Discussion from NWS Buffalo
Anyone gonna chase?
.LONG TERM /THURSDAY NIGHT THROUGH MONDAY/... ...CRIPPLING LAKE EFFECT SNOW STORM POSSIBLE THIS PERIOD... No change in available model output and overall H85 and H5 pattern for late this week into the weekend. There remains high confidence that a prolonged southwest flow lake effect event will take place during this period. A deep longwave trough...featuring a vertically stacked low in the vicinity of Hudson Bay...will keep a flow of seasonably cold air in place over the Lower Great Lakes through the weekend to GUARANTEE a lake response. The `formula` for significant lake snow will then come down to whether there is ample synoptic moisture to work with...and of course the direction of the H85 steering flow. Consensus of both ensemble and deterministic guidance packages are in fairly strong agreement of a southwest flow...but placement of accumulating snow bands will have to be further defined as the event nears. Continues to look like KBUF and KART metro areas and their northern suburbs (at least for a time) are favored.
This event has some historical precedence, with CIPS analogs comparing to Nov 20, 2000, when many became stranded in their vehicles...or the twin storms that made `Snow-vember` infamous with over five feet of snow? While at this point it is impossible to suggest the same for the upcoming event...it is something to keep in mind. Speaking of correlations...local studies from the KBUF office does show some stark similarities in the synoptic pattern for these larger events. The largest events have near stationary plumes of snow...but it is still way too early to get that detailed.
In the wake of a passing shortwave ridge on Thursday...subtle troughing embedded within in the larger scale longwave pattern will produce a deep southwest flow of cold air across Lakes Erie and Ontario. There is a suggestion that the flow will generally be 250- 260 Thursday evening...but with the lakes still relatively warm (nr of abv 10c)...that flow could back some 10 deg over Lake Erie. During the course of Thursday night and Friday...the flow is forecast to back a bit...and this will send well organized lake snow plumes across the Buffalo and Watertown metro areas and potentially into the northern suburbs. Again, placement of these bands will depend on the exact H85 flow...but a southwest (240-250) flow is being favored by guidance at this time. Given the expected presence of moisture up to arnd H7...snowfall rates of 1-2"/hr is becoming more plausible. Details still have to be refined, but there was enough signal and consistency in model guidance to issue winter storm watches Thursday evening through Sunday evening for a potential high impact, long duration lake snow event. If winds back further for longer period of time, then Niagara and Orleans counties would need to be put in a watch as well. Those details can be sorted out next couple days though.
While the steering flow will likely oscillate somewhat during the course of the weekend and into early next week...a cold southwest flow is mainly what is being shown by most of the guidance packages. This would keep lake snows in place to the northeast of both lakes with additional significant accumulations possible at times even beyond when initial watch ends.
