Issue Date: Thursday, May 23rd, 2019
Issue Time: 8:45AM MDT

–Flooding is NOT expected today

Western Colorado is waking up to rain and snow, while the rest of the state has some sort of cloud cover. The exception to the cloud cover is over the San Luis Valley where temperatures are currently in the mid-40°Fs. The next system, which is currently over Arizona, begins to propagate to the northeast today. The jet on the front side of the trough is mixing with some mid-level energy, which is already producing precipitation marked in the water vapor imagery below. Expect scatter storms to continue to increase throughout the day over western Colorado and the mountains as a cold front moves through this afternoon. Currently, the snow line is at ~8 K feet, but expect that to drop once the front passes. Freezing temperatures are forecast over the southern portion of the Southwest Slope tonight.

As far totals, this is a swift moving system due to the jet. Storm motion will be to the NNE at 25 to 30 knots. With dew points in the 40°Fs and rain turning to snow with the passage of a cold front, flooding is not expected. Best accumulation will occur over the western border with snow totals between 3-6 inches over the San Juans by tomorrow morning. The Grand Mesa area may also get a couple of inches of snow once the front passes through the area.

West of the Divide, expect showers and snow (elevations > 9.5K ft) over the Front Range and northern Southeast Mountains. With the storm motion, highest accumulations are forecast along the Continental Divide once again. A few light showers may spill into the adjacent plains with the best chance for measurable rain over the Palmer Ridge, but increased cloud cover is the more likely scenario. Scattered storms with mostly stratiform rain may occur later this morning into this afternoon along the Kansas/Colorado border on the backside of a surface low moving in the panhandle of Texas/Oklahoma. The threat for severe thunderstorms should stay well east of the state, especially with the stable air mass over the plains. Flooding is not forecast.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

 

Zone-Specific Forecasts:

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

Scattered showers, weak thunderstorms and snow are possible today with coverage increasing throughout the day. Strong winds will also be possible over the higher terrains with the jet overhead. Isolated totals by tomorrow morning along the western border could reach 1 inch over the higher elevations, with more general values in a range from 0.25 to 0.6 inches over the valleys. The Lake Christine burn scar will be monitored closely this afternoon, but rainfall should be gradual enough that it won’t cause any issues. The San Juan Mountains will likely wake up to 3-6 inches of fresh snow by the morning. Storms should decrease south to north later this afternoon with all activity ending by 11PM tonight. Flooding is not forecast.

Primetime: Ongoing to 10PM

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

Cool temperatures and stratiform clouds to start the day due to the passage of a cold front overnight. Expect an uptick in storm activity over the Front Range and northern Southeast Mountains this afternoon as the low moves north. Snow accumulations should stay above ~9.5K feet with some gusty winds possible with the jet overhead. Precipitation totals up to 0.5 inches may be possible along the Divide in Clear Creek, Gilpin and northern Park County, but elsewhere totals should be no greater than 0.3 inches. A few of these storms could spill into the adjacent plains, but accumulation will be minimal. Over the eastern plains, some rainfall with embedded convection may be possible. Totals up to 0.25 inches may be possible. Flooding is not forecast.

Primetime: 9AM to 9PM

Issue Date: Wednesday, May 22nd, 2019
Issue Time: 9:00AM MDT

–Flooding is NOT expected today

The system that brought Denver the late season snow is now over northern Nebraska, and in its wake, subsidence and drier air has moved into eastern Colorado. Clear overnight skies and cold temperatures behind the cold front allowed for lows to dip below the freezing mark early this morning. To the west of Colorado, the next system begins to rotate into the area that will impact the state’s weather today and tomorrow. The low pressure is expected to deepen throughout the day, which should pull it a bit further southwest. In turn, this will change the winds aloft over Colorado to southwesterly and eventually southerly tonight. The deepening of the system will allow the shortwave over Arizona and New Mexico to move north into the western Colorado and the mountains, which will help spark scattered afternoon storms.

More northerly surface flow over eastern Colorado and south/southwesterly flow aloft will reinforce the dry air mass in place. The air to the northeast has a bit more moisture in it, so rainfall is forecast over the Front Range and along the Continental Divide as the flow turns more easterly this afternoon near the Palmer Ridge. Over the adjacent plains and eastern Colorado, only partial cloud cover is forecast with a few sprinkles possible along the Urban Corridor.

To the west, dew points will be in the mid-30°Fs to 40°F, so storms today will produce light rainfall and possibly some gusty outflow winds as they move south to north. Small hail is possible with the isolated, stronger thunderstorms, but storms are not expected to reach severe criteria. Afternoon storms should come to an end a couple hours after sundown. With an upper level jet moving into southern Colorado, some gusty winds may be possible over the higher terrains this evening and may help generate a few light snow showers over the higher elevations of the Central and San Juan Mountains overnight. Flooding is not forecast.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

 

Zone-Specific Forecasts:

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

Scattered showers and weak thunderstorms are possible this afternoon as the next system deeps to our west. A little bit of moisture has remained over northeast corner, so some afternoon storms are possible with upslope flow along the Front Range. Totals by tomorrow morning could reach just under 0.5 inches, but will more likely be in the range of 0.25 to 0.4 inches. To the west, storms will travel from south to north. Accumulations will be greatest over the southern mountains, but activity will likely spill into the valleys. Isolated 24-hour totals up to 0.5 inches are possible over the San Juan Mountains and western Central Mountains. Snow should be confined to the highest elevations, but a few inches are likely by morning.  For the adjacent valleys, forecasting 24-hour totals between 0.25 and 0.35 inches where the stronger storms form. Flooding is not expected.

Primetime: Ongoing to 8PM

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

Dry air and subsidence should keep these regions rainfall free this afternoon with the exception of some light rainfall along the highest elevations of the Sangre de Cristo Mountains. Expect cloud cover to increase this afternoon and high temperatures to begin to rebound from the cold snap. Highs over the Southeast Plains will reach the 70°Fs with temperatures 5-10°F cooler over the Northeast Plains. Over the Urban Corridor, highs in the upper 40°Fs are forecast. Flooding is not expected.

Issue Date: Tuesday, May 21st, 2019
Issue Time: 8:50AM MDT

–Flooding is NOT expected today

A lot of folks waking up to snow this morning as rain transitioned to snow for the lower elevations during the early evening hours on Monday. While it is somewhat unusual that there is snow this time of year, the latest date of measurable snow in Denver is June 2^nd. Over the eastern plains (minus the Palmer Ridge), precipitation remained as rainfall and continues this morning. Today, the low pressure system that brought the winter weather will exit northeast into Kansas/Nebraska. However, stratiform rainfall over eastern Colorado will continue on the northwest side of the low. Expecting the rainfall to slowly decrease southwest to northeast this afternoon into this evening as the low moves out of the area. Subsidence and westerly flow will fill in over the Front Range/Southeast Mountains and Urban Corridor by early afternoon, which should decrease the chances for precipitation this afternoon. Throughout the day, the cloud cover should begin to break up (starting south first) with a few isolated, light snow storms possible over the higher terrains this afternoon.

Over western Colorado, scattered showers (valleys) and snow (mountains) are forecast to increase as some mid-level energy and residual moisture combine today. With a drier air mass moving in from the west, accumulations are expected to remain low and favor the higher terrains with slow westerly storm motion. There will be some decent accumulation over the Northern and north Central Mountains thanks to wrap around moisture from the low this morning. Expect light showers and snow to begin tonight over the southwest corner as the jet moves into the area associated with the next low pressure system. Snow levels will likely fall to 7K feet overnight; however, accumulation will be far less than last night. Flooding is not expected today.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

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

Precipitation will start decrease from southwest to northeast today as the low moves into Kansas. Wrap around moisture in the deformation zone will continue showers over the eastern plains. This rainfall should decrease from southwest to northeast this afternoon into this evening along with breakup of the cloud cover. Some light snow showers are possible over the higher terrains. Max 24-hr totals up to 0.4 inches (west) and 1.5 inches (northeast corner) are possible. Activity is forecast to end a couple hours after sundown, and flooding is not forecast.

Primetime: Ongoing to 8PM

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

Snow showers will continue over the Northern and north Central Mountains through this afternoon as wrap around moisture from the low continues. 24-hour snow totals up to 8 inches are possible tomorrow morning over the highest elevations. Scattered showers are also possible over the lower elevations, but without much moisture totals will remain under 0.25 inches. The next system approaches from the west tonight and the jet moves into the southwest corner of the state. This should initiate showers and snow (> 7K feet) over the southwest corner of the state and western, central Colorado overnight into tomorrow morning. Precipitation totals will likely be between 0.3 (valleys) and 0.75 inches (San Juan Mountains). Flooding is not expected.

Primetime: Ongoing to 8AM

Issue Date: Monday, May 20th, 2019
Issue Time: 9:30AM MDT

–Flooding is NOT expected today

The upper closed low that is currently over the Nevada/Utah border will start to move to the southeast today, which will bring cool and wet weather statewide. By tomorrow morning it will be positioned over the southeast Colorado/New Mexico border and bring snow to the lower elevations. With an incoming jet, ample low level moisture with southwesterly flow and plenty of mid-level ascent, expect precipitation to continue throughout today and into tomorrow. Currently, surface maps are indicating heavy snowfall and rain over the southwest corner of the state and moderate snow over the Central Mountains. With southwest flow increasing throughout the day, highest snow accumulations are expected to be over the Continental Divide, with all of the higher terrains receiving some snow accumulation through tomorrow morning. Over the southeast Plains in Baca and Powers Counties, showers continue from a wave of storms that moved through the Southeast Plains overnight.

For today, expect an uptick in widespread showers and snow (> 9K ft). For western Colorado, storm motion will have more of a southerly component during the day, but as the low moves into the southwest corner tonight, storms will wrap around it counterclockwise giving more of a northerly component to the motion. Expecting all zones to get some precipitation with snow levels dropping to 7K ft overnight. Overnight, precipitation should be confined to the mountains, and snow accumulations are expected to be highest over the San Juan Mountains by tomorrow morning.

To the east, the heaviest precipitation over the next 24-hours is expected along a line from Pueblo County to eastern Weld/western Logan Counties as upslope flow and a boundary set up. Some severe thunderstorms with hail are possible with these storms this afternoon, but tonight temperatures drop off significantly. This means there will likely be snow over the Cheyenne and Palmer Ridges by morning with the snow level around 6K feet. There is an outside chance of snow within the Urban Corridor as well, so be sure to bring in outdoor plants or cover them overnight. As the low moves into the southeast corner of the state tonight, downsloping winds to the south should decrease precipitation activity over the Southeast Plains and Raton Ridge. As mentioned, favorable upper level dynamics will keep activity going through the night over the Southeast Mountains, Front Range and Urban Corridor.

Interesting flood forecast as the main threat will occur this afternoon over the Palmer Ridge. Max 1-hr rain rates hover around flood threat criteria if stronger (severe) thunderstorms are able to develop with dew points in the upper 40°Fs to low 50°Fs. However, dry soils and green vegetation decrease the chance for widespread flooding. At this time, going with no flood threat, but should the threat increase enough to warrant a Low threat, a PM update will be issued.

Today’s Flood Threat Map

For more information on today’s flood threat, see the map below. For Zone-Specific forecasts, scroll below the map.

Zone-Specific Forecasts:

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

Upper dynamics, increased low level moisture and a boundary will help form a line of thunderstorms this afternoon over the adjacent plains around the Palmer Ridge/Southeast Plains intersect. There is a possibility for some severe storms in this area with hail up to 1.25 inches. Max 1-hr rain rates up to 1.5 inches are possible with 3-hour totals just under 2 inches. Expecting showers to become more widespread as an MCS quickly forms with the upper air support and moist boundary layer. Max 1-hr rain rates will drop to 0.3 to 0.7 inches when this occurs. Storms will have northerly motion throughout the day with decreasing rainfall from south to north this afternoon as the low moves into the southeast corner of the state. Snow levels drop off tonight, so ongoing, overnight storms will likely cross over into snow by morning over the Palmer and Cheyenne Ridges. There is a slight chance for snow across the Urban Corridor by morning as well. Flooding is not forecast.

Primetime: 11AM to Tuesday morning

Northwest Slope, Grand Valley, Southwest Slope, San Luis Valley:

Southwest flow and the approaching low will pull multiple bands of rainfall with a couple thunderstorms across the lower elevations this morning into this afternoon, so expect an increase in storms throughout the day. Storm motion will be south to north this afternoon and switch to more northerly overnight as the low moves into the area. Since moisture decreases to the north, the highest 24-hr totals are forecast over the Southwest Slope where isolated totals up to 0.7 inches could accumulate. Over the Grand Valley totals up to 0.3 inches are possible. Rainfall is also likely over the Northwest Slop with totals remaining under 0.1 inches.

Primetime: Ongoing to Tuesday morning

Front Range, Northern Mountains, Southeast Mountains, San Juan Mountains, Central Mountains:

Snow level may drop throughout the day some, but for the most part, expecting all precipitation to fall as snow above ~9K ft. Expecting coverage of the precipitation to pick up throughout the day as the low begins to approach and southwest flow increases. The highest 24-hour snow accumulations are expected along the Continental Divide where totals could reach 10-12 inches. More general totals in the 4-8 inch range are forecast for other areas.

Primetime: Ongoing to Tuesday morning