Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 291347 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 947 AM EDT MON AUG 29 2016 .SYNOPSIS... A warm and humid airmass will remain in place today. This heat and humidity will keep a chance of thunderstorms in the forecast... mainly near and south of the Ohio River this afternoon. Slightly drier conditions can be expected Tuesday, under the influence of weak surface high pressure. Thunderstorms will occur Wednesday with the passage of a cold front. Cooler temperatures and less humid air can be expected through the end of the week. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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A nebulous pattern remains in place across the northern Ohio Valley, with a broad area of surface high pressure centered over the northern lower peninsula of Michigan, and weak northeasterly near-surface flow over the ILN forecast area. Upper ridging and weak mid-to-upper-level flow has changed little over the past day or so. An axis of enhanced theta-e extends from the lower Ohio Valley through the southwestern sections of the ILN CWA, and a weak SSW-moving front is evident on NAM/RAP theta-e analysis at 850mb. Though convergence is weak, there should be just enough forcing (combined with any leftover boundaries from yesterday) to allow for some showers and storms to develop again -- especially in the southwestern two-thirds of the ILN forecast area. PoPs have been increased slightly, though the northern tier of ILN counties has been kept dry. The 12Z KILN sounding is similar to the one from yesterday, though with a few slight differences -- slightly warmer upper-level temps and slightly lower precipitable water values (down from about 1.75" to about 1.60"). Modifying this sounding would produce SBCAPE values of around 2000 J/kg (which matches SPC SREF expectations) -- with only a very tiny amount of capping to overcome. This is, however, a little less instability than was generated yesterday. Based on these factors, a repeat performance of yesterday is unlikely, but some threat for additional flooding and gusty winds will certainly exist. Wind flow through the troposphere remains below 15 knots at any given point, so storm motions will again be slow, and prone to storm-scale propagations. Very little confidence, however, in getting a significant amount of storm coverage. The current HWO appears reasonable, but will be expanded slightly based on storm development expectations / the 850mb front / HRRR simulated reflectivity.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... Any convection that develops this afternoon will diminish this evening with the loss of heating. Lows tonight will range from the lower 60s far north, where some drier air will filter in, to the upper 60s far south. Weak surface ridge and a little drier air over the region Tuesday. Have dry forecast Tuesday with only marginal instby in the far south. Highs look to range from the mid 80s nw to near 90 far south. Mid level shortwave begins to work into the western Great Lakes Tuesday night. Expect mainly clear skies in the evening, followed by an increase in mid/high level clouds overnight. Expect lows in the mid and upper 60s. Upper level pattern change with mean trof developing over se Canada and New England and ridge building over the nations mid section. This places the Ohio Valley in a northwest flow with surface front dropping south through the region Wednesday. Forcing is limited with only weak convergence noted in the low levels and even instability is limited. Will continue to limit pops to low chance north and slight chance south. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... High pressure will build southeast across the Great Lakes and continue off the New England coast by the end of the week. The high will continue extend into the forecast area through the weekend. This will provide dry conditions. Temperatures will drop closer to normal Thursday and Friday and then start to warm over the weekend. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... Expect BR/FG to reduce visibilities early this morning in the very humid airmass, enhanced by Sunday`s rainfall. Once the BR burns off by mid morning, VFR should then persist today as high pressure builds into the Great Lakes. Thunderstorms may develop again this afternoon. Latest models show scattered thunderstorms near CVG LUK DAY and ILN, so went with afternoon VCTS there. Sky cover outside of any thunderstorms should stay rather sparse with SCT cumulus and altocumulus. Winds will remain light out of the northeast. Put BR again late in the forecast at LUK and ILN. OUTLOOK...Thunderstorms possible through Wednesday...mainly in the afternoon and evening. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...AR NEAR TERM...Hatzos SHORT TERM...AR LONG TERM... AVIATION...Coniglio

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