Area Forecast Discussion
Issued by NWS Knoxville/Tri Cities, TN
Issued by NWS Knoxville/Tri Cities, TN
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072 FXUS64 KMRX 240519 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 119 AM EDT Fri May 24 2024 ...New AVIATION... .UPDATE... Issued at 1006 PM EDT Thu May 23 2024 Active evening across the region due a strong upper jet moving across the Tennessee valley. Satellite and radar shows a MCV moving across east Kentucky. The upper forcing has produced widespread thunderstorms with a good deal of organization with the convection. Effective shear up to 35 knots and 0-1km shear near 15 knots were favorable to produce supercells especially over southeast Tennessee and southwest North Carolina. Reports of possible funnel clouds also reported as well as PingPong hail. Continued upper forcing continues to produce strong convection over southeast/central east Tennessee, generally south of interstate 40. This activity will move east out of the area soon after midnight. Latest HRRR shows widely scattered to scattered showers continuing through the early morning so will continue with low chance PoPs. Some fog development is possible. && .SHORT TERM... (This evening through Friday) Issued at 307 PM EDT Thu May 23 2024 Key Messages: 1. Strong to severe storms this evening with the main threats being wind gusts and hail, mainly affecting locations along and west of I- 75. 2. Another round of showers/storms is expected Friday afternoon, but mainly in southern sections as an upper level disturbance moves through that area. A few strong to marginally severe storms are possible. Discussion: Convection is starting to blossom in the Plateau and southern portions of the TN Valley. Over the next few hours, this activity will expand and intensify as clouds clear out and surface heating builds. Mesoanalysis shows the best instability to our west, so the storms that are developing in Middle TN will have the best chance of becoming severe, and with a an effective shear max located over the northern Plateau/eastern KY, that area will have the highest severe chance as those storms track NE. Damaging wind gusts and large hail will be the primary threats, and locations that have repeated storms may experience localized flooding. Most of this activity should weaken or exit the area by midnight. Overnight, a moist low level air mass will be in place that will favor fog and low cloud development. The models show that this will be slow to lift in the morning, but by noon we should have some good surface heating to aid in destabilization. In the midlevels, a weak shortwave trough/500 mb vort max will be crossing northern AL and GA in the late morning and early afternoon, which may bring showers to the southern sections as early as 10 AM. CAMS are not in good agreement with the development of convection tomorrow, so confidence is low. But it does appear that areas south of I-40 will have the best chance of showers/storms, and that a few of these could be strong to marginally severe, with wind/hail being the main threats. && .LONG TERM... (Friday night through next Thursday) Issued at 307 PM EDT Thu May 23 2024 Key Messages: 1. An unsettled period with multiple rounds of showers and thunderstorms for much of the period. 2. Some of the storms may be strong to severe at times, with the higher chances for severe storms looking like Sunday and/or Monday. Localized flooding will also be possible. 3. Drier and cooler air moving in toward the end of the period, but a few additional showers and/or storms still cannot be ruled out. Discussion: Unsettled weather pattern will continue, as 500 MB flow remains somewhat flat through the weekend, with a series of disturbances touching off rounds of convection. By Sunday, deepening of a trough near the Great Lakes will usher through a cold front accompanied by organized convection around Monday morning that has caused SPC to put us in a 15+% area in the severe weather outlook. However, as the present Watch attests, chances of severe weather will not be limited to Sunday night/Monday. Furthermore, repeated rounds of rainfall will increase proneness to localized flash flooding from today through Monday. Post frontal precip chances on Tues and Wed will likely be scattered in nature and not likely to be heavy. Models are diverging that far out now anyway, with the ECMWF maintaining something of a blocking pattern, while the GFS has backed off of that solution and instead wants to continue with more of a northwesterly flow across the nation that keeps us impacted by another shortwave or two. We will cheer for the ECMWF`s quieter solution, but will have to wait and see what pans out. && .AVIATION... (06Z TAFS) Issued at 109 AM EDT Fri May 24 2024 Fog development is off to a slow start with lingering high clouds. With ample ground moisture in place, some fog development is expected by morning mainly near TRI. Obs currently (01:12 AM EDT) show fog at a few spots. Shower activity has decreased significantly. Isolated shower activity will be possible overnight and possibly in the morning. Tomorrow afternoon through evening, showers and storms will be isolated to scattered. Confidence is low on timing but it seems like coverage will be spotty. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 83 67 88 69 / 40 40 40 20 Knoxville McGhee Tyson Airport, TN 79 64 85 65 / 50 50 40 30 Oak Ridge, TN 79 63 85 65 / 40 50 50 20 Tri Cities Airport, TN 79 61 81 62 / 40 40 50 20 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM...DH LONG TERM....GC AVIATION...McD