*ALERT For Gully Washing Hit Or Miss Showers And Torrential Downpours In Thunderstorms
Light winds aloft and abundant low-level moisture will continue to support torrential rain producing showers & thunderstorms through coming days. Heavy to excessive rainfall will remain possible with ponding of water and flooding of low-lying, poor-drainage areas, as well as creeks in locations receiving heaviest rain amounts.
Local rainfall amounts of 3.00″ to 4.00″+ where experienced in portions of Wise and extreme northern Scott & Lee counties during the July 30-31 period. Additional heavy rain over these locations would pose an enhanced risk of flash flooding. Please monitor NOAA weather radio and your favorite media sources for possible advisories and warnings which may be needed during coming days.
Mountain Area Weather Headlines
A super-wet summer in the high country of the High Knob Massif has generated more than 20.00″ of rainfall during the June 1 to July 31 period (during 66% of the summer season, or now past the half-way point of Meteorological Summer 2019).
Brilliant sun rays strike gushing whitewater tumbling out of Big Cherry Lake basin during morning hours of July 24. Vapor from the water was visibly rising back upward into the air, during a summer season in which the surface energy budget has been dominated by latent heat flux to an extent even more than typical of this wettest terrain in Virginia.
Wet Summer 2019_High Knob Massif
Big Cherry Lake Dam
(Elevation 3139 feet)
January
6.14″
February
12.50″
March
5.93″
April
6.64″
May
6.75″
June
10.68″
July
10.77″
*2019 Total: 59.41″ (M)
(January 1 to July 31 Period)
12-Month Total: 91.45″ (M)
(M): Some missing moisture in undercatch and frozen precipitation, with partial corrections applied for the 24.4 meter (80 feet) tall dam structure where rain gauges are located.
*Big Cherry Lake basin is the most productive water supply basin per unit area within the Old Dominion of Virginia. Anyone who does not believe this is free to find another basin with higher precipitation totals over a period of years to decades that contains a water supply producing lake watershed.
Looking Ahead To Beginning Of August
Near to well below normal 500 MB heights are being predicted during the first week of August as general upper air troughing occurs over the northeastern USA, downstream of a sprawling upper-level high pressure dome centered over the heartland.
This should generally support an increase in showers and thunderstorms, with near to below average air temps along the Cumberland-Allegheny Front where air will be rising in the mean on western component flow (SW-W-NW) during this time period.
While this pattern will generally support near to below average temperatures across the region, the greatest anomalies will tend to occur where air is also rising in the mean with more condensation, clouds and precipitation.
Although not quite as pertinent during the summer season, both the European and GFS model ensemble means signal this pattern with their teleconnections.
A notable -NAO (negative phase of the North Atlantic Oscillation) will be joined by a developing positive phase of the Pacific North American oscillation (+PNA) through the first week of August.
The Eastern Pacific Oscillation (EPO) is also now showing a negative phase developing during the first week of August 2019, adding more confidence to the forecast for eastern USA upper air troughing.
During winter these are cold teleconnection signals for eastern North America, while during summer they suggest near to below average temperatures which are more tolerable (of course).
Greenland Blocking, a persistent summer feature during 2019, will again be a prominent aspect of the Northern Hemisphere flow field into early August.
