Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
886 FXUS64 KMRX 301743 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 143 PM EDT Thu Jul 30 2026 ...New DISCUSSION, AVIATION... .KEY MESSAGES... Updated at 142 PM EDT Thu Jul 30 2026 - Dry weather with seasonably pleasant temps and humidity through Friday. - A low chance for a few strong Storms Saturday evening/night, with localized flooding possible. - A wet pattern sets up this weekend and continues through next week. && .DISCUSSION... Issued at 142 PM EDT Thu Jul 30 2026 High pressure centered over IL/IN today will settle over the central Appalachians tonight, with a ridge extending south across the Southern Appalachians. Clear, calm conditions tonight will favor fog development for mainly northern sections near bodies of water, much like we saw this morning. Mostly sunny skies and relatively comfortable temperatures/humidity for late July can be expected again tomorrow, though highs will be a couple degrees warmer than today under a building midlevel ridge. Deep moisture starts to increase Saturday morning as a low pressure system tracks into the lower OH Valley, with PW values rising over 2 inches through the day. An initial round of showers/storms will come in the morning with the passage of a shortwave trough, with convection likely to be elevated and sub-severe. A line of convection forms in the afternoon in West TN along the cold front, closer to the main upper trough axis and an upper jet streak. The NAM is quite vigorous in develping this convection as it crosses Middle TN, but by the time it reaches our area (around midnight), it will likely be in a much weaker state. Upper level forcing will be mostly to our north as the jet streak lifts into eastern KY/OH in the evening. While there is some weak deep layer shear present, the nighttime arrival will limit surface-based instability. Joint probability of MUCAPE > 500 J/kg and effective shear > 30 kt is under 20% in our western half Saturday evening. Thus, the severe risk appears low at this time. Flooding may be more of a concern if heavy rain occurs with the morning round, followed by additional heavy rain in the same areas during the evening/overnight round. Model event-total QPF amounts are not impressive (less than 1 inch in most locations), but localized heavy rain and flooding can`t be ruled out. A shortwave trough breaks off from the larger trough on Sunday and slowly tracks across the Deep South through Wednesday, keeping rain chances in the foreast. With the post-frontal surface air mass and persistent trough in the mid/upper levels, temperatures will be below normal for this period. && .AVIATION... (18Z TAFS) Issued at 142 PM EDT Thu Jul 30 2026 Fog at TRI is the main concern for this TAF period, with similar conditions to this morning as clear/calm conditions will be favorable for fog near rivers and lakes. This TAF issuance will follow what happened this morning and have a TEMPO for LIFR conditions between 10-13Z. Otherwise, VFR conditions are forecast. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 66 91 70 85 / 0 0 20 90 Knoxville McGhee Tyson Airport, TN 63 89 68 86 / 0 0 0 60 Oak Ridge, TN 63 88 68 84 / 0 0 0 70 Tri Cities Airport, TN 57 84 64 85 / 0 0 0 40 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ DISCUSSION...DGS AVIATION...DGS