered thunderstorms will be capable of producing locally heavy rainfall, strong winds, small hail, and lightning. A couple of storms will become marginally severe, producing hail up to 1.5 inches in diameter and strong winds up to 60 mph.

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 (north of I-70) and Northeast Plains:

Mostly sunny and a bit cooler today, with an isolated shower/thunderstorm or two along/near the Front Range and Cheyenne Ridge. Drier air has been filtered in and will keep rain rates sufficiently beneath flooding concerns. Maximum rain rates will be 0.2-0.4 inches/hour.

Timing: 2 PM – 9 PM

Urban Corridor (south of I-70), Palmer Ridge, Raton Ridge, and Southeast Plains:

Partly sunny with isolated-to-scattered showers/thunderstorms this afternoon/evening. A few will be strong/severe, with the main threats being locally heavy rainfall, hail (up to 1-1.5 inches in diameter), strong winds (up to 60 mph), and lightning. Maximum rain rates will vary:

Urban Corridor: 0.8-1.4 inches/hour
Palmer Ridge: 1.2-1.6 inches/hour
Raton Ridge and Southeast Plains: 2.0-3.0 inches/hour

Timing: Noon – 10 PM, with a couple thunderstorms rumbling across the far Southeast Plains/Raton Ridge until 1 AM.

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

Partly sunny with isolated-to-scattered showers/thunderstorms expected this afternoon/evening. Rain rates will remain below flash flood thresholds for most areas, but a low threat exists in the southern Front Range and Southeast Mountains where moisture will be best. Maximum rain rates are as follows:

Front Range and Southeast Mountains: 0.8-1.2 inches/hour
Central Mountains, San Juan Mountains, and San Luis Valley: 0.4-0.6 inches/hour

Timing: 11 AM – 9 PM

Northern Mountains, Northwest Slope, Grand Valley, and Southwest Slope:

Mostly sunny with temperatures remaining near, or slightly above, normal. Areas to the north of the front will be a few degrees cooler than yesterday. An isolated shower/weak thunderstorm or two cannot be ruled out over the higher terrain, resulting in mainly gusty winds and lightning. Maximum rain rates will be below 0.4 inches/hour.

Timing: 11 AM – 7 PM

STP 06-25-2016: Another Round of Showers/Thunderstorms over the Mountains and East

Issue Date: Saturday, June 25th, 2016
Issue Time: 9:00 AM MDT

Summary:

A battle between dry and moist air was waged across the region yesterday, with dry air only winning out over extreme western/northwestern Colorado. In those locations, dry and hot conditions prevailed during the afternoon, highlighted by fire weather concerns and Red Flag conditions. A few isolated showers/weak thunderstorms developed during the evening/overnight hours as a cool front pushed through the area.

Further to the east, the moist plume fueled another day of scattered showers and thunderstorms. A few were strong, producing small hail, lightning, gusty winds, and periods of heavy rainfall. The majority of the heaviest rain fell over the Northeast Plains and Southeast Plains where low-level moisture was best. Only one severe storm report was filed yesterday, for 1.50 inch hail 3 miles NW of Snyder (Morgan County). The combination of hail/wind also caused tree damage.

No flash flooding was reported yesterday. Please see the STP map below for a look at 24-hour precipitation totals.

20160625_STPImage
Storm Total Precip Legend

FTB 06-24-2016: Battle Between Dry and Moist Air

Issue Date: 6/24/2016
Issue Time: 10:05 AM

A LOW FLOOD THREAT IS ISSUED FOR PORTIONS OF THE NORTHEAST PLAINS, PALMER RIDGE, SOUTHEAST PLAINS, URBAN CORRIDOR, AND RATON RIDGE.

Current analysis of the water vapor imagery this morning will tell us a lot about the weather expected today. Below, you can see the upper-level low spinning over the Pacific Northwest, with trough-ing extending southward across the West Coast/Great Basin. To the south and east, a broad upper-level ridge remains. Both of these larger scale features are funneling different types of air masses across Colorado (moist air = green arrow, dry air = orange arrow).

The drier air being transported in from the west will lead to a hot and dry day for the lower elevations of western Colorado. In fact, a Red Flag Warning has been issued for portions of the Northwest Slope, Grand Valley, and Southwest Slope. Enough moisture will remain for isolated-to- scattered showers/thunderstorms over the higher terrain of the San Juan Mountains, Central Mountains, and Northern Mountains.

WV_20160624

Along and east of the Continental Divide, deeper moisture and sufficient instability will lead to another period of scattered showers/thunderstorms. Wind shear values are less favorable than yesterday, but a few storms will become strong-to-severe. The main threats will be small hail, strong winds, and lightning, with periods of moderate-to-heavy rainfall.

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, Palmer Ridge, Raton Ridge, and Southeast Plains:

Another round of scattered showers/thunderstorms are expected today/tonight. A few will become strong-to-severe, with the main threats being small hail, strong winds, and lightning. Storm motions will be quick enough to help mitigate the flood threat somewhat. Maximum rain rates vary:

Urban Corridor: 1.0-1.4 inches/hour
Palmer Ridge: 1.0-1.6 inches/hour
Northeast Plains, Southeast Plains, and Raton Ridge: 2.0-2.5 inches/hour

Timing: Noon – 1 AM, storms will end from west to east as they exit the state.

Front Range and Southeast Mountains:

Scattered showers/thunderstorms expected over the Front Range this afternoon/evening, with more isolated coverage expected over the Southeast Mountains. Gusty winds, lightning, small hail, and brief periods of moderate rainfall are the main threats. Maximum rain rates will be 0.5-0.8 inches/hour.

Timing: 11 AM – 9 PM

Northwest Slope, Grand Valley, and Southwest Slope:

Hot and dry conditions are expected today. Fire weather concerns are highlighted by the issuance of Red Flag Warnings for portions of the Northwest Slope, Grand Valley, and Southwest Slope. Higher terrain along eastern fringes of these zones may see an isolated shower/thunderstorm this afternoon/evening, resulting in mainly gusty winds, lightning, and light rainfall. Maximum rain rates from any activity will be 0.15-0.3 inches/hour.

Timing: 11 AM – 7 PM.

A cool front moving southward through the area tonight/overnight may result in a couple isolated showers/thunderstorms developing over the Northwest Slope after 9 PM.

Northern Mountains, Central Mountains, San Juan Mountains, and San Luis Valley:

Isolated-to- scattered showers/thunderstorms are expected over the higher terrain this afternoon/evening, with storm motions allowing for activity to move over valleys with time. The main threats from storms today will be gusty winds and lightning, with brief periods of light-to-moderate rainfall. Maximum rain rates vary:

Northern Mountains and Central mountains: 0.5-0.8 inches/hour
San Luis Valley: 0.4-0.7 inches/hour
San Juan Mountains: 0.6-1.0 inches/hour
Timing: 11 AM – 8 PM.

A cool front moving southward through the area tonight/overnight may result in a couple isolated showers/thunderstorms developing over the Northern Mountains after 9 PM.

STP 06-24-2016: Uptick in Thunderstorms as the Ridge Weakened, Some were Severe

Issue Date: Friday, May 1st, 2015
Issue Time: 9:00 AM MDT

Summary:

Yesterday was quite an active day with widespread showers/thunderstorms across much of Colorado, thanks to a disturbance that shifted across the region. Across the western slope, much of the activity was in shower form, aside from a few stronger thunderstorms that developed during peak heating. To the east, thunderstorms were the main result as better moisture fueled convective activity. A few storms became strong-to-severe. Here are the severe storm reports:

60 mph wind gust: 3 miles N of Crook (Logan County), Crook (Logan County), 1 mile N of Strasburg (Adams County)
80 mph wind gust: 8 miles N of Fort Collins (Larimer County)
Tornado: 5 miles E of Canon City (Fremont County)
1 inch hail: 16 miles NW of Merino (Logan County)
1.5 inch hail: 3 miles NNW of Pawnee Pass (Logan County)

No flash flooding was reported yesterday. For a statewide look at 24-hour precipitation totals, please take a look at the Storm Total Precipitation map below.

20160624_STPImage
Storm Total Precip Legend