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Area Forecast Discussion
Issued by NWS Jackson, MS
Issued by NWS Jackson, MS
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037 FXUS64 KJAN 171800 AAA AFDJAN Area Forecast Discussion...UPDATED National Weather Service Jackson MS 100 PM CDT Sat Aug 17 2024 ...New AVIATION... .MESOSCALE UPDATE... Issued at 1155 AM CDT Sat Aug 17 2024 Rest of today... Morning RAP/water vapor analysis indicates ridge centered over west TX into NM, with our region on the southern periphery of increased northwest flow. Anomalous, tropical PWs near the 2 inch mark & steep low-level lapse rates favor increased microburst potential developing across the I-20 corridor & is being observed in morning mesoanalysis. To the northwest, there have been overnight remnant outflow boundaries & gravity waves that emanated southeast from convective storm complex in south- central AR & propagated to the southeast. This has somewhat convectively overturned areas northwest of the Natchez Trace into the Delta, with some potential for dewpoints to slightly mix down a touch lower. With a shortwave diving southeast into the area & potential for convective initiation in this favorable thermodynamic environment (i.e. 26-28C vertical totals, DCAPE of +1000 J/kg steep lapse rates & northerly flow in the 0-2 to 0-6km layers up to 15-20kts), isolated to scattered diurnal storms, some strong- severe, are a low-medium chance today. After coordination with SPC, the ongoing "Marginal" risk area has been adjusted southward, with the focus of convection along & south of a line from near Bastrop in LA to Yazoo City to Macon in MS. Damaging wind gusts & some hail up to quarter size remain the main concerns. Heat to the northwest of where the most vigorous aftn convection & air is overturned may not have as much Excessive Heat potential, but will be very favorable to the southeast. Left the ongoing Heat graphics & headlines as is. Adjusted rain & storm chances slightly southeast, with only low chance northwest of the Trace (15-20%) & low-medium chance along & southeast (25-45%). Updates are out. /DC/ && .DISCUSSION... Issued at 403 AM CDT Sat Aug 17 2024 Today and Tonight: A moist tropical air mass remains in place across the Lower Mississippi River Valley today, with analyzed PW values of 1.8-2.0 inches this morning representing the 50-75th percentile range for mid August. Northwest flow between a ridge over the Desert Southwest and low pressure system over the Great Lakes is carrying waves in the jet stream across the Great Plains and interacting with a frontal boundary in the region. One such wave overnight steered an MCS into the heart of Arkansas before it lost momentum. A breakaway portion of the energy is continuing east with storms in the Memphis area, while an MCV developed from the remnant MCS and is sustaining training thunderstorms with heavy rain over western Arkansas. Warm advection is ongoing south of the front, helping to bring the heat from the Southwest ridge toward our forecast area. High temps again today should be in the 97-101 range for most of the area. The moist air mass in the region is capable of supporting shower and thunderstorm development with daytime heating again today, and it appears that the wave aloft and convergence along the remnant outflow boundary might favor the eastern and southeastern portions of our forecast area today. Storms will have 2500-3500 J/kg of SBCAPE and 1000+ J/kg of DCAPE to work with, so localized damaging winds are possible with any strong to severe storms. Deep layer wind shear of 10-20 kts will add some organization to storms and favor southeastward moving storms. There is a Marginal Risk for severe thunderstorms tied specifically to this possibility this afternoon and evening, but it is always worth noting some isolated microburst potential exists elsewhere too just given the thermodynamic profile. /NF/ Sunday through next Friday: By Sunday, surface ridging is expected to maximize across the region ahead of a "cold" frontal boundary. Sunday looks to be our hottest day this week, with many areas along and west of I-20 reaching triple digit highs and heat indices. Excessive Heat Warning/Heat Advisory products will be likely on Sunday as dangerous heat stress dominates the beginning of the extended period. In addition to heat, conditions for a Slight Chance (2/5) of severe storms will be possible, with the highest chance of storms along and north of the I- 20 corridor. Enhanced westerly flow along with increased instability will create the potential for damaging wind gusts with with more mature updrafts. The main threat for severe storms looks to exists mostly in the afternoon into the late evening, with hires guidance hinting at a potential MCS moving into SE AR/NW LA by the early evening hours. By Monday into the remainder of the extended period, a much needed break from dangerous heat will take place. High temperatures will range in the upper 80s to lower 90s through Thursday, with lows in the low 60s to low 70s. Rain chances will remain fairly minimal with isolated (15-30%) chances in the far southeast on Thursday and Friday. /AJ/ && .AVIATION... (18Z TAFS) Issued at 100 PM CDT Sat Aug 17 2024 VFR flight conditions are expected to prevail through the TAF period. Scattered cumulus/cirrus cloud cover; however; ceilings aren`t impacted. Between 19Z Saturday-02Z Sunday, VCTS/VCSH/-SHRA will be possible for sites near and south of I-20. Local decreased visibilities and gusty winds above 40 kts will be likely near storms. After 02Z Saturday, quiet conditions will prevail. Additional thunderstorms will be possible Sunday afternoon. /SW/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 76 100 75 93 / 20 20 40 20 Meridian 74 101 71 94 / 20 30 30 10 Vicksburg 76 101 75 93 / 20 20 40 20 Hattiesburg 76 100 76 95 / 30 20 30 20 Natchez 76 100 75 93 / 20 10 30 20 Greenville 75 100 73 91 / 20 20 40 20 Greenwood 75 100 73 92 / 20 20 30 10 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...Excessive Heat Warning until 8 PM CDT this evening for MSZ018- 019-025>029-032-034>037-040>044-047>050-053>057-059>066- 072>074. Heat Advisory until 8 PM CDT this evening for MSZ030-031-033-038- 039-045-046-051-052-058. 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. && $$ DC/AJ/SW