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Forecast Discussion:
The forecast discussion from earlier Saturday (the 10/28 discussion) shows that we are only expecting a trace to maybe an inch of snow in places along I-25 Monday with maybe another dusting Tuesday AM. The 500mb map from Saturday night shows the northerly flow over Colorado due to the big ridge out west (blue line) and deep trough out east (red line).
Figure 2 is the 10 day forecast graph. The orange line is the approximate time that the nice weather comes to an end and the northeast winds begin to blow. This occurs close to 7pm on Sunday with temperatures steadily dropping through to Tuesday morning. With shallow moisture, there is a chance that we won't see snow overnight Sunday into Monday, but - as the NWS points out - we might have freezing drizzle along I-25. The precipitation type will be marginal but hopefully more snow later on Monday morning (Figure 3). Snow is easier to handle in a car than a glaze of ice.
The overall pattern by Monday night (Figure 4) has a big ridge out west and big trough out east of us (in the Great Lakes) but there is a complex set of small short-wave troughs and ridges that will move over Longmont and Colorado throughout Monday and Tuesday mornings.
In the longer range forecast:
Figure 5 shows that the jet stream is somewhat further south that it has been, so temperatures don't approach record highs this week. We do have a ridge in the flow over Colorado Friday night explaining the nice highs of ~65F and lows above freezing later in the week.
Figure 2 does hint at a brief window of clear skies during the trick-or-treat hours where my telescope will be useful showing the Moon and some deep sky objects on Halloween night at the corner of Cherrywood Dr. and Cherrywood Way in NE Longmont. Come on by and say hi to Buzz Lightyear.
