Area Forecast Discussion
Issued by NWS Wilmington, OH

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800 FXUS61 KILN 071429 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 929 AM EST Wed Dec 7 2016 .SYNOPSIS... As upper level low pressure moves east across Ontario and Quebec, cooler and drier air will continue to move into the Ohio Valley today, with temperatures continuing to get colder through the end of the week. A few flurries are possible on Friday, but a more significant chance of rain and snow will move into the region on Saturday night and Sunday. && .NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Satellite imagery shows clearing across the region. However, do expect mid and high clouds to spread back into the area this afternoon. Forecast temperatures look reasonable at this point.
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&& .SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/... By Thursday morning, the lumbering/sprawling area of low pressure north of the region will be moving eastward through Quebec, with deep-layer flow over the Ohio Valley shifting to more of a northwesterly direction. As this occurs, and the aforementioned weak trough axis passes the area, the advection pattern will switch to one that is definitively cold. As this occurs, low-level moisture will remain sparse, but some mid-level moisture will pass through the area. The weak and transient upper jet forcing no longer appears likely to combine with this moisture in a favorable manner, and with the dry air mass through the lowest 5kft-10kft, precipitation is no longer expected for early Thursday morning. All mention of snow / flurries has been removed from the forecast. The cold advection will continue unabated through the rest of the short term period of the forecast. Aloft, the coldest air is expected to be in place on Friday morning. GFS/GEFS/NAM anomalies indicate that 700mb / 850mb temperatures will be about 2.0-2.5 / 1.5-2.0 standard deviations below normal, respectively. This will easily allow min temps to drop into the upper teens to lower 20s on Thursday night and Friday night, even in conditions that are advective and completely unfavorable for standard radiational cooling. In fact, the continued cooling aloft will result in a steep (but shallow) mixed layer near the surface, resulting in occasional stratocumulus through this period of the forecast, with winds will stay in the 10-15 knot range (with higher gusts). Given the positioning of the top of the mixed layer through the first half of Friday, some flurries or light snow showers appear possible, with no apparent potential for accumulation for now. This has been focused mainly in the N/NE sections of the CWA, but a chance of flurries will extend to most of the area. Though conditions are not expected to warm up too much for Saturday, the signs of the change in pattern are evident, as the surface high and 850mb/700mb ridge axis move east through the Tennessee Valley -- bringing a deep-layer change in wind direction. Dry conditions are expected on Saturday, with an overall diminishing in low-level clouds. && .LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... A cold front and wave of low pressure will approach from the west Sunday before crossing the area Sunday night. Rain will be the primary type of precip with the front, with snow mixing in at the start and end of the event. Light precip may linger Monday in the cyclonic flow off the Great Lakes. A few snow showers will be possible Tuesday in northern locations, ahead of an Arctic cold front. Look for below normal temperatures through the period. Highs Friday are forecast to be in the upper 20s, then up to around 30 Saturday. Modestly warmer readings near 40 are expected for Sunday through Tuesday. && .AVIATION /15Z WEDNESDAY THROUGH SUNDAY/... Mid/high level clouds will be streaming across the region in a broad southwest/west flow aloft today. Large upper level low centered just north of the upper Mississippi River Valley will slow rotate east and elongate today into tonight. Some embedded energy in the southwest to west flow around the low will bring another round of mid clouds to the region overnight. Any precipitation looks unlikely with this energy/mid clouds as low levels will be quite dry. OUTLOOK...MVFR ceilings possible Thursday afternoon into Friday. MVFR/IFR ceilings and visibilities possible Sunday. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM... SHORT TERM...Hatzos LONG TERM...Coniglio AVIATION...Hickman

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