This content was originally published by the Longmont Observer and is licensed under a Creative Commons license.
Forecast Discussion:
In a stunning turn of events... the Monday snow storm (and extreme cold event) is BACK!
Before that, we need to look at the wind and heat (and there is a distinct fire danger for later today). Figure 1 gives you an overlook at the next 10 days. We are back to the mid-60's locally for today. We have a ridge overhead (blue line in Figure 2) and stiff down slope winds along the Front Range (Figure 3). This will result in temperatures on the eastern Plains of Colorado some 12-14 degrees F above normal. Get your yard work done!
The longer range forecast:
Then a cold front moves in Sunday night around 10pm or so. Shallow, but very cold air, will move in and low clouds, freezing fog and freezing drizzle are possible Monday morning (visible as a low chance of precipitation and temperatures plummeting below freezing into early morning Monday). Figure 1 shows the temperatures dropping all day Monday and morning snow chances become a good chance of snow after noon as the jet stream moves into place.
Figure 5 shows how the upper air pattern changes from Figure 2 by Monday night. A DEEP trough will power our storm, the jet stream, and bring in extremely cold air. Figure 6 graphically shows this amazing cold air by Tuesday PM. Temperatures are now around 16 to 20 degrees F below normal.
The jet stream will create banded snow events for places. IF Longmont ends up under a band (as is shown on THIS run of the GFS in Figure 7 as thin green lines) then we get 5-6 inches of snow. IF we end up between bands, like areas north of Fort Collins or south of Denver, we only get 1-3" of snow.
Figure 8 is the NAM version, and there is banded snow here too, but we are in the 2-3 inch area on this run. This will change as the next couple of days go by - and where the bands actually set up may not be clear until the storm starts producing heavier snows midday Monday. Nonetheless, back to Figure 1, snow chances drop by early Tuesday morning, but some flurries may keep falling into Tuesday night, highs get almost stuck in the single digits and lows below zero are likely. Bundle up and tune in tomorrow for more!
