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

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452 FXUS64 KMRX 231932 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 232 PM EST Mon Jan 23 2017 .DISCUSSION... Current water vapor imagery and RAP upper air analysis indicates a strong closed low centered across North Carolina. Drier air can be seen moving into the area from the west as a ridge moves in behind the departing closed low. Current radar imagery also indicates this drier air moving in with showers ending from southwest to northeast. However, elevated rain chances will continue across the higher elevations along the TN/NC line and in SW VA with good northwesterly flow behind the exiting system. Regardless, amounts should be light with up to an additional half an inch of rain possible across the high terrain this evening and tonight. Winds across the area are below advisory criteria but there have been a couple of reports of trees down from the gusty winds and saturated ground, therefore, will continue with the advisory as is. Temperatures this afternoon at Newfound Gap have been in the mid to upper 30s and expect there could be some snow mixing in for locations above 5 kft, this evening and overnight. For now, expect amounts of a dusting up to half an inch will be possible for these locations above 5 kft and no winter weather products are anticipated due to the low amounts and impacts. Drier air will move into the Southern Appalachians on Tuesday as a shortwave ridge builds across the region. The pattern throughout the forecast period will remain progressive and this ridge will be short-lived. Southerly to southwesterly flow will return to the area as the ridge axis passes to the east Tuesday night into Wednesday. An upper level trough will track across the Central Plains northeastward towards the Great Lakes during this timeframe. An associated cold front will move across the Mississippi River Valley into the Tennessee River Valley late Wednesday. Strong warm air and moisture advection ahead of the system will push highs on Wednesday up into the 60s areawide with PW values into the 0.8-1.0 inch range. These values are in the 90th percentile for late- January. The higher moisture values are in a narrow tongue ahead of the front late Wednesday and expect the precip. will hold off until then. In addition, not expecting any instability and have only mentioned showers in the forecast. The timing of the system between the models is pretty good so far with late Wednesday/early Thursday being the best chance for precipitation although amounts should generally be under a tenth of an inch. Colder air will advect in behind the system late in the week with temperatures return to near normal for late January. Both the GFS and ECMWF indicate a series of shortwaves troughs will traverse the Southern Appalachians late in the week and into early next week. The GFS soundings indicate enough low-level moisture for light precipitation during this timeframe. The ECMWF is not near as bullish with only some light precip. on Friday with no precip. over the weekend. With the colder air in place, there will be the chance for a few light snow shower/flurries during this timeframe but confidence is low at this time. Regardless, the moisture is limited late in the forecast period and any precipitation would be light. For now, have mentioned slight chance PoPs for much of the extended portion of the forecast. The GFS and ECMWF both indicate a more robust trough early next week that moves through the northwesterly flow aloft. The GFS indicates a bit more moisture with this system and the ECMWF keeps conditions dry. Again, have continued with low PoPs to account for the uncertainty. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 40 58 42 63 / 10 10 0 20 Knoxville McGhee Tyson Airport, TN 43 56 42 63 / 20 10 0 20 Oak Ridge, TN 43 56 41 62 / 10 10 0 20 Tri Cities Airport, TN 42 52 36 63 / 50 10 10 10 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...Wind Advisory until 11 AM EST Tuesday for Cherokee-Clay. TN...Wind Advisory until 7 PM EST /6 PM CST/ this evening for Anderson-Bledsoe-Bradley-Hamilton-Knox-Loudon-Marion-McMinn- Meigs-Morgan-NW Blount-North Sevier-Northwest Monroe-Rhea- Roane-Scott TN-Sequatchie-West Polk. Wind Advisory until 11 AM EST Tuesday for Blount Smoky Mountains- Cocke Smoky Mountains-East Polk-Sevier Smoky Mountains- Southeast Greene-Southeast Monroe. Wind Advisory from 7 PM this evening to 11 AM EST Tuesday for Johnson-Southeast Carter-Unicoi. VA...None. && $$ MA

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