Area Forecast Discussion
Issued by NWS Wilmington, OH

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119 FXUS61 KILN 301048 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 648 AM EDT Tue May 30 2017 .SYNOPSIS... Weak surface ridging should keep conditions dry today. An upper level disturbance along with a cold weak front will bring a chance of precipitation tonight and Wednesday as they move across the Great Lakes and Ohio Valley. High pressure will then build into the area for Wednesday night. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... The center of an upper level closed low across Ontario will meander/rotate north today. For our region, a weak cold front/surface trof axis will move east of the CWFA by mid morning. We should then see weak surface ridging. As a result, mid clouds this morning will give way to FEW-SCT high based cumulus development in the afternoon. It will be slightly cooler than yesterdays readings, ranging from the mid to the upper 70s for most locations, with perhaps an 80 in the far southeast. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/... The center of the upper level closed low will elongate and shift east tonight through Wednesday. As this occurs, an embedded disturbance rotating around the base of this low will propagate across the region. This feature will team up with another weak cold front to bring a chance of showers tonight, and a chance of showers and thunderstorms on Wednesday. The front should clear our eastern zones by Wednesday evening, allowing surface high pressure to build in from the west. After lows in the mid 50s, highs on Wednesday will be slightly cooler again, ranging from the lower to mid 70s. && .LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/... With the cold front moving clear of the area on Wednesday evening, precipitation chances will come to an end, as a relatively dry area of surface high pressure moves into the area. With large-scale troughing over the eastern half of the CONUS, upper flow will remain out of the WNW, keeping the air mass relatively cool and dry (even though the clear skies will allow surface temperatures to reach values near normal on Thursday). With more unsettled conditions in the coming days, Thursday clearly looks like the most tranquil weather day of the extended period. As the surface high moves east on Thursday night, low level flow will back to the southwest, allowing for warm frontal progression to occur. As this developing temperature boundary ends up somewhat parallel to the WNW flow aloft, attention will turn to any potential shortwaves or jet streaks in the flow, which may help to spark convection atop the increasingly favorable boundary layer conditions. Unfortunately, specifics remain tough to pick out in the models, with a lack of agreement in placement and timing for the eventual convective episodes. Thus, will simply ramp PoPs up into the 40-50 percent range through the day Friday, and allow for likely PoPs in the southern half of the CWA on Saturday. In what should be a typical late spring scenario with stronger shear to the north and stronger instability to the southwest, a conditional threat for some severe weather could exist in this time frame. There are even wider differences in how the ECMWF/GFS runs have been handling surface high/low development on Sunday and beyond, making this a low confidence forecast for the second half of the weekend. Overall trends do suggest lower precipitation chances on Monday and Tuesday. The increase in southerly flow should allow for at least a temporary increase in temperatures for Friday, but convective development (or lack of development) will largely influence temperature forecasts from that point forward. This forecast will indicate a very gradual cooling trend through the rest of the extended period, but with temperatures remaining within ~5 degrees of normal. && .AVIATION /12Z TUESDAY THROUGH SATURDAY/... An upper level closed low north of Lake Superior this morning will continue to meander/rotate slowly north across Ontario through the TAF forecast period. For today, our forecast area should be in between weak weather systems. West winds will increase between 10 and 15 knots by 16Z with gusts between 18 and 24 knots. FEW-SCT high based cumulus clouds beginning around 6000 feet will lift to around 8000 feet by late afternoon. For this evening, FEW-SCT altocumulus can be expected with winds diminishing toward 00Z. A weak upper level disturbance and a surface cold front approaching the region from the west will bring more mid clouds and possibly few showers near or after 06Z Wednesday. OUTLOOK...Thunderstorms possible Friday and Saturday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hickman NEAR TERM...Hickman SHORT TERM...Hickman LONG TERM...Hatzos AVIATION...Hickman

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