ALERT For High Water Levels Through Saturday Night Into Early Sunday
Big Stony Creek of High Knob Massif At 8 PM Saturday – February 17
Note that 22 hours of missing data occurred during the flood event, such that the peak was both higher and broader than shown by the hydrograph of the stream level above ( blue line ).
Creeks are near flood stage ( a little below or above ) and will remain at high levels through Saturday night into Sunday, especially where around 1.50″ or locally more of rain fell in the High Knob Massif – Black Mountain corridor during Saturday.
As of 8:00 PM Saturday the stage was only 0.2 feet ( two-tenths of a foot ) below flood stage on Big Stony Creek in northern Scott County. This marks the third time that the creek has reach around or above flood stage in February, and unfortunately it is not likely to be the last time.
A total of 2.24″ of rain has been reported by the automated gauge at Big Cherry Dam since I measured the NWS rain gauge on Feb 14. This has pushed February precipitation to at least 12.21″ ( the 2018 total to nearly 18.00″ and the winter tally to more than 21.00″ ).
Previous Alert
ALERT For Strong Rises On Streams During Saturday Afternoon-Evening And Possible Flooding
Moderate-heavy rainfall will develop and spread across the mountain area Saturday. Due to saturated conditions, and near record February precipitation amounts, strong rises on creeks are expected. Mud-rock slides & local power outages will also be possible.
Remain alert to NOAA weatehr radio and your favorite media sources for possible warnings that may be needed.
Overnight Into Saturday Morning
Low clouds. Areas of dense fog ( widespread at the upper elevations ) and drizzle into the overnight, with freezing fog-drizzle at highest elevations before temps begin rising by morning. Winds N-NE at 5-10 mph into the overnight, then shifting SSE to SW at 5-15 mph, with higher gusts, on mid-upper elevation mountain ridges. Temperatures in the 30s ( around 30 degrees at highest elevations before rising toward morning ). Wind chills in the 20s to low 30s.
Saturday Morning Through The Afternoon
Rain developing by the predawn-morning. Heavy at times into the afternoon. Areas of fog. Winds becoming variable at 5-15 mph, with higher gusts, along mid-upper elevation mountain ridges-plateaus. Temps in the 30s to lower 40s.
Saturday Night Into Sunday Morning
Rain during the evening ( heavy early ) tapering off to showers & drizzle into the overnight. Turning colder with freezing fog-drizzle at upper elevations. Winds NW to N at 5-15 mph, with higher gusts. Temperatures dropping into the middle 20s to middle 30s ( coldest highest elevations ). Wind chills in the 10s and 20s on higher mountain ridges.
Sunday Morning Through The Afternoon
Low clouds & fog giving way to partly sunny skies ( high clouds ). Warmer. Winds SE-S at 5-15 mph, with higher gusts. Temperatures in the 40s to low-mid 50s ( coolest upper elevations ).
Sunday Night Into Monday Morning
Increasing clouds with rain showers developing overnight into morning. Windy. SSE-S winds 10-20 mph, with higher gusts, along mountain ridges-exposed plateaus below 2700 feet. S-SW winds 15-25 mph with higher gusts on mountain ridges above 2700 feet. Temperatures varying from the low 40s to low 50s ( falling into 30s in sheltered valleys during the evening before rising ), tending to rise toward morning.
The currently forecast upper air pattern into next week continues to look most favorable for another high water event, with deep tropical moisture set to generate additional heavy to excessive rainfall. See my updated discussion below for more details.
Weather Discussion ( More R+ )
Sometimes the atmosphere gets stuck in a rut, and in this case it means more heavy rain for locations that need not nary another drop!
High Knob Massif Webcam – University Of Virginia’s College At Wise
Rainfall totals during Friday ranged up to around 0.80″ at Big Cherry Dam of the High Knob Massif, pushing the total for February up to around 11.00″ . Locally higher amounts have also occurred in the high country along the Wise-Scott border ( and the month has 12 more days to go ).
These excessive rain amounts have, of course, not been just restricted to the high country with more than 9.00″ having now occurred in February at the Big Stone Gap Water Plant and the Appalachia Lake Water Plant.
NAM 12 KM Model Total Precipitation Forecast
Forecast models are again converging upon this area once more for the heaviest rainfall amounts through Saturday.
NAM 3 KM Model Total Precipitation Forecast
Forecast amounts of 1.00″ to 2.00″ would not typically be a great concern, but during a month when MAX precipitation amounts are approaching a FOOT in headwater creek basins it has to be taken with respect. It is good that NWS Forecast Offices have come together to post a Flood Watch ahead of this system ( especially since locally heavier amounts will be possible due to orographics and the seeder-feeder process I highlighted in the previous discussion ).
Reference My 021418 Forecast to read about the Seeder-Feeder Precipitation Process and to see recent orographic feeder clouds.
GFS Model Total Precipitation Forecast
Once more, a signal that rainfall will again become heavy is a connection to the tropical Pacific Ocean as shown well by this GOES-16 Mid-Level Water Vapor Image:
Mid-level Water Vapor Image At 10:15 PM on February 16, 2018
This shows up well on the current ( as of Midnight Feb 17 ) streamline flow fields at 700 to 500 MB across the Earth:
The only good news is that the system will be progressive and moving along, with around a 12-hour window where rainfall will have the potential to be moderate-heavy in between chilly air ( currently felt and again to be felt by later Saturday Night into Sunday Morning ).
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
This pattern is truly stuck in a rut between blocking ridges of High pressure.
One blocking High off the southeastern USA coast is acting as a latent heat ( energy ) pump, with anomalous moisture and warmth streaming into the SE USA.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
The other blocking High, over the Gulf of Alaska and Aleutians, is threatening to keep a SW upper air flow locked across the United States through the extended forecast period ( with a Pacific moisture connection ).
I continue to be worried about this forecast setting, which will feature a heavy to excessive rain potential for locations from the Mississippi Valley into at least the western side of the Appalachians ( where flooding has already occurred, as you well know ).
