FTB 07-27-2015: Fast Moving Storms Will Limit Rainfall

Issue Date: July 27th, 2015
Issue Time: 10:15AM

— Flooding is NOT expected today
Elevated Fire Threat for Northern Mountains and Northwest Slope

Today’s water vapor image, below, shows a large disturbance located over the Pacific Northwest, stretching southward into Nevada. Late last week, it appeared that as this disturbance crossed Colorado, it may have subtropical moisture support and pose a heavy rainfall threat. However, the subtropical connection did not materialize and heavy rainfall is not expected as the disturbance races by our state. Despite morning precipitable water values in the 0.8 – 1.1 inch range, there is very dry air just to the west. As this propagates eastward, it will put a cap on rainfall intensities. There are two additional limiting factors to rainfall today. First, the disturbance is moving very rapidly, meaning that storm motion is expected to be in the 25-40 mph range. Second, the surface low pressure noted over Wyoming this morning will induce downsloping flow east of the Divide. Climatologically speaking, downsloping flow is extremely unfavorable for heavy rainfall east of the Divide.

watervapor_20150727For today, we expect mostly sunny skies this morning to quickly give way to scattered thunderstorm activity by early afternoon. Coverage will be highest in the Central Mountains. Storms will race to the northeast across the Plains as the afternoon transitions into evening. Storm activity will quickly diminish around sunset. While rainfall amounts will be limited today, gusty winds, up to 60mph, will accompany many storms.

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

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

Sunny early with a few cumulus clouds developing by early afternoon. Scattered high-elevation storms will develop over the higher terrain and spread eastward. Max 1-hr rainfall will be 0.5 inches over the higher terrain to 0.9 inches over the far northeast. Wind gusts up to 65 mph will be possible with stronger storms. Flooding is not expected today.

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

Sunny to partly cloudy early with scattered afternoon storms possible across the higher elevations. Highest coverage is expected to be in the Central Mountains. Due to fast storm motions, max 1-hour rain rates will be 0.5 inches. Thunderstorms will be capable of wind gusts up to 55 mph. Across the Northern Mountains and Northwest Slope, the combination of very dry air coming in from the west and a sustained period of gusty winds of 40-50 mph will lead to a fire weather danger this afternoon. Please stay tuned to local news sources for specific information. Flooding is not expected today.