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

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271 FXUS64 KMRX 161950 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 250 PM EST Mon Jan 16 2017 .SHORT TERM...
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(Tonight through Tuesday)... After a foggy start to the day, temperatures continue to warm. A break in the cloud cover across NE Tennessee and SW Virginia has allowed sunshine to aid temperatures in climbing into the upper 60s across that area. With thicker cloud cover south, it`s possible that TRI may be the warmest of the three climate sites today. Clouds will fill back in and lower tonight as a cold front approaches from the west. Patches of locally dense fog are possible again late tonight into early Tuesday, but winds increasing ahead of the cold front should help hinder widespread fog development tonight. By late morning, showers are possible across the northwestern portion of the forecast area as the cold front nears. Model solutions still vary a bit -- with some models indicating more moisture and showers ahead of the front than others. For now, have likely PoPs NW and chance PoPs SE for most of the daytime hours. Then, likely PoPs everywhere Tuesday evening into the overnight hours to coincide with the actual frontal passage. There does appear to be enough weak instability by midday Tuesday to support a few rumbles of thunder, mainly across western locations and have carried/added in a slight chance of thunder to account for this along and just before the frontal passage. PoPs will taper off from NW to SE late Tuesday night as the front exits the area. A 40-50kt 850mb jet will accompany the frontal passage. This will result in some gusty winds Tuesday afternoon, especially over higher terrain, but winds look like they should remain below advisory criteria. .LONG TERM...(Wednesday through Monday)... A cold front will be exiting the area Wednesday morning, and high pressure from the surface through the midlevels will be building in from the west through the day. Forecast soundings on Wed show a strong inversion trapping low level moisture in the Valley, so will lean high temperatures on the cool side of MOS guidance. Deep moisture builds back in rapidly on Thursday as the surface high/ridging aloft shift to the east of the mountains. PoPs increase through the day as a trough axis over TX becomes negatively tilted and the southerly 850 mb jet increases to 40+ kts. Favorable upper jet positioning for divergence and 850 mb theta-E values above 320K suggest a mention of t-storms is warranted Thursday night, at least for southern sections. Model agreement on timing of lift gives confidence to increase PoPs to categorical on Thursday night, lowering to chance PoPs Friday. An active and abnormally mild pattern continues through the weekend as the models show a deep closed low developing in the lee of the Rockies. The GFS and ECMWF are in surprisingly good agreement with the timing and positioning of this closed low, taking it to the Mid- MS Valley by 00Z Monday. Thus confidence is high enough to bring likely PoPs into the area for Sunday and Sunday night. The closed low slowly tracks NE across the Ohio Valley on Monday, so we will remain under its influence with scattered showers beneath the low through the day. The question for Monday will be whether temperatures will be cold enough for snow or rain showers. Given the recent warmth and the lack of a strong punch of cold air behind the closed and slow-moving upper low, will keep precip all rain to start Day 7.
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Chattanooga Airport, TN 56 69 54 60 / 30 60 70 20 Knoxville McGhee Tyson Airport, TN 55 67 52 57 / 40 70 70 30 Oak Ridge, TN 54 65 51 57 / 50 70 70 20 Tri Cities Airport, TN 48 66 49 55 / 50 70 70 30
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