Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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036 FXUS63 KIND 151659 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1259 PM EDT Wed May 15 2024 .KEY MESSAGES... - Scattered showers and a few rumbles of thunder through the afternoon. - Rain and storm chances return at times late Thursday into Saturday. - Above normal temperatures for this weekend through the middle of next week. && .SHORT TERM (Today and tonight)... Issued at 234 AM EDT Wed May 15 2024 Through Daybreak. Pockets of locally heavy rain will continue through the night as showers continue to slowly circle around the surface low pressure situated over southern Indiana. The heaviest rain has fallen across northwestern Hendricks county and across the US50 corridor from Vincennes to around Bedford but so far only very limited impacts have been noted due to the sporadic and spatially sparse areas of heavier rain. Over the last hour the rain coverage and intensity has gradually lessened as the better forcing begins to exit and the with the surface low now directly overhead, the moisture flow into southern Indiana has been cut off. Focus going into the morning hours will then be on locally heavy showers on the northwest side of the surface low as it slowly pushes off to the east. Temperatures will remain near steady state in the low 60s through the rest of the night with thick cloud cover helping to insulate the lower levels. Today. By daybreak this morning morning the low pressure system associated the recent rain will begin to exit the forecast area as it moves into southwestern Ohio. The main focus area for rain through the afternoon hours will be associated a residual area of lift around 700mb to the northwest of the exiting surface low. Latest high resolution models are showing that subsidence at around 700mb will begin to inhibit shower formation but also help to keep the clouds in place through much of the daytime hours. Current thoughts are that by early afternoon coverage will be scattered with only isolated showers by later into the day. Thunder will be minimal but not non-existent due to a lack of instability so will cap the thunder mention to isolated through today. The thick cloud cover and lack of southerly flow will also help to moderate temperatures again today with highs only around 70. Tonight. Clouds will likely stick around for much of the night tonight with model soundings showing persistent saturation at the top of the boundary layer, but will have to keep an eye out for any locations that do begin to clear as the recent rains will help to supersaturate the low levels and may allow for some fog formation. The low confidence that things will clear out enough for widespread fog makes a Dense Fog Advisory seem a bit overdone at this time, but will have to monitor things going into this evening. && .LONG TERM (Thursday through Tuesday)... Issued at 234 AM EDT Wed May 15 2024 Progressive...quasi-zonal flow aloft will continue across the country through the end of the week with rain chances returning as early as Thursday afternoon and persisting into the first half of the weekend. A more amplified regime will develop by early next week with a trough in the western states and ridging over the eastern half of the country. This will bring warmer temperatures along with the potential for more substantial convective risks as pieces of energy aloft eject out of the western trough. Thursday through Saturday Despite the presence of surface ridging Thursday morning...model soundings and low level RH progs remain saturated within the boundary layer with the presence of an inversion. Expect a combination of low stratus and fog over the forecast area as a result to start Thursday with some sunshine returning through midday. This will be short lived as moisture ahead of the next storm system will encroach in the region Thursday afternoon. Initially forcing aloft will be weak with showers likely to be light and scattered. The arrival of stronger isentropic lift into the area Thursday night as low pressure passes to the northwest of central Indiana will lead to an uptick in shower coverage and at least some potential for embedded convection with minimal instability. But overall...sounding profiles hints at lingering dry air within the column which will likely keep rain from becoming widespread and overall rates relatively light through daybreak Friday. Moisture advection and forcing aloft will notably increase Friday as the combination of an upper level wave and surface low pressure tracks northeast into the lower Ohio Valley. A strong low level jet will nose into the region Friday afternoon...enhancing isentropic lift and leading to more efficient precipitation rates as strong convergence in the 925-850mb and 850-700mb layers coincide across the Ohio Valley Friday afternoon and evening. In addition..precip water values will peak near 1.50 inches on Friday with model soundings showing a saturated column. All of these factors support a growing threat for locally heavy rainfall and higher rates within convective cells with 1 to 2 inches again possible Friday and Friday night across the forecast area. Considering the recent rains from Tuesday and so far early this morning...localized flooding concerns would be elevated should this setup come to fruition. The model suite diverges with the handling of the upper level wave into the first part of the weekend...and that has implications with respect to rainfall chances and coverage on Saturday. Considering the progressive nature of the flow regime aloft...prefer the solutions supporting convection diminishing by Saturday afternoon as weak high pressure at the surface and ridging aloft attempts to expand into the Ohio Valley. Temperatures will remain seasonable through Saturday with highs in the 70s. The coolest day is likely to be Friday as rain coverage increases with the approach of the upper low and surface wave from the southwest. Saturday Night through Tuesday The presence of weak surface high pressure in tandem with ridging aloft will enable mainly dry conditions Saturday night into Monday. Highs will warm with the upper ridge building into the Ohio Valley with low to mid 80s expected by Sunday and Monday. The forecast remains fluid and low confidence for early next week. There remains a signal for increasing convective activity impacting the region as the ridge flattens and multiple waves aloft traverse west to east across the area. Extended model guidance also continues to highlight a stronger piece of energy ejecting out of the western trough and spinning up a deeper surface low over the upper Midwest by Tuesday or Wednesday. While we remain well too far for specifics...the signal for an uptick in convection and potentially severe weather is present for the early and middle part of next week across the Great Lakes and parts of the Ohio Valley. Temperatures will remain warm with highs in the 80s daily. && .AVIATION (18Z TAF Issuance)... Issued at 1259 PM EDT Wed May 15 2024 Impacts: - MVFR/TEMPO IFR conditions through the afternoon. - IFR or worse visibilities developing late tonight in fog. - A few lingering showers, possibly a thunderstorm. Discussion: As low pressure slowly departs the area, low clouds remain expansive across the region, with widespread MVFR and pockets of IFR. Will carry prevailing MVFR/TEMPO IFR ceilings at all sites through about 22Z, with VFR thereafter. A few showers are lingering across the area, and an isolated thunderstorm cannot entirely be ruled out, but will be far too low probability for a mention. Will carry VCSH for the next few hours to account for showers. Clearing skies and lighter winds tonight will promote fog development, with IFR visibilities likely everywhere. Dense fog is a possibility, and will hint at this with a BCFG mention. Could easily see 1/4-1/2SM visibility for a time near daybreak, given preconditioning of widespread significant rainfall in the past 24-36 hours. Fog will dissipate in typical diurnal fashion tomorrow morning, with a SCT-BKN low end VFR cumulus deck likely to develop on Thursday. Winds will be around 10-11KT or less throughout the period, likely becoming light and variable or calm overnight tonight. Winds will primarily be northerly early, becoming southerly during the day on Thursday. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...White LONG TERM...Ryan AVIATION...Nield