***ALERT For Heavy Rainfall Development Overnight Into Monday With Potential For Water Problems
A strong SW low-level jet will enhance orographic forcing overnight into Monday in advance of an approaching storm system. Heavy to locally excessive rainfall will be possible, especially within the most favored lifting zones centered upon the High Knob Massif & Black Mountains-Tennessee Valley Divide. Those living and driving along streams and within typically flood prone & poor drainage areas should remain alert for the potential of rapid water level rises.
Former Alerts
The Storm Prediction Center Has Issued A Marginal Risk Of Severe Thunderstorm Development During Friday Afternoon-Evening
Friday Afternoon
Showers & downpours in thunderstorms developing. Some storms could be strong to locally severe. SSW-WSW Winds 10-20 mph, with higher gusts, along mid-upper elevation mountain ridges-plateaus. Temperatures varying from 60s in upper elevations to the mid-upper 70s ( warmer south into the Great Valley ).
Friday Night Into Saturday Morning
A chance of hit-miss evening showers-thunderstorms then becoming partly to mostly clear overnight. Areas of fog. Winds shifting NW-N at 5-15 mph. Turning cooler. Temps varying from the mid-upper 40s to the upper 50s ( coolest within upper elevations ).
Saturday Afternoon
Partly to mostly sunny. Blue skies. Pleasant. Light NW-N winds. Temperatures varying from 60s in upper elevations to the low-middle 70s.
Saturday Night Into Sunday Morning
Clear evening skies, then increasing high clouds overnight into morning. Light winds, then becoming SE-S along high mountain ridges and increasing toward morning. Large vertical temperature spread between colder valleys and milder ridges. Temperatures varying from 40s in colder mountain valleys to the upper 50s to lower 60s ridges.
Sunday Afternoon
Partly-mostly cloudy. More humid. Chance of a localized shower or thunderstorm. Light winds, except breezy-gusty on high mountain ridges from the SSW-SW by late. Temps varying from upper 60s to lower 70s in upper elevations to the upper 70s to lower 80s.
Sunday Night Into Monday Morning
Cloudy. Becoming windy across the higher elevations. Showers & downpours in thunderstorms developing. Heavy rainfall totals possible. SSE to SSW winds increasing to 10-20 mph, with higher gusts, along mountain ridges-plateaus below 2700 feet. Winds SSW-WSW 15-25 mph, with higher gusts, on mountain ridges above 2700 feet. Temperatures varying from the upper 50s to mid-upper 60s. Dense fog developing across upper elevations.
Monday Morning Into The Afternoon
Showers & downpours in thunderstorms. Heavy rainfall totals possible. SW winds 10-20 mph, with higher gusts, across mountain ridges-plateaus. Temperatures in the 60s to lower-mid 70s ( coolest at highest elevations ). Dense fog across upper elevations.
A wet and occasionally stormy pattern is expected this week with below average temperatures for August. More heavy rainfall may become possible by later in the week. Stay tuned for updates.
Weather Discussion ( Changeable )
A beautiful weekend featuring chilly night-time temps, with 43 to 49 degrees in cooler mountain valleys, will now give way to a return of deep moisture driven by a low-level jet of strong SW winds overnight into Monday ( Aug 7 ).
NAM 12 KM Model Total Rainfall Forecast Next 60-Hours ( Sunday AM Run )
Although models vary from run to run on precise amounts for any given location, the general trend is clear when also including the European Ensemble Group ( 51-Members ) that a heavy rainfall setting is emerging for the mountain area.
NAM 12 KM Model Total Rainfall Forecast Next 60-Hours ( Sunday PM Run )
Past climatology of many such events, featuring a SW low-level jet, favors heaviest rain amounts being focused upon the High Knob Massif-Landform & Tennessee Valley Divide corridor, and locations along and generally west of the Tennessee-North Carolina border.
Stay tuned to NOAA Weather Radio and your favorite media sources for possible watches and/or warnings that may be needed through Monday.
Previous Discussion
Another cold front with showers and downpours in thunderstorms during Friday will give way to another pleasant weekend in the mountains.
High Knob Massif Webcam – University Of Virginia College At Wise
A general wet pattern is looking to develop next week into mid-August, but exact amounts for any location remain in question and must be updated in coming days.
GFS Model 2 AM Run Friday – Forecast Rainfall Next 10 Days
While the numbers will vary for any given place, the mean of ensembles, such as the favored European Model group, is suggesting that a wet pattern will rule the landscape.
GFS Model 8 AM Run Friday – Forecast Rainfall Next 10 Days
The other main theme will be a continuation of below average temperatures across much of the continental USA, outside of the Pacific Northwest, for late summer.
European Ensemble MEAN 850 MB Temp Anomalies: Days 1-5
Near to above average temperatures are also expected across Florida, but nothing like the heat ( relative ) at higher latitudes across North America.
European Ensemble MEAN 850 MB Temp Anomalies: Days 6-10
It has been a relatively cool summer in the high country of the High Knob Massif, as illustrated by High Knob Lake.
High Knob Lake of High Knob Massif – August 1, 2017
High Knob Lake June-July 2017 Temperatures Average Daily MAX: 71.2 degrees Average Daily MIN: 55.6 degrees June-July MEAN: 63.4 degrees Highest Temperature: 80 degrees Lowest Temperature: 44 degrees
Even cooler temperatures, especially at night, have been recorded within the Big Cherry Lake Basin where average nightly low temperatures have been as chilly as 51 degrees for the combined June-July period ( the lowest summer MIN reaching 38 degrees on June 28 ).
The coolest day-time temperatures have occurred at highest elevations, with 68.4 degrees being recorded on Eagle Knob for the average June-July maximum ( highest summer temp reaching 77 degrees on July 22 ).
