The computer models have shifted the heaviest rain to our immediate north western counties. This means we'll only see about two to three inches of rain between now and Tuesday. Whew! We dodged a bullet on that one but we are not out of the woods yet. Here is the latest thinking from the NWS:
National Weather Service Indianapolis IN 129 PM EDT Fri Jun 25 2021 ...Updated Aviation Discussion... .Forecast Update... Issued at 941 AM EDT Fri Jun 25 2021 Remnants of an overnight MCS are moving through NW portions of central Indiana this morning producing up to an inch of rain in some areas. Observations have signaled occasional lightning strikes in some of the stronger convective cells. Expectations are for this to move to the north; However, another line of thunderstorms behind this looks to further expand rain chances for the late morning and early afternoon. More frequent lightning and heavy rain rates have been observed within this line of thunderstorms. The resurgence of the LLJ and continued moist surface environment will lead to another round of convective initiation in the mid to late afternoon with rain and thunderstorm chances through the rest of today. With strong low level flow and moderate mid level lapse rates (7 C/km), severe thunderstorms cannot be ruled out for this afternoon and evening. The extent of severe weather will largely depend on if the near surface layer can destabilize between MCS clusters along with the general timing of initiation of the pending afternoon MCS. More updates expected later as the afternoon environment comes to fruition, allowing for a better understanding of the severe potential. && .Short Term...(Today through Saturday) Issued at 308 AM EDT Fri Jun 25 2021 Showers continue to increase in coverage across central Indiana early this morning as southwest low level flow strengthens across the mid Mississippi Valley east into the region. An ongoing convective cluster highlighted by a bowing line of storms extended from western Illinois west into Missouri. 07Z temperatures ranged from the upper 60s to mid 70s. Active forecast over the next 36 hours with the main focus on locally heavy rainfall and potential flooding. A sneaky sidebar though with a few severe storms possible...especially later today... with still a lot of detail yet to be worked out with regards to how everything evolves. Upper level ridge over the southern states in the process of being suppressed as a strong upper low tracks across James Bay. In between is a quasizonal regime with a hint of SW flow. Amplification of an upper trough into the northern Plains later today into the weekend will serve to sharpen the southwest flow aloft pointed at the region and particularly the lower Great Lakes with strong ridging remaining to the southeast. Several waves aloft will traverse through the flow and across the region aided by multiple surface lows along a slow moving boundary. the first of these surface waves will track northeast from the mid Mississippi Valley this morning into lower MIchigan this evening. The initial issue is exactly how the convective cluster to the west evolves over the next 6-8 hours and what kind of impact it brings to the forecast area...perhaps as early as daybreak or shortly thereafter. The airmass remains far more stable over central Indiana at the moment than it is near where the cluster is currently. With only a subtle increase in instability through mid morning...expect a general weakening to the convection as it approaches the Wabash Valley...but the presence of weak instability aloft will enable storms to continue through the morning. In addition...enhanced 850mb flow will persist over the region throughout much of the day and considering the progressively deeper moisture overspreading the area evidence by dewpoints already in the upper 60s and PWATs rapidly approaching 2 inches. Convection is likely to impact the forecast area through mid afternoon as it tracks slowly through the region. Expect gusty southwest winds to near 25mph. By late afternoon and early evening...may see a bit of a lull in the wake of the earlier storms before additional convection fires with more energy aloft rolling into the region. There appears to be a narrow window during the early to mid evening where a conditional severe weather risk may exist. Damaging winds would be the primary threat...but laying in the weeds is a sneaky tornado risk with hodographs showing a few hours with 0-1km SRH values up to 200 m2/s2. The problems though is limited instability and overall poor lapse rates that would marginalize convective intensity. That being said...have seen this setup align before in the presence of a deep tropical airmass where LCLs can dip below 3kft. Not sure we can get LCLs quite that low but it is close for a short period of time. This will be something to monitor through the day. Later this evening into tonight...convection will refocus over the northwest half of central Indiana and particularly across the northern Wabash Valley in the vicinity of a low level jet with likely multiple convective clusters with the potential for torrential rainfall and flooding concerns as storms train across the same areas. Will maintain the Flood Watch in its current state over our northwest not just for rain and storms today but especially for tonight. For Saturday...the ridge focused to the east of the area will subtly retrograde through the day with the axis of heavy rainfall likely shifting even further northwest perhaps into northern Illinois and far northwest Indiana. Deep moisture and stronger instability will maintain the potential for isolated to scattered convection but the lack of better forcing aloft as it shifts north of the area may minimize more widespread convection throughout the day. Lower than desired confidence in the details and will largely nudge pops lower than previously forecast. Still could see stronger storms and perhaps a damaging wind gust. Torrential rainfall and localized flooding will remain however the primary concern from storms. Temps...persistent clouds and the convection today will keep temps lower in the upper 70s and lower 80s before rebounding into the mid and upper 80s Saturday with the potential for more sun. Lows tonight will be muggy in the lower 70s. && .Long Term...(Saturday Night through Thursday) Issued at 308 AM EDT Fri Jun 25 2021 Ensemble means suggest an upper trough, initially over the Midwest this weekend, will gradually weaken and shear out across the Great Lakes by the middle of next week. At the surface, a diffuse frontal system will sag southeast through the local area by the early to middle parts of next week. The ensembles continue to indicate an unsettled pattern throughout the extended, with daily chances of convection, courtesy of the upper trough and surface front. Enhanced chances of precipitation may occur around Monday and towards the middle of next week, where the ensembles hint at possible surface waves moving through. Progged precipitable waters near or in excess of 2 inches at times suggest heavy rainfall will be possible throughout the extended. Precipitation chances may tend to diminish by next Thursday, as the upper flow gradually veers more to the west and northwest, which may serve to push the highest precipitable waters off to the southeast.
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