Area Forecast Discussion
Issued by NWS Wilmington, OH

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992 FXUS61 KILN 251053 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 553 AM EST Sat Feb 25 2017 .SYNOPSIS... A much cooler airmass will continue to settle into the region today as a weak upper level disturbance brings a few rain and snow showers. High pressure will build into the Ohio Valley tonight into Sunday, leading to mainly clear skies. Seasonable temperatures will remain in place across the area for Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... A dry slot is evident on IR satellite imagery pushing up across eastern Indiana and far western Ohio early this morning. However, some lower level moisture is spreading quickly back in from the west across western and central Indiana. This will likely pinch off the dry slot across western portions of our fa as we progress through the next few hours. These lower clouds are associated with the leading edge of some better low level CAA and ahead of a mid level trough axis that will push east across the region through early afternoon. The combination of this and some weak low level instability will lead to isolated to scattered shower activity later this morning and into the early afternoon hours. It looks like any pcpn may start off as rain but it should transition over to snow from west to east as the low levels continue to cool off. The low level CAA will keep temperatures nearly steady or possibly slowly falling through the day. Winds will also become gusty in the 25 to 35 mph range today. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/... The trough axis will push off to the east tonight with surface high pressure building into the region later tonight. This will lead to decreasing clouds southwest to northeast and overnight lows in the low to mid 20s. Mostly sunny skies are expected on Sunday with highs in the low to mid 40s. && .LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/... Sunday night surface high pressure will be centered near the coast of NC with southwest flow across the region. At the same time an upper level disturbance over AZ will eject east and push towards the forecast area. Both the GFS and ECMWF have come into fairly good agreement here with this system ejecting east and spilling vorticity across the area Monday morning. As this happens high cloud bases will thicken and slowly lower with precipitation moving in from the west. Initially Monday morning a rain/snow mix will be supported with the entire sounding below freezing except right at the surface. Behind the remnant shortwave Monday afternoon dry mid and upper level air will work into the area helping to cut off the precip a bit. Monday night into Tuesday morning there will be a brief break as the next upper level disturbance over the Mountain West gets its act together. Later Tuesday morning into afternoon the upper level disturbance will push northeast into Minnesota pulling a warm front north across the area. Widespread overrunning will commence with PWATs approaching 0.85". Widespread weak lift will also accompany the WAA which is supported by GFS omega fields. Tuesday afternoon a surface low will track northeast towards WI allowing temperatures to rise into the 60s. Shear values Tuesday afternoon will also become impressive as ILN gets warm sectored with SFC- 3 KM shear 40 + kts at times. GFS soundings currently show a CAP across the area though which would limit convection across the region. Tuesday night into Wednesday morning another upper level disturbance will swing around the base of the upper level trough axis centered over the Western United States and push towards the forecast area. As this happens another surface low will form in the plains and push northeast along a baroclinic zone. At the same the upper level jet will begin to strengthen and briefly place ILN in a RRQ. Also a weak split will occur in the jet. The GFS/ ECMWF/ and CMC all show this happening. The difference between the three is placement of the baroclinic zone (e.g., front), and track of eventual surface low as it heads northeast. The NAEFS shows PWAT anomalies of 2 SD. The GFS also has a PWAT of 1.35" just south of the region. As mentioned above though these small differences in track between models has a big difference on rainfall distribution. The ECMWF is furthest north with the second surface low and has heavier rainfall totals across our northwestern zones while the GFS is furthest south with the track and has the heaviest totals across central KY. The CMC is a compromise between the two and have trended the forecast this direction. Given the RRQ, splitting upper level jet, abundant moisture and lift have raised PoPs for Wednesday. Wednesday evening into Thursday morning a stronger upper level disturbance will push east over the area finally pushing the surface cold front through the area. Thursday afternoon into Friday another upper level disturbance will head southeast out of southwestern Canada and bring a chance of snow and rain to the area Friday morning. GFS soundings completely saturate Friday morning with almost the entire forecast sounding below freezing. As of now mostly snow Friday morning would be expected given the thermal profile of the GFS. Eventual track and strength of this disturbance remains in question though as the ECMWF is weaker with the disturbance so have kept PoPs at chance for now. Friday night into Saturday surface high pressure will dip south into the area from Canada and bring below normal temperatures to the area. Saturday afternoon the surface high pressure will already be east of the forecast area as the upper level trough axis heads east. && .AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
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A narrow dry slot is working east across the area early this morning but it will be short lived as the leading edge of the lower startocu is progressing into western Ohio attm. This is associated with a mid and upper level trough axis that will swing east across the area through this afternoon. This will help the stratocu field pivot eastward across the TAF sites through the rest of the morning. These clouds will likely start off as a lower VFR deck and then transition into a period of MVFR cigs from late morning into the early afternoon hours. Forecast soundings are showing a little bit of low level instability today and this may be enough to produce scattered shower activity later this morning and into the afternoon. The best chance for this appears to be at the northern TAF sites so will carry a VCSH to account for this. Any precipitation may start out as rain but should transition to snow for at least the western TAF sites as colder air filters into the region. High pressure will begin to build in from the southwest tonight. This will lead to decreasing clouds through the remainder of the TAF period. OUTLOOK...MVFR ceilings and visibilities possible Monday, Tuesday night, and Wednesday.
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&& .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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