Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 251923 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 323 PM EDT WED MAY 25 2016 .SYNOPSIS... Persistent southwesterly flow will keep temperatures above normal through the weekend. The combination of the warm temperatures and occasional upper level disturbances moving through the region will lead to chances for showers and thunderstorms through at least the end of the week. && .NEAR TERM /THROUGH TONIGHT/...
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Weak upper level disturbance was helping to provide a few showers across portions of central and south central Ohio this afternoon. Disturbance will shift to the east through late afternoon, and scattered showers will follow suit. Behind this disturbance, there is not a whole lot activity going on underneath plenty of mid/high level clouds within the immediate CWA. As such...there is not a lot instability to work with through late afternoon. We can`t rule out a stray shower or thunderstorm mainly across the west/southwest portion of the CWA where there are a few breaks, but the balance of the late afternoon should be dry. This evening into the overnight hours, guidance suggests another upper level disturbance moving into/through the Ohio Valley and lifting to the northeast. Expect at least scattered showers to make their way into the western CWA and therefore pops have been bumped to high chance in this area, with lower pops remaining further east as there is question as to how far east showers make it before they may dissipate late at night. Can`t rule out thunder particularly across the Tri-State area/western CWA this evening either but overall trend will be for activity that develops to weaken after dark and would primarily be in the form of showers.
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&& .SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...
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We remain in a similar pattern Thursday/Thursday night, being on the western edge of a ridge and south/southwest flow maintaining a warm and also somewhat moist air mass throughout the Ohio Valley. We may begin Thursday with plenty of clouds before the aforementioned upper level disturbance moves outside of the CWA. With some breaks in the afternoon, there should be enough instability for a few mainly diurnally driven showers and thunderstorms but overall forcing looks weak and therefore kept pops in the slight chance to low chance range.
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&& .LONG TERM /FRIDAY THROUGH WEDNESDAY/...
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The certainties of this period revolve around warmer and more humid conditions than normal for late May and early June /high confidence/ and a rather unsettled sensible weather period /moderate confidence/. In the details...at 12Z Friday there is strong clustering/agreement among NCEP/non-NCEP deterministic and ensemble data showing a rather amplified/blocky flow structure across the CONUS. Features of interest will be an evolving/cutoff/closed upper trough off the southeast US coast...and negative height anomalies in the nations mid-section in association with continued longwave troughing underneath ridging across the US/Canadian border north in cntl Canada. Of particular interest...as the deep layered trough continues to develop off the southeast US coast...will be ridging developing on the north/west side of this feature...and downstream of the negative height anomalies in the cntl US. This has direct implications on Ohio Valley temp/precip trends. Unfortunately...once we remove the certainties that Friday-Wed will be warm/seasonably moist in the boundary layer with daily highs in the 80s and nighttime lows in the 60s with dew points in the lower- mid 60s...there/s not much to hang our hats on in terms of sensible weather predictability. The presence of the continued troughing/negative anomalies in the cntl US will keep a weak swly mid layer flow directed into the Great Lakes...thus convectively produced/enhanced perturbations will be a constant threat to evolve east out of plains convective systems. These will inherently run into a height/flow pattern on the nwrn side of the developing sern CONUS trough that will not be conducive to organized/strong lift...and ridging over the Appalachians/Great Lakes will be reinforced. End result - there/s a lack of surface boundaries and/or appreciable stronger s/w troughs moving through the flow to produce more enhanced/higher predictability periods of vertical motion. Thus...precipitation chances will be driven in a very weakly forced manner under marginal flows and instabilities. Thus...there is no choice but to run 20-40% chances of showers/storms each day with the notion that many hours will be dry...and many locations could go several days without seeing rain. A true summertime pattern. It would seem that weak height falls centered later Sunday into Monday with the passage of a very subtle low-level boundary may afford the opportunity to introduce higher rain chances in coming forecasts...but forcing is so weak and soundings unimpressive enough from a shear/instby perspective that it gets tough to justify it.
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&& .AVIATION /18Z WEDNESDAY THROUGH MONDAY/... Weak upper level disturbance will exit the eastern terminals over the next few hours, along with the spotty light showers occurring with it. For tonight, persistent southwest flow aloft will continue. Another embedded disturbance is forecast to past east across the region. High resolution models suggest convective development to our west late this afternoon and evening across Illinois and Indiana. Then, with the gradual loss of diurnal instability, and the lack of strong forcing, precipitation with this feature should decrease in coverage as it moves into our region. Have included a vcsh for western terminals and left it out for the eastern terminals. Predominate conditions should remain VFR, except for kluk where some partial clearing late may allow some river fog to form. Have kept conditions MVFR there for now. On Thursday, upper level southwesterly flow will continue. We may end up being in a lull in terms of embedded disturbances rippling through the flow. Thus...some scattered to broken cumulus is expected with perhaps an isolated shower or storm popping up in the heat of the day. OUTLOOK...Thunderstorms possible Saturday through Sunday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...BPP NEAR TERM...BPP SHORT TERM...BPP LONG TERM...Binau AVIATION...Hickman

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