It has been a wonderful week in our area, but significant changes are expected for the weekend. Good evening, everyone. My name is Chris White, and I am the Chief Meteorologist at Foothills Action Network. I hope you and your loved ones are healthy and doing well despite the sickness that seems to be going around. Here’s some good news that might make you feel better: we have already passed the date of the earliest sunset. Depending on your location in the foothills, the earliest sunset occurred around 5:13 pm. Although the days are still getting shorter overall, the sunsets gradually occur later each day. Meanwhile, the sunrises are still happening later and later. The sun rises around 7:30 am, but by January 1st, the latest sunrise will occur at approximately 7:37 am. Alright then, let’s continue with the weather forecast information you came to read.
High pressure will move out of our area tonight and on Friday. On Saturday, low pressure will develop over the eastern Gulf of Mexico and move toward our area, causing high winds and heavy rainfall on Sunday and possibly Monday. This weather event is expected to have a significant impact. However, things will settle down as dry high-pressure returns to our region next week.
It will be calm tonight and Friday, with clear skies over the area. Due to excellent radiational cooling, temperatures will drop back into the upper 20s across most places except for the mountains. By Friday morning, the mountain regions will experience lows in the low to mid-20s. On Friday, the temperature will rise to the mid-50s, and it will be another beautiful day with plenty of sunshine.
On Saturday, all eyes will be on the Gulf of Mexico as energy from the southern jet stream moves from the plains toward the East Coast. At the same time, an upper-level trough from the northern jet will move south. These two pieces of energy coming together will result in cyclogenesis over the eastern Gulf of Mexico on Friday night or early Saturday morning. The low-pressure system is expected to rapidly deepen and move towards the northeast. The pressure levels with this system are likely to be comparable, if not deeper, than the 1993 blizzard. We do not have any cold air to work with, so it will be all rain outside of the mountains.
This afternoon, models indicated that the low-pressure system will move directly up the coastline, keeping the worst weather to the south and east. This scenario makes the most sense as the low should follow the boundary projected to be off the coast by Sunday morning. However, we will continue to monitor trends over the next day and adjust our forecast if necessary. Although we have a good handle on this forecast, we need to work out the timing, as guidance is 6-12 hours apart for the onset.
We are expecting a dry Saturday with high clouds gradually increasing. High temperatures should climb into the low to mid-50s Saturday Afternoon. Precipitation is not expected until later in the night, starting on the eastern-facing slopes first and then spreading east from there as we work into Sunday Morning. Precipitation develops due to the counterclockwise flow around the deepening low, pulling moisture in from the Atlantic. Southeasterly flow at 850mb (4000-6000ft) will be weak through Saturday Night, so precipitation should remain light through dawn Sunday.
On Sunday, the wind will pick up speed and change direction, blowing from the east-southeast at heights of 850mb. Moisture from the Atlantic and Gulf will get forced up and over the topography, creating heavy rainfall rates across the foothills in the afternoon and evening. These rates could reach 1.5 – 2.25 inches per hour, posing a risk of flash flooding. The severity of this risk will depend on the speed of the low-pressure system and where the convection develops. If the system tracks further south and east, the convection could remain east of the foothills, reducing the risk of severe weather in the area. However, it will be pretty windy on Sunday afternoon through Monday, regardless of the convection. Wind speeds will increase to 10 – 15 mph from the southeast on Sunday morning to 30 – 40 mph later in the day, with a few gusts possibly exceeding 50 mph. These wind speeds, coupled with the heavy rain, could cause damage to trees and power lines that may last into Monday. The low-pressure system will continue to deepen as it moves north, causing long, sustained high winds across the region. Temperatures on Sunday will depend on the track of the low pressure, but we are currently forecasting low to mid-50s across the area in the afternoon. Rainfall totals on Sunday may be between three-quarters and two-and-a-quarter inches (0.75 – 2.25), and we will provide more accurate estimates as the event approaches.
By Monday morning, the low-pressure system will begin to lift northeast, and our flow at the surface will become northwesterly. Northwesterly winds could create a dynamic period of northwest flow snow for the mountains from predawn Monday through Monday evening. The snow wouldn’t make it out of the mountains, though, and skies east of there will begin to clear.
Above: Left Euro low pressure center 10am Sunday / Right GFS low pressure center 10am Sunday
Above: Left Euro peak wind gusts through Monday / Right GFS peak wind gusts through Monday
Above: Rainfall projections through Monday
On Tuesday, high pressure will gradually build into the region. However, we will need to monitor the middle portion of next week for the potential of more unsettled weather, as an upper-level cut-off low is showing up on the long-term forecast. We are forecasting a dry period during this time, but this may change depending on how the trend develops through the weekend.
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