Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN

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951 FXUS64 KMRX 100823 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 323 AM EST Sat Dec 10 2016 .SHORT TERM (Today and Tonight)...
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The coldest morning of the season is currently ongoing with the cold and dry continental polar airmass in place. Most locations at 3 am are in the upper teens and lower 20s with widespread teens expected by daybreak. PW values currently range from around 0.1-0.2 inches, which are near the minimum values for mid-December. Clear skies, light winds, and surface high pressure centered overhead has lead to ideal radiational cooling conditions this morning. Temperatures will begin to moderate some today but will remain below average. The low-level ridge will shift to the east with light southeast to southerly flow returning by the end of the day. The upper level flow will remain mostly zonal but there will still be some upper level height increases across the region. In addition, sunny skies with plenty of insolation will help temperatures climb as well. Therefore, expect highs will be about 5-10 degrees warmer than yesterday with most locations topping out in the mid 30s to mid 40s. This trend will continue into the overnight hours as the cold air retreats to the north and the southerly flow and warm air advection become more established in the low-levels. Overnight lows will generally be in the 20s. PW values will begin to slowly increase tonight but will still remain well below normal for this time of the year with dry conditions continuing throughout the short-term forecast. .LONG TERM (Sunday through Friday)... Tranquil weather will be in place over the area on Sunday with zonal flow aloft and a surface high pressure shifting to our east. This will bring winds around to a southerly direction and allow for the beginnings of a warming trend. Then...scattered rain is expected to move in in advance of an approaching cold front with precip slowly spreading from west to east across the area Sunday night. The main band of rain will push through on Monday and with the warm...moisture southerly flow ahead of the front...expect this to be all rain. The main concern with the frontal passage will be the strong 850mb jet associated with the feature. Should see windy conditions develop over higher elevations late Sunday night into Monday and an advisory or warning may be needed. Scattered rain will linger over the area Monday night as the system exits the area. Models diverge during the rest of the extended. The ECMWF continues to want to bring an area of low pressure up from the south on Tuesday while the GFS keeps this feature to our south and east. Both models are trending toward a weakening...diffuse boundary moving through around Wednesday. So...overall...will keep 20 to 30 pops in place for this period. Thursday...we seem to be between systems...will keep a few lingering pops over the east TN mountains but most of the area should be dry. Another system should come in around the Friday time frame. With cooler air once again moving in behind the last front...could see a mix of rain and snow with this end of the week system.
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Chattanooga Airport, TN 45 28 51 44 / 0 0 10 60 Knoxville McGhee Tyson Airport, TN 39 25 49 42 / 0 0 10 60 Oak Ridge, TN 41 25 49 42 / 0 0 10 60 Tri Cities Airport, TN 38 23 47 39 / 0 0 10 60
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