Area Forecast Discussion
Issued by NWS Wilmington, OH

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228 FXUS61 KILN 161918 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 318 PM EDT Mon Jul 16 2018 .SYNOPSIS... Scattered thunderstorms will continue ahead of a cold front which will push through the area tonight. A drier and cooler airmass will build in for the middle of the week. The next chance for thunderstorms will occur Thursday night into Friday with the approach of the next frontal system. && .NEAR TERM /UNTIL 6 AM TUESDAY MORNING/... Broad mid level weakness/trof over the Ohio Valley, with a weak perturbation passing through the trof this aftn. Weak surface reflected n-s oriented trof evident in moisture convergence field over positions of cntrl IN and west central OH. Moderate instby was fueling the development of deep convection across the area. Have a period of likely pops through late aftn and then decreasing thru the evening. Bulk shear is weak so do not expect much in the way of organization. DCAPE values approach 800 j/kg, so stronger updrafts could produce gusty winds. Expect precipitable water values to approach 2 inches by late aftn. With very light flow (slow storm movement) and in a moisture rich environment, locally heavy rain will be possible. Broad band of westerlies push south with surface front dropping thru ILN/s FA late tonight. With loss of heating expect coverage of storms to diminish this evening but a chance will continue until the front pushes thru the area. Drier air will begin to advect in as the low level winds veer to the northwest and clouds will decrease. Expect lows from the mid 60s northwest to 70 southeast. && .SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/... West-northwest mid level flow with mean trof over the Great Lakes and southeast Canada. Have a lingering chance very early in the southeast counties and then dry across the area. Drier air will advect in on northwest winds. Some afternoon cumulus will be likely with the best coverage across the north. Highs on Tuesday will range from the lower 80s in the northwest to the mid 80s in the southeast. Surface high pressure of Canadian origin will build southeast into the Great Lakes Tuesday night. Drier air will continue to advect into the area with surface dew points dropping into the the 50s. Expect temperatures around 5 degrees below normal with Tuesday nights lows from the upper 50s northwest to near 60 southeast. && .LONG TERM /WEDNESDAY THROUGH MONDAY/... On Wednesday morning, a large area of surface high pressure will be sliding southeast into the Great Lakes and northern Ohio Valley, remaining in place through Thursday as it gradually moves east. This air mass will be a little cooler and drier than the last one, characterized by dewpoints in the upper 50s to lower 60s, and max temps in the lower to mid 80s. In an air mass that will be generally dry (with precipitable water values under an inch) and capped, no precipitation is expected during this period. A return to southerly flow is expected on Thursday night into Friday, as the surface high moves east of the region, and a deepening shortwave moves into the area from the northern plains. There is high confidence in this overall amplification to the pattern, which has been shown through several days of model runs. There is less confidence in the strength of the mid-level wave, and the closed mid-level low that both GFS/ECMWF projections suggest will develop out of it. In fact, the models have oscillated on when, where, and for how long this closed low will actually exist. GEFS ensemble members similarly show a lot of spread with regards to how this feature is being handled. To say the least, there remain considerable timing, strength, and placement inconsistencies. These are forecast challenges that preclude the ability to be more specific with convective expectations. The ILN CWA appears likely to be ahead of the trough axis on Friday and Saturday, suggesting increases in moisture and building instability for both days. After that, the slow progression of the trough -- appearing slightly slower in the runs today than yesterday -- will allow for additional convective development persisting into Sunday and possibly Monday. PoPs have been increased slightly through this part of the forecast. The temperature forecast for Friday was increased slightly, due to the slower progression of the trough. Temperatures for Saturday/Sunday/Monday will be kept conservatively in the lower to mid 80s, with expectations of moisture and precipitation in the area and slightly cooler temperatures aloft. These values are slightly below climatological normals. && .AVIATION /19Z MONDAY THROUGH SATURDAY/... Scattered thunderstorms developing across the region in the moderately unstable airmass ahead of an approaching cold front. Prevailing VFR cigs will drop to MVFR conditions during storms, with brief IFR conditions also possible. Gusty winds will be possible in some of the stronger storms. With the loss of daytime heating, convective activity should diminish in coverage this evening but there will still remain a low chance of showers/thunderstorms until the cold front passes through between 07Z and 09Z. As drier air advects in on northwest winds clouds will scatter out late tonight. Some patchy MVFR fog is possible toward sunrise where clearing occurs but some low level moisture lags. Expect VFR conditions Tuesday with scattered to bkn cumulus clouds at 4000 to 5000 feet. Northwest to north winds at 10-12kt will gust up to 18kts at times Tuesday afternoon. OUTLOOK...MVFR CIGS/VSBYS possible in TSRA on Friday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...AR NEAR TERM...AR SHORT TERM...AR LONG TERM...Hatzos AVIATION...AR

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