103 FXUS61 KBGM 081945 AFDBGM Area Forecast Discussion National Weather Service Binghamton NY 245 PM EST Sun Dec 8 2019 .SYNOPSIS... A large storm moving thorough the Great Lakes will push warm air and rain into the area Monday and Monday night. Colder air will follow the storm on Tuesday bring snow showers that will linger into early Wednesday. && .NEAR TERM /THROUGH MONDAY NIGHT/... Lee wave develops rapidly into a lake runner passing well west of the area. Rapid deepening develops along with a nice jet streak with the forecast area being in the favorable entrance region. So precipitation explodes over the area Monday as the low races up into Quebec. Very cold last night with a good snow cover could keep road temps very cold and allow for a bit of freezing rain tonight, mainly over the extreme northern CWA despite the strong warm advection. No large blocking high keeping the cold air locked as the rain moves so expect a pretty quick warm up. Not anticipating the need for an Advisory at this time, but it could be handled with an SPS. Rapid movement of the system will limit rainfall amounts but snow melt with the rain will bring rises below caution stage. A couple of spots could exceed that or come close, namely the Black river in Boonville and some headwater points on the Upper Susquehanna and Delaware. Hydro watches should not be needed. Rain will become more showery ahead of he cold front Monday night as a dry slot develops along with the upper jet structure pulls out to the north. && .SHORT TERM /MONDAY NIGHT THROUGH TUESDAY NIGHT/... 330 AM Update... A big change of air masses will occur in the short term, with warm conditions Monday night followed by a drop of 20 or so degrees occurring between Tuesday morning to dawn Wednesday. Main issues are if there will be a continued hydrologic response Tuesday, and then details of a rain-to-snow transition behind the front later Tuesday through Tuesday night. Very mild conditions will be in place Monday night to early Tuesday morning due to strong south-southwesterly warm air advection ahead of an approaching cold front. Though rainfall rates will drop off, a surging of dewpoints well into the 40s - even nearly 50 in the Poconos to Catskills - with that wind should accelerate melting of snowpack. The combined influences of that snowmelt with rain leading up to that point, will cause healthy within-bank rises on streams and rivers. The threat for true flooding still appears low compared to a few days ago, since rainfall total expectations have dropped in recent model runs. However, we will still need to monitor just in case. Standing water in poor drainage areas, and elevated streamflows, can be anticipated. Models are well agreed on a deep low zipping through Quebec to Newfoundland Tuesday, trailing a cold front that will pass northwest to southeast across our area during the day. The point of disagreement, is to what degree the front hangs up just to our southeast and thus what happens with a potential final shield of precipitation as cold air overtakes the region late Tuesday through Tuesday night. All operational models have a variation of rain changing to snow, but the only area of good agreement for location for that wave and resultant possible light coating of snow accumulation is Northeast PA east of I-81 and Central NY south of I-88; i.e. the Poconos to Catskills. Some light accumulation could occur further west as well; perhaps even most of our area. However, there is a lot more uncertainty on that west of I-81/north of I-88, and indeed there may be none at all. Monitor the forecast for updates. Highs Tuesday will be in the early morning, in the mid 40s to lower 50s, before temperatures drop midday through afternoon behind the front. Cold air advection will continue through Tuesday night as temperatures fall well below freezing for eventual lows in the lower 20s to near 30. && .LONG TERM /WEDNESDAY THROUGH SATURDAY/... 345 AM Update... Very cold conditions are anticipated Wednesday through Thursday, with lake effect snow showers for some parts of the area, followed by moderating temperatures as we head into the weekend. Arctic air mass will take over Wednesday and especially Wednesday night-Thursday as the Canadian high builds over the area. Boundary layer flow ahead of the high will be westerly or perhaps even west-southwest at times, which will tend to direct heavier lake effect snows mainly north of the area Wednesday morning through evening. That said, clusters of Lake Erie snow showers and flurries can still be anticipated for much of the area, especially Central New York. Westerly winds will gust 15-25 mph Wednesday with highs of mid 20s to lower 30s. Later Wednesday night into early Thursday, subsidence inversion of incoming high will begin to lower yet the dendritic growth zone will also be contained underneath it. As low level flow veers a bit more northwesterly ahead of the high, lake effect off of Lake Ontario may advance across the NY Thruway late Wednesday night, with at least light multibands pressing further southeast Thursday morning. Lows will be in the upper single digits to upper teens. The high pressure and its very dry air eventually win out, ending lingering flurries by afternoon and allowing for at least some sunshine. Highs Thursday are expected to be only 20s areawide. However, we will get into return flow as that high passes by, with moderating temperatures Friday-Saturday. Friday appears dry, but there is plenty of uncertainty during the first half of the weekend as an upper trough digs to our west, and advects in moisture and thus possible precipitation. This may include a snow to mix to rain transition. && .AVIATION /20Z SUNDAY THROUGH FRIDAY/... VFR this afternoon and for much of the night. Only aviation concern is the expected LLWS as higher, more southeasterly winds at the surface are topped just above the boundary layer with a strong southwest wind developing ahead of the approaching trough. Lowered ceilings and visibilities will develop late tonight and on Monday as rain moves into the area. Conditions will eventually become IFR as the rain falls more heavily and the column saturates near the end of he period. Outlook... Monday afternoon into Tuesday...Restrictions likely in rain. Wednesday...Restrictions possible in snow showers. Thursday and Friday...VFR expected. && .BGM WATCHES/WARNINGS/ADVISORIES... PA...None. NY...None. && $$ SYNOPSIS...DGM NEAR TERM...DGM SHORT TERM...MDP LONG TERM...MDP AVIATION...DGM