Area Forecast Discussion
Issued by NWS Memphis, TN
Issued by NWS Memphis, TN
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515 FXUS64 KMEG 220926 AFDMEG Area Forecast Discussion National Weather Service Memphis TN 426 AM CDT Sat Jun 22 2024 ...New SYNOPSIS, DISCUSSION... .SYNOPSIS... Issued at 425 AM CDT Sat Jun 22 2024 A ridge of high pressure will bring mainly rain free weather and very hot temperatures in the middle 90s to the Mid-South this afternoon. Increasing humidity combined with temperatures rising into the upper 90s may result in heat index values at or above 105 degrees for portions of the area Sunday through Tuesday. A cold front will bring the best potential for showers and thunderstorms followed by slightly cooler air for mid to late week. && .DISCUSSION... (Today through Friday) Issued at 425 AM CDT Sat Jun 22 2024 Surface and upper-level ridging remain in place across the Lower Mississippi and Tennessee Valleys early this morning. This is resulting in rain free weather across the Mid-South. A warm and humid airmass is present across the region with 4 AM CDT temperatures in the 70s with surface dewpoints in the upper 60s to lower 70s. Another warm and mainly dry day is expected across the Mid-South today as 925 mb temperatures rise to around 26C, translating into afternoon temperatures into the middle to upper 90s. Heat index values are anticipated to rise to around 100 degrees. The upper- level ridge will begin to retrograde west to the Southern Plains tonight with rain free weather expected to persist across the forecast area. Some timing discrepancies persist with the operational short-term models as a weak back door cold front is expected to drop into portions of the Tennessee Valley Sunday night into Monday. The NAM continues to be the most aggressive of the models bringing the potential for showers and thunderstorms into the area as early as Sunday morning. Meanwhile, the GFS, ECMWF, and CMC lean towards potential Sunday afternoon/Sunday night isolated to scattered convection. HREF Grand Ensemble members show surface-based instability increasing to around 2000 J/kg with overall shear remaining around 20 kts. This weakly sheared environment will present challenges for short-term CAMs to resolve the overall convective coverage/potential. Strong instability and a weakly sheared environment would favor pulse-type thunderstorms mainly during the afternoon and evening hours. However, mid-level lapse rates will remain poor (< 6 C/km) and this may help to mitigate the overall severe thunderstorm potential. Gusty winds would be the main threat if a strong thunderstorm or two were to occur. Confidence is higher with the potential for a Heat Advisory for portions of the Mid-South, especially for areas around and southwest of Memphis on Sunday. Very hot temperatures in the upper 90s combined with surface dewpoints in the lower to middle should yield heat index values at or slightly above 105 degrees. Very hot and humid conditions are expected to continue into Tuesday with a better potential for Heat Advisories to encompass a larger portion of the forecast area. Long-term operational and ensemble model solutions indicate a gradual increase in shower and thunderstorm chances by Wednesday as the upper-level ridge moves to the Southwest United States, and placing the Lower Mississippi Valley on the eastern periphery of the ridge. This will allow for a cold front to move through the area on Wednesday, bringing a temporary break in the very hot temperatures. Temperatures will begin to increase by next weekend as mid-level heights increase back across the region. CJC && .AVIATION... (06Z TAFS) Issued at 1138 PM CDT Fri Jun 21 2024 VFR. Light and variable winds will become SSW by late morning. Guidance is hinting at isolated to scattered -SHRA at JBR at the end of the period. Not enough confidence to add at this time. ACH/AC3 && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$ PUBLIC FORECAST...CJC AVIATION...AC3