Forecast Discussion
Summary
SYNOPSIS
... High pressure over northern New England will continue to extend south along the eastern Appalachians through Thursday. A wave of low pressure will increase the chance of light rain from late Thursday through Saturday. Drier conditions and warmer temperatures return with high pressure early next week.
NEAR TERM /UNTIL 6 AM THURSDAY MORNING/... High pressure remains over Quebec this evening, extending southward along the Appalachians. Aloft, a closed low is located near southern Lake Michigan. Dry low level air (dew points in the mid to upper 40s) continues to win out over the northeastern parts of the CWA with clear skies in place, while overcast conditions remain to the southwest. Some of the moisture may start to work back northward toward daybreak, in addition to an encroach of mid and high level clouds ahead of the low to the west. However, dry conditions are expected. Forecast lows in the upper 40s to mid 50s are in line with the latest guidance. However, places with clear skies and light winds may bottom out more than forecast.
SHORT TERM /6 AM THURSDAY MORNING THROUGH FRIDAY NIGHT/... By Thursday, the high will weaken slightly and allow an upper trough to move further east. Associated moisture will likely begin to work into the area again during the day on Thursday. Onshore flow will yet again bring increased low clouds through the end of the work week. Highs on Thursday will again increase a degree or two compared to the previous few days but with clouds mixing back in, confidence remains a bit low in this solution. By Friday, similar conditions continue through most of the day with clouds remaining in place along with shower chances remaining higher throughout the afternoon and evening. Highs are expected to climb into the upper 60s to even low 70s to finish out the workweek. Overnight lows Friday night will be in the 50s for most areas aside from low 60s right along the shorelines.
LONG TERM /SATURDAY THROUGH WEDNESDAY/... The sunshine slowly returns along with warmer and drier conditions for the weekend into early next week. The resultant upper level trough Friday night and remnants of Ophelia finally kick east while a strong amplitude upper level ridge over the Midwest builds eastward heading into early and middle part of next week. Since we'll sit on the eastern flank of the building ridge the overall flow will change to the north and northwest dragging more dry air in. This will allow the clouds to finally break and temperatures to warm especially during the Sunday through Wednesday timeframe.
Current 12z deterministic/ensemble guidance continues to hint on this as well with the erosion of the wedge in areas west of the Blue Ridge Saturday and areawide Sunday. Most of the guidance still hints on a marine influence with a shallow layer of moisture lingering in the low levels east of the Blue Ridge through at least Saturday afternoon. Some uncertainty remains based upon the quickness (this afternoon's model runs slightly faster) of the upper level trough Friday night into Saturday combined with the placement of the remnant low from what is left of Ophelia off the VA/NC coast.
With the building ridge comes more sunshine and a jump in temperatures. 850 mb temperatures are expected to push into the +10 to +15 degree C range which is near normal to slightly above normal for late September and early October. This will yield highs in the mid to upper 60s and low 70s over the mountains to mid to upper 70s and low 80s east of the Blue Ridge. Overnight lows will remain in the 50s for most outside the mountains/valleys where 40s are possible early next week.