Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 260921 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 421 AM EST Sun Feb 26 2017 .SYNOPSIS...
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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.
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&& .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Clouds are lingering early this morning across northern portions of our area. We are still seeing some light returns on radar too and KCMH has been reporting a few flurries in the past few hours. The 00Z NAM forecast sounding at CMH is showing the better low level moisture intersecting the DGZ for the next couple of hours so we we may see a few flurries linger through daybreak or so. However, surface high pressure will slide across the mid Ohio Valley today with the low level flow backing through the day. This should allow for the clouds across our north to clear out later this morning with mostly sunny skies expected through much of the day. This will also allow for temperatures to slowly moderate through the day with highs in the low to mid 40s.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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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.
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&& .LONG TERM /MONDAY NIGHT THROUGH SUNDAY/...
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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.
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&& .AVIATION /08Z SUNDAY THROUGH THURSDAY/... High pressure will continue to build up into the Ohio Valley through this morning. Skies have been clearing from the southwest and this trend should continue through the pre dawn hours. We will start to get into some return flow as the high pushes off to the east later this afternoon and into tonight. This will eventually lead to an increase in some mid level cloudiness toward the end of the TAF period. OUTLOOK...MVFR ceilings and visibilities possible Tuesday into Wednesday and then again on Thursday. Wind gusts up to 30 kt possible Thursday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...JGL NEAR TERM...JGL SHORT TERM...JGL LONG TERM...Haines AVIATION...JGL

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