There Is Now Increasing Concern About A Developing Upper Air Flow Pattern Which Could Generate Heavy-Excessive Rainfall From Late December Into The First Week Of January 2019. ALERTS May Be Needed.
Former Alerts – None Currently Active
ALERT For The Possibility Of Slick Patches Developing On Roadways Late Sunday Into Sunday Night And The Morning Of Christmas Eve Day ( Beginning At Highest Elevations And Dropping Into The Overnight )
Rain & snow showers will develop across the area this afternoon and continue into tonight with falling temperatures. Slow down and travel safely.
ALERT For Areas Of Dense Fog – Widespread At The Upper Elevations Sunday PM Into Monday Morning
Christmas Holiday Forecast ( Dec 23-26 )
Sunday Afternoon
Cloudy with rain showers developing. Rain mixing with & quickly changing to snow at elevations above 3300 feet. Rain mixing with or changing to snow at middle to lower elevations after sunset. Winds SSE-SSW shifting WNW at 5-15 mph, with higher gusts, below 2700 ft. Winds SSW becoming WNW at 10-20 mph and gusty at elevations above 2700-3000 feet. Temperatures in the 30s to lower 40s, dropping to around 30 degrees at high elevations by late. Wind chills in the 20s & 30s, except 10s at upper elevations in gusts. Areas of fog ( widespread at the upper elevations ).
Snowfall Forecast ( Sunday PM-Monday AM )
Generally a dusting up to 1″
Locally 1″ to 2″ above 3300-3500 feet
Sunday Night Into Monday Morning
Any mix changing to snow showers & flurries. WNW winds 5-15 mph, with higher gusts, below 2700 feet. Winds WNW-NW 10-20 mph and gusty above 3000 ft. Temperatures varying from mid-upper 10s to the mid to upper 20s by morning. Wind chills in single digits and 10s on mid-upper elevation mountain ridges, except below zero in gusts on highest peaks. Fog widespread at upper elevations with riming.
Monday Morning Through The Afternoon
Morning clouds and any flurries giving way to mostly sunny skies. Seasonably cold. Winds WSW-WNW at 5-15 mph with higher gusts. Temperatures varying from 20s at upper elevations to the mid-upper 30s. Wind chills in the 10s and 20s.
Christmas Eve Into Christmas Morning
Mostly clear early then increasing mid-high level clouds. Cold. Light & variable winds. Temperatures varying from 10s to low 20s mountain valleys to the 20s, steady or rising late to near 30 degrees on well exposed mountain ridges-plateaus.
Christmas Morning Through The Afternoon
Partly to mostly cloudy. Slight chance of a sprinkle, flurry, or mixture. Winds SSW-SW at 5-10 mph with some higher gusts ( windiest on mountain ridges ). Temperatures varying from around freezing at the highest elevations to the low 40s. Milder south into river valleys of the Clinch, Powell, Holston.
Christmas Night Into Wednesday Morning
Partly to mostly clear. Cold. Light & variable winds. Temperatures varying from 10s in colder mountain valleys to the 20s ( around 30 degrees on exposed mountain ridges ).
*A wet extended range pattern is being watched which could bring an important flood threat to the mountain region from the end of December into the first week of January 2019 ( ahead of much colder air ).
Stay tuned for updates.
Weather Discussion ( Active Pattern )
This active weather pattern will not even take a break for the Holidays, with an array of systems lined up to impact the mountain region between Christmas Day and New Year’s Day.
Full Christmas Moon On Evening of December 22, 2018
A couple of minor systems, Sunday into early Monday and again later on Christmas Day, will occur as temps rise and fall with these passing waves. Any sticking snow is expected to be light and mostly at the upper elevations ( where significant snow is covering the ground and a White Christmas is now certain* ).
*Mainly at elevations above 2800 feet.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 1-5
A temporarily milder pattern is coming between Christmas and New Year Day, with December 27-30 currently being the period to monitor for significant rainfall. Given snow melt at upper elevations, plus antecedent conditions, this will likely cause more strong water level rises and possible flooding.
European 51-Member Ensemble Mean 500 MB Height Anomalies: Days 6-10
Another system will be developing within a upper air flow regime conducive to heavy-excessive rainfall in the 5-10 day forecast period, from late December into the first week of January 2019.
Stay tuned for later updates on these systems.
Reference Look Ahead on my 122018 Forecast page to see how near-term warming may change around in a big way heading into January and February.
