Forecast Discussion
403 FXUS64 KMEG 211117 AFDMEG Area Forecast Discussion National Weather Service Memphis TN 617 AM CDT Tue Apr 21 2026 ...New AVIATION... .KEY MESSAGES... Issued at 616 AM CDT Tue Apr 21 2026 - Elevated fire danger is anticipated across the majority of the Mid-South this afternoon due to a combination of elevated winds, low humidity, and temperatures in the 80s. - Warm and dry conditions with highs in the low to mid 80s will continue through Thursday, though relative humidity will edge higher. - Warm and humid conditions will prevail Friday through the weekend. Shower and thunderstorms will be possible each day. && .DISCUSSION... (Tonight through next Monday) Issued at 1107 PM CDT Mon Apr 20 2026 00Z upper air analysis showed a large upper low off the Pacific coast, and longwave trough exiting the eastern seaboard. Between these two systems, upper level ridging extended through the Rockies and central Great Plains, undercut by a weak southern branch wave over TX. As we move into midweek, the central plains ridge will transit eastward to the MS River Valley, while south TX wave weakens and moves toward the upper Gulf coast. The net effect for the Midsouth will be a slight increase in 500mb heights. 850mb temps increase to around 10C on Tuesday, which is relatively cool when considering boundary layer temps in the low 80s F. This implies steep low level lapse and deep mixing on a day when minimum surface RH values are forecast range from 20-30%. Where dead fuels remain among the recent vegetative green-up, wildfire danger will be elevated Tuesday afternoon. This is particularly the case where stronger winds are expected over the MS River delta north and northwest of Memphis. Warming dewpoints and moderating winds should moderate wildfire danger Wednesday. The upper pattern will remain progressive during the mid to late week. The bulk of the energy associated with the aforementioned Pacific coast upper low will lift into the northern Great Plains, while a strong zonal southern jet extends around the southern periphery of the low, across the southern Great Plains. By Friday, diffluent midlevel flow will overspread the Midsouth. At such a time, the LREF depicts PWAT values of 1.4 inches (90-95% percentile of climatology). If clouds and early day rainfall don`t stabilize the atmosphere too much, the LREF-depicted surface-based CAPE of 500-1000 J/kg could be realized Friday afternoon. Deep layer shear appears marginal (25-30KT) and it`s a bit early to confidently forecast CAPE. But the ingredients may come together for a few strong thunderstorms and beneficial rainfall. Rainfall chances will continue through the weekend, under relatively strong west/southwest flow aloft and PWATs remaining above the 90th percentile. Medium range model consensus begins to fade by late weekend, but the loose LREF consensus suggests that a southern branch trough will eject from the southern plains into the mid-MS River Valley early Monday. Such a feature could bring a more focused thunderstorm event to the Midsouth, but confidence in such a scenario is limited at this time. && .AVIATION... (12Z TAFS) Issued at 616 AM CDT Tue Apr 21 2026 Confidence is high for VFR conditions prevailing through the period as high pressure builds over the Lower Mississippi Valley. A nearby tight pressure gradient will result in sustained SSW winds increasing to 12 to 16 kts with occasional gusts up to 26 kts after 15Z at all sites except TUP. Winds will decrease by this evening. && .FIRE WEATHER... Issued at 1107 PM CDT Mon Apr 20 2026 A Rangeland Fire Danger Statement is in effect for Tuesday. Minimum relative humidity of 20-30% will accompany 20 foot winds 10 to 20 mph over northeast Arkansas and the Missouri bootheel, and 5 to 15 mph over the remainder of the Midsouth. Humidity will gradually moderate Wednesday through Thursday, in advance of wetting rainfall Friday through the weekend. && .MEG WATCHES/WARNINGS/ADVISORIES... AR...None. MO...None. MS...None. TN...None. && $$ PUBLIC FORECAST...PWB AVIATION...CJC