642 FXUS64 KHUN 190222 AFDHUN Area Forecast Discussion National Weather Service Huntsville AL 922 PM CDT Sun Aug 18 2019 .NEAR TERM...(Rest of tonight) Issued at 922 PM CDT Sun Aug 18 2019 Latest near term model guidance continues to suggest that a weakening mid-level vort max (currently across the lower Great Lakes) will advance eastward into the central Appalachians region by 19/12Z. The trailing trough axis is expected to drift more slowly southeastward across the TN Valley, and although lift directly related to this feature will be rather weak, it could be sufficient to generate isolated showers/thunderstorms based on the amount of elevated CAPE evident in point forecast soundings. We have introduced a slight chance POP for all forecast zones beginning late this evening to address this potential, and also indicated the development of patchy fog across portions of the CWFA between 08-13Z. Due to the anticipated development of a steep inversion in the boundary layer across our region, any storms that form should be slightly elevated, with the main threats coming from lightning and locally heavy rainfall. Otherwise, we expect slightly warmer and more humid conditions overnight as compared to previous nights, with lows in the l-m 70s. .SHORT TERM...(Monday through Tuesday) Issued at 210 PM CDT Sun Aug 18 2019 The start of the new work week will be much the same as we've experience the last few days. The ridge over the Southwestern CONUS will build eastward, while surface flow remains light. This will limit the deep layer moisture return across the TN Valley, while weak subsidence provides for an even lesser chance for showers and thunderstorms on Monday. Despite this, there may be just enough moisture in the lower levels for an isolated thunderstorm to develop during our peak heating hours Monday afternoon. By Monday night, a weak area of low pressure will lift northward from the northeastern Gulf of Mexico and slowly drift through Georgia on Tuesday. This feature doesn't look to impact the TN Valley much before it dissipates, however we could see some of the associated moisture filter into the forecast area. Given this increase in moisture, the coverage to thunderstorms will be slightly higher than those observed on Monday, but PoPs will still be in the lower chance range. Temperatures will be a couple of degrees above normal for this time of year. Highs on Monday and Tuesday will depend on the coverage of storms, but with a relatively low coverage expected, temps should warm into the mid 90s. Am not overly confident on how much of the area will see the upper 90s, but with the building ridge, temps may be a degree or two too low. Model dewpoints have been a little on the high side, so those were lowered with this forecast package, which in turn lowed the relative humidities forecast for Monday and Tuesday. So, with all of that said, heat index values are forecast to stay just below criteria but hot nonetheless. Overnight lows will be mild, with temps falling into the lower 70s Monday night and Tuesday night. .LONG TERM...(Tuesday night through Saturday) Issued at 210 PM CDT Sun Aug 18 2019 The upper ridge will linger of the region on Wednesday, before it breaks down in response to an upper low swinging into the Great Lakes region. Wednesday will be fairly similar to Tuesday, though with more moisture over the area, thunderstorm coverage will be a bit higher. Thunderstorm chances really begin to increase on Thursday, as flow aloft weakens further and guidance suggests several weak waves moving through the area. Given the uncertainty with this type of pattern in the extended period, PoPs were capped at chance on Thursday. On Friday, a strong shortwave is expected to move through the region which will provide a greater focus for convective development during the afternoon. Thus, likely PoPs were kept in the forecast. The upper level pattern will remain fairly zonal headed into next weekend, with scattered thunderstorms possible again on Saturday. Overnight, confidence is on the lower side with regard to the forecast through the long term period, as forecast guidance diverge quite a bit. Temperatures through the extended will be near to slightly above normal for this time of year. Highs will warm into the lower to mid 90s each day, with overnight lows in the lower 70s. && .AVIATION...(For the 00Z TAFS through 00Z Monday evening) Issued at 633 PM CDT Sun Aug 18 2019 VFR conditions will persist through the next 24 hours at both the KHSV and KMSL terminals. Winds will generally remain light and variable and dry weather is expected to continue through Monday, although an isolated afternoon shower cannot be completely ruled out. && .HUN WATCHES/WARNINGS/ADVISORIES... AL...NONE. TN...NONE. && $$ NEAR TERM...70/DD SHORT TERM...73 LONG TERM...73 AVIATION...25 For more information please visit our website at weather.gov/huntsville.