Area Forecast Discussion
Issued by NWS Wilmington, OH

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492 FXUS61 KILN 261803 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 103 PM EST Sun Feb 26 2017 .SYNOPSIS... High pressure will push quickly east across the region today resulting in dry conditions and seasonable temperatures. A fast moving upper level disturbance will bring the chance for some rain showers late tonight and into the day on Monday. A warm front will lift north across the area on Tuesday, leading to warmer temperatures and a continued chance for showers. More widespread rain showers will overspread the Ohio Valley region Tuesday night into Wednesday as a cold front sags slowly southeast through mid week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Blended observed values into forecast conditions for temps and dewpoints this afternoon - made no change to the expected high temperature. Given the dearth of cloud cover in the region and the distance to the cloud shield further to the west in southern Illinois, updated sky conditions to reflect a more sunny Sunday in our portion of the Ohio Valley.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/... High pressure will push off to the east tonight and this will allow for increasing southwesterly flow overnight and into Monday morning. A weak mid level short wave will push quickly east across the area Monday morning but there is quite a bit of model differences in pcpn coverage among the 00Z models. The 00Z ECMWF is the most aggressive and will lean a bit more this way as there is a 30-40 knot 850 jet nosing up into the mid Ohio Valley by mid Monday morning. As the short wave moves off to the east and the low level jet begins to weaken and also shift east, will taper off pops heading through the afternoon. Lows tonight will be in the mid 30s so suppose there could be a chance for a brief mix with snow depending on just how fast any pcpn develops later tonight. However, thermal fields on both the NAM and GFS soundings support primarily liquid pcpn later tonight and into Monday morning, so have kept pcpn all rain. Highs on Monday will range from the upper 40s north to the mid 50s south. && .LONG TERM /MONDAY NIGHT THROUGH SATURDAY/... Monday night will start off dry as a shortwave exits the region and surface high pressure moves east out into the Atlantic ocean. At the same an upper level trough axis will be located over the western United States with a series of upper level disturbances ejecting east out ahead of the trough axis. One of these disturbances will then move over the area early Tuesday morning pulling a warm front through the CWA. As this happens widespread overrunning will commence. Looking at GFS potential temperature surfaces the lowest condensation pressure deficits are forecasted to occur near the OH/ MI border. Due to this think the FA will likely see rain but higher totals will be north. GFS forecast soundings for Tuesday morning also don`t completely saturate which also helps to undermine confidence. Tuesday afternoon through Wednesday the pattern will turn more active as an upper level disturbance will eject east Tuesday morning allowing surface cyclogenesis to occur over the plains. The surface low will then track northeast Tuesday afternoon towards southern WI. As this occurs forecast soundings begin to destabilize across our southwest. Into Tuesday evening forecast soundings destabilize across the entire region. Looking more closely at GFS/ NAM/ ECMWF forecast soundings does show a weak CAP in place but this looks questionable given weak shortwaves traversing the area. Also on the forecast soundings is a great deal of shear. SFC - 1 km shear is averaging around 30 kts with SFC - 3 km SRH around 450 m2/s2. MU CAPE values also are mostly around 700 J/kg. Better upper level support does appear to be down south towards Arkansas though (at least for Tuesday afternoon). Given the above SPC has the OH valley in a slight risk for day 3. Tuesday night into Wednesday morning a potent jet streak that was over Arkansas/ Missouri will push northeast bringing ILN into a RRQ. Also Tuesday evening another upper level disturbance will rotate around the upper level trough axis that was centered over the Mountain West and head northeast. As this occurs another surface low will form along a stalled front that will run from Texas into Iowa. As the second surface low pressure forms Tuesday afternoon it will ride northeast along the baroclinic zone with the upper level disturbance helping to progress the upper level trough axis east. By Wednesday morning the second surface low will be in Illinois/ Indiana along with the surface cold front. At the same time Wednesday morning the upper level jet will begin to split over Kentucky. PWATs across the CWA are forecasted to be around 1.30" (or 97th percentile according to the NAEFS). It should be noted that at this time a subtropical ridge will be anchored east of Bermuda with strong low level southwesterly flow through the region. This flow will originate from the Gulf of Mexico with the NAEFS indicating WV transport approaching the 99th percentile. Further evidence of strong moisture transport can be found in 850 mb winds averaging around 50 kts (97th percentile for this time of year). Given the strong upper level lift, stalled boundary, surface low, anomalously high PWATS and moisture transport have kept categorical PoPs from Wednesday morning through the day. WPC has also included the area in a day 3 marginal for excessive rainfall. Wednesday evening the cold front will finally start to move east and clear the CWA Wednesday night. Drier air will work into the area Thursday morning but with lapse rates steepening across the region can`t completely rule out the chance of some light snow (esp across the north). Thursday night the upper level disturbance that brought showers and thunderstorms to the area on Wednesday will wrap up over southeastern Canada with another upper level disturbance heading southeast from Alberta. The track of this clipper is in general agreement but minor differences between the ECMWF/ GFS/ CMC equate to differences in QPF. The ECMWF and GFS have snow forming across our northern zones and more towards northern Ohio while the CMC is further south. Any precipitation that does form will likely be snow. Friday into Saturday the upper level trough axis will head east allowing high pressure to spill southwards across the eastern United States. Sunday, surface high pressure will be centered across the southeast United States as an upper level disturbance heads east across Michigan. && .AVIATION /18Z SUNDAY THROUGH FRIDAY/...
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Slowed the timing of the cloud cover in the TAF groups and do not have cigs or vsbys drop into the MVFR category until shortly before daybreak at KCVG/KLUK with the onset of any light rain. Held off on prevailing rain for the remaining TAF sites and have VCSH starting at 14z with MVFR cigs. Expect VFR conditions until rain begins tomorrow. OUTLOOK...MVFR ceilings and visibilities possible Tuesday into Wednesday along with a chance of thunderstorms. MVFR ceilings and visibilities along with wind gusts to 30 kts will be possible on Wednesday and late Thursday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...JGL NEAR TERM...Franks SHORT TERM...JGL LONG TERM...Haines AVIATION...Franks

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