Area Forecast Discussion
Issued by NWS Wilmington, OH

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220 FXUS61 KILN 051153 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 653 AM EST Mon Dec 5 2016 .SYNOPSIS... High pressure will build into the region today. The high will quickly move off to the northeast tonight and Tuesday as low pressure moves into the Ohio Valley. A cold front will follow on the heels of the low Tuesday night, bringing drier and cooler weather behind it for mid week. Much colder weather is expected by the end of the week as another cold front pushes across the region. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Surface high pressure will settle across the middle Ohio Valley by midday. Model soundings continue to indicate that low level moisture in the form of clouds will remain trapped beneath a subsidence inversion through at least midday. Thereafter, they suggest that enough dry air aloft will mix with the moisture, along with some diurnal heating, to allow the clouds to erode. If this occurs, the erosion process should work its way north and east toward sunset. Even so, considerable high level clouds will already be over the region well ahead of the next weather system. Have taken the cooler side of guidance for highs in anticipation of a slow erosion process. Highs will range from the upper 30s north to the mid 40s far south. && .SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/... Operational models remain in great agreement in terms of synoptic scale systems to affect our region during the short term period. Have taken a blend of these, along with high resolution models, to better time the onset and exit of precipitation tonight into Tuesday. High pressure will move off to the northeast tonight. Meanwhile, upper level energy will pivot from the lower Mississippi River Valley to the Tennessee and Ohio Valleys tonight into Tuesday. Lows tonight will not drop off too much due to thickening clouds. Warm, moist ascent in the form of a low level jet, will spread rain northward into the region after midnight. Temperatures across the far north will be near freezing toward Tuesday morning. For now, it looks like precipitation should stay in the form of rain as it arrives when readings creep above freezing. On Tuesday, the upper level energy will be associated with a surface low that will pass northeast through the Ohio Valley. Widespread rain is expected, with perhaps more showery precipitation in our southeast near the surface low. This system will be a quick mover, and associated low over the Ohio Valley will weaken as a coastal low takes over off the mid Atlantic region by Tuesday evening. Thus, most precipitation should be out of our region by then. A cold front will follow on the heels of this system, allowing drier and cooler air to filter into the region behind it by Wednesday morning. A consensus blend of raw 2 meter temperatures was employed tonight into Tuesday night to better capture the non diurnal fluctuations. Wednesday will be a quiet, cooler day as high pressure ridging settles into the Ohio Valley. Models continue to advertise a large scale upper level trough to dig southeast into the Great Lakes and Ohio Valley through the end of the week. A cold front is expected to precede this trough, passing east/southeast through our region Wednesday night into Thursday. The 00Z ECMWF has backed off on trying to develop a surface wave along the front. As such, it is much drier with this system which is similar to the 00Z GFS. Have reduced the chance of light snow to low chance for late Wednesday night into Thursday morning due to this trend. Highs on Thursday will be the beginning of a downward trend in temperatures, ranging from the upper 20s northwest to the mid 30s southeast. && .LONG TERM /FRIDAY THROUGH SUNDAY/... This period will be characterized moreso by temperature impacts rather than precipitation impacts - though the latter will still need to be watched for next weekend. Confidence assessment - there`s really pretty decent agreement in larger scale evolution of the flow into next weekend between higher resolution deterministic runs and parent ensemble means. There`s much higher confidence on temperature evolution Fri-Sun vs. precipitation, with the season`s first /well advertised/ cold spell centering on Friday with temp departures some 10-20 degrees below normal. It appears that cold flow across the Great Lakes Friday will be more zonal in orientation which should keep lake effect snow showers downwind of the Great Lakes and north of our region. Some stratocumulus clouds, however, may be capable of a few flurries given its intersection within the dendritic growth zone. For the upcoming weekend, progressive shortwave energy is advertised to move across the Great Lakes. Very low confidence with the forecast next Sat/Sunday - as it is noted that ensemble plumes /GEFS and ECMWF/ get extremely noisy in Days 7-10 suggesting the pattern is of very low confidence with how the energy next weekend evolves. Both data show the deterministic runs trending away from their respective ensemble means by Day 8, suggesting caution in next weekend`s forecast. Per confidence assessment above - not a great deal of confidence how shortwave energy and associated rain/snow chances look for Sunday and this lingers beyond Day 7 depending how energy ejects within the upper trough. For right now have middle-range snow chances developing Sunday with transition from south to north given warm advection. && .AVIATION /12Z MONDAY THROUGH FRIDAY/... Widespread MVFR ceilings (generally 1000-2000 feet AGL) remain in place, and will stay in place through at least the late morning / early afternoon. There is at least some chance that MVFR ceilings will persist into the evening, and a SCT015 group will be kept in the TAFs to suggest this possibility. Westerly winds will diminish and become light and variable over the next several hours. A relatively calm period of weather this afternoon and evening will not last long. Whether or not the current stratocumulus deck dissipates, additional clouds will begin to develop and lower tonight and into the overnight period. Rain is expected to move into the TAF sites early Tuesday morning, with conditions gradually diminishing to MVFR and eventually IFR. OUTLOOK...MVFR/IFR ceilings and MVFR visibilities are expected on Tuesday with rain. MVFR ceilings will persist into Wednesday morning. MVFR ceilings are possible again on Friday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM...Hickman SHORT TERM...Hickman LONG TERM...Binau/Hickman AVIATION...Hatzos

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