379 FXUS64 KMOB 051017 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 517 AM CDT Sat Sep 5 2020 .NEAR TERM UPDATE /Now Through Sunday/...Early morning surface analysis indicates a weak cold front pushing into central portions of MS and AL, and is approaching our interior southeast MS and southwest AL counties as of 4 AM CDT. Scattered mid and high level clouds are spreading overhead across the area and surface observations show little in the way of fog development early this morning, though there is still opportunity for a few sites to briefly drop to 2-4 statute mile visibility reductions, especially over southern parts of the area ahead of the approaching boundary. The weak front is forecast to slowly sink southward across the region through this afternoon as surface high pressure builds across the Mid-Mississippi and Tennessee Valley regions and into northern MS/AL. Probably the most notable sensible weather element associated with this boundary will be a much drier airmass that will be advecting into interior southeast MS and southwest and south central AL by this afternoon where dewpoints are forecast to fall into the upper 50s to mid 60s. Dewpoints will be slower to mix out closer to the coast and may hold around 70 to the mid 70s into this afternoon. Upper level ridging will continue to extend across the north central Gulf Coast region today and hot temperatures are expected over the forecast area today with this feature overhead despite the weak boundary slipping across our area. Short range model guidance also shows low level thermal ridging becoming enhanced over southern portions of the CWA ahead of the approaching front, with 925 mb temperatures between 25-26.5 C, which may be a degree or two C higher than yesterday. We trended high temperatures today close to and maybe a degree or two higher than the blended guidance this afternoon, particularly over the southern zones. Highs are forecast to range between 94-97 over the southern half of the region, and a little cooler between 90-94 over interior southeast MS and southwest AL. The challenge for the forecast today was the dewpoints, particularly how much they may mix closer to the coast. Some of the guidance indicated dewpoints mixing into the upper 60s over our southern zones again by this afternoon, but could still hold in the lower to mid 70s near the immediate coast as a weak seabreeze develops. The dewpoint forecast was trended maybe just a bit lower than the NBM guidance this afternoon, which yielded maximum heat indices between 105-108 over much of the southern CWA. Thinking was this was close enough to advisory criteria to go ahead and issue a Heat Advisory for the southern zones this afternoon, especially considering the amount of outdoor activities that may be occurring with the Labor Day Weekend. Moisture convergence along the weak surface front/seabreeze may initiate isolated convection near the coast, but coverage should be few and far between. Capped POPs just below 15% but kept isolated mention with 10% coverage mentioned in the forecast. Cooler temps return tonight - lows should range in the mid 60s to around 70 degrees inland and in the lower to mid 70s near the immediate coast. A similar pattern returns Sunday with isolated to locally scattered storms possible mainly along and east of the I-65 corridor. Another hot day is expected with highs in the lower to mid 90s but a drier surface airmass (dewpoints in the 60s) should result in lower max heat indices. A low risk of rip currents continues through the weekend. /21 && .SHORT TERM /Sunday night Through Tuesday night/...A westward drifting upper system over the western Caribbean combines with an upper trough over the eastern Conus to bring a mean upper trough along the east coast Sunday night into Monday. More upper level shortwave energy moving around the eastern edge of an upper ridge stretching east over the southern half of the Conus combines to form another upper trough over the Southern Plains, leaving upper high pressure stretching northeast from the western Gulf of Mexico to the Tennessee River Valley. A low level ridge that has built southwest over the Appalachians organizes a bit more, bring a more northeast to easterly low level flow to the northeastern Gulf coast and nearby portions of the Southeast, shifting a stalled surface boundary along the northcentral/northeastern Gulf coast farther south over open Gulf waters in the process. With a more northeasterly component to the low level flow advertised by today's guidance, moisture return off the Gulf is slowed significantly from yesterday's 00z guidance. One item that is consistent from yesterday's guidance is the GFS advertising a weaker northerly push in the Near Term, leaving a bit high available moisture, mainly south of I-65 Monday. By sunrise Wednesday, a strong upper low digging southeast over the western Conus/ US Rockies shifts the upper ridge over the Southeast eastward, leaving an upper ridge stretching west over the eastern Conus, with a weak upper trough centered over Florida. For Sunday night through Monday night, a generally dry forecast is expected. A few afternoon thunderstorms near the coast are possible Monday as a seabreeze moves inland from the coast, but northward extent will be limited. As stated above, most guidance is advertising dryer conditions Monday due to the limited moisture availability. Have also leaned on the warmer end of guidance with respect to Monday's high temperatures, with a drier airmass and upper level subsidence the cause. High temperatures in the low to mid 90s inland, around 90 along the coast are expected. The drier airmass will also allow for better overnight radiational cooling, especially over areas northwest of I-65. Low temperatures Sunday night are expected to range from the mod 60s northwest of I-65 to upper 60s to around 70 southeast and low 70s along the coast. Monday night, low temperatures ranging from the upper 60s to around 70 northwest of I-65 are expected, low to mid 70s south. Tuesday into Tuesday night, with the upper ridged building west over the eastern Conus, the low level ridge over the eastern Conus shifts south a bit, bringing a more east to southeast flow to the Southeast and an increase in Gulf moisture. Rain chances will see an uptick Tuesday, though best rain chances remain southeast of I-65. Tueday's high temperatures will see a bit of a downward trend with increased mid and upper level cloud cover expected from the increase in daytime cloud cover and moisture levels. High temperatures ranging from the upper 80s to around 90 expected. Low temperatures Tuesday night will see an uptick with the increased moisture levels, with readings from around 70 to low 70s inland, mid to upper 70s along the coast. /16 && .EXTENDED TERM /Wednesday Through Friday/...Global models continue to come into much better agreement through the extended period. This leads to increasing confidence during the period. The ECMWF has come around the GFS solution of being more progressive with the upper trough over the plains which will eject northeast into the midwestern states late in the week. An associated cold front will move into southeast late in the week, potentially bringing some slightly cooler and drier air to the area for next weekend. Although they do still differ in the speed of the upper trough, due to how fast the upper ridging over the southeastern states breaks down. Either way, good chance POPs, mainly afternoon and evening in daily diurnal pattern, will continue trough the extended term period. High temperatures will be in the upper 80s to lower 90s. Low temperatures will continue to range from the upper 60s to lower 70s inland to the mid 70s near the immediate coast. /13 && .MARINE...No impacts expected throughout the week outside of an increasing chance of showers and thunderstorms Sunday through Tuesday. /21 && .PRELIMINARY POINT TEMPS/POPS... Mobile 96 69 93 69 92 71 89 72 / 10 0 10 0 20 0 30 10 Pensacola 96 73 93 72 90 74 89 74 / 10 0 20 10 20 10 20 20 Destin 94 76 91 75 89 76 88 75 / 10 10 30 10 20 10 20 20 Evergreen 94 68 93 68 92 70 88 71 / 10 0 20 10 10 0 40 10 Waynesboro 92 66 91 64 92 68 89 69 / 10 0 10 0 10 0 30 10 Camden 92 66 92 67 92 69 88 70 / 0 0 10 0 10 0 30 10 Crestview 97 69 93 69 93 71 90 71 / 10 0 30 10 20 0 40 10 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...Heat Advisory from noon today to 6 PM CDT this evening for ALZ261>266. FL...Heat Advisory from noon today to 6 PM CDT this evening for FLZ201>206. MS...Heat Advisory from noon today to 6 PM CDT this evening for MSZ078-079. GM...None. && $$ This product is also available on the web at: http://weather.gov/mob