161 FXUS61 KCLE 291140 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 640 AM EST Wed Dec 29 2021 .SYNOPSIS... A weak high pressure system will build over the area for the first half of Wednesday. Low pressure centered over Ontario will move a cold front east across the area beginning Wednesday evening into Thursday. High pressure will again build over the area on Thursday into Friday before the next low pressure system will impact the area Friday afternoon through the weekend. && .NEAR TERM /THROUGH THURSDAY/... The fog has evolved quite a bit across the area, with much of the northern tier of counties seeing visibilities between 1/4 to 4SM. As a result, a Dense Fog Advisory has been issued for these counties through 10AM today. With sunrise and gradually warming temperatures, the fog should slowly dissipate into the early afternoon, however gloomy conditions will persist through much of the day. No other changes were made with this update. Previous Discussion... Patchy fog has begun to develop across the area, with the largest reductions in visibilities reported throughout the northern counties. Visibilities in these areas are as low as 1SM up to 5SM. This will be the primary weather concern through approximately 14Z and will need to continue to be monitored for more widespread development. With low confidence in the extent of fog through the morning hours, have opted to put it in the HWO but have held off on any headlines. It is important to note that patchy fog will likely linger through the morning commute, so motorists should use caution and allow plenty of distance to stop. Once the fog dissipates this morning, much of today will remain dry as a weak high pressure lingers over the area. High temperatures will reach into the low 40s. This will be fairly short lives as another low pressure tracks northeast into Ontario this afternoon, moving a cold front across the area beginning this evening near 00Z. This will result in rain/snow showers to gradually push east overnight. With overnight lows expected to range from the low 30s in NW OH to the upper 30s across the southeastern tier of counties, much of the precipitation will likely be a rain/snow mix, resulting little to no snow accumulation. Showers will diminish from west to east on Thursday as the cold front moves east of the area. Behind the departing front, another high pressure system will build over the area bringing another short period of dry conditions across the area. High temperatures on Thursday will be a bit warmer reaching into the low to mid 40s. && .SHORT TERM /THURSDAY NIGHT THROUGH SATURDAY NIGHT/... Mainly dry warm front pushes back northeastward into the region Thursday night into Friday as a stronger surface low organizes over the southern plains area. This is response to a sharply digging upper trough over the four corners region, and will eject into the plains. Surface low will then race up the Ohio Valley into the southern Great Lakes as the southwest flow aloft continues to be very active. The moisture axis where the strongest low level moisture advection occurs will set up just to the south of the CWA however, and our area will get split by that and a deformation zone to the north. The forecast is not dry by any means, but this could be the difference in significant amounts of rain in the short term. A shift in that moisture axis northward by 150 miles could result in a major change to the forecast rain amounts. Otherwise, given the aforementioned storm track, mild conditions are expected again in the short term, but will be in the midst of changing for the fat western zones as Canadian high pressure will replace the milder airmass behind the cold front as we head into the long term period. && .LONG TERM /SUNDAY THROUGH TUESDAY/... 850mb temperatures plummet from the mid single digits to the minus teens by 00Z Monday. A trailing upper trough axis brings snow to the region Sunday, which will be largely dependent on the remaining available low level moisture in the column as to how impactful this could end up being. At the same time, northwesterly flow brings a lake effect component into the mix. Will have POPs showing this accordingly, but to not want to commit to specific wind directions and targeted areas yet for days 5 and 6. However, still want to make sure it will be known that lake effect snow is a distinct possibility for the end of the weekend into the beginning of next week until the track of the surface high into the central Appalachians makes the low level flow non supportive of such activity. Likely going to be into below freezing max temperatures Sunday and Monday with slow modification into the middle of next week. && .AVIATION /12Z Wednesday THROUGH Sunday/... Widespread IFR/LIFR conditions have moved across much of the area this morning as areas of dense fog and low ceilings have settled in. A Dense Fog Advisory has been issued through 15Z for KTOL, KCLE, KCAK, and KYNG due to visibilities being reduced to 1/4 to 2SM this morning. Visibilities will gradually improve through the morning with sunrise aiding in increasing temperatures and the burning off of fog. Unfortunately ceilings are expected to linger in primarily IFR range, possibly low end MVFR for brief periods through the entire TAF period. Visibilities will again deteriorate this evening as a cold front begins to move east across the area, increasing the potential for rain/snow showers through the end of this TAF period. No snow accumulation is expected. One thing to note is many of the near term guidance is suggesting the potential of fog again for much of the area tonight. Confidence was low in this, especially with the boundary moving through the area and shower activity expected. Have opted to lower visibilities to IFR again during this period, but the potential of fog will need to be monitored with upcoming forecasts. If fog does again develop, some LIFR conditions may again move into the area. Winds through the period will remain light and variable. Outlook...Non-VFR possible in rain on Wednesday night. Non-VFR likely within rain on Friday night and Saturday. && .MARINE... While the weather pattern remains active for Lake Erie with frequent precipitation through the forecast periods, the lake impacts should be modest. Wind directions will change quite frequently as previous forecasts have suggested given the fact that surface lows and highs will be tracking either directly over the lake or in the near vicinity of it. That said, sustained winds and wind gusts should stay below 15kts until Saturday. Once waves subside today, heights should be less than 3ft through Saturday as well. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Dense Fog Advisory until 10 AM EST this morning for OHZ003- 006>011-013-014-018>023-033. PA...Dense Fog Advisory until 10 AM EST this morning for PAZ002-003. MARINE...None. && $$ SYNOPSIS...Campbell NEAR TERM...Campbell SHORT TERM...26 LONG TERM...26 AVIATION...Campbell MARINE...26