Area Forecast Discussion
Issued by NWS Wilmington, OH

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000 FXUS61 KILN 220013 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 813 PM EDT Sat Oct 21 2017 .SYNOPSIS... High pressure will shift off to the east through the day on Sunday, providing for one last day of dry conditions and above normal conditions. An upper level disturbance and an associated cold front will bring an increasing chance of showers Sunday night into Monday. This will also usher in a cooler airmass for next week. && .NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
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While high clouds continuing to push through the region, still plenty of gaps in clouds and winds slackening a little more, so have nudged overnight lows just slightly lower, in especially the eastern area where approaching trough axis and the tightening gradient will keep winds lighter overnight. Still generally mid 50s for lows, but near 50 east.
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&& .SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/... The mid level trough axis will shift east out of the Mississippi Valley and into the lower Ohio Valley Sunday into Sunday night. As it does, short wave energy rotating through the base of the trough will lead to a developing surface wave/low that will approach our area late Sunday night. The 12Z models have trended a little faster with this so have sped up pcpn onset a few hours for Sunday night, especially across our southwest. Highs on Sunday will be somewhat dependent on cloud cover, but in continued southerly flow, highs should still push well into the 70s. Lows Sunday night will be in the upper 50s to lower 60s. && .LONG TERM /MONDAY THROUGH SATURDAY/... The long term will open up with a pattern change taking place as a surface low approaches the CWA from the southwest. The pattern will be rather complex with a potent upper level low ejecting northeast over Kentucky as it takes on a negative tilt. At the same time an upper level trough axis will be located over the central United States. During the day Monday the upper level low will move overhead along with a wedge of PVA. PWATs with the low are expected to surge to around 1.50" across the area or near record values for this time of year. Even though instability is lacking Monday it should be noted that low level shear values are extremely impressive. SFC to 1 km bulk shear is nearing 45 kts across the southeast. We will continue to watch this to see if any instability can work its way north. The other concern with this system will be the potential for heavy rain. For now, most model totals remain in the one to two inch range (esp. across the south and east). Confidence on rainfall totals still remains low though as most GEFS members indicate around one inch. Monday night into Tuesday the surface low will exit east with a weak cold front pushing through. The main upper level through axis that was to our northwest Monday afternoon will begin to deepen and head southeast towards the ILN forecast area Tuesday morning. As this occurs 850 mb temperatures will start to drop with highs not even expected to reach 60 degrees Tuesday. In fact, Monday looks like the warmest day of the extended. During the day Tuesday the upper level low will then move overhead. As the core of the upper level system moves overhead 850 mb temperatures will slowly drop below 0 degrees C across the western zones. Due to the upper level low and steepening low level lapse rates have kept the chance of precipitation in Tuesday. Wednesday the upper level low will take its time to exit the area allowing the chance of showers to continue across our eastern zones. By Thursday morning the upper level low will be exiting east with the best ageostrophic convergence overhead. As this happens weak surface high pressure will temporarily move overhead with winds going calm. Temporary clearing is also scheduled to take place which will make temperatures in the mid 30s possible Thursday morning (maybe a freeze even if things line up right). Thursday the upper level low will eject east with mid level heights temporarily rising in the afternoon. 850 mb temperatures also briefly rise to around 8 degrees C, but looking at the GEFS and EPS thinking is that high temperatures will probably be in the upper 50s to around 60 degrees Thursday. Friday though Sunday another upper level low will deepen across midwest Canada as heights rise off the Pacific Northwest coast. 850 mb temperatures behind this system fall to around 7 degrees C below zero. Timing remains highly variable here though so have only trended temperatures down at this time. && .AVIATION /00Z SUNDAY THROUGH THURSDAY/...
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As the area becomes less dominated by the upper ridge pushing east and a trough approaches from the mid Mississippi valley, some increased high and mid clouds, but nearly all VFR expected through the period. Continued with some potential for MVFR visibility at KLUK, as while there should be slightly more wind tonight, plenty of breaks in the mid and high clouds may yield an 08-12z period of mvfr. OUTLOOK...MVFR ceilings and visibilities possible Sunday night through Wednesday.
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&& .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...JGL NEAR TERM...JDR SHORT TERM...JGL LONG TERM...Haines AVIATION...JDR

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