Area Forecast Discussion
Issued by NWS Northern Indiana
Issued by NWS Northern Indiana
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493 FXUS63 KIWX 250719 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 319 AM EDT Wed Sep 25 2024 .KEY MESSAGES... * Lake effect rain showers early this morning followed by isolated showers area-wide this afternoon. * Rain showers associated with a tropical system enter the forecast late Friday afternoon through the weekend. * Seasonable temperatures are replaced by a temporary dose of fall by the middle of next week. && .DISCUSSION... Issued at 317 AM EDT Wed Sep 25 2024 Lake effect rain showers this morning give way to isolated showers this afternoon. This occurs as there is hint of destabilization and weak impulses of mid-and-upper-level vorticity in the vicinity of stacked upper-level low moving across the mid-Mississippi Valley. Moisture return is modest, primarily because the cold front that moved through yesterday (now approaching the Appalacians) is the primary focus of such moisture advection. Additionally, early- morning thunderstorms ongoing over Arkansas and Oklahoma will negatively impact any poleward moisture transport in the short term. Therefore, I`ll hold steady with the inherited isolated shower mention. While fog has failed to materialize early this morning, fog is plausible again tonight per ensemble forecast soundings. But, this is at odds with high-resolution visibility guidance which indicates otherwise. Dew point depressions will be low, but afternoon forecast soundings appear well-mixed leaving me to think our local moisture source could dry out, thus limiting the fog risk. With this dichotomy, I`ll omit fog for now but pass on to the next shift for consideration. Friday through the weekend, our weather will be driven by a closed low over the southern Mississippi River Valley interacting with what is currently Tropical Storm Helene. This low will gradually drift north toward drought-stricken southern Ohio Friday and Friday night. The in-house blend still strikes me as woefully too-fast with the local arrival time of POPs. This happens among the backdrop of high pressure over the Great Lakes that needs to be displaced. So, Friday will be primarily dry but some showers could slip into the far southern US 24 corridor late in the day. POPs then increase through Friday night. Passing showers will persist through the weekend, though there will be some dry time here and there. Look out next week as a brief, but big temperature change is favored. While the aformentioned low swirls just off to our south this weekend, a ridge centered over the southern 2/3 of the CONUS will promote anomalous 500-mb heights and permit our local temperatures warm into the upper-70s Monday. Tuesday, in comes a Canadian cold front. This kicks the cut-off low well to the east and our high temperatures Wednesday will be locked into the 60s. Temperatures rebound soon after. && .AVIATION /06Z TAFS THROUGH 06Z THURSDAY/... Issued at 105 AM EDT Wed Sep 25 2024 Generally stayed close to the existing TAFs for this issuance. Stratus is blossoming quickly between KSBN and KFWA and this was captured accordingly in the TAF. Fog is becoming less certain amid this rapidly developing stratus field which will likely preclude any fog development at KFWA, while a mid-level cloud deck at KSBN has most likely squashed the FG potential there. Forecast cross sections are rather soupy though the day but with decreased subsidence through time which should allow any subsidence inversion to ease late-morning. Isolated showers are anticipated (lake effect or otherwise) but indeed, coverage will be isolated. Therefore, carried on with the dry TAF for now. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...None. && $$ DISCUSSION...Brown AVIATION...Brown