629 FXUS64 KMOB 142102 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 402 PM CDT Fri Aug 14 2020 .NEAR TERM UPDATE /Now Through Saturday/...Will start the near term period with a weakness in the geo-potential height aloft characterized by a broad synoptic scale trough draped from the OH River Valley to the central Gulf coast. Embedded in the mean northwesterly flow aloft between the trough and the nose of a deep layer ridge over TX, satellite shows a notable area of cold cloud tops/enhanced lightning dropping southeast into the MS Valley of eastern AR/northwest MS. The evolution of this feature is of primary concern in the very near term. Ahead of the complex, an assessment of environmental moisture is primed for convective support/maintenance with PWAT values 1.9 to 2.2 inches. These values stand some 110 to 120% of normal when comparing to climatology. The local air-mass is unstable with MUCAPE values on the order of ~2500 J/Kg on average. Shear is weak at present ahead of the southeastward moving complex, with the better values displaced to its west over northern LA to across the Red River Valley of TX/OK. However, a modest increase in vertical shear is possible going into the remainder of the day as mid level impulse /short-wave trough moves across the deep south. Also, with a favorable pre-storm environment of moisture and instability, the HRRR/WRF ARW is showing a well defined linear convective line developing and moving southeast across southeast MS this afternoon and moving to the coast by evening. Forecasters are beginning to see this in radar trends upstream. To aid in ascent is the presence of a broad surface pressure trough along the I-65 corridor. A marginal risk of severe storms is updated to now include southern MS to southwest AL through 7 PM this evening. Torrential downpours will also accompany the stronger convection and this could lead to some localized, minor flooding issues. Will carry the likelihood of convection spreading east southeast this evening with some decrease in coverage noted by the middle of the evening. While convection typically diminishes late in the evening into the overnight hours this time of year, the presence of the shortwave trough atop the area will serve to keep at least isolated to scattered storms going through a good portion of the night. There are indications that an enhanced coverage of storms will be likely along the immediate coast and offshore during the overnight/pre dawn hours. Scattered to numerous storms are expected to continue into Saturday morning, however there is likely to be some decrease in coverage over inland SE MS/SW AL by the afternoon as the shortwave trough begins to move east and drier air starts to move into the area. The greater coverage in clouds and precipitation will tend to keep highs in check, mostly in the upper 80s to near 90 Saturday. Lows remain in the 70s, typical for this time of year. /10 && .SHORT TERM /Saturday night Through Monday night/...An upper trough will be in place over the eastern conus Saturday night, with the base reaching as far south as the northwest Gulf of Mexico. This trough will move off toward the eastern seaboard and weaken Saturday night and Sunday, while a larger upper trough over central Canada and western Great Lakes digs toward the southeast. This feature will eventually carve out a second upper trough over the eastern conus and northern gulf Tuesday night. An associated surface low with the first trough will be located initially near the Carolinas with a surface trough/weak cold front extending southwestward across southern/central Alabama into southern Mississippi. As the surface low moves off to the northeast, surface winds will shift to the northwest over the forecast area Saturday night into Sunday morning as the boundary hangs up near the coast, then slips into the northern gulf Sunday night bringing a light north wind. Meanwhile, a longwave ridge mainly over the western and south central states and strengthens. This pattern will bring a deep layer light northerly flow over the forecast area which ushers progressively drier air into the region on Sunday, with precipitable water values dropping to 1.1-1.3 inches. These PWATs however will recover back to between 1.5 to 1.9 inches on Monday a slug of moisture between 850-700mb is advected into the region from the northwest. Predominately isolated lingering convection will be possible Saturday evening roughly along and southeast of I-65, and may linger near the coast overnight. Only expected very isolated showers to develop Sunday afternoon across the southern half of the forecast area, mainly along the weak surface boundary. Dry conditions will prevail from Sunday night through noon Monday, with mainly isolated convection forming Monday afternoon. Dry conditions will return Monday night. Highs on Sunday and Monday will be in the lower to mid 90s with afternoon heat index values of 98-105. Lows Sunday and Monday nights will range from the lower 70s inland to the mid/upper 70s at the coast. A low risk of rip currents continues through the period. /22 && .EXTENDED TERM /Tuesday Through Friday/...The ECMWF and GFS are in excellent agreement with the upper level pattern through midweek as they maintain the upper trough over the eastern conus, with the base reaching as far south as the southwest Gulf of Mexico. The models then diverge with the upper pattern as the GFS develops a broad upper cutoff low pressure area over the southern Mississippi River region by Thursday morning. This low then migrates toward the southwest over the northwest gulf by Thursday evening, with the center wobbling just off the southeast Texas coast through the remainder of the extended term. As for the ECMWF, it maintains an upper trough over the eastern conus and western Gulf of Mexico. A weak surface ridge will remain over the northern gulf with a weak synoptic flow in place, resulting in light and variable winds. A more diurnal pattern of convection is expected, with the best chance of showers and thunderstorms (scattered to occasional numerous) occurring during the daytime hours due to decreasing daytime stability. Also maintained isolated to low-end scattered showers into the early evening hours and after mid-morning hours. The hottest temperatures will occur on Tuesday with highs in the low to mid 90s. High temps will then be in the mid/upper 80s through the remainder of the period, with some locations reaching around 90 degrees. Low temperature in the 70s Tuesday night will cool slightly into the upper 60s to mid 70s. /22 && .MARINE...Some of the more organized storms this afternoon and evening will be moving from the northwest to southeast and could be problematic if caught on open water in hampering efforts to get to safety. The strongest storms can contain wind gusts in excess of 40 knots, brief reductions to visibility to a mile or less in heavy rain and frequent, potentially deadly lightning. /10 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...None. FL...None. MS...None. GM...None. && $$ This product is also available on the web at: http://weather.gov/mob