Area Forecast Discussion
Issued by NWS Wilmington, OH

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615 FXUS61 KILN 171036 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 636 AM EDT Tue Sep 17 2019 .SYNOPSIS... High pressure over the Great Lakes will have strong influence over the weather across the Ohio Valley through the remainder of the week, keeping dry conditions and comfortable humidity across the area. However, with very dry ground the temperatures will continue to run well above normal particularly during the daytime, with nights remaining much closer to normal. Today will be the coolest day of the next five, with highs in the upper 70s to middle 80s, with widespread 80s thereafter. The next appreciable chance at a more widespread measurable rain will come later Sunday into Monday as cold front shifts through the region. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Yesterday`s cold front will be well south/west of the local area at 12Z this morning, with strong 1023mb high over southeast Canada. Modest northeasterly low-level flow around this high will continue a weak backdoor-type low-level cold advection regime across the forecast area today, making today a little bit cooler than yesterday, and likely the coolest day of the week. This morning - GOES RGBs and Fog Product showing eruption of stratus as the cold advection catches up to a still-moist boundary layer over Ohio/Indiana. This stratus had been expected to settle south toward the Ohio River, but recent data has veered low level wind flow enough that it now appears the southward progression of stratus will approach I-70 after sunrise and begin to push more west than south, effectively stopping the intrusion near/north of Dayton/Columbus. Once the diurnal heating cycle kicks in, expect this shallow stratus to begin to mix out on the modest northeasterly breezes, with the fringes of the stratus lifting into a broken stratocumulus deck before things become more cellular in nature late in the morning to early afternoon. For the rest of the forecast area, a healthy mix of sunshine and fair weather cumulus with forecast soundings very stable above the boundary layer during peak heating and precipitable water remaining near to slightly below normal. Would expect dewpoints /after starting in the lower 60s this morning/ to mix back into the upper 50s on afternoon breezes which should make for quite the enjoyable afternoon. With late afternoon 925mb temperatures peaking around 18C /north/ and 21C /south/, expect highs to range from around 80F in the north and the mid 80s in the south. This is after taking into consideration the very dry / parched ground which is helping high temps obliterate the statistical MOS just about every day for the past week. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... Continued very quiet weather over the forecast area as strong high pressure over southeast Canada continues subsidence and very dry northeast flow over the Great Lakes. Expect a good valley fog episode later tonight in the usual spots with the drier boundary layer airmass allowing lows to drop back into the 50s. On Wednesday, modification of the low level airmass will continue under strong insolation and very dry soils. With 925mb temps rising to 19C /east/ to 22C /west/, this will push high temperatures well into the 80s area-wide. Would not be surprised to once again see a rogue 90F reading or two in areas of northern KY where soils are particularly dry and the warmest low level thicknesses reside. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... A large scale mid level ridge will dominate the weather regime across the Great Lakes and the Ohio Valley from Wednesday night into Saturday. The anomalous ridge will keep the forecast dry with high temperatures averaging much above normal for mid September. As has been pointed out in previous discussions, model performance with high temperatures have been poor, perhaps they are not capturing the very dry conditions that have developed across the region. Thus, have been starting with a model blend, then raising high temperatures 3 to 4 degrees, which fits more in line with 925 mb mixed temperature relationships. This results in highs in the upper 80s to around 90 with lows in the lower to mid 60s. Aforementioned mid level ridge is expected to become suppressed during the Sunday/Monday time frame as a mid level trough moves into the Great Lakes. This should eventually push a slow-moving cold front southeast into the area. An increase in deep moisture and the boundary will bring a chance of showers, perhaps a rumble of thunder, during the Sunday/Monday forecast. Highs in the mid and upper 80s Sunday should cool into the upper 70s to the lower 80s by Monday. Lows will remain in the lower to mid 60s. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... Stratus has expanded as expected across much of northern Ohio and is sinking southwest on light northeast flow. Currently have a well-timed bank of IFR stratus heading toward CMH/LCK with expected arrival at those two airfields around 13Z if it holds together. Right now, have not seen any indication that it won`t so have included a brief TEMPO this morning of IFR ceilings at both sites, before its forward progress should slow and it begins to erode on the leading edge owing to heating/mixing. This should lift the stratus into a broken MVFR deck which should become more cellular with time as it dissipates. Other area of stratus well north of KDAY should not impact that terminal but it is sinking southward somewhat so this will need to be watched through the morning. Otherwise, valley fog is plaguing KLUK and this should continue through 13Z before burning off. Light fog is also possible at KDAY/KILN in before burning off around 13Z. During the day, expect few-sct cumulus under sct-bkn cirrus. Mainly clear skies and light winds tonight with another valley fog event expected at KLUK. Have brought visibility down after 06Z there with TEMPO to IFR visibility later in the night toward sunrise. OUTLOOK...No significant weather expected. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Binau NEAR TERM...Binau SHORT TERM...Binau LONG TERM...Hickman AVIATION...Binau

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