Elliott on Nicole and the weekend:
By the end of the week, my attention turns to the remnants of what is currently Subtropical Storm Nicole several hundred miles east of the Bahamas. Nicole is projected to make landfall along the east coast of Florida Wednesday night as a strong tropical storm or Category 1 hurricane. It may remain over the Florida Peninsula on Thursday or briefly emerge into the eastern Gulf of Mexico before setting its sights on the Southeast. Nicole's northward turn from Thursday night into Friday can be attributed to strong, west-to-southwesterly flow in advance of a deep, upper-level trough (dip in the Jet Stream) moving into the central U.S. A strong cold front at the leading edge of the trough will traverse the eastern half of the nation from west-to-east from Thursday night through Saturday night and ultimately absorb Nicole. As this occurs, Nicole's remnant low pressure system is expected to accelerate northeastward, reaching the southern New England coastline no later than Saturday afternoon. Nicole's track will play a large role in determining how much rain falls across southern PA and northern MD on Friday and Friday night. It's certainly within the realm of possibilities that Nicole's remnant low passes close by or directly overhead. Regardless of the exact track, rain should overspread the region from south-to-north late Thursday night into Friday morning and continue through Friday night. The heaviest rain should hold off until after the Friday afternoon commute, but I'd still expect slowdowns and use extra caution on the wet roadways. Rain should taper off rather quickly from southwest-to-northeast late Friday night into Saturday morning but not before at least 2-3 inches falls across the Lower Susquehanna Valley. Due to another stretch of abnormally dry conditions since Ian's remnants in early October, Nicole's rainfall should be largely beneficial. Barring an unexpected slowdown in Nicole's forward speed, flooding shouldn't be a concern except in low-lying and poor-drainage areas. Moist, southerly flow ahead of Nicole will prevent this from being a "cold rain" like what ocurred with Ian in early October. Highs should easily reach the low-to-mid 60s on Friday, and dewpoints will briefly surge back into the upper 50s or low 60s, as well.
A strong pressure gradient, or change in pressure, between Nicole's remnant low pressure system and an area of high pressure building into the northern Plains will be responsible for strong, gusty winds on Saturday. The cold front that Nicole merges with should move through eastern PA immediately after the rain tapers off. In what meteorologists call a "dam-breaking event," the drastically colder air west of the mountails will crash into areas farther east on the wings of howling, west-to-northwesterly winds. These events are notorious for producing dangerous crosswinds with gusts up to 50 mph.. sufficient to also cause sporadic tree and powerline damage. At the very least, it'll be necessary to "hold onto your hats" Saturday and prepare for a dramatic shift in the weather pattern. Temperatures may still reach or exceed 60°F Saturday morning but should "fall off the cliff" Saturday afternoon or evening in the wake of the cold front. By Sunday morning, temperatures may only be in the upper 20s or low 30s as an Arctic air mass settles over the Great Lakes region. Due to the combination of strong, west-to-northwesterly winds and very cold air moving over the still-warm waters of the Great Lakes, the first lake-effect snow event of the season is likely from Saturday night into Monday downwind of Lakes Erie and Ontario. Although flurries shouldn't reach southeastern PA, mostly cloudy and blutery conditions will accompany highs no better than the 40s and wind chills in the 30s Sunday afternoon. In a matter of a week, we'll be trading shorts, t-shirts, and sunscreen for coats, gloves, and chapstick.. what a rude awakening and downright nasty plunge into winterlike weather! -- Elliott
