092320 Forecast

The 14th Annual High Knob Naturalist Rally will continue virtually through this week and next.

In the wake of general 1.50″ to 2.00″ rains over the high country there was an array of orographic and lenticular cloud formations.

Watch the right, sunset lit side of the slides during the darker images around sunset to best see stacked, lenticular mountain waves that are nearly stationary and extend across a much larger portion of the massif (opening slides show lingering, orographic cap clouds in wake of rains).

Remnant rains of Beta pushed the 12-month precipitation total at Big Cherry Dam to nearly 100.00″ (98.89″), which may be broken by the end of September.

Interactive Doppler Radar-Lightning Detection System

Previous Discussion

Rainfall late Thursday Night into early Friday is expected to become enhanced as tropical moisture interacts with the right-rear entrance region of a strong jet streak aloft.

Interactive 250 MB Jet Stream Streamline Field_USA

GFS Model_200 MB Height And Wind Streamline Forecast_11 PM on 24 Sept

The Big Chill Is Coming

*Looking ahead, to the end of September and early October, an early winter-like pattern will be taking shape with much below average temperatures looking increasingly likely across the eastern portion of the USA.

GFS Model Ensemble Mean_500 MB Height Anomaly_30 Sept 2020

While the GFS Ensemble pattern is impressive, the European Ensemble Mean is even colder and more impressive for the first few days of October. Air becomes so cold, in fact, that the first flakes of snow may fly along the Appalachians (especially at upper elevations) if the ECMWF ensembles are on target.

Certainly this would not be that unusual for the mountains, with accumulating snow common at upper elevations in the High Knob Massif during October (strong cold air intrusions being detrimental to autumn color along highest crestlines).

At the least, a pattern favorable for widespread frost and freezing temperatures will be developing into early October.