FXUS61 KILN 161739 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 139 PM EDT Mon Jul 16 2018 .SYNOPSIS... Thunderstorms will develop today 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. && .NEAR TERM /UNTIL 6 PM THIS EVENING/... Broad mid level weakness/trof in the mid levels over the Ohio Valley today. A couple of weak perturbations to pass through the trof today, with models showing a weak surface reflected n-s oriented trof developing across ILN/s area this aftn. Moderate instby develops in the warm sector with ML CAPE values of 1200-1600 J/KG anticipated. Expect scattered storms to develop in this airmass with the best coverage over the southern and eastern counties. Bulk shear is weak so do not expect much in the way of organization. DCAPE values approach 1000 j/kg, so stronger updrafts could produce gusty winds. Model precipitable water values are forecast to increase above 2 inches. These values are typically fcst too high but expect 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. Temperatures at or a little above normal today with highs in the mid to upper 80s. && .SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/... Tonight, precipitation chances will be highest at the beginning of the period and will decrease with the loss of daytime heating. Meanwhile as the cold front pushes through the region, convection will end from northwest to southeast. By 12Z Tuesday, the front will be lingering in the southeast counties. An isolated shower will be possible early Tuesday morning. High pressure will gradually build in on Tuesday. Dewpoints will gradually lower throughout the day. Highs on Tuesday will range from the lower 80s in the north to the mid 80s in nrn KY. Dewpoints will continue to dry out Tuesday night as the high pressure settles into the region. Lows Tuesday night will drop to 60-65. On Wednesday, the surface high will be centered over the Great Lakes. Skies will be mostly sunny and highs will be in the upper 70s to lower 80s. && .LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/... High pressure will remain in place for several days. This air mass will be a little cooler and drier than the last one, characterized by dewpoints in the lower 60s (Wednesday and Thursday) 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 model cycles. 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. There has definitely been a trend toward a slower and deeper solution, which will keep the ILN CWA in a regime of cyclonic flow and occasional precipitation chances through next weekend. The forecast has been trended in this direction, with PoPs increased for Saturday and Sunday. The temperature forecast for Friday/Saturday/Sunday will be kept conservatively in the lower to mid 80s, with expectations of increased moisture and precipitation in the area. These values are slightly below climatological normals. && .AVIATION /18Z 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...Hickman/AR/Sites NEAR TERM...AR SHORT TERM...Sites LONG TERM...Hatzos AVIATION...AR
