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Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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904 FXUS63 KIND 210659 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 259 AM EDT Sun Jul 21 2024 .KEY MESSAGES... - Dry and seasonable today - Scattered showers possible tonight focused over the southeast half of the area - Chances for rain/t-storms and increasing clouds through at least mid-week may help keep temperatures slightly below normal && .SHORT TERM (Today and Tonight)... Issued at 259 AM EDT Sun Jul 21 2024 Mid and high level clouds continue to increase in coverage over the region early this morning as moisture aloft gradually advects in from the southwest. The remnants of high pressure at the surface and ridging aloft keeping an overall dry airmass across central Indiana. 06Z temperatures were primarily in the 60s. A slow moving upper level low over the Missouri Valley this morning will pivot east into the region by early Monday...picking up progressively deeper moisture from the southwest by late tonight. This will bring at least an isolated to scattered risk for showers and a few rumbles of thunder into the southeast half of the forecast area overnight ahead of the weakening upper wave. Despite the noted increase in moisture aloft...dry air and subsidence lingers below 500mb this morning. While moisture will gradually infiltrate lower through the column...it will take all day and likely some of tonight to effectively eradicate the layer of dry air above the boundary layer with little forcing aloft ahead of the upper wave. Cloud coverage will be prevalent today focused largely above 10-15kft with at least some scattered cu development for the afternoon courtesy of diurnal heating. Light showers will likely remain south of the forecast area through early evening with any precip chances holding off until tonight. Despite the weakening of the upper wave...a subtle increase in forcing aloft ahead of the feature and broader moisture advecting into the region will likely be enough to enable scattered showers to move into the southeast half of the forecast area overnight with a lower threat further northwest across the region. Cannot entirely rule out a few rumbles of thunder with the showers but instability is limited and overall moisture profiles via model soundings are not particularly impressive. Temps...even with increase cloud cover today...low level thermals are supportive of highs rising into the low and mid 80s. Lows tonight will largely be in the mid 60s. && .LONG TERM (Monday through Saturday)... Issued at 259 AM EDT Sun Jul 21 2024 A more unsettled pattern is expected through at least midweek as guidance shows upper troughing persisting across the eastern CONUS with gulf moisture advecting northward. This will lead to increasing humidity and chances for precipitation. Daytime heating over sufficient lower tropospheric moisture should support scattered diurnal convection. There will be a weakening upper low moving across the area though forcing from the feature looks to be negligible. An upper wave approaching the region late Tuesday was expected to provide stronger synoptic forcing for precipitation. Latest guidance has trended south with the greatest forcing for ascent from the wave now likely to remain closer to the Ohio River. This has resulted in lower chances for rain/storms though scattered diurnal convection is still possible. The best chance for precipitation now appears to be late in the day Wednesday as a deeper trough diving south helps to push a frontal boundary across Indiana. Confidence in the forecast for Thursday is lower due to diverging model regarding the timing of the aforementioned front and how quickly dry air moves in behind it. If drier air quickly moves in early Thursday quiet weather conditions would be expected during the day. A slower frontal passage could potentially keep sufficient PBL moisture in place for scattered showers or storms, especially in the afternoon as destabilization from daytime heating occurs. The front will likely move out by Thursday night allowing for dry conditions to return late this week. Look for temperatures to remain slightly below normal for much of the extended period. && .AVIATION (06Z TAF Issuance)... Issued at 1240 AM EDT Sun Jul 21 2024 Impacts - No impacts expected Discussion: VFR conditions will continue throughout the forecast period. Moisture aloft will gradually increase across the area as a broad weak upper wave approaches from the west. Dry air will linger above the boundary layer before diminishing tonight. This will lead to an increase in mid and high level clouds throughout the day with diurnal cu developing for the afternoon again. Light northeast winds are expected. As the upper wave arrives this evening and sharpens...potential for isolated showers will increase across the southeast half of central Indiana. At this point...coverage is likely to remain low enough to keep out of the forecast. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Ryan LONG TERM...Melo AVIATION...Ryan