FXUS64 KJAN 071053 AAA AFDJAN Area Forecast Discussion...UPDATED National Weather Service Jackson MS 553 AM CDT Fri May 7 2021 .UPDATE... Updated for 12Z aviation discussion && .AVIATION... 12Z TAF discussion: VFR conditions will prevail through Saturday morning. /22/ && .DISCUSSION... Today and tonight: Cooler than normal and dry through the period. Early morning water vapor imagery/RAP analysis showed the circulation through an amplified upper level ridge over the Rockies and a large upper level trough over the eastern CONUS. The resulting northwest flow aloft across our region will help a >1022mb high move over our CWA from the northwest today then shift east of Mississippi tonight. This will result in a light return flow by sunrise Saturday morning but low temperatures will be in the low to mid 50s. Normal lows run in the upper 50s to lower 60s. Highs today will range from the lower 70s northeast to the upper 70s south. our normal highs run in the lower 80s. /22/ Saturday through Thursday: The flow aloft will become more zonal this weekend after an upper- level ridge breaks down on Saturday. The change in pattern should allow a shortwave to slide east in the flow Saturday night into Sunday, while an accompanying surface low develops over the central High Plains and ejects east. Return flow in the wake of departing high pressure and ahead of the surface low will help to bring deeper moisture back across East TX, northern LA, and the reaches of the MS Delta by Sunday afternoon. As the low pressure system's attendant cold front moves south into this increasingly unstable air mass, thunderstorms are expected to develop along and ahead of the front. SBCAPE values of 1500-2500 J/kg in this plume of deeper moisture should be sufficient enough for thunderstorms to develop strong updrafts, while strengthening deep layer shear (30-40 kts 0-6km shear) should be enough to organize some supercells. Severe weather threats will primarily be hail and damaging wind gusts. Drier air (PWATs less than 1.25 inches) lingering in the eastern half of Mississippi should limit shower and thunderstorms in central and eastern Mississippi until the overnight hours. Flow aloft should propagate storms eastward through the afternoon and evening, eventually spreading even across Mississippi. With the loss of daytime heating, expect the threat for severe weather to decrease. But high moisture content, the presence of a weak cold front sagging into the region, and westerly flow in the lower levels will increase the threat for training heavy rainfall and flash flooding into Sunday night. A Limited threat area for flash flooding has been added to the Hazardous Weather Outlook text and graphics for Sunday night to account for this. The area of greatest concern will be where the front focuses heavy rain overnight, currently expected to be through far northeast Louisiana, far southeast Arkansas, and northwestern portions of Mississippi and the Delta. Depending on where convection occurs along the front and how outflow from storms can reinforce it, the stalling frontal boundary will likely serve to focus additional waves of thunderstorms and heavy rainfall across the Gulf Coast region and areas inland on Monday, Tuesday, and Wednesday. We will continue to monitor trends in the guidance and outlook any areas of greater severe and/or flooding risk as needed, but current trends suggest the threat for flooding may shift to the southern half of our forecast area for early next week. For the time being though, there is enough uncertainty in place and timing that no additional outlook areas will be highlighted with this forecast. By Thursday, an upper-level trough moving across the northern and central CONUS should sweep deeper moisture east of our forecast area, with drier air arriving once again from the west. /NF/ && .PRELIMINARY POINT TEMPS/POPS... Jackson 75 52 82 62 / 0 0 0 3 Meridian 75 50 82 58 / 0 0 0 0 Vicksburg 76 53 84 64 / 0 0 0 4 Hattiesburg 77 52 82 60 / 0 0 0 0 Natchez 77 55 83 64 / 0 0 0 3 Greenville 74 55 83 65 / 4 1 0 6 Greenwood 74 54 82 64 / 0 4 0 4 && .JAN WATCHES/WARNINGS/ADVISORIES... MS...None. LA...None. AR...None. && $$ NF/22