FTB 07-19-2017: Heavy Rainfall for the High Country and Western Slope

Issue Date: Wednesday, July 19, 2017
Issue Time: 10:45AM MDT

LOW flood threat for portions of Front Range, Urban Corridor, Palmer Ridge, San Juan Mountains, Central Mountains, Northern Mountains, Grand Valley, Northwest Slope

Moisture has returned to the Western Slope today. The Grand Junction sounding this morning showed 1.04 inches of Precipitable Water, while Denver was at 0.84 inches. The upper level ridge shifts a little to the east today and builds north throughout the day. This will allow the surface High pressure system to pull moisture into the western portion of the state with south and southeasterly winds. PW in the western portion of the state is expected to rise to 1.2 inches. These surface winds will also pull the dry air over into the southeast portion of the state confining the moisture on the eastern plains to the north. Values north will rise to 1 inch. Currently there is a band of showers over the southwest Colorado moving north that will begin to dissipate by late morning. Dense fog was reported of the Northeast Plains, but should burn off quickly with the sunrise.

Upslope flow will set up again today with the storms starting to fire over the higher terrain around 11AM. An upper level wave will help enhance lift over the western portion of the state along the border. It lifts north throughout the day and will exit over the northwestern portion of the state late this evening. Paired with high moisture, storms are expected to be slow moving and produce heavy rain; especially those forming near the upper level disturbance. Rain rates just over 1 inch 1-hour are possible with 3-hour totals up to 2 inches. Grand Junction NWS has issued a Flood Watch from 10:00AM this morning until midnight tonight. Heavy rainfall could lead to flash flooding in canyon country, over burn scars and in dry streams or creeks. Other threats include small hail, gusty winds, rock and mud slides, street flooding and small stream flooding. The return of moisture paired with upslope flow is particularly dangerous for burn scars. These will need to be monitored closely throughout the day. Storms will be confined to the higher terrains and favor the western portion of the state where there will be better lift and moisture. An isolated thunderstorm or two over the Urban Corridor and Palmer Ridge cannot be ruled out as the storms move off the mountains. These threats include gusty winds and brief heavy rainfall. Storms over the high terrain will begin to dissipate around 10PM with the exception of the Northwest Slope and Northern Mountains where storms may continue until midnight.

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, scroll below the map.

Flood Threat Legend

 

Zone-Specific Forecasts:

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

Storms will continue to move north and dissipate through late morning. Partly cloudy skies are likely with storms beginning to fire over the higher terrain around 11. High moisture, an upper level disturbance and slow moving storms will warrant a low threat today. A Flash Flood is in effect until midnight tonight. Threats include mud slides, debris flows and flash flooding. 1-hr rain rates just over 1 inch and 3-hr rain rates up to 2 inches are possible. Burn scars will need to be monitored closely. There is Low flood threat for today.

Primetime: 11AM to 12AM

Front Range, Urban Corridor, Palmer Ridge, Southeast Mountains:

Sunny this morning becoming partly cloudy this afternoon as storms begin to form over the higher terrain. Max 1-hr rain rates are expected to be 1.1 inches. Storms should favor the higher terrain, but an isolate storm or two over the Urban Corridor or Palmer Divide near the mountains cannot be ruled out.

Primetime: 12PM to 10PM

Northeast Plains, Southeast Plains, Raton Ridge, San Luis Valley:

Sunny and hot today. Fog over the Northeast Plains should burn off quickly with the heating from the sun. Temperatures in the upper 90’s are expected for the eastern plains today. There is no flood threat.