The Next Storm/Next Snow Forecast Discussion from the Cherrywood Observatory – March 12 , 2018

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Figure 1: Current surface map and radar map from Sunday afternoon from weatherunderground.com

Forecast Discussion:

Yesterday’s front has made it to the Four Corners area and a healthy amount of rain and snow has moved across Arizona and New Mexico (Figure 1). The water vapor satellite image (where moist air is grey/white and dry air is yellow to orange) shows a dry flow overhead in Longmont, and a clump of moisture to our southwest.  IF that blob drifts northeast, virga (rainfall that evaporates before reaching the ground) is the most likely weather type.

Figure 3 is the surface map for Tuesday morning -the stationary front is finally drifting eastward allowing warm air to hit for midweek and beyond. The ridge is overhead Wednesday morning. We’ll have southwest winds, down slope flow, and compression under the ridge.  All good reasons to see 70’s F this week. Figure 5 is the departure from normal surface temperatures for Wednesday PM – Longmont is in the 12F above normal category (again!).

Figure 1: Current surface map and radar map from Sunday afternoon from weatherunderground.com
Figure 2: The water vapor satellite image from Sunday afternoon and the weather channel.
Figure 3: The forecast surface map for the U.S. Tuesday morning from NCEP.
Figure 4: The 500mb upper air forecast map from the GFS for Wednesday AM.
Figure 5: the surface temperature departure from normal forecast map from tropicaltidbits.com. Longmont is the pink dot that is hard to see in the pink colors.

The longer range forecast:

The trough, and next significant storm, is expected to impact our area Monday-ish next week. An earlier system is visible in the forecast maps now. A system will move through the state on Saturday.  Like so many storms, the maximum precipitation to the west of Longmont will be underway Saturday morning. Down slope flow keeps us dry as a Plains low pressure system organizes. By Saturday midday – the Low is entering Kansas and the precipitation has hopped over us (with down slow flow keeping us dry and a bit warmer)  hitting the northeast Colorado Plains.  Can someone try to order a good rain or snow storm on Amazon Prime? We know it’ll be delivered quickly if that were possible.

Figure 6: the 6 hour precipitation rate and type map for Saturday morning 3/17. Longmont is the pink dot. From tropicaltidbits.com
Figure7: the 6 hour precipitation rate and type map for Saturday afternoon 3/17. Longmont is the pink dot. From tropicaltidbits.com
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John Ensworth works from Longmont as the Principle Investigator for the NASA Science Mission Directorate Earth and space science education product review through the IGES (The Institute for Global Environmental Strategies – www.strategies.org) . He is in his 14th year running this review. He is an astronomer (from the 2nd grade onward) and became a meteorologist (in the 5th grade) when a thunderstorm in Arizona rained on his telescope when the weather service had only forecasted a 10% chance of rain. He has college degrees in physics and astronomy and climatology and a graduate degree in meteorology and earth science. He lectures at the Little Thompson Observatory in Berthoud, the Estes Park Memorial Observatory in Estes Park, and for a number of online universities. He built and runs a backyard observatory near Pace and 17th in northeast Longmont where he has lived for 8 years with his wife, daughter, son, and two cats. Invitations to open house nights at this observatory, LTO, and EPMO will be posted with future discussions when they are scheduled. Forecasting severe weather and snow amounts via text lead to this column. He began texting friends about the weather right after the September 2013 flood. The readers of this column will, hopefully, keep him honest in what he ‘thought’ he had forecasted for ‘the most recent’ storm.

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