Area Forecast Discussion
Issued by NWS Mobile, AL
Issued by NWS Mobile, AL
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581 FXUS64 KMOB 151602 AFDMOB Area Forecast Discussion National Weather Service Mobile AL 1102 AM CDT Sun Sep 15 2024 ...New UPDATE... .MESOSCALE UPDATE... Issued at 1102 AM CDT Sun Sep 15 2024 15.12Z upper air analysis shows a west northwest flow pattern at high levels over the central Gulf coast, southwest of a H20/H30 upper low over the central Appalachians. Within the westerlies aloft, a series of jet streak maxima (ranging 70-90kts) was analyzed within the southern stream. Working down into the mid/lower levels, forecasters see a complex low pressure system situated from the Mid-South to southwest MS, with a few trough axis spokes extending out from the low which are providing a focus for ascent within a moist and modestly unstable local environment characterized by SB Capes ranging 1000-2000 J/KG. A look at 15.12Z pwat values along the central Gulf shows highest values => 1.87" (LIX) being right near 1 standard deviation above the climatological means for mid September. At the surface, a quasi- stationary front was draped west to east across the central Gulf coast. Along the boundary, a wave of frontal low pressure was analyzed along the MS Sound. Radar shows returns lifting northward over the interior in response to the more southerly component in layer flow east of the low/mid level low pressure system, while returns near and south of the coast are tracking more eastward along and south of the surface front. Considering the players mentioned to enhance forced ascent, environmental instability and sufficient deep layer moisture, showers and storms are forecast to trend higher in areal coverage through the remainder of the day. The weakened state of bulk shear values at this time, suggest that storms will remain sub-severe. The main threats in storms today look to being efficient, locally heavy rain rates and perhaps instances of flooding in those areas subject to poor drainage where storms move over/or slowly across the same areas. It is difficult to nail down just where the heaviest rain axis develops as convection is just beginning. But moving forward, forecasters anticipate a general area of excessive rain/slight risk of localized flooding to be aligned along and west of a line from Butler to Grove Hill to Atmore AL to Ft. Walton Beach FL. Mobile and Baldwin Co`s may see an increased threat of flooding rains. There is also the possibility of a few waterspouts near shore. /10 && .PREV DISCUSSION... /issued 658 AM CDT Sun Sep 15 2024/ ..New AVIATION... AVIATION... (12Z TAFS) Issued at 658 AM CDT Sun Sep 15 2024 MVFR to IFR ceilings will impact much of interior south central and southwest AL and portions of the western FL panhandle early this morning. Ceilings should become predominantly MVFR over these areas by around 15Z and generally linger through the afternoon. Scattered to numerous showers and thunderstorms will develop, especially by this afternoon. Convective activity will be efficient rainfall producers and will have reduced visibility to MVFR to IFR thresholds. MVFR to IFR ceilings will develop over all of our region after 03-06Z this evening and linger into the overnight hours. Potential also continues for scattered overnight showers and storms, some with locally heavy rainfall and localized visibility restrictions to IFR. /21 PREV DISCUSSION... /issued 507 AM CDT Sun Sep 15 2024/ .New NEAR TERM, SHORT TERM, LONG TERM, MARINE... NEAR TERM... (Now through Monday) Issued at 507 AM CDT Sun Sep 15 2024 The remnant mid level circulation from Francine remains located in the vicinity of northern MS early this morning. A weak surface boundary has become draped from portions of MS and into coastal AL. Most areas are starting off dry early this morning with the exception of a few light rain showers that are drifting NW over interior southwest and south central AL as of 430 AM. A more unsettled weather pattern is expected to take shape across our forecast area today and tonight. The mid level low pressure system is forecast to slowly retrograde westward over northern and northwestern MS through tonight. A weak surface low pressure system is also expected to slowly meander/drift westward over southern MS and southeastern LA through this evening. The surface boundary should become oriented from interior parts of southeast MS and into coastal portions of AL/the far southwestern FL panhandle today and tonight. Deep layer moisture should pool along the boundary with precipitable water values increasing to 1.9 to 2.2 inches per some of the latest CAMs and short range forecast model guidance. Low level convergence along the boundary along with weak shortwave impulses along the base of the mid level trough will support the development of numerous showers and thunderstorms later this morning and especially during the afternoon/evening hours. A narrow band of enhanced instability with MLCAPE values up to 1000-1500 J/KG also looks to become oriented over the region today. Convection may have a tendency to develop and train over southwest AL/southeast MS this afternoon and evening, generally moving from S/SE to N/NW in the relatively light deep layer south/southeasterly flow regime. There will be increased concerns for heavy rainfall, especially with convection that may tend to train over a few locations. Showers and storms may also be efficient rainfall producers considering the deeply moist airmass that will be in place. Some locations may pick up in excess of 1-3" of rain with locally higher amounts in excess of 4+" within a relatively short period of time. While the overall confidence in exceeding FFG values remains low enough to preclude the issuance of a Flood Watch, we will be messaging at least a limited potential for flash flooding over southeast MS and portions of southwest AL and the far western FL panhandle through this evening. The 00Z WRF-ARW and 06Z HRRR, along with 00Z HREF ensemble probability matched mean products have been showing potential localized bullseye QPF values in excess of 4-5" over portions of Mobile, Baldwin, and perhaps even into far southwest Escambia FL counties through late tonight and we may have to monitor these locations closely for an elevated flash flood potential through the next 24 hours. The unsettled weather pattern continues into Monday as broad troughing remains in place over our region between Francine`s retrograding mid level circulation and the next tropical or subtropical system that will be pivoting into the Carolinas. Precipitable water values will remain enhanced between 1.8 and 2 inches across our region along the residual surface boundary. We will maintain high chances (50-70%) of showers and thunderstorms across the forecast area again Monday and we may have to once again watch for pockets of heavy rainfall and localized flooding concerns. High temperatures will be cooler today and Monday, generally only reaching around 80 to the lower 80s over interior areas, with a few locations in the mid 80s. Lows tonight are forecast to range in the upper 60s over interior communities and in the lower 70s along the immediate coast. A LOW rip current risk continues along area beaches for the next several days. /21 SHORT AND LONG TERM... (Monday night through Saturday) Issued at 507 AM CDT Sun Sep 15 2024 Rain chances will remain elevated through Tuesday as an upper low meanders over the Carolinas and into the Tennessee Valley. This places the base of the upper trough over the local area. At the same time, a lingering surface boundary will be positioned along coastal portions of the area with a general west to east orientation. Deterministic guidance indicates this front may try to lift slightly northward on Tuesday with a subtle surface low lingering along the front. The combination of this surface boundary, lower heights aloft, and PWATs around 1.8-2 inches will aid in the development of showers and storms on Tuesday and into Tuesday evening. Given the placement of the surface front, the higher rain chances are expected to be focused along the southern two thirds of the area and especially closer to the coast where the current forecast has scattered to numerous showers and storms. Similar to the last few days, these storms will be capable of producing heavy rainfall which could lead to some localized flooding concerns on Tuesday. The good news is that the pattern will trend drier on Wednesday and especially into the latter part of the week. The upper low over the Tennessee Valley will amplify and slide southeastward through Saturday as upper ridging over the Mississippi Valley builds further overhead. The aforementioned surface boundary will also become diffuse over the Gulf waters during this time. This will place the local area within deep layer northwesterly to northerly flow through Saturday. While there may be an isolated shower or storm over eastern portions of the area on Wednesday, the presence of much drier air will keep rain free conditions in place through the remainder of the week. High temperatures will trend higher as ridging builds east with values rising into the upper 80s and to around 90 degrees by Thursday and Friday. /14 MARINE... Issued at 507 AM CDT Sun Sep 15 2024 Winds/waves will be locally higher near scattered to numerous marine storms that will develop today and into the early part of the week. Light and variable flow this morning will become light southerly to southeasterly this afternoon. A generally light to occasionally moderate easterly flow will return Sunday night into the early part of the week. Winds become light and variable in direction again by midweek. /21 && .PRELIMINARY POINT TEMPS/POPS... Mobile 70 84 68 84 68 87 70 89 / 50 70 40 50 10 10 0 10 Pensacola 72 83 72 83 72 86 72 89 / 60 70 50 60 10 20 0 10 Destin 72 82 73 84 73 86 73 89 / 60 60 50 50 20 20 0 10 Evergreen 67 83 65 86 66 89 65 91 / 60 60 30 40 10 10 0 10 Waynesboro 68 80 65 84 64 86 63 89 / 60 70 20 30 0 10 0 0 Camden 67 79 65 83 64 85 63 87 / 60 50 30 20 0 10 0 0 Crestview 69 84 68 85 67 88 67 91 / 50 60 40 50 10 20 0 10 && .MOB WATCHES/WARNINGS/ADVISORIES... AL...None. FL...None. MS...None. GM...None. && $$ This product is also available on the web at: www.weather.gov/mob