Evolving numerical guidance now includes the possibility of heavy snow Thursday into Friday
Wednesday, April 15, 2015
As discussed in yesterday’s forecast blog, model guidance has since evolved and we now have the possibility of heavy snows tomorrow afternoon extending into Friday. The American GFS has finally joined the other models in forecasting a consolidated circulation center that is currently spinning to our west. Furthermore, all models are now forecasting a more northward track of the cutoff low across Colorado which greatly increases our chance for significant snow.
The cutoff low is forecast to move southward along the Colorado - Utah border before being nudged eastward by the kicker wave mentioned yesterday approaching the West Coast. Even though the flow aloft will turn easterly for our area, this normally dry scenario can sometimes produce impressive snowfall when a TROWAL (TROugh of Warm air ALoft) develops. A TROWAL develops when warm and moist air is lifted ahead of the storm and rotates counter-clockwise around the parent low. The lifting of this elevated unstable layer over the cooler air near at lower elevations can create impressive precipitation rates, and it appears we may benefit from that process.
I do not have a lot of confidence in this solution since a small change to the track of the storm will change the location of this TROWAL. But the possibility exists for moderate to heavy snows from tomorrow afternoon through Friday afternoon. We may still get the 2-6” originally forecast for the hill, or we may get as much as 10-20”. Furthermore, the valley will also see significant snowfall if the wetter solution verifies.
Lastly, for those headed west for mountain biking, the slower and farther north solution offered by this morning’s model guidance would have the Grand Junction and possibly Moab areas wet through Friday, with cool conditions lasting at least through the weekend.
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