Area Forecast Discussion
Issued by NWS Wilmington, OH

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019 FXUS61 KILN 210023 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 723 PM EST Fri Jan 20 2017 .SYNOPSIS... Southerly flow will continue to bring above normal temperatures into Saturday. Low pressure is then forecast to organize over the southern Plains Saturday night. The low will strengthen as it moves across the southern U.S. on Sunday. The low will eventually move to the upper Ohio Valley and mid Atlantic region by Monday. The chance of rain will increase Sunday into Monday as the system approaches. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/... Our region will remain warm sectored overnight as southerly flow continues. High resolution models suggest that a few showers may develop across the Whitewater and Miami Valleys as well as west central Ohio within the weak WAA regime. Otherwise, skies will generally be mostly cloudy. Lows will range from the upper 40s to the lower 50s. && .SHORT TERM /6 AM SATURDAY MORNING THROUGH SUNDAY NIGHT/... Saturday will be more of a transition day before the next major weather system has an affect on our area Sunday into the first part of next week. Have used a blend of the 12Z GFS and 12Z ECMWF as they seem to be handling the track of the weather system better through this period. On Saturday, skies will remain mostly cloudy. Southerly flow will continue, which will allow for another warm day in the upper 50s to the mid 60s. For Saturday night, there is conflict among operational and high resolution models as to whether weak WAA along with an upper level impulse will produce much in the way of precipitation as it moves south to north across the region. Have kept pops in the 20 to 30 percent range. Given the late arrival of the precipitation, have showers only as instability will be waning during evening. For the period Sunday into Sunday night, an upper level low and its associated surface low will strengthen as they move east across the southern U.S., and then northeast as the system rotates toward the upper Ohio Valley/mid Atlantic region. A deformation zone will develop on the northwest side of the surface low. This zones will wrap back into our area, bringing an increasing threat for showers as it pivots back to the northwest. Temperatures on Sunday will still be warm but just a tad cooler than Saturday given clouds and neutral advection. Lows will drop into the 40s Sunday night as low level northerly flow develops in response to the surface low nearby. && .LONG TERM /MONDAY THROUGH FRIDAY/... By Monday morning, almost-stacked low pressure will be centered near southwestern Virginia, with the surface low slightly north of the mid-level circulation. The overall progression of this system has slowed slightly in recent model runs, with precipitation expected to be ongoing across the ILN CWA on Monday morning, and likely continuing for 12-24 hours after -- gradually ending from SW to NE. With greater confidence in the precipitation pattern, PoPs were raised slightly from the previous forecast. The switch to northerly flow will result in a drop in temperatures from Sunday to Monday. Cooler conditions will continue into Tuesday as clouds remain in place, with low-level winds beginning to shift to the west, and eventually the southwest. A narrow ridge will move east through the area on Tuesday night into Wednesday, shifting the pattern firmly to warm advection for a relatively short period of time. It is at this point in the forecast that confidence in specifics becomes poorer, with increasing spread between the timing and magnitude of features between GEFS members and between the 12Z GFS / 12Z ECMWF. However, there is high confidence in the general pattern, with a surface low and upper trough moving through the Great Lakes. This will allow a cold front to move east through the Ohio Valley at some point on Wednesday, though limited moisture will limit the chances for precipitation. Ahead of the front, the pressure gradient will increase, and some slightly gusty conditions may occur -- along with temperatures well above normal. Max temps were increased for Wednesday, slightly above the model consensus. Behind the front, cooler conditions through the end of the week. There is a very large amount of spread in the timing of additional precipitation chances on Thursday and Friday, as a general pattern of broad troughing moves over the Great Lakes and Ohio Valley through the end of the week. Temperatures during the low end of the diurnal cycle may be cool enough to support some snow, depending on when precipitation occurs. && .AVIATION /00Z SATURDAY THROUGH WEDNESDAY/... Warm front is through the CWA and stalled over northern Ohio this evening. Ceilings have improved to VFR in the warm sector and are topped by high clouds this evening. Stratification of the lower layers of the atmosphere is a possibility tonight but an inversion that would definitely realize a stratus deck is not present. Will monitor upstream sites and the warm advection on southwest winds at 2-3kft may be strong enough to keep the moisture at these levels mixed enough for sct cloud cover overnight or at the minimum a higher bkn deck than is in the forecast. Still have a low cig/vsby restriction towards daybreak across the CWA and TAF sites which is also in higher question than usual this evening. Removed VCSH at KCVG/KLUK as new model guidance suggest a later possibility of even more widely scattered showers on Saturday evening. OUTLOOK...MVFR/IFR ceilings possible into Saturday, and then late Sunday into Wednesday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM...Hickman SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...Franks

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