Area Forecast Discussion
Issued by NWS Mobile, AL

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741 FXUS64 KMOB 240500 AAC AFDMOB Area Forecast Discussion...UPDATED National Weather Service Mobile AL 1200 AM CDT Thu Aug 24 2017 .DISCUSSION...Updated for latest aviation discussion below. && .AVIATION... 06Z issuance...VFR conditions expected overnight. VFR conditions will prevail in most areas on Thursday, except for MVFR to IFR conditions in and around scattered showers and thunderstorms. /13 && .PREV DISCUSSION... /issued 909 PM CDT Wed Aug 23 2017/ DISCUSSION...See updated information for land areas below. UPDATE...Radar imagery shows scattered showers and thunderstorms continue to develop along a weak cold front moving slowly south across northern portions of the area. Due to the slow movement of the storms, heavy rainfall will continue to be the main threat along with frequent cloud to ground lightning. The showers and thunderstorms will continue to weaken through the late evening as the boundary layer cools. The current forecast remains on track and no significant updates are needed at this time. /13 PREV DISCUSSION... /issued 638 PM CDT Wed Aug 23 2017/ DISCUSSION...Updated for latest aviation discussion below. AVIATION... 00Z issuance...VCTS will gradually dissipate this evening with VFR conditions expected overnight. VFR conditions will prevail in most areas on Thursday, except for MVFR to IFR conditions in and around scattered showers and thunderstorms. /13 PREV DISCUSSION... /issued 403 PM CDT Wed Aug 23 2017/ NEAR TERM /Now Through Thursday/...Sfc to h5 ridge of high pressure over the eastern and north central Gulf of Mexico stretching north over the north central gulf and se states will begin to break down from west to east tonight and on thu in response to Tropical Depression Harvey entering the sw Gulf and Bay of Campeche. To the north a broad upper trof mostly over Appalachians and Eastern conus will continue to slowly shift eastward through thu afternoon. In the wake of the upper trof to the north a weak frontal boundary is noted pushing down across lower parts of Al and Ms and possibly just north of the NWFL coast by early Thu morning leading to slightly drier/cooler conditions at the surface across most of the northern half of the forecast area on Thu. a light northerly wind at the surface for most locations in the morning will also make conditions feel almost fall like through about mid morning. Less coverage of showers and thunderstorms can also be expected overnight near the coast and offshore and over interior sections of the forecast area during the day on Thu due to less forcing aloft and more stable conditions in the boundary layer beginning later this evening continuing through Thu afternoon. Model soundings reflect these lower values on Thu with pwats dropping below 2 inches across most of the northern half of the forecast area with a warm nose also showing around 9k ft in most of the model soundings in the area. For the rest of today and this evening showers and thunderstorms will form out ahead of the weak front boundary and move south towards the coast. With moderate instability combined with mid to upper lapse rates mostly above 6.0 c/km a few strong storms will still be possible later this afternoon and early this evening. Gusty straight line winds possibly up to 40 mph or slightly better, very heavy rain and frequent cloud to ground lightning will be the main threats with the stronger storms through early this evening. As mentioned above temperatures will be slightly cooler tonight especially over the northern and western locations ranging from the upper 60s to lower 70s, and the middle 70s further south to the immediate coast. Highs Thu will be near seasonal averages ranging from the upper 80s to lower 90s for all locations. 32/ee SHORT TERM /Thursday night Through Saturday night/...Harvey is forecast to continue tracking northwest over the southwest Gulf of Mexico, and make landfall along the Texas coast late in the week. Meanwhile, a weak upper level trough should remain over the eastern conus. Will continue with the upward trend toward higher precipitation chances from isolated to scattered on Friday to scattered to numerous on Saturday. There is at least some potential for a heavy rain and frequent lightning to occur with the stronger storms. In addition, an increase in long period swells across the coastal waters Friday and into the weekend should lead to an increased rip current threat along area beaches. High temperatures Friday will range from 87 to 93 degrees, and from 84 to 87 degrees on Saturday. Low temperatures will be close to normal, ranging from 69 to 73 degrees inland areas, with mid 70s along the coastal sections. /22 LONG TERM /Sunday Through Wednesday/...Impacts across the forecast area in the long term remain largely dependent on the track and size of Harvey. For now, anticipate that the system will remain west of the area through the middle of next week, but that would still place us in the eastern quadrants that have the potential to produce the most rain and tornadoes. However, this far out there is still much uncertainty, but will continue the trend toward high precipitation chances (scattered to numerous) throughout the long term. There is at least some potential for a heavy rain and or severe weather event to occur over the forecast area during the Monday through midweek timeframe. Long period swells will likley remain across the coastal waters, keeping an elevated rip current threat along area beaches. Due to the expected increased in overall cloud coverage and high rain chances, high temperatures Sunday through Wednesday will be about 5 to 10 degrees below normal, ranging from 80 to 85 degrees. Low temperatures will be close to normal through the long term, ranging from 67 to 72 degrees inland areas, with mid 70s along the coastal sections. /22 MARINE...High pressure over the north central gulf will weaken from west to east for the remainder of the week in response to Tropical Depression Harvey tracking northward over the western Gulf. As a result increased swell from Harvey will begin to propagate east and north over the north central Gulf and marine area later in the week and over the weekend, and into next week. A light southwest flow this afternoon will shift north then build slightly overnight and early Thu, then shift northeast to east and diminish later in the day. Easterly winds and seas will begin to build on Fri and continue through early next week as Harvey continues to move slowly northward over the extreme westerly Gulf. All marine interests should stay tuned to the National Hurricane Center and their local forecast office in Mobile Al for further updates on the forecast track of Harvey and its impacts later in the week and over the weekend, continuing into next week. 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

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