Area Forecast Discussion
Issued by NWS Wilmington, OH

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094 FXUS61 KILN 231752 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 152 PM EDT Thu Mar 23 2017 .SYNOPSIS... Return southeast flow will allow temperatures to modify today. A warm front will push northeast through the region tonight, bringing a few showers to the area. Temperatures will continue to warm on Friday as southerly flow increases. A low pressure system over the central Plains will slowly move into the Great Lakes and Ohio Valley this weekend. Warm temperatures will continue along with an increasing threat of showers and thunderstorms. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Initial band of mid clouds has moved into the northwest counties. It appears that these may decrease in coverage as they continue east. Additional mid clouds will start to move in from the west late in the day. Little to no change to forecast highs.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/... Models are in fairly decent agreement in terms of positions and of subsequent forecasts of synoptic scale systems. For tonight, a mid level ridge will build northward and eastward into the Ohio Valley. As this occurs, a warm front will push northeast through our area. Clouds will thicken this evening with a few showers possible for locations north of the Ohio River overnight as this area will be on the southern fringe of better moist/isentropic lift farther to the north. Lows will bottom out early, then steady out or slowly rise toward morning as southerly flow increases. Temperatures will range from the lower 40s northeast to the upper 40s southwest. On Friday, the Ohio Valley will be warm sectored in the wake of the warm front while a mid level ridge axis shifts east. Models are indicating quite a bit of low level moisture in the return low level southerly flow. This will likely result in stratus clouds early on which will likely convert over to low level cumuliform clouds during the afternoon. As a result, have kept skies mostly cloudy. Despite cloud cover, stiff southerly winds with gusts in the 20 to 30 mph range will boost highs into the mid and upper 60s. && .LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/... An unsettled pattern will be setting up over the Ohio Valley through the weekend, turning more progressive but continuing to be active going into the early part of next week. On Friday night, the ILN CWA will be within a regime of generally low pressure, stuck between highs off the southeast coast and over northern Ontario. The 500mb pattern will be amplifying in the vicinity of the Ohio Valley, even as relatively tranquil conditions are expected at the start of the long term forecast period on Friday night and Saturday morning. Well within the warm sector, heights will be rising as ridging builds into the Mississippi Valley, with a frontal boundary remaining nearly stationary across Michigan and New York. To the west, a complex stacked low pressure system will begin to take shape over the plains, moving slowly east -- near St Louis by Sunday morning, then finally clearing the Ohio Valley by Monday morning. Confidence continues to increase in the overall timing and placement with this system, though the 00Z ECMWF solution remains slightly slower than the 00Z GFS. The first part of Saturday is generally expected to be dry, outside of a few showers developing in the continued isentropic ascent. It is expected that there will be several rounds of showers (and potentially thunderstorms) along with this system, running primarily from Saturday evening through Sunday afternoon. Though the overall motion of the low will be slow, the juxtaposition of upper support, low level moisture transport, and 500mb vorticity advection will result in the possibility of multiple time periods in which showers and possibly thunderstorms will be able to develop. There continues to be strong agreement in a well- defined wave moving through the region late Saturday evening through Sunday morning, and this period has been timed out with categorical PoPs. On either side of this (Saturday afternoon and Sunday afternoon) the forcing is not as well defined, but showers and storms will be possible -- without seeing the mesoscale details, getting more specific on timing is not yet possible. Thunder has been included as a possibility on both days as well. This system will have a respectable feed of theta-e and a tight/compact 850mb- 700mb low, so forcing and moisture should be sufficient for widespread precipitation. In general, the modeling of instability has been very fickle -- changing slightly from run to run, never higher-end, and largely limited by the moist profile and poor mid- level lapse rates. Building off of that analysis, with questionable instability, the possibility for heavier rainfall or strong storms is less certain -- also owing to differences in model specifics and a pattern that is not necessarily a classic setup for either threat. Nonetheless, with decent moisture and some turning in the wind field near the low, there is at least a low-end potential to watch and refine the forecast for in the next few days. As the low weakens and moves away from the area late Sunday into Monday, the weather pattern over the Ohio Valley will become very wavy -- characterized with short wavelengths and progressive motions. A narrow ridge behind the stacked low will provide a reasonable chance for dry conditions for early Monday, but the busy 500mb pattern will mean that this dry period will not stick around for long. Though there are some timing and amplitude differences (even within the GEFS member spread) the next wave is expected to move through Monday night into early Tuesday, producing widespread precipitation across the area. However, until timing is better handled, PoPs will be kept at 50 percent for this feature. Subsidence behind the wave will likely lead to drier conditions Tuesday night into Wednesday. The continued warming trend into Saturday is likely to bring temperatures into the upper 60s to lower 70s, with warmest conditions in the southeastern CWA, where precipitation is more likely to hold off until later. Precipitation will keep the temperature forecast a little lower for Sunday, before warming again slightly on Monday -- with the air mass changing very little in general, as the main boundary will remain well north of the area. This will change after Tuesday, as the Monday night / Tuesday wave will bring a cold front into the region, beginning a slight cooling trend going into the middle of the week. Nonetheless, temperatures should still remain above normal, even on Wednesday. && .AVIATION /18Z THURSDAY THROUGH TUESDAY/...
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Mid clouds will spread across the region early in the TAF period. A warm front will lift across the area after 00Z. There could be a few light showers with this, particularly from KDAY to KCMH/KLCK. However, the probability is low and even if they do occur, there would be no impact on flight category. So that potential has not been included in the TAFs. Southeast winds will veer to the south once this front moves through. In addition, low level winds will increase in speed leading to low level wind shear until around 13Z. Lower clouds will spread into the area on Friday morning. Confidence is low concerning what level these clouds will be. At this point have only lowered KDAY to MVFR, but it is certainly possible that MVFR ceilings could affect more areas. OUTLOOK...MVFR ceilings possible Friday afternoon and evening. MVFR ceilings and visibilities likely Saturday night into Sunday along with a chance of thunderstorms. MVFR ceilings and visibilities will be possible again Monday night into Tuesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM... SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...

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