Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 221709 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 109 PM EDT Sat Oct 22 2016 .SYNOPSIS... The region will find itself under northerly flow today as it is trapped between a strong low pressure system over New England and building high pressure in the lower Mississippi Valley. This will bring cool conditions today. By Sunday, the high will be over the southeast U.S. which will turn the winds to the south bringing a quick warm up. Another cold front will drop temperatures for the beginning of the work week. && .NEAR TERM /THROUGH TONIGHT/... Surface high pressure is extending from the lower Mississippi Valley region into IL/IN, with a similar pattern at 925mb. Cool northwesterly flow exists on the east side of the axis of the high. A much broader 700mb ridge over the western two-thirds of the country is leading to a longer spread of northwesterly flow...keeping temperatures fairly cool in the lowest couple kilometers off the surface. Because moisture through 700mb is not especially thick, clouds have formed in patches across the ILN forecast area, with some big breaks in between. Not easy to put this pattern into a sky grid, but the overall trend through the next 6-12 hours will be for generally cloudier conditions in the northeastern ILN CWA, and generally clearer conditions in the southwestern ILN CWA. Temperatures will be similarly arranged, with warmer conditions near Cincinnati and cooler conditions near Columbus. Overall, however, no significant changes were made to the going forecast. Previous discussion > With a closed H5 low located over the ne U.S., the region is under a northerly CAA flow. This is bringing lake effect clouds down across the area. However, the low level flow is beginning to back, allowing breaks in the clouds. These breaks will work se into the fa this morning. Unfortunately, H8 temperatures will remain below 0C today and as diurnal heating kicks in, lapse rates should kick over and the sc will redevelop. Therefore increased the cloud cover for the late morning into the afternoon. Winds will pick up again today as mixing occurs. Gusts will range from 10-15 in the Tri-state to 20-25 in Central OH. With the cloud cover to help limit the solar insolation, temperatures will be well below normal again, reaching the lower to mid 50s. This will be 5-10 degrees below normal. && .SHORT TERM /SUNDAY THROUGH MONDAY/... The upper level low will kick e tonight allowing the H5 heights to rise. At the surface, high pressure will work from the lower MS valley into the se U.S. Still expect some lingering clouds tonight as this transition occurs. Temperatures aloft will be warming tonight, but feel that there will be enuf decoupling of the boundary layer that sfc temperatures will see a normal diurnal drop. By Sunday, sfc winds will have turned to the sw. This will bring in warmer air and with a lack of cloud cover temperatures will warm to near 70 in the Tri-state and mid to upper 60s elsewhere. Models bring a H8 jet of 40 to 50 kts across the fa, so expect some wind gusts to around 30 mph on Sunday. Sunday night a cold front will drop down from Lake Erie. There is enuf moisture will the system to produce some clouds with fropa, but right now it is looking like the front will come through dry. By sunrise Monday, the front will be south of the Ohio River, leaving the fa mostly clear. Monday will be a little cooler under northerly surface winds. Highs will range form the upper 50s in Central and West Central OH to the mid 60s in nrn KY. && .LONG TERM /MONDAY NIGHT THROUGH FRIDAY/... Tuesday morning surface high pressure will move in from the north allowing winds to go mostly calm . Some high clouds may be moving in from the west, but chances seem to be growing that frost may be possible. During the day Tuesday a shortwave will move over the midwest and head east. At the same, the upper level trough axis over New England will pull east. In response to the shortwave, a surface low will form near the Nebraska/ Iowa border. During the day Wednesday the shortwave will strengthen and start to wrap up. Both the GFS and ECMWF are in pretty good agreement with this and have the shortwave wrapping up into a low over Wisconsin Wednesday evening. Across southwest Ohio low level flow will continue to increase ahead of the low with strong upper level divergence. Divergence will come from the RRQ of the upper level jet streak along with upper level diffluence from the splitting of 250 mb winds. Instability at this time looks limited but shear profiles are impressive (SFC-1km ~35kts via GFS forecast soundings). Any change in the placement of the low will easily change the values and orientation of the bulk shear vectors though. Future model runs will help to continue to refine this. Thursday afternoon into Friday the shortwave will push east but the ECMWF and GFS differ on how the shortwave ejects. The ECMWF picks up the shortwave in the main flow moving a cold front through the area. The GFS on the other hand washes the shortwave out and slowly pushes it southeast. The CMC has the shortwave diving into southeast Texas and appears to be the outlier. For now have kept the forecast trended towards ECMWF. && .AVIATION /17Z SATURDAY THROUGH WEDNESDAY/...
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Scattered to broken cumulus clouds have developed across the region. Most of these clouds are now VFR, though there have been some brief MVFR ceilings at times. Winds today will remain out of the northwest, with gusts of up to around 20 knots. Skies will gradually clear tonight, as winds back to the west and weaken. Clear skies should continue into Sunday, with southwesterly winds expected to gust to around 20 knots. OUTLOOK...No significant weather expected.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...JGL/Sites NEAR TERM...Hatzos/Sites SHORT TERM...Sites LONG TERM...Haines AVIATION...Hatzos is the U.S. government's official web portal to all federal, state and local government web resources and services.