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Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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149 FXUS64 KMRX 160103 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 903 PM EDT Mon Jul 15 2024 ...New UPDATE... .UPDATE... Issued at 900 PM EDT Mon Jul 15 2024 |Late afternoon and early evening storms have ended. Expect partly cloudy skies south and mostly clear north with patchy fog forming late. Temperatures this evening are in the mid 80s to around 90 and should cool slowly into the mid 60s northeast to mid 70s southwest which will not change for morning lows in the update. Change is to remove showers and storms except a few in eastern mountains another hour or so. Tuesdays weather looks similar to todays with isolated to widely scattered showers storms mid afternoon to early evening in southern areas. Updated forecast sent. && .SHORT TERM... (This evening through Tuesday) Issued at 306 PM EDT Mon Jul 15 2024 Key Messages: 1. Isolated convection again on Tuesday with main coverage across the south. 2. Continued hot temperatures with mostly dry conditions in the short term. Discussion: Mesoanalysis is showing some areas of around 2000 J/Kg MLCAPE this afternoon with isolated convection along the higher elevations, mainly across western higher elevations of the Cumberland Plateau and Clinch Mountains. Some gusty winds could be expected with the stronger storms, but severe weather is unlikely. Areas that do receive rain will have some patchy fog overnight into Tuesday morning - such as the Sequatchie Valley. The weak upper level trough/col will shift southeast on Tuesday with weak southwesterly flow across far southeast Tennessee and southwest North Carolina. Northwest flow and increased subsidence will limit convection across the northern zones of our forecast area with slight chance/chance PoPs across southern/southeastern counties. MLCAPE will be near 2000 J/Kg according to RAP forecast soundings with some dry air in the boundary layer keeping LFC heights relatively high and providing a risk of localized winds with the strongest pulse convection. Overall, the severe wind risk is very low. && .LONG TERM... (Tuesday night through next Monday) Issued at 306 PM EDT Mon Jul 15 2024 Key Messages: 1. Excessive heat is expected to die down with the passing of a front and falling of pressure heights throughout the atmosphere. 2. The frontal passage will bring widespread storms across the area Wednesday into Thursday. Higher than normal moisture may lead to scattered showers for the remainder of the period. Tuesday Night through Thursday Night The period begins with the continuance of a ridging pattern for our region, with a high pressure center located off the Atlantic Coast. The shortwave trough to our southwest has been cut off and seems to be drifting as a low pressure center further south throughout the period. Ridging is ended by a frontal passage and a return to a troughing pattern by Thursday. The timing of the frontal passage is uncertain, but it seems to move into the area by Thursday night. The ECMWF brings the front through our area quicker and a tad further south than the GFS. Surface temperatures are expected to exceed 90 degrees once again on Wednesday, with heat indices likely to exceed 100 degrees due to increased humidity. The frontal passage is proceeded by a stark rise in PWATs, with values around 1.9 inches. The majority of our region is under the WPC marginal risk for excessive rainfall due to the higher than average moisture. Wind profiles signal the potential for training convection which could lead to some higher rainfall amounts in areas. Overall, MLCAPE values will be near or below 1000 J/kg for much of the region, with the some localized higher values. Deep layer shear is unimpressive ahead of the front but rises with its passage, potentially leading to higher rainfall amounts on Thursday. With this event, the potential of flooding is in question, however we can expect the ongoing lack of precipitation to lower that potential. The main risk of these storms is going to be locally strong wind gusts. Friday through Monday We can expect the frontal boundary to linger over the area for the remainder of our period after its initial passing. The GFS and ECMWF signal a drop in pressure heights following the frontal passage, which could lead to a break from the excessive heat. While temperatures are likely to lower, PWATS remain unseasonably high, which will allow weak instability to persist. Precipitation is likely during this period and will be mostly diurnally driven and not unlike most summertime convection. The southeastern ridge strengthens towards the end of our period, however moisture remains quite high for the time of year. && .AVIATION... (00Z TAFS) Issued at 726 PM EDT Mon Jul 15 2024 VFR conditions should continue through the next 24 hours with light winds. TSTMS vicinity of CHA and TYS until sunset tonight or 01Z, then rapid dissipation of showers and storms with low chances Tuesday afternoon between 18Z and 00Z. Prob30 for TSTMS are in afternoon forecast from south to north at all 3 sites at that time. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 74 96 76 95 / 20 40 20 80 Knoxville McGhee Tyson Airport, TN 73 96 75 93 / 10 30 30 80 Oak Ridge, TN 72 95 74 93 / 10 20 30 80 Tri Cities Airport, TN 68 93 72 91 / 10 30 30 80 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...TD LONG TERM....BW AVIATION...TD