textproduct: Jackson

KEY MESSAGES

- Isolated severe storms are possible in the northwest Tuesday evening.

- Heat and humidity more typical of early summer can be expected along with increasing thunderstorm chances this week into the weekend.

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

DISCUSSION

Issued at 219 PM CDT Mon May 18 2026

Rest of the week into weekend (Tuesday through Sunday)...

Longwave trough will be ejecting into Canada and Hudson Bay region. Persistent summertime pattern of seasonable warmth (4F to 8F above and highs in 88F to 92F) and moisture (forecasts of 1.5 to 1.9 inches) will be the norm. Diurnal shower and thunderstorm activity will be a concern ahead of a few perturbations in the southwesterly flow (20 to 55 percent) and increased heat and humidity. With some steep lapse rates (vertical totals near 27C to 29C), some strong to isolated severe storms remain possible Tuesday and into mid week. There is anticipated of afternoon development in the Plains should sink southeast into the Ozarks in the evening and make it into the area by late afternoon into early evening. Storm mode is a question but even a southeast traversing cold pool could initiate some strong to isolated severe thunderstorm activity into Tuesday evening. While there could be some diurnal activity between 3-5PM, the concern for severe storms will be mainly after 6PM and last until just after midnight. The ongoing HWO graphic remains valid, but the timing has been slowed down into the evening to just after midnight (6PM Tuesday through 2AM Wednesday). Deep flow/bulk shear will be light (15-25kts) and variable and storm organization will need to be in tandem to the southwesterly low level flow. This could hinder any southeastward propagating MCS, which is alluded to in some convective allowing model (CAMs) output. With generally southerly to southwesterly flow in the low levels, cold pools may eventually get out of balanced and more cold pool dominant, decreasing the severe potential closer to Interstate 55 and central portions of the area closer to or just after midnight. Damaging wind gusts and hail remain the main concerns.

As a stronger wave swings into the Great Lakes and surface low ejects into eastern Canada (995mb to 1000mb), front will shift south southeast towards the Gulf states. Several perturbations will enhance upper diffluence, increasing ascent and moisture advection. This will drive higher coverage of rain and storms (45 to 90 percent Wednesday and Thursday). High temperatures will be seasonable (mid to upper 80s Wednesday to low to mid 80s rest of the week) with lows less seasonable, from 8F to 12F above (upper 60s to low 70s). With less seasonable temperatures, humidity and lapse rates, some stronger storms are likely and marginally severe storms remain possible. Mid to deep layer bulk shear will remain sufficient (around 30kts), with low level shear around 15-25kts. This will keep potential marginally severe concerns through the remainder of the work week (Wednesday through Friday). Rain totals for the week will be around a couple of inches (1 to 3 inches), which will help lessen some long term drought concerns. Large scale synoptic pattern (i.e. southwesterly return flow, warm advection, high PWs near 2 inches) will persist, keeping rain chances high late week into the weekend (70 to 90 percent Friday through Sunday). Some low end severe potential cannot be ruled out, but lower severe probs and less heat and shear juxtaposed will keep mention of anything in HWO on a day-to-day basis, each day dependent on previous day's storm evolution. Rain totals will add up (additional one to three inches, with storm total rain through the weekend of 4 to 6 inches), continuing improvements to long term drought concerns. /DC/

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 71 86 / 10 30 40 60 Meridian 71 90 70 88 / 10 20 20 30 Vicksburg 74 90 70 85 / 10 40 50 80 Hattiesburg 72 89 69 88 / 0 20 10 50 Natchez 75 90 71 86 / 20 50 60 80 Greenville 74 91 71 83 / 10 40 60 90 Greenwood 75 91 71 85 / 20 30 60 90

JAN WATCHES/WARNINGS/ADVISORIES

MS...None. LA...None. AR...None.