A weak cool front traveled in before sunset and put down sprinkles around the Wyoming border and Ft. Collins Monday PM (Figure 1). Things stabilized after dark and a few drops hit Longmont. Now we return you to your regularly scheduled warm-up.
The longer range forecast:
We do have an interesting ‘bonus’ storm that may give Longmont some measurable rain come Thursday PM and Friday AM. We’ll cover this, now, instead of the weekend pattern change and unsettled turn to the weather expected then.
The next four images will be a quick study of the difference between the GFS (Global Forecast System – from our National Weather Service) model and the ECMWF (European Centre for Medium-Range Weather Forecasts) model.
Figure 2 is Friday morning at 500mb heights with a low center in NW Kansas. Figure 3 is the European model for the same time with the low closer to Longmont. I always cover the 500mb level for simplicity and consistency, but we have maps at lower levels (like the 850mb and 700mb) and higher (like the 300mb) heights. Storms are not always vertically stacked in the atmosphere, which can impact their speed and severity.
Figure 4 is the 700mb map (at and below ground level for the Rockies) with the Low just east of town late Thursday PM on the GFS. Figure 5 for the same time at 850mb (even lower – so extrapolated for levels below ground level) from the European model. The Low center is off on the Kansas boundary in the lower atmosphere.
The European is better positioned for mountain snows (and rain for us) – but both now give us some weather by Friday AM.
Figures 6, 7 and 8 are the Thursday PM, Friday early AM, and Friday AM surface maps showing the surface low, from the GFS, out east of us and stalling briefly in NW Kansas. Some nice wrap-around precipitation hits Longmont (even though there is a strip of down slope dry air that forms mid-storm, grrrr).
Figure 9 shows total water amounts by Friday morning around 1/2 inch for Longmont. This is a nice gift out of nowhere … as long as it doesn’t vanish back into model-nowhwere.