Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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183 FXUS63 KIWX 171838 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 238 PM EDT Mon Jun 17 2024 .KEY MESSAGES... - There are nearly daily low chances for showers and thunderstorms this week, especially in the afternoon and evening hours. Expect coverage to be widely scattered. - Excessive Heat Warnings and Advisories are in effect due to an extended period of hot and humid conditions. Max heat indices this week will range from around 95 to 105, with the highest values in the warning area and in urban locations. Overnight lows in the 70s will provide little relief from the heat. High temperatures will be in the upper 80s and 90s. && .DISCUSSION... Issued at 230 PM EDT Mon Jun 17 2024 Ridging over the east coast of the CONUS along with troughing over the west coast allows plenty of warm air and moisture to stream into the area over the next few days at least into Saturday. Initial placement of height anomalies is farther east in this forecast period, but they do begin to shift more westward especially as we head into the latter part of the work week, which indicates the better chances for warmer temperatures and perhaps to be unscathed by any chances for pop showers/storms during that time frame. With the height anomalies farther east to begin the period, a vort max is able to ride northward along its periphery and provide a chance for showers and thunderstorms after midnight tonight into Tuesday morning. There is some possibility for left over debris clouds that could cut into how warm temperatures become on Tuesday, but am still expecting a thorough stream of moist dew points into the area with ~70F degree dew points still on the table. Additionally, should the clouds begin to break up, it wouldn`t take very long to heat back up to advisory threshold during the late morning/afternoon time frame. As such, have decided to hoist the advisory for areas north of US-24 and keep the warning for areas south of US-24 for Tuesday, especially with the limited cooling off of temperatures overnight as a result of the continued upper 60s to 70F degree dew points. One wrinkle in this would be if dew points stay below the upper 60s from maybe if more afternoon mixing takes place if clouds break up again. As mentioned before, the height anomalies begin working into the area on Wednesday and the weakening/more limited shower chances begin to increase confidence on the mid to late week heat being the most intense. It still looks like areas west of IN-31 have the lowest chance to see hot heat indices based on dew points falling back into the mid to upper 60s. Will still continue the excessive heat warning south of US-24 where the highest heat looks to reside during the late week period. What to do with the areas north of US-24 will be the main question moving forward, but continued minApT values around 75 still likely keep the "not enough nighttime recovery" impact in play. Even still, am not quite ready to extend the heat advisory possibility through the period with the chance that models aren`t capturing some vort max correctly that could bring a chance for showers/ clouds. There is some indication that the ridge may be able to break down either Sunday or Monday as a cold front pushes through in concert with a deepening upper low moving across the Northern Great Lakes/ southern Canada area. This would bring more comfortable air in for the first half of next week. High temperatures Sunday and Monday are in the mid 80s with dew points stepping down into the mid 60s on Sunday and down into the 50s on Monday. && .AVIATION /18Z TAFS THROUGH 18Z TUESDAY/... Issued at 120 PM EDT Mon Jun 17 2024 Expansion of a scattered cu field is readily apparent across much of Indiana as convective temperatures have been met in an unstable atmosphere. While VFR conditions are expected to dominate most, if not all, of the forecast there are a few challenges that need to be monitored that are not necessarily captured in the TAFs. Any subtle features passing through the area could easily pop a shower or thunderstorms at either site this afternoon and early evening. The greatest concern at this point is an area of persistent convection across east central IL, approaching KRZL. While trends suggest this may stay just west of KSBN, outflow boundaries from the convection could easily move east and provide lift for additional showers/storms. A few of the models actually key in on the KSBN area for one or more rounds of storms late afternoon into the early evening, but no consistent signals remain. For now have opted to go VCSH at both sites with timing and duration of any shower/storm difficult to capture at this point. While loss of heating will bring any precip chances to an end this evening, a weak disturbance, currently producing widely scattered showers across portions of Kentucky, will drift north late tonight into Tuesday morning. Think there will be at least an increase in mid/high clouds but some question as to chances for showers with this feature. Given the low confidence, have introduced a broken high cloud deck for the time being late tonight and defer to later forecasts for possible inclusion of showers/storms. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Tuesday for INZ005>008- 012>015-020-022-023-103-104-116-203-204-216. Excessive Heat Warning until 8 PM EDT Friday for INZ009-017- 018-024>027-032>034. OH...Excessive Heat Warning until 8 PM EDT Friday for OHZ001-002- 004-005-015-016-024-025. MI...Heat Advisory until 8 PM EDT Tuesday for MIZ078>081-177-277. Air Quality Alert until midnight EDT tonight for MIZ078-177- 277. MARINE...None. && $$ DISCUSSION...Roller AVIATION...Fisher