####018003632#### FXUS63 KILX 040013 AFDILX Area Forecast Discussion...Updated Aviation National Weather Service Lincoln IL 713 PM CDT Fri May 3 2024 .KEY MESSAGES... - Near daily chances for showers and thunderstorms over the next week as a series of fronts advance across the region. The Tuesday through Wednesday period looks particularly active, with medium confidence in thunderstorms capable of producing all severe weather hazards. && .DISCUSSION... Issued at 127 PM CDT Fri May 3 2024 Current GOES WV imagery depicts a strong upper-level low positioned over western Ontario with more subtle shortwave energy ejecting out of the Great Basin. Model guidance remains in excellent agreement that shortwave energy lifts into the Northern Plains and Upper Midwest regions overnight, ultimately helping to force a synoptic cold front into western Illinois Saturday afternoon. A plume of low-to-mid 60s dewpoints is progged to advect northward ahead of the cold front, and SBCAPE values should be able to achieve 1000-1500 J/kg with CINH eroding in the presence of steep 0-3 km lapse rates (> 7.5 C/km). This all adds up to likely (> 60% chance) thunderstorm development Saturday afternoon along and ahead of the cold front. Coverage of Saturday storms could be limited by somewhat underwhelming deep-layer shear profiles, with much of the area at or below 30 kts in the vicinity of the cold front. Updrafts may struggle to become organized or struggle to stay organized, especially some of the early updrafts, and recent CAMs hint at this as well. Nevertheless, CAPE/Shear profiles are just good enough to support the potential for an isolated severe hail and wind threat. As storms move toward and east of I-55 Saturday evening, the severe potential should gradually fade. This will largely be due to the loss of daytime heating and the lack of a LLJ to help augment instability. This thinking lines up well with SPC's Day 2 Marginal Risk, which ends the threat near the I-57 corridor. Flooding should not be a concern with the Saturday storm event. NBM Mean QPF is around 0.25", and this guidance only offers a 10% chance that rainfall exceeds 0.75", which is well below 3-hour flash flood guidance. The rest of the weekend through Monday should be fairly low drama, with the main frontal zones displaced just to our south. Attention quickly turns to the Tuesday - Wednesday timeframe as persistent, deep southwest flow envelops the region ahead of an elongated upper-level low. While we're running lean on details at this timeframe, the synoptic pattern (kinematics/thermodynamics) being modeled supports a multi- day severe weather threat across portions of the Plains and Midwest. This strong signal in the global models is also reflected in the analogs and machine learning tools for severe weather potential. MJA && .AVIATION... (For the 00z TAFs through 00z Saturday Evening) Issued at 711 PM CDT Fri May 3 2024 VFR conditions should continue through most of the forecast period, though conditions will likely deteriorate locally along and west of I-55 near the end of the period as a broken line of thunderstorms develop with a cold front. Variable, but predominantly northeast, light winds will veer to southerly between 13z and 16z with some localized stronger gusts (along with heavy rain, small hail, lightning) possible with the line of storms. Bumgardner && .ILX WATCHES/WARNINGS/ADVISORIES... None. && $$ ####018006629#### FXUS63 KJKL 040015 AAA AFDJKL AREA FORECAST DISCUSSION...UPDATED National Weather Service Jackson KY 815 PM EDT Fri May 3 2024 .KEY MESSAGES... - Shower and thunderstorm potential returns to the forecast through the next 7 days. - Cooler than in recent days, but temperatures are forecast to be above normal through the next 7 days. && .UPDATE... Issued at 745 PM EDT FRI MAY 3 2024 23Z sfc analysis shows low pressure having moved a little closer to the area from the west and this has pushed the protective area of high pressure out of Kentucky. Accordingly, return flow moisture has helped fuel showers across the region today along with a few thunderstorms. Currently, the best batch of convection is west of the I-75 corridor. This is expected to drift east with time - but weaken. The extra clouds around today along with the showers have kept temperatures on the cooler side compared to yesterday. The latest obs have temperatures generally in the upper 60s to lower 70s. Meanwhile, amid light and variable winds, dewpoints have moistened into the low to mid 60s for most spots. Have updated the forecast mainly to fine tune the PoPs and thunder chances through the night per radar and CAMs trends. Did also add in the latest obs and tendencies for the T/Td/Sky grids. These adjustments have been sent to the NDFD and web servers along with a freshening of the zones, SAFs, and HWO. && .SHORT TERM...(This evening through Saturday night) Issued at 332 PM EDT FRI MAY 3 2024 An active pattern remains across the Bluegrass State through the short term. Large upper low/trough configuration remains over the far northern US and south-central Canada with an active jet stream from the Central Plains to Upper Great Lakes region. Meanwhile, upper ridging remains persistent along the East Coast, and will begin to move offshore Saturday night as the aforementioned upper low begins to move northeast toward eastern Canada at that time. This leaves eastern Kentucky under the influence of a moist and active regime with periodic shortwave disturbances moving across the region through Saturday evening. Currently a disturbance is beginning to exit to the east this afternoon, but will be followed by another tonight into Saturday morning that will bring another round of showers and possibly a few thunderstorms. Models suggest low-level instability is somewhat lacking but there is sufficient elevated instability to warrant a few claps of thunder from time to time, especially west of I-75. Fog formation overnight will be dependent on any lulls in precipitation as well as any potential partial clearing. Lows tonight will range from the mid-50s in the cooler sheltered valleys to lower 60s elsewhere. Another disturbance appears to be well-timed with any daytime heating to help produce more widespread showers and thunderstorms Saturday. Given high PoPs and cloud cover through the day temperatures will struggle to reach the current forecast highs of upper 70s. PoPs gradually lower through Saturday evening through the overnight as a trailing shortwave crosses the area with shortwave ridging building in from the southwest after midnight. Sky cover will likely trend downward but this would likely then promote fairly widespread fog formation late Saturday night into Sunday morning, especially in the river valleys. Expect forecast lows Saturday night similar to tonight's forecast, with mid 50s to lower 60s. .LONG TERM...(Sunday through Friday) Issued at 540 PM EDT FRI MAY 3 2024 The models generally agree on a fairly stagnant long wave pattern across the CONUS through the majority of next week. A seasonably strong 500 mb low pressure system will start out over the West Coast early Sunday morning, before swinging east, residing over the northern Rockies/northern High Plains by early Tuesday. This feature will then elongate and gradually dampen with time as it moves over the Upper Midwest, with a broad positively tilted trough aligning from the Great Lakes back through the Desert Southwest. This will keep west to west southwest flow across the Ohio and Tennessee valleys aloft, with several progressive short wave troughs to move through the region at times. At the surface, a quasi-stationary front will be aligned just north of the area through early next week, before a cold front approaches by the end of the next work week. This will all result in unsettled weather across eastern Kentucky through the long term forecast, with daily chances of showers and thunderstorms. Have generally stayed a bit below the blended guidance on PoPs for the days where the overall forcing is weaker and/or less certain, as it is known to overdo more diurnally influenced convection. At this time, rain chances look to peak on Monday (80-90%), and then again on Thursday (70-80%), with better forcing at play. The rest of the period will feature chance PoPs (30-60%). Temperatures will average 5-10 degrees above normal, with lows mainly in the lower 60s, while highs range from the upper 70s to lower 80s most days. && .AVIATION...(For the 00Z TAFS through 00Z Saturday evening) ISSUED AT 815 PM EDT FRI MAY 3 2024 Occasional showers will continue through much of the period, though nailing down timing at any one TAF location is difficult. Models seem to move a decent chance for convection east through the evening - fading out after midnight. Accordingly have carried some prevailing showers - thunderstorms included at SME initially - across the aviation forecast area into the night. Any storm could produce locally heavy rainfall and gusty winds, along with brief periods of MVFR or IFR visibilities. MVFR CIGs will also be possible at times this evening during peak shower/thunderstorm activity and again into dawn across the northern terminals. If shower activity and thicker clouds taper off sufficiently overnight we will likely see at least some fog develop at some of the TAF sites. Conditions improve Saturday morning with still a decent chance for storms from midday on, though. Winds will be light at less than 10 kts and generally out of the south to southwest through the forecast period. && .JKL WATCHES/WARNINGS/ADVISORIES... NONE. && $$ UPDATE...GREIF SHORT TERM...CMC LONG TERM...GEOGERIAN AVIATION...CMC/GREIF