Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 240003 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 803 PM EDT SAT JUL 23 2016 .SYNOPSIS... Upper level ridge will allow for continued hot and humid conditions through the weekend. A cold front will move through the area on Monday allowing for thunderstorms across the region. && .NEAR TERM /THROUGH SUNDAY/... No significant changes to the overnight forecast other than to tweak sky cover...trying to anticipate degree of cirrus blowoff from western Great Lakes MCSs. Did raise overnight low temps just a bit but overall an insignificant edit. Think skies largely remain clear to partly cloudy overnight as MCS crosses Lake Michigan/northern Indiana overnight and dramatically weakens per multiple HRRR runs and 23.12Z HRW-ARW. Fog was maintained in some areas as previously forecast given very moist boundary layer...light winds...and a good period of clear skies into at least the first half of the overnight. On Sunday...decided to expand the Heat Advisory northward to encompass entire CWA...this based largely on trends seen in new 23.18Z GFS/NAM and 23.15Z SREF (members and mean) which all indicated higher dewpoints into the forecast area than forecast based on previous runs. Thus...this allowed for a ~2F+ bump in dewpoints in the forecast tomorrow which pushes central/west central Ohio into the 100-102F range. There is still concern of impacts from MCSs crossing the Great Lakes later tonight and into Sunday morning pushing outflow/convective debris clouds into this area, but recent 23.18Z runs are also drier in tropospheric RH hinting that cloud may not have much impact on temps overall tomorrow. Tough call...but given accumulative impacts of heat...decided this trend in 18Z runs was enough to expand and get this message out this evening. && .SHORT TERM /SUNDAY NIGHT THROUGH MONDAY NIGHT/... Approaching shortwave trough later Sunday night will bring increasing chance of storms as the night wears on...but coverage is still not expected to be overly high during this time period. On Monday there will be a better chance for thunderstorm activity as a cold front moves through the region. In addition, some of these storms may be severe with damaging winds. The best chance for severe weather will be across the southern half of the forecast area with better timing with peak heating. Before these storms move through heat index values across far southern portions of the forecast area are expected to be near 100 degrees. Precipitation will gradually taper off Monday night with only some thunderstorms across far southern portions of the forecast area remaining by the end of the short term. With the passage of the frontal boundary all but the far southern portions of the forecast area are expected to drop down into the 60s Monday night. && .LONG TERM /TUESDAY THROUGH SATURDAY/... Cold front will stall out near/just south of the Ohio River during the mid-week. Lower precipitable waters are forecast to press southward through much of northern and central Indiana/Ohio behind the front, but near/south of the front drying will be minimal. As such, will continue with a chance of primarily diurnal convection Tuesday through Wednesday in the vicinity of the front, roughly areas along and south of the Ohio River. Further north, enough dry air should be present to preclude thunderstorm development. By Thursday, whatever is left of the stalled boundary will lift back north as a warm front, allowing a moist air mass to return to the entire CWA. Guidance suggests multiple shortwaves moving across the Ohio Valley through the end of the week and perhaps even into Saturday. This supports chance pops for thunderstorms during this time. Temperatures are forecast to favor near average to slightly above average values through the long term. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/... No significant changes to ongoing TAFs through the next 12 hours. Still like the idea of light/variable flow tonight as sct-bkn cirrus from upstream thunderstorm activity crosses the TAF sites. Still expecting MVFR vsbys at most TAF sites after 07Z and continue with IFR at LUK. Some light swly flow picks up on Sunday morning into the afternoon with likely some cumulus forming quickly. There may be some convective debris remnants from overnight/early morning Great Lakes thunderstorm complexes...but not enough confidence to do anything more than some sct-bkn cirrus at this time. Think the thicker/lower clouds remain further north. During the afternoon on Sunday...scattered vfr cumulus expected with any shra/tsra remaining isolated with better chances relegated to later Sunday night into Monday. OUTLOOK...Thunderstorms possible Sunday night through Monday and again Thursday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...Heat Advisory until 8 PM EDT Sunday for OHZ026-034-035-042>046- 051>056-060-062>065-070>074-078>082-088. Excessive Heat Warning until 8 PM EDT Sunday for OHZ061-077. KY...Heat Advisory until 8 PM EDT Sunday for KYZ089>100. IN...Heat Advisory until 8 PM EDT Sunday for INZ050-058-059-066- 073>075-080. && $$ SYNOPSIS...Novak NEAR TERM...Binau SHORT TERM...Novak LONG TERM...BPP AVIATION...Binau

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