Area Forecast Discussion
Issued by NWS Huntsville, AL
Issued by NWS Huntsville, AL
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588 FXUS64 KHUN 250455 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 1155 PM CDT Fri May 24 2024 ...New AVIATION... .NEAR TERM... (Rest of tonight) Issued at 955 PM CDT Fri May 24 2024 Scattered but intense thunderstorm activity which was occurring earlier this evening in the vicinity of a mesoscale outflow boundary across southeastern AR/northern MS will continue to dissipate as it drifts southeastward late this evening. Attention for the remainder of the overnight period will turn to a broad axis of frontal convection currently in progress from southern Lake MI southwestward into eastern OK/western AR. Guidance from recent versions of the HRRR as well as most members of the 12Z HREF suggest that a forward propagating MCS will ultimately evolve out of this convection (likely the portion currently extending from southeastern MO into western AR) and spread southeastward into northern AL/southern TN early Saturday morning. However, as is typically the case with these events, there are subtle differences in timing, intensity and path of the projected MCS. At this point, our best guess is that this feature will arrive in the northwest portion of the forecast area by 4 AM CDT (but could potentially arrive as early as 2-3 AM if a well developed cold pool in its wake leads to east-southeastward acceleration). Although some weakening may occur as the convective complex spreads further southeastward through 7 AM, elevated CAPE of 1000-1500 J/kg and modest WNW flow aloft of 20-30 knots will support a risk of strong-severe storms, featuring wind gusts (up to 50-60 MPH) and hail, in addition to frequent lighting and locally heavy rain, which could result in minor flooding after rainfall received earlier today. POP and weather grids have been updated to reflect the scenario mentioned above, and other elements of the forecast appear on track. As temperatures begin to approach forecasted lows in the m-u 60s, some patchy fog will be possible (particularly across northeast AL). && .SHORT TERM... (Saturday through Monday) Issued at 329 PM CDT Fri May 24 2024 This convection should fade in intensity a few hours after sunrise as it moves to the SE. The rest of the day Sat for the most part looks to be dry. That said, this area is in a conditionally unstable environment, with daytime heating and steeper lapse rates making a regeneration of afternoon showers and storms not a zero chance. Staying with a dry forecast, muggy conditions are expected to close out the week with highs rising into the mid/upper 80s, and lows that night in the mid/upper 60s. Sunday should be even warmer with highs topping out around 90, with marginal shower and thunderstorm development possible. Things look to change more dramatically Sunday night, as a system now moving across central California heads rapidly to the east. This system as it traverses the CONUS will help develop a synoptic low near the Front Range on Sat, with this low moving to the Great Lakes. As it nears the Great Lakes on Mon, it will bring a cold front towards this area. Lift occurring east of this boundary and our region in an unstable environment will be favorable for the development of more organized convection. A few items to note with this system. It appears to be taking a more northward track per successive runs and was a bit slower. IF this trend continues, it would help lower an overall severe threat. A Slight Risk that this area is delineated in the Day-3 outlook has shifted a bit to the north. Also a greater distance from the parent low would help in this regard. Despite those items, the timing of the strongest forcing will be in the late night into Monday morning. CAPE values in the 1000-2000 J/kg and helicity values from 100-200 m/s and deep shear in the 40-55kt would support all modes of severe weather, with damaging wind gusts the main threat. A chance of showers and storms should continue into Monday, as the main front finally moves in a NW-SE manner across the area. && .LONG TERM... (Monday night through Thursday) Issued at 247 AM CDT Fri May 24 2024 A broader troughing pattern sets up Monday night for the eastern CONUS and will persist through the remainder of next week. While our next chance at storms is a lower end potential on Wednesday, the pattern overall looks to be drier with temperatures closer to daily average values in the low to mid 80s. && .AVIATION... (06Z TAFS) Issued at 1155 PM CDT Fri May 24 2024 There have been no significant changes to previous aviation forecast reasoning, as VFR conditions persist across the region early this morning, with lgt SSE flow and patchy BR/FG forming in a few locations. Between 6-9Z, storms currently in progress across eastern AR are predicted to grow into a forward propagating MCS that should spread east-southeastward through northern AL in the hours around sunrise. Due to increasing confidence in this scenario, we have introduced TEMPO groups for MVFR cigs/vsby at MSL/9-13Z and HSV/10-14Z. AWWs for lightning/strong winds and perhaps some hail may be required during this timeframe. VFR conditions will return by mid-morning; however, additional but more isolated TSRA could redevelop across the region by 20-21Z near a mesoscale boundary in the wake of the morning MCS and linger thru 2Z before dissipating. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...None. TN...None. && $$ NEAR TERM...70/DD SHORT TERM...RSB LONG TERM...30 AVIATION...70/DD