579 FXUS64 KHUN 052324 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 624 PM CDT Wed Jul 5 2023 ...New AVIATION... .NEAR TERM... (Remainder of today and tonight) Issued at 322 PM CDT Wed Jul 5 2023 Based on latest radar data, the coverage of diurnal shower and thunderstorm activity has been a bit greater than originally anticipated (primarily across the southwestern corner of the CWFA), and we have made minor adjustments to POP grids for the rest of the afternoon to account for this. Present indications are that this convection will continue to spread east-southeastward in conjunction with the movement of a subtle 500-mb shortwave trough and should exit the CWFA prior to 0Z, posing only a risk for brief wind gusts of 40-50 MPH, small hail and lightning. This evening, we will be monitoring the progression of a broader region of convection (associated with another mid-level trough) that currently extends from eastern MO/western IL into southwestern AR. Although this activity may tend to diminish in both coverage and intensity with the onset of nocturnal cooling this evening, the initiating disturbance is predicted to approach the region in northwest flow aloft between 9-12Z, and if an outflow boundary can manage to make it into our region then we may experience redevelopment of showers and thunderstorms beginning late this evening. Due to a wide range of solutions offered by the CAMs, we have only included a low-medium chance POP (25-35%), with highest values in northwest AL. Otherwise, we expect partly cloudy and warm/humid conditions to persist, with lows in the u60s-m70s and some spotty development of light mist/haze beginning late this evening. && .SHORT TERM... (Thursday through Friday night) Issued at 322 PM CDT Wed Jul 5 2023 As we discussed this morning, it appears as if the region will remain along the northern edge of a broad subtropical ridge (and southern periphery of the stronger mid-latitude westerlies) through the short term period, with the coverage of convection likely tied to the passage of a couple of mid-level waves that will cross the region in the flow aloft. Based on latest model consensus, the first wave should be impacting the region tomorrow morning and may initiate development of thunderstorms shortly after sunrise (particularly across our eastern zones). Although this could potentially impact the coverage of convection tomorrow afternoon, we will maintain a fairly high POP (55-60%) due to the abundance of moisture within the lower troposphere and potential for mesoscale boundary interactions. Highs are currently predicted to be in the u80s-l90s, but this will be dependent on cloud cover and may need to be increased by a couple of degrees in future updates. Another, slightly more defined mid/upper-level wave will begin to shift eastward into the region late Thursday night-Friday morning, and could easily result in a coverage of showers and thunderstorms greater than what is presently indicated in the grids. However, there are some indications that a subtle intrusion of slightly drier and more stable air from the north may occur as a weak cold front settles into upper portions of the TN Valley, and we have only indicated POPs in the 40-45% range. Highs are once again predicted to reach the u80-l90s, with lows in the u60s-m70s. && .LONG TERM... (Saturday through Wednesday) Issued at 322 PM CDT Wed Jul 5 2023 The synoptic pattern will begin to change a bit early this weekend, as the region will become increasingly influenced by stronger flow aloft around the periphery of an upper low that will remain situated along the western shore of Hudson Bay from Saturday-Sunday. A well-defined vort max embedded within the circulation around the low is predicted to track southeastward from the Mid-MO Valley into the Lower-OH Valley on Saturday, before lifting northeastward into the central Appalachians Saturday night. This system will likely be accompanied by upscale growth of convective clusters to our northwest, which may reach the local area as an MCS late Saturday afternoon or evening. West- northwest flow aloft will strengthen to 25-35 knots upon the arrival of this system, and should result in a greater risk for severe wind and hail beginning late Saturday afternoon. Another pronounced disturbance aloft is predicted to shift southeastward into the Ozarks/Mid-South regions Sunday afternoon before turning eastward through the TN Valley early Monday morning. This system will also carry a high-likelihood of MCS development that could potentially impact our region from late Sunday afternoon-early Monday morning, and will also feature a risk for more widespread severe thunderstorm coverage. Extended range guidance suggests that deep-layer flow will veer to NW by late Monday afternoon, as the initiating disturbance begins to migrate slowly northeastward into the central Appalachians. This will allow for another brief intrusion of slightly drier continental air from the north on Tuesday/Wednesday, with lows falling back down into the m-u 60s and only a low (20-30%) chance of mainly afternoon showers and thunderstorms. && .AVIATION... (00Z TAFS) Issued at 624 PM CDT Wed Jul 5 2023 VFR conditions will continue at both terminals for now, with vicinity showers ongoing this evening at HSV. There is also a low chance (30%) of thunderstorms impacting the MSL terminal with recent activity in NW AL, leading to potential periods of MVFR conditions due to decreased visibilities overnight. Tomorrow, low to medium chances of thunderstorms (30-50%) are in the forecast, leading to decreased visibilities and periods of MVFR conditions at both terminals. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...70 SHORT TERM....70 LONG TERM....70 AVIATION...HC