WEATHER BRIEFING: Friday, December 29th, 2017

HIGHLIGHTS: A weekend reprieve, then back into the freezer next week.

After several days of cold temperatures, the first part of the weekend will serve as a slight break from the worst of the cold weather, as temperatures on Friday and Saturday will make it into the 40s and up near 50 degrees (on Saturday). Nighttime temperatures will still be chilly, falling into the 20s Friday and Saturday night. We will return to the arctic temperatures on Sunday, as it will be the first of at least six straight days where we will struggle to reach the freezing mark for high temperatures. The reason for this cold snap is a deepening trough that will be located over the eastern United States for the next 7-10 days. Not only will this trough provide frigid temperatures, it will also keep us dry for the foreseeable future. Specifically, the positioning of the trough is such that any organized disturbance that develops to our west will be forced southward into the Gulf of Mexico, or will be torn apart. While this is not good news for snow-lovers, it will at least help things feel slightly warmer during the daytime.

Take a look at these maps below as they try to explain some of the reasoning behind the upcoming week's weather.

 GFS Forecasted 500-hPa Geopotential Height and Height Anomalies for Sunday Morning. Notice how the trough in the east is relatively flat looking. This would suggest somewhat of a backing off of the extreme cold.

GFS Forecasted 500-hPa Geopotential Height and Height Anomalies for Sunday Morning. Notice how the trough in the east is relatively flat looking. This would suggest somewhat of a backing off of the extreme cold.

 GFS Forecasted 500-hPa Geopotential Height and Height Anomalies for Monday Morning. Notice how the trough in the east has amplified relative to Sunday Morning. This would suggest greater amounts of cold air intrusion into our area.

GFS Forecasted 500-hPa Geopotential Height and Height Anomalies for Monday Morning. Notice how the trough in the east has amplified relative to Sunday Morning. This would suggest greater amounts of cold air intrusion into our area.

 European Model (ECMWF) Forecasted 500-hPa Wind Speed and Direction with 500-hPa Geopotential Height (lines) for next Monday evening. Typically, storms will be steered by the direction of the flow at this and other upper levels. Notice how the flow is predominantly west-to-east, suppressing convection and keeping storms well to our south.

European Model (ECMWF) Forecasted 500-hPa Wind Speed and Direction with 500-hPa Geopotential Height (lines) for next Monday evening. Typically, storms will be steered by the direction of the flow at this and other upper levels. Notice how the flow is predominantly west-to-east, suppressing convection and keeping storms well to our south.

 Compare the previous image to this 500-hPa Geopotential Height map from December 8th. On this map, the flow over our area is southwest-to-northeast, which allows disturbances to track up into the Carolinas and tap into Gulf Moisture. This pattern setup led to the winter storm from earlier this month. This and other factors explains why moisture will be limited over the next 7-10 days.

Compare the previous image to this 500-hPa Geopotential Height map from December 8th. On this map, the flow over our area is southwest-to-northeast, which allows disturbances to track up into the Carolinas and tap into Gulf Moisture. This pattern setup led to the winter storm from earlier this month. This and other factors explains why moisture will be limited over the next 7-10 days.

Have a great weekend!

Chase Scott Graham