Area Forecast Discussion
Issued by NWS Louisville, KY
Issued by NWS Louisville, KY
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301 FXUS63 KLMK 191353 AFDLMK Area Forecast Discussion National Weather Service Louisville KY 953 AM EDT Sun May 19 2024 .KEY MESSAGES... * Patchy dense fog east of I-65 this morning. * Dry and unseasonably warm weather through Tuesday. * Unsettled weather returns by Wednesday, with rounds of showers and thunderstorms possible through the end of the week. Severe storm potential remains uncertain, with somewhat higher confidence in the potential for localized flooding. && .UPDATE... Issued at 952 AM EDT Sun May 19 2024 High pressure is centered close to the region this morning, allowing for dry and calm weather across central Kentucky and southern Indiana. Patchy valley fog has largely dissipated by this point, leaving the area with sunny skies. Temperatures have surged upward into the 70s according to latest obs, recovering somewhat faster than expected. It is possible that we could overperform on temperatures today; however, a scattered cu field should develop over the next few hours to temper the amount of heating. With the exception of small upward adjustments to near term T grids, the forecast is on track at this time. Have added a 5% PoP east of I- 65, just to account for a few taller cu this afternoon which could produce an isolated quick shower; however, almost all should remain dry today. && .SHORT TERM /THROUGH MONDAY/... Issued at 325 AM EDT Sun May 19 2024 Synopsis...Upper-level pattern will consist of high pressure ridge building across the southern and eastern portion of the country as trough amplifies to the west. At the surface, broad area of high pressure will slowly move from the Mississippi Valley towards the Mid Atlantic and Northeast US while a weak cold front stalls over the Upper Ohio Valley. This morning...NT RGB satellite imagery and webcam pictures confirm fog developing over the Bluegrass and Cumberland regions this morning with more isolated coverage to the west. Surface observations indicate visibilities anywhere between 4-7 SM, which agrees fairly well with previous runs of the HRRR and RAP models. On the other hand, another widespread dense fog event is not anticipated at the moment based on the shallow moisture depth depicted in the LEX ACARS and subsaturated conditions in the near- surface layer reported by the KY Mesonet relative humidity inversion profiles. That being said, patchy dense fog will be likely in the valleys and protected areas east of I-65. Any instance of radiation fog will dissipate by midmorning. Rest of Today and Tonight...Mid-level subsidence along with a dry airmass will yield mostly sunny conditions with highs in the mid to upper 80s. Winds will remain light and from the northeast as primary surface pressure center located north of the forecast area drifts eastward. Daytime heating will promote a high-based cumulus layer, but no precipitation is expected as weak updrafts remain capped below 700-mb and any mesoscale triggering mechanism stays well to north. For tonight, winds will remain light while slowly shifting to the east-southeast and although fog may once again form, it will be more isolated and mainly confined to the valleys thanks to moisture depletion via evapotranspiration. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Issued at 325 AM EDT Sun May 19 2024 Monday through Tuesday Night... Deterministic and ensemble guidance is in general agreement with an upper level ridge axis being oriented from the southern Plains into the Ohio Valley during this time frame. Model soundings through the period show warm temperatures aloft as well a plenty of subsidence which will keep convection at a minimum for Monday and Tuesday. Winds will be out of the south to southwest during the period and above normal temperatures are expected across the region. The question of how high temperatures will go is in question. Recent rainfall events have led to saturated soils across the region and vegetation is quite green. So while the models suggest upper 80s to near 90 for Monday and Tuesday, we`ll probably end up a bit cooler than that. For now, current thinking is that we`ll end up in the 82- 87 degree range for daily highs with overnight lows in the 60s. Toward the end of the period (Tuesday night), we may see our first chances at rainfall as weakening convection along a cold front push in from the west toward sunrise Wednesday. Wednesday through Saturday... As we move into the mid-week time frame, cold frontal boundary will push toward the region from the west. Weakening convection is likely to be in progress Wednesday morning and this activity should continue to weaken as it pushes eastward. The surface cold front looks to stall out to our west, while stronger synoptic scale forcing moves northeast from the Midwest into the Great Lakes. Latest machine learning guidance has trended a bit more west/northwest with the severe threats on Wednesday. Model soundings across our region do show instability being present Wednesday afternoon. However, with warmer temperatures aloft, rather weak shear across the area, and the stronger forcing well to our west/northwest, the threat of organized severe looks marginal at this time. Given anticipated atmospheric recovery, scattered showers and storms are likely Wednesday afternoon with gusty winds and marginally severe hail as the main threats. Highs Wednesday will be in the low-mid 80s with overnight lows in the low-mid 60s. For Thursday through Saturday, model agreement continues to diverge here as the GFS and its ensembles are more aggressive in pushing a cold front through the region on Thursday. However, the Euro and its ensembles disagree and keep the frontal boundary across the Ohio Valley during the period. Small perturbations moving through in the southwest flow aloft would be responsible for episodic bouts of convection moving through the region. Model soundings do show instability available for convection, but the main belt of westerlies will be confined well north of our area, so our environmental shear remains quite low. Overall threat of severe weather looks pretty marginal given the forecast shear values. The stalled out boundary though may be a sign that heavy rainfall and possible hydrologic issues may be the main threat during this period. Highs during the period will likely be near normal with upper 70s and lower 80s for highs with overnight lows in the low-mid 60s. && .AVIATION /06Z TAFS THROUGH 12Z MONDAY/... Issued at 638 AM EDT Sun May 19 2024 Discussion...Intermittent dense fog was observed at LEX and RGA earlier this morning, but recent observations indicate some visibility improvements at those terminals. Expect fog to completely dissipate by 13 or 14Z with prevailing VFR conditions the rest of the day and also tonight as stable and dry airmass settles in. Additionally, surface high pressure will keep light northeast winds today turning calm or variable overnight. && .LMK WATCHES/WARNINGS/ADVISORIES... KY...None. IN...None. && $$ UPDATE...CSG/SRM SHORT TERM...ALL LONG TERM...MJ AVIATION...ALL