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650 FXUS64 KMOB 180934AFDMOBArea Forecast DiscussionNational Weather Service Mobile AL434 AM CDT Sun Aug 18 2024...New NEAR TERM, SHORT TERM, LONG TERM, MARINE....NEAR TERM...(Now through Tonight)Issued at 433 AM CDT Sun Aug 18 2024An upper-level trough, currently located over the Great Lakes region, is expected to amplify throughout the day today and dig further into the southeast US. Current analysis shows that mid-level flow is currently out of the northwest over our region and is helping to advect in a pocket of drier air aloft. This drier air can be seen in satellite water vapor products, as well as upstream 00Z soundings from BMX and JAN, with the driest air located generally within the 400-600mb levels. At the surface, an outflow boundary from the storms that pushed through the area yesterday lingers offshore. Looking upstream, our highly anticipated mid-August cool front is currently located across northern Arkansas and into Tennessee. This boundary will continue pushing southward throughout the day today, likely entering our local region by the evening hours and moving offshore overnight. Prior to its arrival, the primary concern across the area will be the heat. The incoming drier air should help to scour out cloud cover, leading to ample sunshine during peak heating. Additionally,model guidance continues to suggest that dew points will attempt to mix out given the dry air aloft and northwesterly flow pattern in place. If this were to occur, temperatures should easily climb into the upper 90s, potentially into the 100-102 degree range overinland counties where the better mixing potential exists. An Excessive Heat Warning is in place for counties west of the Tombigbee River, as well as Baldwin county, for heat indices up to110-115 degrees and a Heat Advisory is in place elsewhere for heat indices of 105-110 degrees (these products are in effect from11am through 7pm CDT). It should be noted that although lower dewpoints could keep heat indices a bit lower than forecast, decidedto leave our current heat products unchanged due to the high uncertainty to the overall degree of mixing. As we head into the late afternoon and especially into the evening hours, the front will be located over central AL/MS, approaching our northern counties. In addition, the aforementioned outflow over the Gulf looks to quickly surge northward (likely being induced by the sea breeze circulation) during this time period. Storms look to develop to our north as the front moves in and upper-level flow becomes more diffluent. Coverage should start off more as a broken line when storms initially develop along the front due to the dry air in place. Very strong DCAPEs upwards of 1400 J/kg will allow for outflow to surge forward, with additional storms developing along the outflow. As the front approaches our northern counties and interacts with the northward-propagating seabreeze boundary, storms may evolve into a more bonafide line/MCS due to the increase in low-level moisture and instability (MLCAPEs to around 2000-3000 J/kg). Increasing deep-layer shear will also help in the organization of these storms (0-6km shear around 30-40 knots; 0-3km shear of 25-30 knots). The main concern with this line of storms will be damaging winds in excess of 60mph, potentially up to 70mph where embedded bowing segments occur. Cannot rule out a few instances of large hail in some of the stronger cores. Although forecast hodographs show some decent curvature in the lower-levels, not really anticipating much of a tornado threat given the very strong DCAPEs helping to maximize cold pool propagation, leading to a more 'outflow-dominant' setup. Timing of this line remains rather tricky at the moment, but current guidance suggests that it should enter our northern counties by around 6pm-8pm and should move offshore by around 2am-4am. Rain chances quickly decrease by sunrise as the front moves into the Gulf. Lows will range from the low to mid 70s inland to the upper 70s along the coast. /96&&.SHORT AND LONG TERM...(Monday through Saturday)Issued at 433 AM CDT Sun Aug 18 2024A "cold" front will push through the region Monday morning inresponse to a highly amplified trough positioned along the eastern seaboard. There could be a small chance of rain along the immediate coast early Monday morning as the front pushes through, however, a significant surge of deep layer dry air will quickly shut off precip chances as the day progresses. High temperatures will remain on the hot side Monday despite the frontal passage with mid to upper 90s expected. Lower humidity values will keep heat indices in check, so we are not expecting a continuation of heat advisories. Even drier air will move into the area through midweek and we are likely to see afternoon dewpoints mixing out into the upper 50s to lower 60s, which is certainly atypical for mid to late August. So while highs will stay near or a little above normal, low temperatures will drop to below normal levels. Wednesday morning will be the coolest of the week with lows droppinginto the low to mid 60s well inland. Areas closer to the coast willsee upper 60s/lower 70s. The east coast trough will begin to lift out Thursday and Friday.However, guidance has come into good agreement that a piece of thetrough will be left behind. This lingering vorticity will developinto a closed upper low and slowly retrograde west across the northern Gulf through the weekend. This will signal a return ofrain chances late in the week into the weekend, mainly across thesouthern half of the area, as moisture rebounds on the east side of the upper low. The increased rain chances and cloudiness will help keep temperatures near normal levels. 34/JFB&&.MARINE...Issued at 433 AM CDT Sun Aug 18 2024Southwest to west winds will increase this afternoon andespecially into tonight ahead of an approaching front. Small craftshould exercise caution over the Gulf waters tonight as winds willincrease to 15-20 kt. Mariners will need to be on the lookout for strong to severe storms progressing from north to south into and through the marine area this evening into the late night hours. The storms will carry the potential for significant wind gusts.An offshore flow develops by Monday as the front pushes offshore.No significant wind/wave impacts are expected through Thursday. 34/JFB&&.MOB WATCHES/WARNINGS/ADVISORIES...AL...Excessive Heat Warning from 11 AM this morning to 7 PM CDT this evening for ALZ051-052-261>266. Heat Advisory from 11 AM this morning to 7 PM CDT this evening for ALZ053>060.FL...Heat Advisory from 11 AM this morning to 7 PM CDT this evening for FLZ201>206.MS...Excessive Heat Warning from 11 AM this morning to 7 PM CDT this evening for MSZ067-075-076-078-079.GM...None.&&$$This product is also available on the web at:www.weather.gov/mob
