As the summer solstice approaches, we are reminded that the devil is always in the details when it comes to summer forecasting. Today is a good example of that. As shown in the visible satellite image, below, this morning’s mostly cloud free conditions across Colorado are a testament to the strength of the strong upper-level ridge. The ridge is centered directly over the Four Corners this morning. Compared to yesterday, dewpoints have crept up slightly west of the Continental Divide<\/span>, but even with that, the Grand Junction PW<\/span> shows a meager 0.48 inches of water vapor with most of that held high above the boundary layer<\/span>. In short, little if any rainfall is expected west of the Continental Divide<\/span> today. East of the Continental Divide<\/span>, Denver’s sounding showed a PW<\/span> of 0.49 inches, which is below normal for this time of year. However, higher PW<\/span>, just under 1 inch, was observed at the North Platte (NE) and Dodge City (KS) soundings. Furthermore, model guidance appears to be biased low in all measures of moisture such as PW<\/span>, which was underestimated by 10-20% along the CO\/KS\/NE borders. Even larger dry biases were noted in the high-resolution guidance today. As shown below, this morning’s 4AM (10Z) run of the HRRR underestimated the 8AM dewpoints across eastern Colorado by up to 6F. This is a very large bias for only a 4-hour forecast, which can easily make the difference between heavy rainfall and dry conditions. The bias is likely a testament to both how shallow the moisture is, along with the presence of isolated<\/span> pockets of higher moisture due to wet soils remaining from the wet May. Returning the focus back on today’s forecast, we see a few forcing features of note. First, a cool front (more appropriately called a wind shift boundary) was noted over central Wyoming, which will race south across eastern Colorado this afternoon. Second, another wind shift boundary was also noted in northeast Colorado, with higher dewpoints and more southerly winds to its south. We expect these features to help concentrate the stronger storm activity today along eastern Northeast Plains, near the Kansas border. With forecast soundings indicating the potential for training<\/span> cells due to the combination of (i) deep southerly boundary winds, (ii) light northerly winds aloft but (iii) weak shear<\/span> overall, a Low flood threat has been issued for a small part of the Northeast Plains for isolated<\/span> flash flooding<\/span>.<\/p>\n Elsewhere, isolated<\/span> to scattered<\/span> showers and thunderstorms are expected mainly over the higher terrain east of the Continental Divide<\/span>. But, with only shallow boundary layer<\/span> moisture, flooding is not expected for these areas although short-term moderate rainfall will be possible.<\/p>\n![\"\"](\"https:\/\/archive-coftb.dewberryanalytics.com\/wp-content\/uploads\/2021\/06\/vis_markup-4.png\")
<\/a><\/p>\n<\/a><\/p>\nToday’s Flood Threat Map<\/strong><\/h3>\n