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Area Forecast Discussion
Issued by NWS Jackson, MS
Issued by NWS Jackson, MS
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737 FXUS64 KJAN 151727 AFDJAN Area Forecast Discussion National Weather Service Jackson MS 1227 PM CDT Thu Aug 15 2024 ...New AVIATION... .MESOSCALE UPDATE... Issued at 902 AM CDT Thu Aug 15 2024 A few showers and storms have popped up this morning along a boundary in the vicinity of I-55 and should continue to increase this afternoon and evening, especially south of I-20. Morning sounding analysis and microburst checklist yield a chance for microbursts this afternoon, so isolated severe wind gusts could be possible. Additionally, hot and humid conditions will persist and should yield heat indices in the 105 to 112 range. This has prompted the issuance of a heat advisory for eastern areas and an excessive heat warning for central MS, SE AR and NE LA, as well as the HWY 98 corridor. That said, there has been a downtrend of dewpoints this morning, and dewpoints will play an important role in both hazards today, so will have to continue to monitor this for future updates./SAS/ && .DISCUSSION... Issued at 500 AM CDT Thu Aug 15 2024 Through the End of This Week: Heat and Humidity. Hard to say it is good for much, but in this case the increased humidity is at least enough to bring rain chances to our forecast area. That`s a positive for sure. The disturbance which moved south across the area yesterday is still in the region and may provide some enhanced rain chances farther south toward the Gulf Coast this afternoon and evening. A pool of 2.0+ PW air will be located south of Interstate 20 today, but even the drier air farther north should still have enough moisture (PW > 1.6-1.7) today to support some isolated showers or storms. The influence of the ridge aloft will be felt as temperatures climb into the mid and upper 90s before most shower or storm activity gets going. Forecast soundings show possibility of greater than 2000-3000 J/kg of SBCAPE and around 1000 J/kg of DCAPE, so some strong storms with gusty winds cannot be ruled out. Given the observed heat index values yesterday and the forecast for today/tomorrow/Saturday, felt it was reasonable to upgrade the western and southern portions of the forecast area to an Excessive Heat Warning and advertise "Extreme" dangerous heat impacts on the local HWO graphics to account for multi-day threat of 110+ heat indices especially west of Interstate 55 and down into the Pine Belt. Pop up showers or storms may provide some localized relief, but it appears we are in for a multi-day heat wave with the ridge centered to our west bringing the heat and surface ridging centered to our east keeping the humidity in place. A low pressure system pivoting over the Great Lakes will nudge a cold front toward the Mid-South/Interstate 40 corridor by Saturday afternoon, with increased jet stream winds accompanying the front southward. The increased flow and wind shear is expected to support severe storm development in the vicinity of the front Friday into Saturday, with storms then possibly moving southward into better instability either day. There is a Marginal Risk for organized severe storms Friday afternoon into evening for far northern parts of our area, and then across more of the CWA by Saturday afternoon and evening as the front moves into the area. Sunday into Next Week: Model guidance shows the front to get a better push southward toward the Gulf Coast Sunday into Monday. Main differences behind the front will be drier air and slightly cooler mornings (upper 60s vs mid 70s). Afternoons will feel cooler too, though mainly because of the lost humidity. /NF/ && .AVIATION... (18Z TAFS) Issued at 1223 PM CDT Thu Aug 15 2024 VFR conditions will prevail through the period with scattered clouds building this afternoon and into tonight. A few popup showers and storms are possible this afternoon, particularly I-20 and south. These should clear later this evening. Visibilities could lower to 6SM at southern sites tomorrow morning, with patchy fog possible, not likely to impact overall air travel. Winds will prevail from the southwest around 3 to 5kts./SAS/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 76 97 77 97 / 20 50 10 40 Meridian 75 97 74 97 / 10 50 10 50 Vicksburg 77 97 77 97 / 20 30 10 20 Hattiesburg 76 96 75 97 / 30 50 10 40 Natchez 76 96 75 96 / 30 30 10 20 Greenville 77 99 77 98 / 10 20 10 20 Greenwood 77 99 77 97 / 10 30 20 30 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...Excessive Heat Warning until 8 PM CDT this evening for MSZ018- 019-025>027-034>036-040>043-047>049-053>055-059>064-072>074. Heat Advisory until 8 PM CDT this evening for MSZ028>033-037>039- 044>046-050>052-056>058-065-066. LA...Excessive Heat Warning until 8 PM CDT this evening for LAZ007>009-015-016-023>026. AR...Excessive Heat Warning until 8 PM CDT this evening for ARZ074- 075. && $$ NF/NF/SAS20