FXUS64 KJAN 181718 AAA AFDJAN Area Forecast Discussion...UPDATED National Weather Service Jackson MS 1218 PM CDT Mon May 18 2026 ...New MESOSCALE UPDATE, AVIATION... .KEY MESSAGES... - Heat and humidity more typical of early summer can be expected along with increasing thunderstorm chances this week. - Isolated severe storms are possible in the northwest Tuesday. && .MESOSCALE UPDATE... Issued at 1218 PM CDT Mon May 18 2026 Rest of today and tonight... The region remains on the western periphery of subtropical ridge parked just east of the Atlantic seaboard and amplified mean troughing, with the center over the Rockies. The cold core and attendant surface low/frontal system will eject into the northern Plains to Great Lakes region tonight. With warm/moist advection (thermal profiles at 850mb in the mid to upper teens and PWs of 1.5 to 1.75 inches along and west of Interstate 55), increased cloud coverage and isolated to scattered rain and storm chances will be possible across southern to southwest MS and northeast LA this afternoon into early evening. GOES East and observed soundings to the east indicate drier thermal profiles (1.0 to 1.2 inch PWs), so rain chances should remain low to non-existent. Seasonable warmth is expected today, some 4F to 8F above (highs: 86F to 91F). Thermodynamic parameters remain sufficient (7.0 deg C mid level lapse rates;25C to 28C vertical totals; MLCAPE (800-1200J/kg) and SBCAPE (1200-2000J/kg). Deep shear (20 to 25kts) that could support some strong storms in the west this afternoon to evening but confidence in severe storms remains low. This has a feel of a typical diurnal summertime storm afternoon, but a rogue multicell storm or microburst cannot be ruled out. Return flow of low level moisture will bring some low clouds and visibility reductions. Probabilities remain low for dense fog and some light wind will be present. Thus, no mention is needed in HWO just patchy visibility reductions in the Pine Belt by daybreak. Forecast was shipped out earlier. Lows will be seasonably warm, some 10F to 15F above (70F to 72F east of I-55 to 73F to 75F along and west of I-55). /DC/ && .DISCUSSION... Issued at 330 AM CDT Mon May 18 2026 Through Tonight: Continued warmer than normal through the period with afternoon rain chances limited to the southern half of the CWA. Surface ridging from the east will remain across the Gulf coast states while our flow aloft remains southwesterly downstream of an upper level trough swinging across the Four Corners region. This will help maintain a warm moist airmass over our CWA. Latest PWATs were running just above an inch and three quarters with surface dew points being observed in the upper 60s to lower 70s. Wl start off with some patchy fog in the southeast but daytime heating of our moist airmass will lead to isolated to scattered showers and thunderstorms during the afternoon and mainly south of Interstate 20. The distinct diurnal nature of the convection will result in the convection dying off rapidly around sunset. The probabilities of fog development are lower for Tuesday morning but patchy light early morning fog is possible in the southeast again. /22/ Tuesday through Sunday: A frontal boundary will continue to progress towards the southeast before stalling north of the CWA. Ongoing showers and storm chances are expected through the extended period. Highs (ranging in the 80s) will remain near seasonal averages and lows (upper 60s/near 70 degrees) will run +5-8 degrees above seasonal averages over the extended as well. Precip chances ranging from 40% to 95% with greatest chances on Wednesday (95%) and Friday (90%) with 80-95% are likely. On Tuesday, the boundary gradually push into the area, interaction with the present deep-layer shear and CAPE near the MS Delta, may promote a few severe storms in the area. As a result, a 'Marginal' risk for severe weather will be possible over the MS Delta region Tuesday. A HWO graphic will be introduced to reflect the severe risk area. As the boundary stalls, multiple shortwave disturbances are expected to traverse the region, providing addition moisture and increasing rain chances Wednesday into the weekend. Organized severe weather is not anticipated as instability won't be as favorable, however, an isolated severe storm or two may be possible. Estimate rainfall amounts may range from 1.0-3.5 inches over the course of this week and the weekend. Received rainfall will help alleviate the ongoing drought over the ArkLaMiss region. /SW/ && .AVIATION... (18Z TAFS) Issued at 1218 PM CDT Mon May 18 2026 VFR flight categories will prevail at area TAF sites this afternoon and into this evening. An isolated thunderstorm or two can't be ruled out during the late afternoon hours, but these will quickly dissipate around sunset. If observed on-site, a reduction in flight categories to MVFR/IFR status will be possible. Another bout of MVFR/IFR ceilings will be possible at sites mainly along south of the Interstate 20 corridor early Tuesday morning, with a reduction of visibilities to MVFR/IFR status around day break due to patchy fog at namely KPIB and KHBG. Through Tuesday morning, categories will steadily improve to VFR status as both patchy fog and low stratus erode. Breezy southerly winds will subside a bit this evening to between 3-8 knots. /19/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 73 89 70 86 / 10 40 50 70 Meridian 71 90 68 88 / 10 20 30 30 Vicksburg 74 90 70 84 / 10 40 60 90 Hattiesburg 72 89 69 89 / 0 20 0 40 Natchez 75 90 71 85 / 20 50 60 90 Greenville 74 91 70 83 / 10 40 60 90 Greenwood 75 91 70 84 / 20 30 70 90 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ DC/SW/19