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<\/a><\/p>\nAs shown in today’s water vapor image, below, a very active pattern remains in the eastern Pacific Ocean and western North America. The southward extent of the disturbances, and most notably the continued occurrence of cut-off circulations, is what makes this pattern a bit unusual for this time of year. Typically, late May is a time when the southwest United States upper-level ridge gradually begins to build in the lead-up to the monsoon<\/span> season.<\/p>\n Beginning close to home, we see Colorado will be under a transient (i.e. passing) mid-level ridge, leading to excellent weather for most of the state. However, the next precipitation event, Event #1, will quickly be developing from two separate areas. An upper-level trough<\/span> currently off the Washington state coast will move southeastward towards Colorado. This will cause synoptic-scale upward motion in the upper-levels, while steering a cold front across the state over the weekend. Meanwhile, the cutoff disturbance northeast of Hawaii will also gradually be picked up by the jet stream<\/span> flow, prolonging the duration of unsettled weather mainly east of the Continental Divide<\/span>. As shown in the GEFS forecast PW<\/span> plumes, we see a very distinct surge of moisture in the Denver forecast, with PW<\/span> approaching 1 inch. However, one important caveat regarding heavy rainfall chances is that the strong cool front will likely limit instability along and north of it. In fact, the trend in model guidance over the past 24-48 hours has significantly cooled boundary layer<\/span> temperatures north of I-70, which will cause more gentle, stratiform precipitation here. The real area of interest for this event, from the perspective of heavy rainfall and flooding will be over the southeast quadrant of Colorado, where Saturday and Sunday will have a well-juxtaposed combination of moisture, instability and relatively light steering winds to warrant an Elevated flood threat. Unlike the past two precipitation events, heavy rainfall will likely be the dominant threat with Event #1, as opposed to severe weather, given relatively weak wind shear<\/span>.<\/p>\n Before moving on, and of relevance to Event #1, it is worthwhile to discuss just how impressive some of the spring precipitation has been across parts of eastern Colorado. The map below shows 30-day total precipitation as estimated by the NOAA Stage IV product, which takes into account both rainfall gauges and radar estimates. Widespread<\/span> parts of eastern Colorado have received over 5 inches of rainfall, with isolated<\/span> locations exceeding 8 inches and approaching 10 inches over this period. For reference, 10 inches of rainfall over eastern Colorado over a 30-day period equates to roughly a 1% chance of occurring (i.e. also sometimes referred to as a 1 in 100 year event). If the precipitation totals forecasted for Event #1 materialize, some of these locations could approach or even exceed 0.2% (1 in 500 year) or even possibly 0.1% (1 in 1000 year) chances of occurrence. Given that all of this rainfall has occurred, thus far, without significant flooding is certainly welcome news.<\/p>\n<\/a><\/p>\n<\/a><\/p>\n