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Area Forecast Discussion
Issued by NWS Wilmington, OH
Issued by NWS Wilmington, OH
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316 FXUS61 KILN 140742 AFDILN AREA FORECAST DISCUSSION National Weather Service Wilmington OH 342 AM EDT Wed Aug 14 2024 .SYNOPSIS... Surface high pressure will continue to bring dry weather conditions through mid week. The next chance of precipitation will arrive late Thursday into Friday as a frontal system approaches the Ohio Valley. The threat for precipitation will continue through the weekend as low pressure tracks through the Great Lakes. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Upper level pattern characterized by a long wave trof over New England and southeast Canada and a ridge over the MS Valley. This places the Ohio Valley in northwest flow with a large area of surface high pressure over the Great Lakes. In dry airmass expect only a few to scattered cumulus clouds along with a few high level clouds spilling over the ridge to our west. As the ridge nudges a little east we will observe height and thickness rises yielding temperatures a few degrees warmer than yesterday. Under mostly sunny skies expect highs to range from the lower 80s north to the upper 80s south. && .SHORT TERM /6 PM THIS EVENING THROUGH 6 PM THURSDAY/... Narrow mid level ridge axis to build east into the area early Thursday. Diurnally driven cumulus clouds will dissipate with the loss of daytime heating yielding mostly clear skies this evening. High level clouds will then increase toward sunrise Thursday. Overnight lows to bottom out in the lower 60s in most locations. Exceptions - A few upper 50s will be possible in the far eastern typical cold spots and some city locations will remain in the mid 60s. Narrow mid level ridge to quickly build east across the area Thursday. A lead mid level shortwave in the wake of this ridge to approach the area Thursday afternoon. Model consensus shows best forcing and moisture to remain to our west during the daylight hours. Therefore, have limited any mention of a shower to chance/slight chance and confined these pops to west central Ohio late in the day. Most locations will warm to readings in the mid and upper 80s. The exception is the northwest - where clouds and possible showers will keep highs in the lower 80s. && .LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/... On Thursday evening, the axis of a mid-level ridge will be passing eastward through the Ohio Valley. On the back side of the ridge, theta-e advection aloft will begin, with a significant amount of moisture increasing above 850mb. A broad mid-level trough will be moving east across the northern tier of states, reaching the upper Midwest by 12Z Friday morning. On the southern periphery of this broad trough, forcing will be on the increase over the Ohio Valley, as a result of some shortwaves rotating around the base of the trough. Convection is expected to be ongoing to the west of the ILN CWA on Thursday night, associated with an initial shortwave. Initially surface based (and possibly strong) this convection will eventually weaken as it moves east of the instability axis, reaching the ILN CWA after 06Z. The boundary layer is expected to remain generally stable during this time frame, so any storms arriving early Friday morning will be elevated and with only a low probability of severe weather (a marginal wind threat as indicated by the SPC D2 outlook). Overall, precipitation will be fairly widespread, as a result of the forcing and increasing deep-layer moisture. Likely PoPs have been included for much of the forecast area in the 06Z-15Z time frame. Attention will then turn to the potential for additional convective development on Friday afternoon. The potential strength of these storms will be dependent on several factors, including the degree of contamination from the morning precipitation. Model soundings suggest the atmosphere will destabilize, though the degree is unclear, especially as there are differences in the handling of lapse rates (particularly mid-level lapse rates). There does appear to be some broad forcing for ascent as a result of the trough, as well as some renewed 925mb-850mb theta-e advection during the afternoon. Wind shear appears sufficient for some degree of storm organization, and precipitable water values will be approaching two inches. Though uncertainty remains, this setup does support at least some lower-end risk for severe weather and heavy rainfall. Specific timing details and thermodynamic profiles will be the main questions, and uncertainty on those factors precludes a greater concern as of now. Models are coming into somewhat better agreement on the progression of the trough over the weekend. It will be moving slowly, but may only briefly develop into a closed low before it continues moving east. The Ohio Valley will be on its southern periphery, in a regime of generally westerly flow -- with chances for precipitation continuing. PoPs will be kept in the forecast each day from Saturday through Monday, but with gradually diminishing chances from one day to the next due to temporal forecast uncertainty and the fact that stronger forcing will likely be displaced to the north and east with time. Temperatures in the middle to upper 80s are expected Friday, with cooler values in the lower to mid 80s over the weekend and into next week. && .AVIATION /07Z WEDNESDAY THROUGH SUNDAY/... Large area of high pressure to continue to offer mainly VFR conditions thru the TAF forecast period. Exception is KLUK valley location where some brief MVFR vsby restrictions are possible toward sunrise. Few to scattered VFR diurnal cumulus to develop this afternoon. These clouds will dissipate with sunset leaving mostly clear sky conditions heading into this evening. Light northerly winds at 5 knots or less persist overnight. Light winds veer to the east/northeast today at speeds less than 10 kts. OUTLOOK...Thunderstorms are possible Friday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...AR NEAR TERM...AR SHORT TERM...AR LONG TERM...Hatzos AVIATION...AR