577 FXUS61 KCLE 051634 AFDCLE Area Forecast Discussion National Weather Service Cleveland OH 1134 AM EST Fri Jan 5 2018 .SYNOPSIS... Arctic high pressure centered over Ontario and the northern plains states will slowly move across the Great Lakes by Saturday and off the east coast on Sunday. Winds will come around from the south on Sunday ahead of the next cold front which should cross the area on Monday. && .NEAR TERM /THROUGH SATURDAY/... Update...Adjusted cloud cover again based on satellite. No other big changes needed at this time. Original...Not much change in the pattern through Saturday. The core of the coldest air will settle across the Great Lakes and the northwest flow will persist as the upper low drops through the trough aloft. The lake effect is limited now by ice cover. Northwest and north central Ohio will have clear to partly cloudy skies. The clouds and lake effect snow showers will continue to occur down wind of the open water east of Cleveland with a persistent upstream connection to Lake Huron. The Lake Huron contribution is the difference from light snow to a more moderate to locally heavy snowfall rate in the higher terrain. The Huron band should drift westward for a while today as the trough aloft deepens, then drift back eastward tonight. Really a tough call between a Lake Effect Snow Warning and the advisory given the long duration. Some areas will have a gradual but significant accumulation of snow, locally over a foot by Saturday morning, but with the shifting of the bands and the lack of heavy, white-out snow, will continue with the advisory and just emphasize that there will be locally higher amounts. Will also mention blowing snow at about 15 mph and higher. The Lake Michigan lake effect clouds will begin to spread east tonight into Saturday as winds begin to back to west-southwest and there is increasing shear. It may not get as cold as forecast tonight if we get enough clouds and will take a degree or two back from the earlier forecast tonight. Lows will still be down around zero and below in most areas and will continue with the wind chill advisory. The lake effect will take a while to taper off on Saturday but the inversion is progged to lower and winds will back and the shear will start to increase so it will get lighter. Temperatures will be similar to today or a couple of degrees warmer on Saturday. && .SHORT TERM /SATURDAY NIGHT THROUGH MONDAY NIGHT/... A moderating trend expected late this weekend into early next week. One more frigid night expected Saturday night as surface ridge builds east across the region. This will bring an end to any lingering lake effect snow across NW PA. Mostly clear skies in the evening will allow temperatures to fall off rather quickly, with lows in the single digits below zero expected. Southerly flow/WAA will allow for temps to climb into the mid to upper 20s across much of the area on Sunday. Main focus of this period remains precip potential late Sunday through Monday, as a pair of systems track east across the northern Great Lakes and Tennessee valley. This will force a cold front through the area Sunday night and Monday. Models are starting to align with the timing of the systems/front. The are also a bit faster with the northern stream system, which brings a bit of light precip into the northern part of the forecast area Sunday afternoon. Will keep slight chance/low chance pops north of a Marion to Youngstown line for Sunday afternoon. Likely/cat pops are forecast from west to east across the area late Sunday night through Monday morning, tapering off from west to east in the afternoon. Precip type is still very uncertain at this point. Overall, the models continue to exhibit a colder trend with temperatures aloft. However, warmer boundary layer temps with temps hovering near or just above freezing late Monday morning through the day lend to the potential for a mix. For now, thinking that snow will dominate Sunday afternoon through Sunday night, with a potential mix of rain snow during the day Monday late morning/early afternoon, changing back to mainly snow late Monday afternoon. Highs in the mid 20s on Sunday will warm to the low/mid 30s on Monday. && .LONG TERM /TUESDAY THROUGH THURSDAY/... A warming trend looks increasingly likely next week, with models converging on the solution of southerly flow and upper ridging across the eastern CONUS through Wednesday night. A surface ridge will build quickly east across the region Monday night into Tuesday, bringing an end to any lingering precip in the wake of a cold front and any lingering lake effect snow on Tuesday. Highs on Tuesday are expected to be in the upper 20s to around 30. With lows in the mid/upper teens Tuesday night, temps are expected to jump into the mid 30s on Wednesday. Highs may reach the upper 30/lower 40s on Thursday before a cold front moves east through the region. Models are fairly consistent with a strong upper trough moving eastward across the CONUS midweek, ushering a strong cold front through the area sometime Thursday. Details on the strength and evolution of this system are still uncertain, however will include chance pops at this point, with decent moisture return ahead of the front and fairly strong forcing. && .AVIATION /12Z Friday THROUGH Tuesday/... VFR conditions will continue with the exception of the lake effect snow, which is mostly confined to extreme northeast OH and northwest PA. MVFR and occasional IFR conditions will continue in the lake effect snow showers. Elsewhere, some VFR stratocumulus will develop on Friday. MVFR stratocumulus possible Friday night as winds start to become more westerly and the lake effect clouds from Lake Michigan begin to spread across northern Ohio. Winds will remain gutsy at times through this evening. OUTLOOK...Lake effect snow expected to continue across the primary snowbelt of extreme northeast OH and northwest PA into Saturday. IFR possible all terminals Sunday night and Monday in snow or a wintry mix. && .MARINE... Northwest flow will continue over the lake today through Saturday. Winds in the 15 to 25 knot range are generally expected today and tonight. Will continue the Heavy Freezing Spray warning for the open waters, but have cancelled it for zone 166, where ice cover has formed. Winds will back to southwest Saturday night into Sunday as a surface high moves east across the lake. Southwest winds continue through Monday before becoming westerly Monday night as a cold front moves across the lake. Rapid ice growth will continue across the open waters today through Saturday, with open waters becoming confined to north of Erie east to Dunkirk/Lake Erie Beach. && .CLE WATCHES/WARNINGS/ADVISORIES... OH...Wind Chill Advisory until noon EST Saturday for OHZ003-006>014- 017>023-027>033-036>038-047-089. Winter Weather Advisory until 7 AM EST Saturday for OHZ014. PA...Wind Chill Advisory until noon EST Saturday for PAZ001>003. Winter Weather Advisory until 7 AM EST Saturday for PAZ002-003. MARINE...Heavy Freezing Spray Warning until 10 PM EST this evening for LEZ167>169. && $$ SYNOPSIS...Kosarik NEAR TERM...TK/Kosarik SHORT TERM...Greenawalt LONG TERM...Greenawalt AVIATION...Kosarik MARINE...Greenawalt