Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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213 FXUS63 KIWX 191734 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 134 PM EDT Wed Jun 19 2024 .KEY MESSAGES... * There is a Marginal Risk for isolated severe storms mainly along and east of Interstate 69 this afternoon. The main threat is isolated strong to damaging wind gusts. * Hot and humid conditions expected through Saturday with just slight chances of storms. Peak afternoon heat indices will approach 100 degrees, hazardous to sensitive and vulnerable groups. && .DISCUSSION... Issued at 350 AM EDT Wed Jun 19 2024 Persistent heat/humidity will continue to be the primary forecast concern this period. A Marginal Risk of severe storms has been introduced for this afternoon/early evening, mainly along and east of Interstate 69 for isolated damaging thunderstorm wind gusts. For today, portions of northeast Indiana/northwest Ohio should be in favorable position for some influence from sheared upper level short waves lifting northeast out of the Lower MS Valley. 00Z RAOB last evening from Nashville does indicate some slightly stronger 35-45 knot flow in upper levels associated with this forcing. Weakly confluent low level flow across NE Indiana/NW Ohio today may provide some focus for isolated afternoon/early evening convection, which also should be a zone of best low level moisture quality given some modest low level moisture transport working in from the Ohio Valley. Surface based CAPES along and east of I-69 should increase into the 1000-1500 J/kg range this afternoon. Overall weakly sheared environment and modest instability would suggest minimal severe risk, but shallow warm/moist profiles beneath drier mid level air should support some moderate downdraft CAPES on the order of 1000-1200 J/kg that could support some isolated strong/severe downdrafts. Areas east of Interstate 69 have been placed in Day 1 Marginal outlook, with isolated damaging winds as the main threat this afternoon. Otherwise in the meantime, difficult to discount isolated showers and storms developing this morning given the approach of the sheared upper level forcing and gradually moistening low levels that could allow some weak elevated instability to be realized. Not much change made to maximum temperature forecast today, but extent of cloud cover and isolated convection will complicate hourly temperature trends. Extensive mid and high clouds blanket the area this morning, but these clouds should tend to erode from west to east this afternoon. Some concern this could be a limiting factor from realizing full low to mid 90s max temperature potential today, but areas across the east should see slightly higher dew points in comparison to yesterday. Peak afternoon heat indices should be in the mid to possibly upper 90s. For Thursday and Friday, guidance continues to suggest some slight retrogression of pattern and subtle mid/upper level height rises across the Great Lakes/Ohio Valley. Best chances of diurnally enhanced isolated/scattered showers and thunderstorms should be across the north given potential of weak short wave to eject out of Central Plains into the Lower Michigan Thursday afternoon. Peak afternoon heat indices should once again top out from the mid 90s to around 100 (warmest for southern half of the area). Persistence forecast continues for Friday, although precip chances may be more muted for most of the area given mid/upper level ridging more firmly entrenched. A very shallow cool frontal feature across the southern Great Lakes could provide some focus for isolated afternoon convection across far NE Indiana/SC Lower Michigan Friday afternoon, but low level moisture quality may be a bit less impressive by this time. For Saturday, little change in large scale pattern expected with a more substantial upper level short wave trough still displaced to the west across central CONUS. Confidence continues to creep upward that heat indices near 100 will persist into Saturday, with current expectation that scattered convection will hold off until Saturday night. Will not extend heat headlines into Saturday yet, but this will be something to examine over next few shifts. The best chance of showers and thunderstorms still looks to be in the Saturday night into early Sunday timeframe as this upstream trough and associated cool front push across the region. This should push highs back down into the 80s for Sunday and Monday, but heat may build once again Tuesday-Wednesday. Confidence is low on heat index magnitudes toward end of this forecast period however, as chances of showers and thunderstorms and increased cloud cover may characterize this period with a series of northern stream short waves skirting across Northern Plains into the Great Lakes. && .AVIATION /18Z TAFS THROUGH 18Z THURSDAY/... Issued at 128 PM EDT Wed Jun 19 2024 VFR conditions likely to dominate at both sites through the period with light winds. A weak boundary has passed through KSBN and while a shower or storm can`t be fully ruled out, better chances will reside east of the site. At KFWA, an area of weak convergence was noted from KMZZ across KFWA and to the NE. Cu field has been more agitated in this area with the FWA observer reporting TCU in the area. a few showers/storms have been trying to develop east of KHHG, moving NE, but have been struggling to strengthen or last very long. As outflow boundaries continue to be produced, additional cell may develop and could push towards KFWA for the first couple of hours before the local convergence shifts east. Contemplated a tempo group for showers and even a VCTS, but confidence in the site being impacted and lasting more than 15 to 20 minutes. As a result, went VCSH for a few hours and if coverage sufficiently increases/last beyond the first hour or 2 will amend. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...Heat Advisory until 8 PM EDT /7 PM CDT/ Friday 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. Air Quality Alert from midnight tonight to midnight EDT Thursday night for INZ020. Air Quality Alert until 11 PM CDT Thursday for INZ103-203. 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 Friday for MIZ078>081-177-277. Air Quality Alert until midnight EDT tonight for MIZ177-277. MARINE...None. && $$ DISCUSSION...Marsili AVIATION...Fisher