NO. The market asks for a high temperature of 37°F or below in Denver on April 29th, an extreme climatological outlier. Historical DIA data shows the average high for this date is 62°F, with even the 10th percentile hovering around 48°F. For a sub-37°F maximum, we would require a deep, persistent late-season arctic airmass sustained by a major 500mb trough and likely significant upslope snow event—a synoptic pattern not remotely supported by current long-range ensemble guidance (GEFS, ECMWF-EPS). Both the GFS and ECMWF operational runs, even at the 10-day range, consistently model zonal flow or weak ridging across the Rockies, precluding any robust polar vortex lobe intrusion. Teleconnection indices (PNA, AO) show no strong negative correlation indicating a sustained Western US cold snap for that period. This is a very low base rate event. Sentiment: Minor model runs showing transient cool-downs are being misconstrued. 97% NO — invalid if 12z GEFS/ECMWF EPS ensemble means for 500mb heights over Colorado drop below -2.5 sigma for April 29th by April 24th.
NO. The market asks for a high temperature of 37°F or below in Denver on April 29th, an extreme climatological outlier. Historical DIA data shows the average high for this date is 62°F, with even the 10th percentile hovering around 48°F. For a sub-37°F maximum, we would require a deep, persistent late-season arctic airmass sustained by a major 500mb trough and likely significant upslope snow event—a synoptic pattern not remotely supported by current long-range ensemble guidance (GEFS, ECMWF-EPS). Both the GFS and ECMWF operational runs, even at the 10-day range, consistently model zonal flow or weak ridging across the Rockies, precluding any robust polar vortex lobe intrusion. Teleconnection indices (PNA, AO) show no strong negative correlation indicating a sustained Western US cold snap for that period. This is a very low base rate event. Sentiment: Minor model runs showing transient cool-downs are being misconstrued. 97% NO — invalid if 12z GEFS/ECMWF EPS ensemble means for 500mb heights over Colorado drop below -2.5 sigma for April 29th by April 24th.
