FXUS63 KIWX 151700 AFDIWX Area Forecast Discussion National Weather Service Northern Indiana 100 PM EDT Thu Oct 15 2026 .KEY MESSAGES... - Scattered rain possible today, mainly west of I-69. - There is a Marginal Risk of severe storms (mainly wind) along and south of US Route 24 this evening. Confidence in severe weather is low. - Turning much cooler and windy for Friday with some lake effect rain showers expected. Watching for frost chances, which appear the most possible Sunday morning, but Saturday morning's chances cannot be ruled out. && .DISCUSSION... Issued at 245 AM EDT Thu Oct 15 2026 Surface high pressure slides eastward this morning across the northern Great Lakes. This allowed drier air to seep into the area behind the slowly southward-moving cold front from Wednesday. This front quickly turns around into a northward-moving warm front today as a deep upper low forces a surface low northward along the western extension of the baroclinic zone down to the Southern Plains. So, the attention turns to the timing of the surface warm sector's arrival to see if we can get surface-based or only elevated convection. The GFS still has areas of large scale ascent moving through the area this afternoon whereas the ECMWF appears to have most of the better lift moving north of the area. The drier the low levels can get and maybe lesser cloud cover before sunrise would be better for instability formation. Indications in both the NAM and the HRRR are that the surface warm front waits until 2 to 4z to get into our southern 1 to 2 rows of zones, which would allow a short time period (1 to 3 hours?) for surface-based convection after that. The main ingredient of concern is the shear, which the HRRR indicates has around 45 kts of EBWD shear. Now, because the low levels up to 850 mb are essentially saturated, LCLs are sub-1000m, but instability is 500 J/kg or below. So, perhaps there could be some shallow supercells or cells with embedded rotation. With the moist PWATs around 1.8 inches, heavy rain rates could occur, but cell motions are rather fast likely limiting overall flood threat; that and the fact that we've been dry for so long. The other possibility would be a moisture loaded core- collapsing damaging wind threat, but that weak of instability may also limit that threat. The cold front slides through overnight meaning the rain threat is out of the area by 12z Friday. The aforementioned upper low is squeezed northeastward out ahead of a diving upper low from Canada. On it's back side is a strong 1040 mb surface high indicative of relatively cold air that its bringing with it. This brings in a couple of hazards that we'll get to describing here including lake effect rain, gusty winds, and potentially a frost chance. For the lake effect rain, the lake needs to get some instability going first as well as low level convergence and a return of low level moisture behind the cold front. Northwest wind convergence combines with these features around 12z Friday and would expect the intensity of lake enhancement to increase through around 18z when the vigorous vort max swings through. Given lake temps of 62 degrees, BUFKIT NAM soundings indicate 15 to 25 degree delta T values with tall lake induced inversions during the afternoon. However, there are indications that dry air begins to work into the low levels during the evening hours after the low level trough moves through and trajectories go more northerly. Low level moisture moves out of the area and there are indications that rain subsides by 12z Saturday, but could see lake effect clouds lingering Saturday morning, especially in the west. Then, northwest winds swinging through Friday evening gust between 30 and 40 mph, highest along the surface trough, which could bring downa stray 45 mph gust. Now, the cold air coming in Friday night has 850 mb temps down to -2C 12z Saturday morning before warming ensues. The pressure gradient slackens overnight into early Saturday morning and cloud cover also dissipates overnight bringing some questions about how scattered out clouds can be east of US-31. Given forecast lows securely in the 30s Friday night, we'll have to watch for frost chances then, but wind and cloud cover complicate chances. A dry day continues on Saturday and surface high pressure overhead continues to keep the area calm wind-wise. Which allows a second opportunity for frost Saturday night as the core of the cold air lifts northeastward. Forecast lows dip down into the 30s again, but an increased gradient attempts to enter from the north. This appears to be the only complication for another frost attempt Saturday night. Looking ahead, even over the next 2 to 3 days, anomalous high pressure building near Greenland causing blocking to build peaks during the 16th to 21st of October. This is about the time that the NAO/AO dips negative. Meanwhile, the aforementioned baroclinic zone has pushed eastward potentially stalling along the eastern seaboard and forming an upper low or continuing to push eastward. Either way, this allows a sprawling area of high pressure to remain across the area until at least around Thursday of next week and potentially even longer keeping dry air overhead. && .AVIATION /18Z TAFS THROUGH 18Z FRIDAY/... Issued at 1259 PM EDT Thu Oct 15 2026 Low pressure over far northern MO this afternoon slowly lifts northeast through the TAF period. Disorganized area of showers ahead of a warm front is slowly approaching from the SW. The inherited PROB30 -TSRA remains on track. Questionable instability limits confidence in thunder at both KSBN and KFWA. A period of IFR to even LIFR ceilings are favored at KSBN as the low's centroid moves near the terminal. Wind veers and quickly increases in speed during the overnight. Lake effect rain showers occur just beyond this TAF period. && .IWX WATCHES/WARNINGS/ADVISORIES... IN...None. OH...None. MI...None. MARINE...Small Craft Advisory from 11 PM this evening to 11 AM EDT Friday for LMZ043-046. Gale Warning from 11 AM Friday to 2 AM EDT Saturday for LMZ043- 046. && $$ DISCUSSION...Roller AVIATION...Brown