Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 200604 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 204 AM EDT Mon Mar 20 2017 .SYNOPSIS... Surface high pressure will move east of our area tonight. A surface low will track from the Middle Mississippi Valley, across the Ohio Valley Monday night, bringing showers and a few embedded thunderstorms. Precipitation may linger into Tuesday as a disturbance moves across the region. && .NEAR TERM /UNTIL 6 AM THIS MORNING/...
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Lingering clouds over the northeast will exit the area as surface high pressure shifts east of the area and flat mid level ridging builds in. This ridge will provide a mainly clear temporary period for most of the remainder of the night. Focus shifts to convection that develops over the mid MS Vly due to low level jet and elevated instability. Expect these storms to develop over nrn IL and track/develop to the southeast overnight pushing into ILN/s western counties toward 12Z. These initial storms will be in a weakening stage and therefore expect mainly showers with some embedded thunder. Temperatures to drop to lows from 30 to 35 will some minor increase late as clouds increase and winds become southeast. Previous discussion... Surface high pressure overhead this afternoon will slowly push east tonight with clouds also slowly eroding this evening. High temperatures will also average in the mid 40s across the region as clouds have helped to keep temperatures down a bit. Tonight low temperatures will be in the mid 30s with weak southerly flow returning Monday morning. Cirrus will also start to move into the area Monday morning as the next upper level disturbance approaches from the west.
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&& .SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/... Monday morning surface high pressure will be east of the region with pressure falls occurring over the midwestern United States. Also at this time weak pockets of PVA in the mid-levels will be traversing the region. Adding to the lift will be weak widespread WAA ahead of a low level trough axis. The GFS is fairly weak with the PVA but still has enough of a disturbance for weak lift (via Omega) to occur over the area. The NAM is slightly stronger with the disturbance and has correspondingly higher Omega values. Not surprisingly the ARW, NMM, NCEP WRF, WRF Dart, and NSSL WRF all show a decaying system of weak storms Monday morning in some form or fashion. Forecast soundings at this time don`t look all that impressive on the GFS (not fully saturated) but there is a stout inversion in place at 900 mb. The NAM forecast soundings look similar to the GFS but show better saturation. Both soundings show the inversion at 900 mb which support the development of elevated thunderstorms. 850 to 500 mb lapse rates on the NAM also approach 7 degrees C/ km. Monday afternoon into evening another weak upper level disturbance will approach from the west with a disorganized surface low. The NAM tries to pull the surface low further east than the GFS which allows for slightly higher MU CAPE values. A surface cold front will also be pushing through at this time. Again high res models show a line of showers and embedded thunderstorms forming along the front. Given the lapse rates some small hail will be possible in any stronger storms that form. Monday night the cold front will push south of the forecast area with high pressure building in from the north. && .LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/... Frontal boundary will be south of the Ohio River on Tuesday. With models trending toward a drier solution showing the front farther south, kept a chance of showers mainly in southern locations. As the upper flow turns northwest, surface high pressure is forecast to provide dry weather on Wednesday. Unsettled conditions are expected to return Thursday and Friday when a warm front develops near the Southern Great Lakes, resulting in a chance of showers mainly in northern counties. A cold front swinging through on Saturday will bring the likelihood for showers and a few thunderstorms. A few showers may linger Sunday in residual moisture and forcing behind the slow moving front. Temperatures will exhibit variations typical of early spring. Highs in the 50s Tuesday will be followed by readings around 40 Wednesday under cold advection on a northerly flow. Highs will rise to the 60s by Friday with the area in the warm sector. Highs are forecast to settle back into the 50s Sunday due to weaker cold advection. && .AVIATION /06Z MONDAY THROUGH FRIDAY/...
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Surface high pressure ridge will continue to move off to the east for the remainder of the overnight hours. Our focus then shifts toward the northern Illinois/northern Indiana region where models continue to advertise a developing low level jet focused into this region. Majority of high resolution/convective allowing models develop showers and thunderstorms in this region, and then dive the cluster southward into our western forecast area by 12Z. Thus, have introduced predominate showers at the western terminals this morning. Given the very elevated nature of the convection, conditions should remain VFR for the most part. However, some pockets of MVFR conditions can not be ruled out, especially near KDAY. VCTS has been employed for now, and will monitor trends to see if any airport becomes threatened by predominate or brief thunder. By late this morning, convection will continue south and eventually dissipate as it moves into retreating dry air. For the remainder of the afternoon, focus once again turns toward our northwest. An area of low pressure and a cold front will be moving east/southeast to our region. Again, most models concur that showers and embedded thunderstorms will get going across northern Indiana and northwest Ohio. This precipitation will be fed by another developing low level jet and low level convergent flow. For now, the best chance for rain showers/embedded thunder is poised for the northern terminals. KCVG/KLUK will be on the edge of the likelihood of precipitation, so only a VCSH is being used as of now. MVFR conditions will develop in the precipitation. As the front slips by to the south, cooler air and an increasing subsidence inversion will lower ceilings into the IFR category. Most precipitation should end after 06Z across our south as the front continues to move away. OUTLOOK...MVFR/IFR ceilings expected Tuesday morning. MVFR ceilings and visibility`s possible Friday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines NEAR TERM...Haines/AR SHORT TERM...Haines LONG TERM...Coniglio AVIATION...Hickman

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