Area Forecast Discussion
Issued by NWS Cleveland, OH

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000 FXUS61 KCLE 100345 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1045 PM EST Fri Dec 9 2016 .SYNOPSIS... Cold northwesterly winds will continue to flow across Lake Erie and produce Lake Effect Snow for the snowbelt tonight. As high pressure begins to ridge into southern Ohio tonight into Saturday it will nudge the snow showers up the lakeshore into NW PA. The area of high pressure will be short lived with the next storm system moving from the southern Plains into the central Great Lakes Sunday into Sunday night. && .NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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Despite some movement and disruption of the heavy band over the last 2 hours, the heaviest snowfall remains where it has been most of the day from northeast Cuyahoga County eastward into southern Lake/Northern Geauga and Ashtabula Counties. Surface winds clearly show this area of convergence with southwesterly winds on land while observations along the lakeshore are out of the northwest. The surface trough is expected to strengthen along the eastern lakeshore overnight with a gradual trend for bands to shift northeast late tonight into Saturday. Models do show some drying near 700mb spreading in from the west overnight but also show some large scale ascent towards morning ahead of an approaching shortwave. Overall expect to see bands strengthen as they shift north into Lake County in the morning and eventually along the Erie Pa lakeshore Saturday afternoon. If bands do set up in Erie County as expected on Saturday, then the Warning may need to be extended through Saturday evening. Previous discussion...Hi-res guidance has been generally poor with handling the dominant bands coming onshore between Euclid and Willoughby and in Ashtabula county. The southwest band has moved little despite hi-res guidance trending the band southward into eastern Cuyahoga through the afternoon. Snowfall reports have been exceptional with this band, with 1-2" per hour rates with thunder snow being reported. Have upped snowfall amounts through 7 PM considerably from Euclid/Willoughby southeast to Chesterland/Chardon. This also prompted an upgrade to a Lake Effect Snow Warning for Cuyahoga and Trumbull counties, given reports quickly approaching criteria and additional snowfall expected. Expect this band to continue for the next few hours and move very little, perhaps only diminishing in organization and intensity a little bit. Still expecting snow to increase further southwest into Cuyahoga, including downtown Cleveland, through 7 PM and after. Models continue to show favorable trajectories from Lake Michigan bands, and organization of these bands further west along the lake. Latest radar trends are possibly showing a main band organizing along the western basin. Overall, expecting two main bands oriented mainly west/east impacting northern Cuyahoga inland and northwest Ashtabula inland to NW PA. Current thinking is that the further southwest band will become more disorganized towards 04-06Z, with the further northeast band staying more organized a bit longer. Trended pops and snowfall amounts around this idea, which is fairly similar to previous forecast. General snowfall amounts overnight are forecasted in the 3 to 5 inch range in NW PA and Cuyahoga/Lake/Geauga, but wouldn`t be surprised to see higher/lower amounts where the bands persist/miss, and overall variable accumulations.
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&& .SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY NIGHT/... Dominant lake band will be reorienting along the lakeshore and lifting northeast during the day Saturday as 925mb flow backs southwest into the afternoon hours. The band should still be rather impressive with thermodynamically favorable environment, impressive lapse rates, ample boundary layer moisture and modest shear/flow. Trended the band up along the lakeshore through the day, with pops diminishing from southwest to northeast. Snow amounts during the day Saturday not changed too much from previous forecast, with general 2 to 5 inch amounts, with possible higher amounts in NW PA where bands persist with 1"+ per hour rates. The last of the lake effect will shift east early Saturday night as ridging increases and the flow becomes southwest. An expansive area of warm advection will be underway across the midwest as a lead short wave tracks east in a relatively fast jet aloft. High clouds will already be increasing across northwest Ohio by sunset Saturday evening and some light snow will develop later Saturday night from west to east as the low level jet increases across the midwest. The system will probably be rather complex by Sunday. Heights aloft will be trying to rise. The initial surge of warm advection snow might try to taper off but will not bet the house on it since the low level jet will continue to increase and eventually some gulf moisture will begin to sneak in from the southwest. We will likely see a general 1 to 3 inch snowfall from late Saturday night into Sunday afternoon, perhaps locally 4 inches across northwest or north central Ohio. The next surge of precipitation will develop in advance of the main trough by Sunday evening. Surface temperatures and precipitation type will be problematic as we continue to warm through the column. Snow will likely mix with and change to rain in much of the area Sunday night as the surface low tracks across the Great Lakes and the south flow continues. A little sleet and a period of freezing rain is possible during the transition. Do not have a good estimate on the timing and duration of the snow and potential freezing rain. I could even see thunder Sunday night ahead of the cold front. A winter storm watch will likely be needed for the time period from late Saturday night into Sunday night for at least part of the area. Highs on Sunday will probably approach freezing, then temperatures will rise Sunday night. && .LONG TERM /TUESDAY THROUGH FRIDAY/... Models not in good agreement on the timing of the next systems overall...but the trend is definitely the same. Setting up for the coldest temps of the new season as an arctic front blasts through on Wednesday. ECMWF a little faster with the front than the GFS but either way by daybreak Thursday 850mb temps plunge to -20c and by Thursday evening -24c. Expect highs in the teens and lows in the single digits on Thursday. Best chance of snow with the system will be in the snowbelt. The cold lingers through the end of the work week. ECMWF builds high over the area on Friday while the GFS about a day slower...so superblended Friday. && .AVIATION /00Z Saturday THROUGH Wednesday/... Lake effect still going strong in the northeast portions near the lake with intense band just north of Cleveland into northeast Ohio. Main band is slowly lifting north through the night and should be oriented west to east across the lakeshore area. A band will slip into the CLE terminal area for a few hours this evening. Another band will develop into Erie, especially toward morning. Rest of the terminals will see improving conditions as flow shifts around to the southwest tomorrow and this should bring an end to the lake effect snow for the time being. Winds will be strongest 10 to 20 knots near the lake and around 10 knots elsewhere. OUTLOOK...Lake effect shsn mainly for Eri Saturday into Saturday night. Widespread light to moderate synoptic snow Sunday into Monday for the entire forecast area. Lake effect snow will continue in the snowbelt east of CLE into Tuesday. && .MARINE... Have let the small craft advisory expire on the Western Basin as the winds have diminished to 10 to 20 knots. Conditions will remain choppy with 2 to 4 foot waves. Small craft will continue over the Eastern 2/3 or the lake with a west flow of 15 to 20 knots. SCA ends late Saturday as high pressure moves quickly across the lower lakes and the winds turn to the south. Small craft likely needed again on Monday as another system moves across the Great Lakes. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Lake Effect Snow Warning until 4 PM EST Saturday for OHZ012>014-089. Lake Effect Snow Warning until 10 AM EST Saturday for OHZ011. Lake Effect Snow Warning until 7 AM EST Saturday for OHZ023. PA...Lake Effect Snow Warning until 4 PM EST Saturday for PAZ001>003. MARINE...Small Craft Advisory until 4 PM EST Saturday for LEZ146>149. && $$ SYNOPSIS...Greenawalt NEAR TERM...KEC/Greenawalt SHORT TERM...Greenawalt/Kosarik LONG TERM...DJB AVIATION...Lombardy MARINE...DJB

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