349 FXUS64 KMOB 041618 AAC AFDMOB Area Forecast Discussion...UPDATED National Weather Service Mobile AL 1118 AM CDT Sat May 4 2019 .DISCUSSION...See updated information for land areas below. && .UPDATE...Late AM Deep convection is now crossing extreme southeast LA and will soon move eastward into southern MS. The latest high resolution HRRR 1 km AGL reflectivity forecasts are initializing well and will use it to adjust near term PoPs accordingly. This guidance shows widespread showers and embedded storms to spread eastward over the interior southeast MS zones through 1 PM and then continue eastward thereafter across southwest AL and into portions of the northwest FL Panhandle into mid afternoon. A few storms strong to briefly severe with damaging winds the main threat and perhaps hail up to a quarter size possible. Tornado threat minimal. /10 && .PREV DISCUSSION... /issued 1010 AM CDT Sat May 4 2019/ DISCUSSION...See updated information below. UPDATE...04.12Z upper air analysis shows a vigorous southern stream mid level impulse aligned over the TX/LA border. Surface cold front was draped from the Mid-South to near Shreveport LA and southwest into central TX. Ahead of the mid level energy and southeast of the frontal position, an organized area of deep convection/enhanced lightning activity was moving eastward over south central LA extending southward from there to about 200 miles off the central LA coast Gulf coast. East of this area, showers and embedded storms have already been moving northeast up across the southern MS this morning. An assessment of the pre- storm environment shows an abundance of instability with SB Capes already ranging from 2000-3000 J/KG over the central Gulf coast. H50-H70 mid level lapse rates range from 6.5-7C/KM. Considering the instability present coincident with an eastward shift of deep moisture and enhanced ascent as the mid level feature approaches from the west, the radar will become more active with time as convective activity fills in. A slight risk of severe storms is maintained over the entire area with the main threat continuing to be damaging winds and perhaps instances of hail up to around a quarter size. Forecasters have noted some weakly defined rotation in the radar storm relative velocity data in a few of the morning cells, but these have lacked persistence and depth. This is consistent with the weakly defined low level wind profiles in place and 0-6KM bulk shear values 20-30 kts on average. Thus, the tornado threat is considered to remain at minimal. As far as forecast timing of weather today, will be making some modifications to today's PoPs as the event unfolds, which will also be dictated by radar trends. Of note, if a more pronounced cold pool forms in the wake of the storms, a slightly faster eastward translation of storms is likely and will monitor. /10 PREV DISCUSSION... /issued 654 AM CDT Sat May 4 2019/ DISCUSSION...Updated for latest aviation discussion below. AVIATION... 12Z issuance...Mostly MVFR cigs through 05.12z. Could see brief periods of IFR cigs and visibilities mostly in low stratus, light fog and heavy rain in and around scattered to numerous showers and thunderstorms this afternoon and evening, followed by some light fog and low status after midnight tonight continuing through 05.12z. Winds will be mostly southeast to south at 8 to 12 knots later this morning continuing through early this afternoon becoming south to southwest later this afternoon and this evening, then southwest to west near sunrise Sun morning. A few strong to severe thunderstorms will also be possible this afternoon and evening with damaging straightline winds, large hail and frequent cloud to ground lightning be the main threats. 32/ee PREV DISCUSSION... /issued 449 AM CDT Sat May 4 2019/ NEAR TERM /Now Through Saturday night/...Showers and thunderstorms are still expected to form out ahead of a dampening shortwave trof approaching from the west. With the lack of good consistency with both the spectral and hi-res model solutions there still is a little uncertainty on the timing and departure of the bulk of heavier convection moving across the forecast area this afternoon and tonight with the ECMWF guidance still holding on to decent coverage over most of the eastern half of the forecast area through early Sun morning. With somewhat limited forcing aloft along with limited vertical and speed shear out ahead of the main upper system, the main driving forces continue to be decent surface based instability setting up with the daytime heating today combined with marginal to strong lapse rates in the lower to mid levels of the boundary layer, along with initial wetbulb zero values generally below 10.5 kft. As a result, still believe the main threats with the heavier convection continues to be damaging straight line winds, heavy rain and frequent lightning associated mostly with bowing segments along a well defined squall line moving into western sections of the forecast area early this afternoon, then spreading further east across remaining areas through mid to late afternoon, possibly lingering into the evening and overnight hours. Ahead of the main band of convection isolated to scattered thunderstorms are also noted while wetbulb values are the lowest possibly leading to some medium to large hail beginning by early to mid afternoon. As a result, will continue to mention a slight risk for some storms to possibly become severe which is consistent with the current thinking from the Storm Predication Center in Norman OK. As always stay tuned to your local forecast office at www.weather.gov/mob/ for possible updates on this developing weather situation later today. Temperatures today will continue to be near or just above seasonal norms. Highs will range from the upper 70s to lower 80s for most inland areas and the mid to upper 70s along the immediate coast. Lows tonight will range from the lower to middle 60s for most inland areas the upper 60s to near 70 along the immediate coast. 32/ee SHORT TERM /Sunday Through Monday night/...The shortwave trough axis will push to the east of our forecast area Sunday morning, with mainly zonal flow aloft setting up across region Sunday afternoon through Sunday night. The weak frontal boundary or surface trough axis will stall roughly across southwest and south central Alabama late Sunday morning into Sunday afternoon. Residual moisture on the western side of the departing shortwave trough along with weak convergence along the boundary will support keeping a low chance of showers/storms in place, especially over central and eastern portions of our region and along the boundary Sunday. A much drier airmass aloft will move across our forecast area Sunday night, so we will maintain a mostly clear and dry forecast going into the evening and overnight hours. High temperatures Sunday afternoon are forecast to range in the lower to mid 80s, with lows on Sunday night averaging just a little cooler in the upper 50s to lower 60s over our northwest zones, with readings in the mid 60s to around 70 degrees near the immediate coast. The dry zonal mid level flow pattern will persist into Monday afternoon, followed by weak shortwave ridging aloft building overhead by Monday night. Mostly clear skies and continued dry weather is expected to continue into Monday night. Highs Monday should trend a little warmer in the upper 80s to around 90 degrees over much of our interior, while readings warm into the lower to mid 80s generally along and south of the Interstate 10 corridor. Lows Monday night should range in the 60s over most locations. /21 LONG TERM /Tuesday Through Friday/...The ridge aloft is expected to shift eastward across the southeastern states on Tuesday and Tuesday night, as southwest flow aloft returns over our area ahead of the next shortwave trough that is forecast to lift toward the Mississippi Valley region. There are some timing discrepancies with this next trough in the operational medium range guidance, but there is enough indication of a gradual increase in moisture and ascent to include a chance of showers and thunderstorms over our western zones Tuesday and Tuesday night, while keeping a lower (slight) chance of convection over eastern portions of the area. A generally moist west to southwest flow aloft looks to prevail across much of our region through the middle to latter half of the week to the north of a building ridge of high pressure aloft over the Gulf of Mexico. This pattern, along with moist southerly low level flow will support keeping a chance of showers and storms in the forecast each day through the end of the week. Warm temperatures continue through the extended period, with highs mostly in the mid 80s to around 90 over inland areas, and lower to mid 80s along the coast each day. Overnight lows will be mild in the upper 60s to lower 70s. /21 MARINE...A light to moderate southerly wind flow will continue through tonight ahead of an upper level system and weakening cold front approaching from the west northwest. For later today and tonight a few strong to possibly severe thunderstorms are still expected with this pattern, moving across western sections of the marine area by early to mid afternoon, then spreading further east late this afternoon through this evening, possibly lingering through early Sunday morning. Damaging straight line winds, heavy rain and lightning along with some medium to large hail continues to be the main threat with the stronger thunderstorms. By early Sun a moderate southwest to westerly flow is expected, diminishing later in the day before shifting to the north northeast late Sun night into early Mon. A light to moderate southeast to southerly flow redevelops late Mon through midweek as weak high pressure redevelops over the eastern and north central Gulf. 32/ee && .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