HEADLINES
– The Race is ON! No weather-related threats.
– It will be mostly cloudy and unseasonably cool.
– Scattered showers over far southwest central Indiana Sunday.
– Widespread rain Tuesday, with rumbles of thunder possible.
– Temps recovering to near normal levels by the second half of next week.
TODAY’S MAP
NWS TECHNICAL DISCUSSION
The short term features fairly benign conditions for all of Central Indiana as high pressure remains the dominant weather influence at the surface. A northwest flow regime aloft will advect in higher clouds this morning and through the weekend with the best moisture advection and forcing for ascent remaining well south and west of Indiana. A very cool airmass is still in place over the Great Lakes as the source region from the high overhead is from Central Canada. E/NE winds today will keep this cooler airmass at the surface, while higher clouds limit substantial surface heating. ACARs soundings over the past 12 hours show a fairly high subsidence inversion aloft, around 750mb, allowing for deep mixing and steep lower and mid level lapse rates during peak heating of the day. Despite a cool airmass overhead, this deeper mixing and periods of sunshine today should allow for surface temperatures to make it into the upper 60s to lower 70s. Winds through the mixed layer are fairly light, so even with deeper mixing winds should remain under 10 mph. For tonight, not expecting temperatures nearly as cold as the past few nights where some rural, low lying locations dropped into the upper 30s with patchy frost. Higher clouds and light NE winds should prevent temperatures from plummeting too much overnight. Forecast lows range from the mid 40s in North Central Indiana to the low to mid 50s in SW and South Central Indiana. && .LONG TERM (Sunday through Friday)... Issued at 310 AM EDT Sat May 24 2025 The long term period starts off on a dry and mild note across Central Indiana; however wet weather returns next week for portions of the state. .Sunday... High pressure keeps its influence on surface conditions for Central Indiana on Sunday, while an area of low pressure and frontal boundary approach from the southwest. Aloft, forecast soundings indicate moisture advection increasing in the mid and upper levels as subtle waves pass through within the jet stream resulting in mostly cloudy skies Sunday. Dry antecedent conditions and lack of low level moisture advection should keep the boundary layer dry enough to inhibit precipitation development across most of Central Indiana. The best forcing for ascent and moisture for precipitation should remain further south in the lower Ohio Valley and Ozarks where the warm frontal feature sets up. Model trends over the past several days support this set up keeping rainfall away from the region until at least late Monday night. Some guidance tries to portray isolated showers over Central Indiana Sunday, however in reality, this will likely present itself as virga. So while it may look like it could rain Sunday, dry lower levels will likely result in rainfall evaporating before reaching the surface. Would not rule out a drop or two making it to the ground, especially south of I-70, but overall expect a dry day. Clouds and NE winds keep temperatures below average for this time of year with highs only in the mid 60s. .Next week... The overall weather pattern begins to shift next week as the upper jet becomes more west-southwesterly aloft and the storm track lifts northward into Indiana. Closer to the surface, high pressure begins to lose its influence over the state as a developing area of low pressure in the Plains and associated frontal boundaries lift northward into Indiana. Low pressure is expected to ride along the warm front extending over the Ohio Valley and provide perhaps the best opportunity for more widespread rain and embedded thunderstorms Monday night through Tuesday. The focus for greatest convective coverage will again be over southern counties in closest proximity to the warm front and track of the surface low. By Wednesday, an upper low will be in place over the Upper Great Lakes while Indiana is in in the wake of the passing surface low to the east. While it is difficult to forecast subtle waves within the upper jet this far out, this pattern would support continued mostly cloudy conditions with showers as weak waves rotate around the upper low to the north. Keeping the forecast more pessimistic mid week based on the overall weather pattern. Confidence decreases mid to late next week and into the following weekend as some longer range models have been consistent in showing another cut off low pattern developing. Guidance usually struggles with patterns featuring weakly forced systems, so confidence remains low in the finer details this far out. For now, keeping a close eye on the potentially cool and wet pattern going into early June as any warm up back to normal may be fairly brief. Should the forecast pan out with highs remaining below 70 through at least Tuesday here at Indy, this would mark a consecutive string of 8 straight days of sub-70 degree weather extending back to this past Tuesday 5/20. The last time Indianapolis experienced this for such a long period of time this late in the Spring was from 5/25 to 6/2 in 1889. The search for a return to more persistent warmth likely is still 7-8 days out and possibly beyond with 80s likely to return by early in the week of June 2.

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