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<\/a><\/p>\nFor almost all Flood Threat Outlooks, it is usually necessary to look far westward across the Pacific Ocean to get a heads up on Colorado’s precipitation chances over the coming weeks. Interestingly, this is not the case during this 15-day Outlook. As can be seen in the water vapor image, below, the domain includes only a bit of the eastern Pacific. After the passage of a weak disturbance, identified as Event #1 that will bring light to moderate precipitation mainly for eastern areas, the atmospheric pattern becomes remarkably persistent. This is due to the development and migration of a blocking ridge to become situated along the Montana\/Saskatchewan border.<\/p>\n
As can be seen in the long-range 500-mb height anomaly forecast, below, once this ridge sets up across southern Canada by later this week, it will move little over the next 7 or so days. In fact, there is a high degree of consistency across ensemble guidance (both GFS and ECMWF) that this will occur. With such a ridge position, significantly above average temperatures can be expected immediately under the anomalous ridge. However, Colorado will lie on its southern periphery meaning the temperature signal is weaker (although generally above average temperatures are expected throughout this entire Outlook period). The more notable impact of this ridge position is that it is far enough north to allow for the advection<\/span> of relatively moist easterly flow into southern Colorado, including west of the Continental Divide<\/span>. This will certainly be welcome news for western slope residents who have been in a notable dry streak throughout most of June. This pattern resembles that of the desert southwest monsoon<\/span>; but without distinct moisture surges, we avoid calling it as such for the time being.<\/p>\n Looking at the ensemble Precipitable Water<\/span> forecast plumes, below, note the persistent increase in moisture at Grand Junction. By July 7th<\/sup>, the PW<\/span> is forecasted to finally get above average across western Colorado, for the first time in weeks. That is the good news. The bad news is that while PW<\/span> is a good predictor of precipitation chances<\/em>, it is a rather poor predictor of precipitation amount. Thus, we have stayed conservative for this Outlook and have not posted an elevated flood threat for western Colorado yet, because at this time rainfall rates are expected to stay below flood intensity levels. However, given the persistence of the pattern, this may certainly change as the finer details become clearer during the next 3-5 days.<\/p>\n<\/a><\/p>\n<\/a><\/p>\n