Area Forecast Discussion
Issued by NWS Wilmington, OH

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209 FXUS61 KILN 152358 AFDILN Area Forecast Discussion National Weather Service Wilmington OH 658 PM EST Thu Nov 15 2018 .SYNOPSIS... Low pressure will move through the area tonight, bringing snow as it moves to the east. An area of high pressure will then develop over the region for Friday and into the weekend, providing cooler and drier conditions. Temperatures will remain cooler than normal through much of next week. && .NEAR TERM /UNTIL 6 AM FRIDAY MORNING/... Current forecast is well in hand and no changes were made this evening beyond the first hour or two in temperatures. 100% snow moving east fairly quickly this evening is captured nicely and any change to the forecast would be ill-advised at this moment in time. Previous discussion: Surface observations are proof that the inversion has totally mixed out over the ILN CWA, as temperatures at the surface are now solidly above freezing, but rain has already begun to transition to snow. Most of this snow has been generally light so far, with radar echoes becoming more scattered over the ILN CWA, but there will be one feature to watch as the evening progresses. Water vapor satellite shows that the center of the compact mid-level low is currently located over far southern Indiana. A curved band of snow has developed in a favorable region for ascent just ahead of this low, which will continue to develop as it moves ENE into the ILN forecast area this evening. Earlier model runs had trended toward cooler boundary layer conditions, and this expectation continues -- most, if not all, of this precipitation will fall as snow. Snowfall forecast amounts have been increased from the previous forecast, with around an inch in the Cincinnati area, lesser amounts to the north and south, and greater amounts in the eastern half of the CWA. Where snow may persist the longest, over central Ohio, some amounts approaching two inches appear possible. In addition, if moisture becomes shallow while there is still lift ahead of the center of the low, a brief period of freezing drizzle may also occur. Right now, the freezing drizzle scenario looks like a lower-probability possibility, given that more of the model soundings suggest moisture will remain deep enough for ice crystal introduction. In collaboration with JKL/RLX/CLE and others, an SPS was issued for tonight, mainly to highlight the potential for a brief period of snow accumulations. With the recent colder model solutions, it is unsurprising that min temps also needed to be adjusted slightly downward, now in the upper 20s to around 30. && .SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/... Though a trough moving across the Great Lakes on Friday will be a close call for the ILN CWA, it looks like precipitation (light snow) associated with this feature should remain north of the forecast area. At most, perhaps some flurries may affect the northern tier or two of counties. This means that Friday and Friday night should be dry, as high pressure begins to build into the southern tier of states. One thing the passing trough will do is briefly pick up the winds, which will gust to the 20-25 knot range out of the WSW on Friday -- primarily in the first half of the day. The wind direction in the boundary layer suggests perhaps a little bit of warm advection on the west side of the Appalachians, but barely getting into the southeastern ILN CWA if at all, leading to another day of well below normal temperatures -- especially since skies should be cloudy to mostly cloudy. Max temps are forecast to range from the upper 30s to lower 40s, with min temps in the upper 20s on Friday night. && .LONG TERM /SATURDAY THROUGH THURSDAY/... The extended period begins with a cold front located in the southern Great Lakes. The models bring this front into northern sections Saturday and then work it farther south, while weakening it. Much of the pcpn is post frontal, which brings on a slight chance of pcpn into the extreme nwrn counties on Saturday afternoon. As the front sags south Saturday night into Sunday, the precipitation chances increase and move southeast through the forecast area. Right now the best precipitation chances appear to be Sunday afternoon into Sunday night when some upper level support swings through. Precipitation type will be a mix of rain and snow, based mainly on the diurnal cycle. Highs Saturday and Sunday will range from the upper 30s in the northwest to the upper 40s in southeast. By Monday, northwest flow aloft develops, and high pressure begins to build in at the surface. The GFS continues to try and bring a disturbance down in the northwest flow on Tuesday, but this is not currently supported by the other models. So, will keep next week dry. The first part of next week will be on the cool side with highs Monday from the mid 30s northwest to the lower 40s in the southeast. On the back side of the high there will be a gradual warm up, with highs by Wednesday ranging from 40 northwest to the upper 40s south, and the mid 40s to the lower 50s on Thanksgiving day. && .AVIATION /0Z FRIDAY THROUGH TUESDAY/... IFR to LIFR cigs and mvfr vsbys occasionally dropping to IFR will be the rule for the next several hours. Snow will move east but increase in coverage in the Scioto Valley as the surface circulation tracks towards eastern Kentucky. Low cigs will persist through the forecast with abundant low level moisture trapped under an inversion between 1500-2kft. The gradient will tighten during the morning and gusts to 20kt will be possible across the area, calming down in the afternoon. Dewpoints in the upper 20s will maintain a healthy dewpoint depression from the temperature and not be supportive of any fog development. However, the amount of moisture trapped at the surface under a relatively low ceiling may necessitate a vsby reduction at times when the winds calm down tomorrow night. OUTLOOK...MVFR/IFR ceilings will continue into Friday night. MVFR conditions are possible again from Saturday night through Sunday night. && .ILN WATCHES/WARNINGS/ADVISORIES... OH...None. KY...None. IN...None. && $$ SYNOPSIS...Hatzos NEAR TERM...Franks/Hatzos SHORT TERM...Hatzos LONG TERM...Sites AVIATION...Franks

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