Area Forecast Discussion
Issued by NWS Memphis, TN
Issued by NWS Memphis, TN
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891 FXUS64 KMEG 220244 AFDMEG Area Forecast Discussion National Weather Service Memphis TN 944 PM CDT Tue May 21 2024 ...New UPDATE... .UPDATE... Issued at 940 PM CDT Tue May 21 2024 A very mild night across the Mid-South at this hour. Temperatures are in the upper 70s to lower 80s with mid 60s dewpoints along and west of the Mississippi River. Immediately to our west, a tornado watch was issued about 30 minutes ago. The latest KLZK radar sweep reveals a line of several supercells to the north and west of Little Rock. The environment there is well supportive of all hazards with over 2000 J/kg of MLCAPE, 60 knots of bulk shear, and 300 m2/s2 of SRH. Storm motion is pretty healthy at around 40 mph and a couple of warnings are currently in effect in LZK`s CWA. Downstream, the latest mesoanalysis data over eastern Arkansas is less robust. The majority of the region is capped with and MLCAPE values around 1000 J/kg. The latest Hi-res model guidance suggests that the storms will likely congeal into a line and contain pose a large hail and damaging wind threat. Although LCLs are around 1500 meters, a low-end tornado threat will also exist, mainly in eastern Arkansas. Additionally, mid-level lapse rates are exceptional coming in around 8.5 C/km. Storms are progged to arrive in eastern Arkansas within the next 2 hours or so. The overall trend should be a weakening state, but the discrete supercell north of Little Rock may continue to chug east with only slight weakening into eastern Arkansas. The line or storms will likely weaken and break apart as it approaches the Mississippi River around midnight. Although there is no official mesoscale discussion, the chance of a convective watch should remain below 50 percent. Increased PoPs in the short term to account for the faster storm arrival. The rest of the forecast is in good shape with no further edits needed at this time. AC3 && .SYNOPSIS... Issued at 327 PM CDT Tue May 21 2024 A ridge of high pressure will weaken tonight with a cold front bringing a return of shower and thunderstorm chances back to the Mid-South. A strong to severe thunderstorm is possible across portions of northeast Arkansas and the Missouri Bootheel late tonight, However, the greatest potential for severe thunderstorms will be Wednesday afternoon into Wednesday night across the Mid- South. Damaging winds will be the primary severe weather threat with a secondary threat of large hail, heavy rainfall, and possibly a tornado. A period of unsettled weather will persist across the Mid-South beginning late tonight and continuing through early next week. && .DISCUSSION... (This evening through next Monday) Issued at 327 PM CDT Tue May 21 2024 GOES-16 Water Vapor Satellite trends this afternoon show a mid- level trough moving into the Upper Midwest, an elongated upper-level ridge present from the Great Lakes Region back through the Southeast U.S. and portions of the Lower Mississippi Valley. This has resulted in another warm and dry afternoon with temperatures in the middle to upper 80s as of 2 PM CDT. Strong to severe thunderstorm potential will remain the predominant concern in this afternoon`s forecast issuance, especially for the next two days. Short-term models indicate the aforementioned upper-level ridge will begin to break down tonight across the Lower Mississippi Valley with 20-30 dm 500 mb height falls occurring north of I-40. A mid-level shortwave trough and associated cold front will drop into the Mid-South late tonight into Wednesday morning bringing a return of showers and thunderstorms back to the area. Short-term models, particularly the operational CAMs have struggled with the overall evolution of convection across the Mid-South into Wednesday night. Nonetheless, a broken convective line is expected to gradually weaken north of I-40 overnight. Steep 700-500 mb mid-level lapse rates, surface-based CAPE values, and 0-6 km bulk shear values between 40-45 kts suggest a potential for strong to severe thunderstorms initially with damaging winds and large hail being the severe weather threats until the storms become elevated late in the night. This weakening convection is expected to leave behind outflow boundaries which may interact with with an MCS/MCV to produce redevelopment of showers and and thunderstorms across the Mid- South Wednesday afternoon into Wednesday evening. Large hail and damaging winds will continue to be the primary severe weather threats, with a secondary threat of heavy rainfall as precipitable water values will remain high. A tornado or two may be possible if there is enough streamwise vorticity available in the pre- convective environment as can be the case with MCVs. Operational and ensemble model runs indicate an unsettled pattern will persist for Thursday through early next week as the aforementioned cold front washes out over the Lower Mississippi Valley and another front drops into the region for Memorial Day. Additional strong to severe thunderstorms are possible during this period, especially for portions of the forecast area Thursday and again on Sunday. CJC && .AVIATION... (00Z TAFS) Issued at 611 PM CDT Tue May 21 2024 Two rounds of showers and thunderstorms are expected to move through the Mid-South during the forecast period. The first round of thunderstorms will enter portions of northeast Arkansas after midnight and spread across much of region through the overnight hours before weakening sometime Wednesday morning. Another round of thunderstorms are expected for Wednesday afternoon. In between the two rounds of thunderstorms, a period of MVFR ceilings are expected. Winds will be mainly from the south at 10 to 15 knots with periods of higher gusts. && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$ PUBLIC FORECAST...CJC AVIATION...ARS