Area Forecast Discussion
Issued by NWS Wilmington, OH

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462 FXUS61 KILN 260006 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 806 PM EDT Sun Sep 25 2016 .SYNOPSIS... High pressure centered northeast of the area has provided another day of dry and warm weather for the region. A cold front will move into the area Monday morning, bringing a chance of precipitation. Behind this front, temperatures will become cooler for the rest of the week, and will be slightly below normal for late September. && .NEAR TERM /UNTIL 6 AM MONDAY MORNING/... A broad area of high pressure extending down into the northeastern United States will slowly slide east as an upper level low currently over the midwest pushes east. As this occurs weak ridging over the western United States will setup allowing the low to dive southeast. This will help to push a surface cold front into our western zones between 10 and 12z. Lows ahead of the front will only fall into the mid 60s with upper 50s possible across the far northeastern zones. && .SHORT TERM /6 AM MONDAY MORNING THROUGH TUESDAY NIGHT/... The cold front will then clear the CWA between 18 and 21z Monday afternoon. Confidence with the timing of the front remains high while coverage of precipitation is a little more uncertain. PWATS are currently around 1.30" (90th percentile for this time of year) but instability is paltry ahead of the front. ML Cape on the GFS forecast soundings is less than 500 J/kg in most places while the NAM has ML Cape values around 500 to 1000 J/kg. Given the frontal passage is expected mostly in the morning (except for Scioto and other eastern counties) instability should be limited. Lift will come from the front but even then saturated equivalent potential temperature lines don`t really compact until the front reaches our eastern zones. The given above would support weak showers with a possible rumble of thunder across our western zones with a line strengthening as it exits our CWA. High res models are in general agreement with this solution. The 850 mb frontal passage lags the surface frontal passage and is more aligned with the better PVA. The WRF dart and NSSL WRF show this as some weak showers behind the precipitation associated with the cold front. Monday afternoon behind the front strong cold air advection and 20 to 25 kt winds will start to mix down. Both NAM and GFS soundings are supporting wind gusts of around 20 mph via momentum transfer. The better chance for breezy winds will be across the northwest which will likely see the CAA during most of the diurnal cycle. Across our far southeastern counties highs approaching 80 degrees will be possible with temperatures holding steady or falling behind the front. Have continued to advertise a non- diurnal curve for Monday. The vertically stacked low will continue to mature and occlude Monday into Tuesday with a tight low level gradient keeping winds breezy. Mixing will also be greater Tuesday with forecast soundings showing mixing up 800 mb possible. GFS soundings are showing gusts up to 30 mph possible while the NAM is more in the 25 to 30 mph range. Tuesday night into Wednesday another wedge of positive vorticity will rotate south bringing increasing clouds and moisture back to the area. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... A closed upper level low will settle down across Upper Ohio Valley region through the end of the work week. The 12Z GFS has trended a little more in line with the ECMWF with this feature, now hanging it back across our region through Friday before trying to push it off to the east over the weekend. Meanwhile the 12Z ECMWF hangs on to the low even longer, keeping it in place across our area through the weekend. As a result, will go ahead and allow for some low chance pops through at least Friday and will try to show at least a little bit of a diurnal enhancement in the pops. Will also nudge up sky cover through the afternoons to allow for some diurnal type cloud development. If the forecast continues to trend toward what the ECMWF is indicating, pops may need to eventually be added to next weekend too. Temperatures through mid week will be a bit below normal with highs in the 65-70 degree range Wednesday and Thursday. Will then allow for a gradual warmup with highs into the low to mid 70s through the weekend, but this may be on the warm side if the low does end up hanging back. && .AVIATION /00Z MONDAY THROUGH FRIDAY/...
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Sharp upper level ridge over the region ahead of a trof moving through the northern plains will keep most of the night VFR. The upper level trof will progress east into the Great Lakes Monday. Conditions will start to deteriorate late tonight with the approach of a cold front from the west. Low and mid clouds will increase after midnight, with a few showers possible toward sunrise. Showers with MVFR ceilings are likely to affect all TAF sites starting around 12z. Have continued to keep thunder out of the forecast with low instability and isold nature of any potential convection. With the passage of the cold front winds will shift to the west and gust up to 25 kts. The system is progressive and showers will end by afternoon with skies clearing late in the day. OUTLOOK...Breezy west winds expected on Tuesday with gusts between 25 and 30 knots.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Haines NEAR TERM...Haines SHORT TERM...Haines LONG TERM...JGL AVIATION...AR

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