ALERT For Widespread Freezing Conditions Developing Saturday Night Into Sunday AM With Unseasonably Cold Wind Chill Factors On Exposed Middle-Upper Elevation Mountain Ridges
*A Freeze Will Also Be Possible In Mountain Valleys That Have Calm Winds During Sunday Night-Monday AM As Strong SW Winds Develop Across Mid-Upper Elevation Ridges ( Caution Advised For Strong SW Winds At High Elevations, Mainly Above 3000 feet Into Monday AM ).
Overnight Into Saturday Morning
Mostly cloudy. A chance for sprinkles, with a period of light rain & showers to the southeast toward the TN-NC border. Turning colder. Winds W-WNW at 5-15 mph, with higher gusts, on middle-upper elevation mountain ridges-plateaus. Temps dropping into lower 30s at the High Knob Massif summit level by morning, with 40s at middle-lower elevations below 2700 feet.
Partly sunny. A period of mostly cloudy skies possible. Windy. Winds WSW-W at 10-25 mph, with higher gusts. Chilly with temperatures varying from upper 30s to low 40s at highest elevations in the High Knob Massif to the lower-middle 50s ( milder south toward the Tri-Cities and locally in downslope locations of the Russell-Levisa Fork basins ). Wind chills in the 20s to lower 30s along upper elevation mountain ridges.
*A period of enhanced winds along and behind a cold front will occur Saturday afternoon into Saturday evening. Gusts of 30-50 mph will be possible during this time. Caution Is Advised.
Saturday Night Into Sunday Morning
A period of clouds with a chance for a valley sprinkle or light rain shower and upper elevation flurry or light snow shower. Turning colder with skies becoming partly cloudy to mostly clear by morning. Winds becoming NW at 10-20 mph, with higher gusts. Temperatures dropping into the upper 10s to low 20s at highest elevations to the middle-upper 20s to around 30 degrees. Wind chills in the single digits & 10s along upper elevation mountain ridges. Wind chills in the upper 10s & 20s on middle elevation ridges.
Sunny & cold for the season. Winds becoming SW at 5-15 mph, with higher gusts. Temperatures varying from the upper 30s-lower 40s at upper elevations in the High Knob Massif to the upper 40s to middle 50s. Unseasonably cold wind chills in the 20s to lower 30s at highest elevations.
*Updated At 12:15 AM Monday
Sunday Night Into Monday Morning
Mostly clear. A large vertical temperature difference developing between mountain valleys with calm winds and middle-upper elevation mountain ridges with strong winds. SSW-WSW winds 15-25 mph, with higher gusts, developing into the overnight-morning on mid-upper elevation ridges, especially at elevations above 2500-2700 feet.
Temperatures varying from 20s to lower 30s in colder valleys to readings in the 40s, or rising into the 40s, along middle-upper elevation mountain ridges-plateaus.
The strongest SW winds are expected to be mainly above 2500 to 2700 feet overnight into Monday morning, with 30-40+ mph gusts being possible along mountain ridges. Wind speeds will increase with mixing at middle-lower elevations, below 2700 feet, into the day ahead of and along an approaching cold front.
*Another widespread, hard freeze is expected into Tuesday Morning amid another period with very cold wind chills for this time of year ( especially at middle to upper elevations ).
A major, winter-like blast of cold air with a snowfall potential is looking likely by late this week into next weekend. Stay tuned for details.
Weather Discussion – Colder Pattern
Although most hate to hear it, a winter-like jet stream pattern is taking shape across North America with renewal of western USA ridging-eastern USA troughing in the upper air flow regime.
While up-down temperature variations will continue, it is clear that the pattern heading through next week and well into April is looking to be colder than average with even a few chances for snow in the mountains ( an anomalous for this time of year pattern that, as past climatology shows, may eventually generate some significant snowfall – at higher elevations, especially, of course ).
This was the pattern that I expected for March; however, that got side-tracked by a number of factors including development of an anomalous sub-tropical cut-off low and blocking Atlantic ridge as well as continued pulses of wave activity over the Arctic following an anomalously strong Sudden Stratospheric Warming event.
A record dry to one of the driest March’s ( depending upon the location ) on record got the pollen season off to an early start and has early spring flowering species running some 1-3 weeks ahead of schedule. Repeated bouts of significant cold upcoming will, no doubt, be detrimental to some of these early blooming species.
Many native ephemeral wildflower species, like this lovely Rue-anemone above, will not be hurt and are use to cold as well as being covered up by spring falls of snow.
The pattern shown at the start of April, with ridging over both coasts of the USA ( above ) and cold air in the middle diving south and southeast ( below ) is forecast to become more intense with expansive troughing across the eastern USA during the next 10 days or more.
This is shown well by the 51-Member European Ensemble group where the MEAN 500 MB Height Anomalies become stronger and more intense from Days 1-5 into Days 6-10.
This is very impressive, especially for a 51-Member MEAN, with troughing below making any winter period proud. At this time of year the cold air will be late season, modified, but still very significant ( especially with respect to early spring warmth observed by day during March ).
A rough idea of how cold it will get, in the MEAN, is given by looking at the 51-Member Ensemble group’s 850 MB temps and their departures from normal ( in colors ).
During the next 10 days the 32 degree ( 0 degree Celsius ) line at 850 MB hovers over, or near, southwestern Virginia with mean temperature departures being 10 degrees ( F ) or more below average ( in the MEAN ).
In reality, some members of the 51-Ensemble group are much colder and some warmer than others, with the above being the MEAN of all averaged together during each 5-day period. Thus, one has to also figure that with intervals of warm air advection some of the cold spells will be well below the mean of departures shown.
The Bottom Line – An early start to spring in March is going to be stopped during the next 1-2 weeks as mean temperatures turn much below average.
While up-down temperature variations, both day-to-night and between days, are expected to continue the forecast pattern features colder than average temps and the potential for certain cold surges to be very significant ( with even some snow in the mountains ).
Stay tuned for updates as daily weather variations are worked out as time passes.