Weather Headlines

*Strong to severe thunderstorm development will be possible Wednesday (June 5).

Shower and thunderstorm development, with a threat of heavy rain and locally damaging winds and hail, is being monitored for Wednesday.

The threat of heavy to locally excessive rainfall is also being monitored for late week into early next week during the June 7-11 period.

Previous Headlines And Discussion

A gusty wind shift to the north will bring much cooler air into the mountains late Sunday Night into early Monday AM, with temperatures at high elevations falling into middle to upper 40s versus mid-upper 50s at lower-middle elevations. Wind chills will drop into the 30s at highest elevations.

*Update – Minimums in the 30s to lower 40s were observed within colder mountain valleys into the morning hours of June 4 (as expected).

The Mountain Empire will be on the southern fringe of unseasonably cool air, with values 10-20+ degrees below average for early June, that will be centered over the upper Great Lakes and New England during Monday into Tuesday of June 3-4.

Temperatures on Monday will be autumn-like, especially in the high country, with max readings varying from 50s to lower 60s above 3000 feet in the High Knob Massif to the upper 60s to lower 70s at lower-middle elevations (warmer to the south in the Great Valley of eastern Tennessee).

This will set the stage for chilly temperatures into Tuesday AM, with only the potential for high clouds acting to prevent readings from reaching their full cooling potential. MIN temperatures in the 30s are expected in colder mountain valleys from the High Knob Massif northeast along the Appalachians into Pennsylvania and New York where such cold temperature will become more widespread in nature. MINS in the 40s to low 50s will be common across much of the area, outside of colder mountain valleys.

Microclimate links the atmosphere, biosphere, hydrosphere-cryosphere and lithosphere together (they collectively dictate it) with a few indicator species in the High Knob Massif being Betula alleghaniensis, Viburnum lantanoides, Trillium undulatum, Maianthemum canadense, Osmundastrum cinnamomeum, Catharus fuscescens, Catharus guttatus, Cardellena canadensis, Setophaga caerulescens and Setophaga magnolia to note a few.

Having cold temperatures, and even frost, in high valleys from the High Knob Massif to Burkes Garden northeast in selected locations, known as frost pockets, through the eastern West Virginia highlands into western Maryland is nothing atypical during summer.

Dewpoints around 875-850 MB are a key factor in locations where high terrain reaches upward into this elevation zone. July 17-August 14 is the only period not to feature a night to freezing or below in Burkes Garden, which has the longest data period of any station in southwestern Virginia.

Research at the University of Virginia’s College At Wise is showing that high valleys in the High Knob Massif tend to run colder than Burkes Garden on average, but any given night may be different and Burkes Garden may be colder depending upon the cloud cover, surface conditions related to decoupling and dewpoints at upper elevations between these two Appalachian frost pocket locations.

The current terrain model forecast heading into Monday Night-Tuesday AM will be favorable for decoupling of boundary layer winds with unseasonably dry, low dewpoint air within the 900-800 MB zone. The only negative factor could be high clouds at altitudes above 25,000 to 30,000 feet in the atmosphere.

A stormy pattern with a notable above average precipitation trend, especially along the front ranges of the mountains, will develop in wake of this cool spell. This argues against unseasonable June heat and instead for muggy conditions with a positive feedback developing between surface moisture, cloudiness, and general wetness.