####018005726#### FXUS64 KMRX 031841 AFDMRX Area Forecast Discussion National Weather Service Morristown TN 241 PM EDT Fri May 3 2024 ...New SHORT TERM, LONG TERM... .SHORT TERM... (This evening through Saturday) Issued at 240 PM EDT Fri May 3 2024 Key Message: A few instances of small hail, gusty winds, and locally heavy downpours are possible this afternoon with showers and thunderstorms. Discussion: Currently showers and thunderstorms are traversing across much of the southeastern United States being aided by a shortwave moving through the Tennessee Valley this afternoon. As of this writing there is predominantly just rain showers, but increasing instability means we'll likely see more thunderstorms moving through the southern Appalachians through the rest of the evening. Soundings and CAMs are still showing a few hundred (maybe up to near 1000) J/kg of MLCAPE the rest of this afternoon. Combine this with a fairly week lapse rate and very little shear, and the chances for widespread sever weather continue to look low. With that being said an individual thunderstorm could bring brief heavy rain, small hail, and gusty winds in areas that have destabilized this afternoon. With how slow these storms are currently moving and the possibilty of multiple storms over a small area, the biggest threat the rest of the afternoon/evening is likely to be flooding of low lying or poor drainage areas. As we head into the overnight hours we should see a lull in activity, and although the threat of rain does not go away, but the risk of lightning and strong storms really decreases as the shortwave exits the area and the atmosphere becomes more stable overnight. On Saturday we will likely see a similar story as today, with morning showers transitioning into afternoon thunderstorms with heavy rain, small hail, and gusty winds as the primary hazards in the strongest storms. Forecast soundings show a similar environment with weak to moderate CAPE and weak shear, so once again widespread severe weather looks unlikely. && .LONG TERM... (Saturday night through next Friday) Issued at 240 PM EDT Fri May 3 2024 Key Messages: 1. An unsettled pattern is expected through the extended period with daily scattered to numerous showers and storms. More organized convection is possible by Wednesday/Thursday of next week. 2. Temperatures will be generally above normal. Discussion: We start the period with a fairly weak upper level flow pattern over the region and a short wave moving through. Most model guidance suggest the short wave will exit by early Sunday, with short wave ridging building in. This may allow for less coverage of showers and thunderstorms Sunday afternoon, but it still looks like there will be enough moisture and instability for at least scattered convection. The upper level ridging looks to be short lived as another short wave aloft moves in Sunday night/Monday, along with more numerous showers and thunderstorms. Models suggest modest instability with MLCAPES likely around 100J/kg or less for both Sunday and Monday and shear will be on the weak side given the weaker flow. However some stronger storms with gusty downburst winds will be possible as well as locally heavy rainfall rates given the near 90th percentile PWATs (around 1.4 inches both days). The unsettled pattern will continue for the Tuesday through Friday time frame, although timing of individual short waves in the flow is uncertain. Ensembles do suggest a more dynamic pattern developing with the upper jet nosing in from the west/northwest then dipping south, and mean 850 mb flow will likely increase to 30+ kts and may exceed 40 kts at some point during the period. In addition, a cold front is forecast to be moving in from the northwest by the end of the period. There are still model differences and timing questions, but the data does indicate that by Wednesday we will see an environment with potentially better thermodynamics and deep-layer shear sufficient for more organized convection than in the earlier part of the extended period. This will bear watching going forward. The long term period will generally feature temperatures above seasonal normals, although precipitation timing/coverage may help to hold high temperatures down on some wetter days, and the cold front moving in Friday is expected to help hold temperatures Friday down closer to normal although timing that far out is of course still very uncertain. && .AVIATION... (18Z TAFS) Issued at 111 PM EDT Fri May 3 2024 Showers and thunderstorms can be expected in the southern Appalachian region through the rest of the daytime hours today. Difficult to say exactly when a storm may impact a terminal and there could be several rounds of storms through the evening hours. Expect mostly showers, but cannot completely rule out lightning in the vicinity of the airports. We should see a lull in activity overnight, with more widespread storms and lightning expected tomorrow. && .PRELIMINARY POINT TEMPS/POPS... Chattanooga Airport, TN 84 66 81 64 / 70 70 80 30 Knoxville McGhee Tyson Airport, TN 77 63 78 63 / 80 70 90 50 Oak Ridge, TN 76 63 78 62 / 90 60 90 40 Tri Cities Airport, TN 79 61 76 59 / 70 50 90 60 && .MRX WATCHES/WARNINGS/ADVISORIES... NC...NONE. TN...NONE. VA...NONE. && $$ SHORT TERM... AVIATION... ####018004465#### FXUS62 KCAE 031841 AFDCAE Area Forecast Discussion National Weather Service Columbia SC 241 PM EDT Fri May 3 2024 .SYNOPSIS... Increasing moisture and shortwave energy will lead to active weather for the weekend through early next week with showers and thunderstorms likely. For the remainder of next week, expect well above normal temperatures and at least a slight chance of showers and thunderstorms each day. && .NEAR TERM /THROUGH TONIGHT/... Temperatures continue warming through the low to mid 80s across the forecast area with cumulus also developing as weak southeast to southerly flow pushes moisture into the area. WSR-88D imagery shows showers along the western periphery of the forecast area with a few moving into the northern CSRA. Although there is moisture and instability across the area flow across the area is weak and a trigger mechanism is lacking. As such expect the showers to continue developing along with a few thunderstorms through the remainder of the afternoon and into the evening. With sunset and loss of heating convection will diminish however during the early morning and sunrise hours the chances of showers and thunderstorms will increase as a short wave with divergence aloft moves into the area. Shower and thunderstorms chance at daybreak will be around 40 percent in the western Midlands through central CSRA quickly tapering to less than 14 percent in the eastern Midlands. High temperatures this afternoon will generally be in the mid to upper 80s with lows tonight in the low to mid 60s. && .SHORT TERM /SATURDAY THROUGH SUNDAY NIGHT/... The axis of an upper trough is expected to continue sliding eastward, putting us in a southwest flow aloft regime for the next couple of days. A series of embedded shortwaves are forecast to move over the region. At the surface, high pressure off the coast remains generally in place, allowing for southeast surface winds across the forecast area. As a result of this combination, PWATs are expected to increase to 1.6-1.7 inches, which is near the climatological top of moisture for this time of year. With this amount of moisture available, expect scattered showers and thunderstorms to spread across the area Saturday and Sunday, with peak coverage in the afternoons. With a lack of low level forcing mechanism, most of the activity is likely to be driven by the passing shortwaves. With the ridging aloft, instability and shear are limited, especially shear. Therefore, severe thunderstorms are not really expected. With the widespread cloud cover and scattered shower and thunderstorm activity, daytime temperatures are forecast to be closer to average for this time of year compared to the past couple of days. The increased moisture is expected to keep temperatures several degrees above average each night. && .LONG TERM /MONDAY THROUGH FRIDAY/... A persistent pattern of broad ridging, with passing shortwaves over the Southeast is expected to bring a continued summer-like pattern to the region. This should lead to nearly daily shower and thunderstorm chances through midweek, but coverage is anticipated to steadily decline after Monday. Temperatures are also expected to gradually increase due to the stagnant pattern aloft, with highs mid to late week in the lower to mid 90s. && .AVIATION /18Z FRIDAY THROUGH WEDNESDAY/... VFR conditions into the early morning then increasing potential for restrictions. Southeast to southerly flow continues to push moisture into the region with a few showers currently west of the terminals. Over the next couple of hours expect the showers to near AGS/DNL with VCSH beginning around 22z then 04/00z for CAE/CUB. With little dynamic support for the convection confidence is too low to include timing into any terminal. With daybreak additional moisture will move into the terminals as flow turns southerly and cigs begin lowering in response to increasing instability. With the increasing clouds tonight fog is not expected. EXTENDED AVIATION OUTLOOK... Late night/early morning fog possible through the period. Scattered to numerous showers and thunderstorms expected Sunday and Monday with decreasing chances Tuesday onward. && .CAE WATCHES/WARNINGS/ADVISORIES... SC...None. GA...None. && $$ ####018006372#### FXUS63 KLOT 031842 AFDLOT Area Forecast Discussion National Weather Service Chicago/Romeoville, IL 142 PM CDT Fri May 3 2024 .KEY MESSAGES... - A dry and cool night is in store with overnight lows in the mid to upper 40s. - Tomorrow (Saturday) will be warm with highs in the upper 70s to lower 80s, and increasing chances (60 to 70%) for showers and thunderstorms in the evening especially across northern Illinois. - Periodic shower and thunderstorm chances next week, with some potential for strong to severe storms Tuesday. && .DISCUSSION... Issued at 130 PM CDT Fri May 3 2024 Through Saturday night: A surface high pressure system continues to meander through the Lower Great Lakes region and is leading to mostly sunny skies, light north to northeasterly winds, and generally pleasant temperatures (at least away from Lake Michigan). With our area on the western flank of the surface high tonight, quiet conditions will prevail. Light winds, clear skies, and a dry airmass will facilitate efficient radiational cooling and allow for overnight lows to fall into the mid to upper 40s. Tomorrow, low-level flow will turn southeasterly and eventually southwesterly as the surface high pulls further away to the east and an upper-level short-wavelength trough approaches from the west. Low- level moisture advection will allow for humid air across central Illinois and Indiana to quickly return northward and into our area by mid-afternoon. Even with filtered sunshine, the advection of a plume of seasonably warm 850mb temperatures near +13C (into which the boundary layer will build) will help boost afternoon highs into the upper 70s to lower 80s. Chances for showers and thunderstorms will increase during the afternoon hours in two apparent waves. The first will be with an axis of remnant convection (originating from the Plains tonight), due to arrive sometime in our area early tomorrow afternoon. An ensemble of CAM guidance suggests the leading axis of showers and storms may outrun the best forcing provided by the upper-level shortwave and an associated cold front lagging to the west, and fight a pocket of dry mid-level air in place across the Lower Great Lakes. As a result, chances for showers and storms appear higher later in the afternoon and toward evening along the cold front as it moves across the area (50 to 70% chance from west to east ahead of the cold front). With the upper-level shortwave and associated jet streak expected to lift northeastward toward the Upper Peninsula of Michigan (e.g. remain somewhat displaced from the instability axis further to the south across our area), any convective cell tomorrow afternoon and evening should behave in a "pulse" like fashion with overall limited storm-scale organization. As a result, the main threats with any storm tomorrow will be locally gusty winds, small hail, downpours, and lightning strikes, similar to yesterday (and consistent with a level 1/5 threat for severe weather). In all, tomorrow looks like another quintessential spring-like day. Coverage of showers and storms will decrease after sunset as the cold front approaches northwestern Indiana. Temperatures behind the front will fall into the upper 40s (northwest) to mid 50s (southeast) early Sunday morning as northwesterly winds become predominant. Borchardt Sunday through Friday: Ensemble guidance depicts deep upper level trough developing across the western and central CONUS heading into next week, with a closed upper low developing across the Northern Plains Monday. A series of mid-level short waves are progged to rotate around the south and southeast periphery of the circulation as it slowly drifts east, eventually lifting the front across the lower Ohio Valley northward as a warm front later Monday night into Tuesday. Some spotty elevated showers are possible as early as Monday afternoon and evening as warm/moist advection develops atop the warm frontal slope, though really becomes more focused into the local area Tuesday into Tuesday night. This appears to be the period with the greatest potential for thunderstorms, some potentially strong to severe given strong mid-level wind fields and warm/moist/conditionally unstable low levels. Temperatures looks to surge back into the upper 70s/around 80 Tuesday afternoon, with surface dew points rising into the 60s as the warm front lifts across the area. Periodic shower and thunderstorm chances linger through the mid-week period, as ensembles continue to indicate the upper trough drifting east across the upper Midwest/Great Lakes region through the end of the forecast period. Blended NBM guidance maintains chance pops both Wednesday and Thursday, especially during the more diurnally-favored afternoon/evening hours. Higher low-level Theta-E air mass gradually gets shunted east of the area during this time, with temperatures gradually settling into the lower 70s by Thursday. Ratzer && .AVIATION /18Z TAFS THROUGH 00Z SUNDAY/... Issued at 1231 PM CDT Fri May 3 2024 - There is no impactful weather expected through the current forecast period Lingering MVFR cigs over Northwest Indiana are slowly eroding away as a cold front exits the area through the afternoon. Northeast winds around 10 knots are expected through the day, gradually rotating to the southeast by Saturday morning and diminishing slightly. Guidance is suggesting a fairly low level inversion developing Saturday morning. With enough flow above 1000 feet, it should result in a FEW low to mid level clouds developing; however, some areas in Northwest Indiana might have moments of lower vis around 4 SM, but dense fog is not expected. By Saturday afternoon, winds will become southwesterly ahead of the next passing cold front. Rain showers are expected to accompany this front, but not arriving until after the current forecast period for any of the TAF sites. DK && .LOT WATCHES/WARNINGS/ADVISORIES... IL...None. IN...None. LM...None. && $$ Visit us at weather.gov/chicago