Area Forecast Discussion
Issued by NWS Indianapolis, IN
Issued by NWS Indianapolis, IN
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475 FXUS63 KIND 300654 AFDIND Area Forecast Discussion National Weather Service Indianapolis IN 254 AM EDT Mon Sep 30 2024 .KEY MESSAGES... - Isolated to scattered showers through late today - Areas of fog late tonight into Tuesday morning - Mainly dry conditions with nearly seasonable temperatures to open up October && .SHORT TERM (Today and Tonight)... Issued at 254 AM EDT Mon Sep 30 2024 Isolated light showers and pockets of drizzle continue to drift southwest across the region early this morning on the northwest flank of the upper low. with thick stratus once again draped over most of the forecast area...temperatures remained steady state in the mid and upper 60s. This will be the final day with the upper low and remnants of Helene in the vicinity of the region as an approaching strong upper trough moving through the Canadian prairies and northern Plains. The upper trough will help to kick the upper low off to the east and away from the Ohio Valley as it weakens further. While clouds and the potential for scattered showers will linger today...the loosening influence from the upper low should ensure increased heating and more breaks in the cloud deck by this afternoon. First off...the boundary layer remains saturated which the IND ACARS sounding shows nicely. With increasingly drier air filtering in aloft...ceilings have slipped back into the 1000-2000ft level currently with a few locations even lower than that. The lower stratus will linger over much of the region through the morning with the possibility for patchy fog as well focused over southeast counties where there has been some scattering of the stratus. Northeast winds remain around 10mph but should fall back towards daybreak. Pockets of light showers and drizzle will also remain over the southeast half of the forecast area over the next several hours. As mentioned above...the lower stratus will lift and at least partially mix out this afternoon as the drier mid level air begins to work down into the boundary layer. Shallow instability this afternoon may be enough to generate a few showers focused especially across the southeast half of the forecast area in closest proximity to the departing upper low. By early evening...expect showers to diminish as deeper low level moisture shifts east and heating is lost. The focus for tonight will transition to fog and perhaps stratus redevelopment as well. Despite the presence of an overall drier column of air...near saturated conditions will linger in the near surface layer as winds go near calm. The setup is supportive of broader fog development late tonight through daybreak Tuesday. There remains uncertainty with respect to the degree of clearing of the stratocu which may serve to limit fog in some areas. For now will highlight the potential for areas of fog late. Temps...warmer temperatures are expected this afternoon with increased breaks in the stratocu. Much of the forecast area should warm into the mid 70s. Lows tonight will again fall into the low to mid 60s. && .LONG TERM (Tuesday through Sunday)... Issued at 254 AM EDT Mon Sep 30 2024 Mainly quiet weather is anticipated through the long range. A progressive quasi-zonal jet stream is located along the US-Canadian border, and should remain at that general latitude through the coming week. The long wave pattern suggest a trough and associated cold front swinging through roughly every 3-4 days, with the first arriving on Tuesday. A second cold front looks to arrive Friday or Saturday, and then potentially a third by Sunday or early next week. Some showers are possible with each frontal passage, but heavy amounts of precipitation are not expected. Reason being is that deep moisture is displaced far to our south, and no strong sub-tropical connection looks to become established prior to frontal passage. Each front should bring a reinforcing shot of dry continental polar air. Good radiational cooling potential is likely as surface high pressure builds in behind each front. Tuesday and Wednesday night, for instance, may see temperatures dip well into the 40s. Highs rebound nicely into the 70s under full sun. Given the above pattern, drier than normal conditions are favored through the long range and perhaps beyond. Near average temperatures are expected. Average highs are in the low 70s with lows in the low 50s. && .AVIATION (06Z TAF Issuance)... Issued at 1249 AM EDT Mon Sep 30 2024 Impacts: - MVFR to IFR ceilings through the morning...improving to VFR by mid to late afternoon - Patchy fog possible late tonight and toward sunrise Discussion: Dreary conditions continue with pockets of drizzle drifting southwest across central Indiana. Ceilings will slip back through the overnight to 500-1000ft with patchy fog in light northeast flow. Expect these ceilings to gradually lift to MVFR by midday then VFR by mid to late afternoon as drier air aloft finally works its way down into the boundary layer. As the remnants of Helene finally move away to the east by this evening...drier air will advect into the region with some scattering of the stratocu deck. A strong signal for fog and perhaps widespread and dense in spots is in place for late tonight and early Tuesday as a sharp inversion develops in the near surface layer. Will address this in greater detail for the 12Z TAF issuance. && .IND WATCHES/WARNINGS/ADVISORIES...None. && $$ SHORT TERM...Ryan LONG TERM...Eckhoff AVIATION...Ryan