Forecast Discussion
514 FXUS64 KMEG 181540 AFDMEG Area Forecast Discussion National Weather Service Memphis TN 1040 AM CDT Sat Oct 18 2025 ...New DISCUSSION, AVIATION, FIRE WEATHER... .KEY MESSAGES... Updated at 1040 AM CDT Sat Oct 18 2025 - A cold front will pass through the Mid-South Saturday evening, bringing a threat of strong to severe storms. Damaging wind is the primary severe weather threat. - Temperatures will cool significantly starting Sunday into next week with highs in the upper 60s to mid 70s. Lows will generally be in the 40s. && .DISCUSSION... (This afternoon through next Friday) Issued at 1040 AM CDT Sat Oct 18 2025 Some loosely organized convection has started to gather along the leading edge of a cold front draped across the Southern Plains as of 11AM Saturday. As we move into the afternoon, this convection will start to become more linearly aligned and keep a very progressive forward motion as it approaches the Mid-South. Latest CAMs are in pretty good agreement that the line of storms will be at the western doorstep of our CWA by about 23Z/6PM. Given how quickly the front is moving, most of this convection should be out of our area shortly after midnight. Digging into the parameter space, instability is certainly going to be the limiting factor tonight. The HREF mean SBCAPE field depicts a corridor of about 1500 J/kg over the ArkLaTex this afternoon that quickly gets pinched off after 00Z. By the time any of the convection actually arrives this evening, we`ll most likely only be working with 500 J/kg of instability at best. While this isn`t much, a moderately sheared environment in a transitional season setup like this doesn`t necessarily need a lot of instability to be problematic. With bulk shear on the order of 50 kts, these storms will have plenty of organizational support to hold together as they make their way across the Mid-South tonight. In terms of hazards, damaging winds are the primary threat. DCAPE values (via point soundings) in excess of 800 J/kg will support hefty downdrafts with storms on the leading edge of the front. In addition, the environment looks moderately sheared in the midlevels, which indicates a strong potential for bowing segments of storms in any multicell clusters. As far as the low levels go, again there is moderate 0-1 km shear to speak of (~20 kts), but the orientation of all the kinematic fields is essentially parallel to the storm motions we are expecting. This does not really allow for much of any spin, which is reflected in the very meager helicity at all levels. Especially because this convective mode is looking extremely linear, there is very little mesocylonic tornado threat. If a tornado does develop, it will likely be a very quick spinup embedded in a QLCS on the low end of intensity. Hail is essentially negligible at this point considering our 500-700 mb lapse rates are expected to be right around 5.5 C/km this evening, if not lower. While PWATs are in the upper echelon of climatology for October, storms will most likely be moving too fast to cause noteworthy flooding issues. This is not looking like a scenario for training storms either, so any heavy downpours should be short-lived. QPF for the entire FROPA is about 1 inch max. After the front moves through shortly after midnight, temperatures take a drastic plunge. A tight pressure gradient tomorrow will encourage relatively "brisk" NW winds, aiding the CAA that will keep temperatures in the 60s for most areas Sunday afternoon. Monday morning looks like the first genuinely chilly morning of the season so far; 40s are expected areawide due to the combination of optimal radiational cooling conditions and residual CAA. A reinforcing (mostly) dry cold front is expected to move through on Tuesday, further locking in this cool pattern. Temperatures will be at or just below normal through at least Friday in the low 70s. In short: cool days, chilly nights. CAD && .AVIATION... (18Z TAFS) Issued at 1040 AM CDT Sat Oct 18 2025 Latest CAM guidance still indicating the best potential for TS to occur at TAF sites will be between 23-01Z at JBR, 1-3Z at MEM, and 2-5Z at MKL and TUP. This aligns well with the latest TCF guidance. A few lingering post-frontal showers may occur at JBR, MKL, and MEM overnight with much drier air filtering in on Sunday. A lingering tight pressure gradient will result in gusty NW winds on Sunday. && .FIRE WEATHER... Issued at 1040 AM CDT Sat Oct 18 2025 A cold front will move through the Mid-South tonight, bringing about 1 inch of wetting rain. Starting Sunday, cool and progressively drier conditions are expected. Afternoon MinRH values will likely fall below 30% by Tuesday and continue hovering in the 25-30% range through at least Thursday. As such, minor fire danger is noted midweek. However, winds should be light enough to mitigate significant fire weather concerns. Humidity increases again at the end of the week. && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$ PUBLIC FORECAST...CAD AVIATION...CJC