Technical Discussion
Synopsis:
An area of low pressure will continue to spin over Eastern Canadian seaboard as a blocking high over Greenland prevents any eastward progression. As result, the winds will continue to flow from the northwest off from the Great Lakes, creating bands of heavy snow showers, especially in the northwestern portion of the state. This kind of weather setup will stay until Wednesday; some parts of northwestern PA may see up to a foot of snow before the snow ends on Thursday. A small ridge of high pressure will build into the region after the Canadian low finally lifts northward. The snow showers will gradually end on Thursday. An Alberta clipper system is going to pass by to the north and only brining as a chance of light snow showers on Friday.
Short-term (Monday-Wednesday):
A highly amplified ridge will continue to form a blocking high over Greenland on Monday. As result, a large area of 500-mb trough will sit above the northeastern United States and keep the heights on the end throughout the forecasting period. With pieces of upper-level energy swinging around the base of the 500-mb trough, multiple low pressures will develop along the Eastern Canadian seaboard and retrograde westward back to continental Canada. The developing storms will keep the winds predominately from the northwest off the Great Lakes. Cold air flow over warmer lake waters will allow bands of snow showers to form and travel down toward Pennsylvania. If the conditions are favorable enough ( i.e strong northwesterly flow and good dendrite forming mechanism), some of these snow bands will pack a lot of moisture as they stretch across both Lake Superior and Lake Erie. Some parts of the western PA will see up to a foot of snow before Wednesday.
Mid-term (Thursday – Friday night):
The lake-effect snow will gradually become less favorable throughout the day on Thursday as the 500-mb trough finally gets a chance to lift northward. The northwesterly flow will weaken along with the trough's departure and with the absence of strong northwesterly flow, the snow showers will gradually end on Thursday. A ridge of high pressure will building over the region Thursday night between the departing trough and the next incoming trough over Upper-Midwest. Partly cloudy skies will prevail on Friday before an Alberta clipper system associated with the Midwest trough approaches. Clouds will once again thicken Friday evening and some snow showers might breakout, but only with light accumulations as the clipper system will be relatively moisture starved.
Long-term (The weekend)
The guidance models continue to agree on the presence of a storm somewhere on the eastern 1/3 of the United States. However, the timing, strength, and track of this potential storm are still largely up in the air as of now. Most of the models have their own preference on where this low is going to go, how strong this storm is going to be, and when the storm is going to form. The 12z GFS this morning brings a decent strength inland low over the Northeast. If this solution is true, then the prospect of snow chances does not look too good for Pennsylvania as the majority of the state will be under the warm sector of the storm. The ECWMF model is on the inland-end of the extreme, bringing a primary low across the Upper-Midwest and into South-Central Canada and possibly a secondary low developing along its cold front over the Northeast. The precipitation type will also be rain if this solution holds true. The Canadian model, however, is on the offshore end of the extreme. If the Canadian model is true, then majority of the Northeastern U.S will see a major snow storm Sunday night and into Monday next week.
-by David Wang
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