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Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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161 FXUS63 KIND 300524 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 124 AM EDT Sun Jun 30 2024 .KEY MESSAGES... - Cooler and less humid Sunday and Monday - Heat returns on Tuesday and Wednesday - Rain/storm chances return Wednesday onward && .FORECAST UPDATE... ...Strong to Severe Thunderstorms Possible the Remainder of the Evening... Latest mesoscale analysis was showing CAPES to 4000 J/kg over the Wabash Valley with lesser CAPE over east central sections, closer to where the bowing line went through late this afternoon. Radar was showing widely scattered thunderstorms from south central Indiana into the Wabash Valley, closer to the outflow from the earlier convection. Meanwhile, a cold front extended from near the northeaster Indiana and southern lower Michigan border to around Rensselaer and points southwest. This front will move to the I-70 corridor late this evening and south central Indiana overnight. The front will interact with the strong, albeit weakening instability and 70+ degree dew points to trigger more convection. Marginal shear but strong instability suggests a few severe storms will be possible with damaging winds the main concern. The thunderstorms should move to the southeast of the area toward morning as the front clears and much drier air moves in. This will also allow for clearing northwest to southeast and cooler temperatures with lows in the lower 60s northwest to around 70 southeast looking good. The northwest post frontal winds should keep fog from being an issue. && .MESOSCALE UPDATE... Issued at 603 PM EDT Sat Jun 29 2024 The bowing line of thunderstorms that produced some damaging winds along its path has moved southeast of central Indiana. Meanwhile more isolated benign cells were forming over the Wabash Valley and east central Illinois as well as further north, closer to the synoptic cold front that was extending from near South Bend southwest to Kankakee. The atmosphere has recovered in a big way over east central Illinois into north central Indiana, ahead of the front with CAPEs to 4500 J/kg. Meanwhile, further southeast along the bowling line path, CAPEs have dropped below 1000 J/kg and CIN has resulted. So, think the Wabash Valley activity will not be a huge concern moving into a more worked over atmosphere. However, convection may light up along and ahead of the front and be at least a semi-concern later this evening as the front gets closer. && .SHORT TERM (Today and tonight)... Issued at 146 AM EDT Sat Jun 29 2024 Forcing for ascent this morning is primary from warm/moist advection preceding a low amplitude shortwave trough upstream. The effects of the shortwave itself are otherwise minimal on our atmosphere at this latitude. These are difficult patterns to forecast precision with regards to timing of convection. Current thinking is the anomalous moisture plume at both low levels and aloft will continue supporting scattered to numerous showers, and modest instability will support isolated thunder. A small midlevel vorticity maxima likely augmented by ongoing convection in Missouri may result in an uptick in convective coverage early this morning as it moves east and interacts with deeper moisture plume. In fact, some new convection and lightning strikes are occurring as of this writing in west-central Illinois. This will probably expand and reach Indiana around daybreak. There will probably be a decrease in coverage and intensity by late morning or midday as the core of the low level jet and moisture plume shifts eastward. Diurnal convection may increase ahead of the front late afternoon into the evening. CAPE/shear parameter space may be marginally supportive of a few strong to severe wind gusts. This should mean a relative minimum in convective coverage during the early-mid afternoon time frame. Temperatures should be similar to yesterday but richer influx of moisture will result in noticeably more humid conditions. As the low- amplitude shortwave trough passes, it will nudge a drier continental air mass in overnight along with modest cold advection bringing temperatures down slightly compared to previous nights. && .LONG TERM (Sunday through Friday)... Issued at 146 AM EDT Sat Jun 29 2024 Sunday and Monday... The low amplitude meridional pattern will continue through the long term. Initially, this will lead to cool, calm conditions with surface high pressure and upper level troughing for Sunday and Monday, and should allow for generally clear skies and highs around 80. Winds will veer post frontal passage today and continue to be northerly to northwesterly through Monday. With mostly clear skies and dew points in the 40s, overnight lows should be well below normal for both Sunday and Monday night. Current forecast is for lows in the 40s each night. Tuesday through Friday... The next phase of the this pattern will arrive mid week, with broad ridging developing aloft. By Tuesday, 850mb temps rise by about 5-10 degrees, which under full sun and efficient mixing corresponds to highs in the mid to upper 80s. The primary axis of warm air will then arrive Wednesday, with highs expected to be back into the 90s. This upper ridge will continue to remain aloft keeping temperatures above normal through the end of next week. Even though upper level ridging will be in place across the Ohio Valley, precipitation chances will still increase as a succession of weak waves develop within broad upper level diffluence in the right entrance region of the upper jet. This should lead to variable thunderstorm chances Wednesday through Friday, until a frontal boundary moves through late week, decreasing surface moisture. Its still too early to pinpoint specifics regarding timing and potency of thunderstorms Wednesday through Friday of next week. Ensemble guidance is highly variable on how the low level disturbances develop and pass through the Ohio Valley, of which will greatly influence surface conditions over central Indiana. For now, understand and prepare for thunderstorms to potentially interrupt holiday plans next week, and stay alert for updates as forecast confidence increases over the next several days. && .AVIATION (06Z TAF Issuance)... Issued at 124 AM EDT Sun Jun 30 2024 Impacts: - None Discussion: A cold front is moving through central Indiana now and will cause winds to shift to northwesterly. Until the front comes through there could be a few patches of shallow ground fog, given the significant moisture and modest radiative conditions developing. Clear conditions will return and VFR is expected to prevail. Some gusts approaching 20 knots are possible midday and through the afternoon. && .IND WATCHES/WARNINGS/ADVISORIES... None. && $$ UPDATE...MK SHORT TERM...BRB LONG TERM...Updike AVIATION...BRB