Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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365 FXUS63 KIND 211623 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 1223 PM EDT Sat Sep 21 2024 .KEY MESSAGES... - Hot and dry Today - Thunderstorms moving in overnight - Turning cooler and more active with greater rain chances Sunday through early next week && .FORECAST UPDATE... Issued at 944 AM EDT Sat Sep 21 2024 Fog from earlier this morning continues to diminish across the northwest half of central Indiana. Still some pockets with visibilities under a mile and have an SPS to cover that over the next 60-90 minutes as that dissipates. Elsewhere...skies are mainly clear. 13Z temperatures were generally in the upper 60s and lower 70s. Weak surface high pressure with ridging aloft will reestablish across the region today bringing one more hot afternoon with dry conditions. Model soundings show increasing subsidence north of the remnant boundary which has settled near the Ohio River. That in addition to the redevelopment of a strong capping inversion will pull drier air back to the surface as mixing increases into the afternoon. Have pulled dewpoints back into the 50s by later today over the northern half of the forecast area with slightly higher dewpoints further south. Highs will make a push for 90 degrees again but this will be the last hot day before the pattern shifts to cooler with a greater risk for rain beginning Sunday. Zone and grid updates out. && .SHORT TERM (Today and tonight)... Issued at 301 AM EDT Sat Sep 21 2024 Overnight fog and timing and coverage of additional convection later today and tonight will be the main concerns for the short term. Early morning radar was showing the convection was shrinking in coverage and diminishing. This trend should continue with little or no lingering activity by 09z as the atmosphere stabilizes. Fog will be the next issue as clearing, residual boundary layer moisture and very light to calm winds were shaping for an ideal radiational fog setup especially over northern sections and the Wabash Valley where temperatures were closing in on their dew points. Hi-Res soundings and the Hi-Res models in general are all supporting this with the best timing in the 09z-13z time frame. After, getting a recent report of quarter mile or less visibility in Tipton and Hamilton counties and talking with adjacent offices, will post a dense fog advisory through 13z for our northern third and the Wabash Valley and mention patchy sense fog elsewhere. By morning, the front will be stalling near the Ohio River and then return north as a warm front during the day. Ridging from the Great Lakes to Texas should keep it dry at least most of the day, although some of the CAMs attempt to trigger afternoon convection over southwest parts of central Indiana, where mixed CAPEs will rebound to as high as 2000 J/kg per DESI. The big limiting factor will be lack of synoptic forcing, but left over boundaries and or weak impulses moving through the ridge could be enough. For now, will leave PoPs out. Otherwise, the fog should burn off by 13z or so as mainly solar heating should allow temperatures to recover back into the upper 80s to lower 90s during the afternoon. This will be the last of the well above normal temperatures through at least next week. The ridge will move east of the area tonight as an upper wave moves into northern Ontario as a center of surface low pressure moves to Lake Michigan and associated cold front stretches from the low center to northern Missouri by 12z Sunday. Hi-Res soundings are indicating a deep moist profile overnight tonight with near max moving average PWATs and at least some weak instability. This supports 60% PoPs toward 12z Sunday over the Wabash Valley tapering off to 20% PoPs over the I-65 corridor. && .LONG TERM (Sunday through Friday)... Issued at 301 AM EDT Sat Sep 21 2024 Longer term guidance continues to show a fairly abrupt shift back to much more seasonably mild conditions and potential for scattered to numerous showers and a few thunderstorms, particularly late in the weekend into the early portion of the work week. Uncertainty increases greatly from mid week and beyond as guidance begins to diverge significantly in its handling of the large scale pattern and how quickly the upper troughing will depart the region, along with the potential for tropical remnant influence. Nonetheless, there appears to be solid potential for the first appreciable rainfall in many parts of central Indiana in two to three plus weeks, which may arrest further deterioration in the local hydrologic situation - though the ongoing drought conditions are unlikely to be significantly alleviated without multiple episodes of soaking rainfalls totaling several inches. The couple of inches that appear possible throughout the coming week will not be enough to offer dramatic improvement. With the shifting and weakening of the upper level ridge, temperatures will moderate significantly, with highs likely to be in the 70s much of the coming week, much closer to seasonal norms. && .AVIATION (18Z TAF Issuance)... Issued at 1223 PM EDT Sat Sep 21 2024 Impacts: - Rain and thunderstorms are possible by Sunday morning Discussion: All fog has burned off from earlier this morning leaving mostly sunny conditions with light and variable winds as high pressure reestablishes over the region. Expect a gradual increase in mid and high level clouds by late day into tonight as a frontal boundary moves into the mid Mississippi Valley. The front will approach the region Sunday morning with chances for rain and embedded thunderstorms spreading into central Indiana from the west after daybreak. Likely to see brief restrictions within storms on Sunday. Winds will remain light and variable throughout the forecast period. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ UPDATE...Ryan SHORT TERM...MK LONG TERM...Nield AVIATION...Ryan