... A deep low pressure system will lift away from the Carolina coast on Sunday resulting in slightly warmer temps and mostly sunny skies. A couple of weak and dry cold fronts will move through the area Monday and Tuesday but temperatures will gradually warm Wednesday through Friday ahead of the next cold front expected late next week.
NEAR TERM /THROUGH SUNDAY/... As of 200 PM: A slow-moving low remains off the South Carolina coast. Seasonably strong high pressure is centered over the St Lawrence Valley beneath convergent 500mb flow. The net result is a somewhat CAD-like pattern for our area, featuring a breezy northeasterly sfc flow in the Piedmont and a robust midlevel inversion. While the layer beneath that inversion is shown to be nearly saturated, little forcing exists aside from convergence between the aforementioned systems. Precip has diminished as a result, and while some intermittent drizzle or light rain could result this aftn and early evening, it likely won't amount to much. PoPs remain slight-chance at best.
As the low moves further offshore tonight, some drying occurs in the currently saturated layer, which lets the PoPs fall off. Continued cold advection and reduced cloud cover will bring min temps a few degrees below climo. Though the high will migrate eastward on Sunday, the convergence will help maintain its strength, and the offshore low will continue to drive a cold NE flow. This should hold aftn maxes two or three categories below climo in the NC Piedmont, despite insolation. The southwest CWFA will be less impacted by the cold airmass, nearly reaching climo.
SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/... As of 245 pm EST Saturday: The short-term (Monday and Tuesday) will be fairly benign across the area despite the passage of a couple shortwaves and attendant cold fronts, for the cold fronts will be weak and there will be very little moisture to work with. The first upper-level shortwave arrives early Monday morning around the base of a larger (longwave) trough and despite its potency as it becomes negatively tilted over the Ohio Valley, it follows too quickly behind the departing coastal low to tap into any Gulf moisture and at worst brings mostly cloudy skies to much of the area overnight Sunday into early Monday. Given a progressive pattern, the wave and front quickly move by the area Monday while yet another shortwave arrives Monday night, dropping much further south towards the Gulf Coast on Tuesday. This results in yet another round of cloud cover but again, there is very little moisture to work with. However, the favorable, upslope northwest low-level flow should be strong enough in combination with shortwave forcing to justify a slight chance PoP along the central NC/TN state line Tuesday. Temperatures quickly moderate above freezing Tuesday morning in the western mountains so expect liquid to be the primary phase with any isolated shower that develops.
The cloud cover should help to keep min temperatures ever so slightly warmer both Sunday night and Monday night compared to Saturday night, with lows at or just below normal. Despite some insolation each day following the passage of each weak front, the shortwaves will keep thicknesses in check and highs will stay stagnant at about 4-6 degrees below normal.
LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/... As of 245 pm EST Saturday: It seems like the extended forecast has been a battle between the EC/Canadian and GFS for the past few weeks, and this continues to be the case. But first, the good news is that there is decent consensus that upper-level heights rise significantly behind the short-term shortwave train as a potent closed-low develops over California, inducing a transient longwave ridge over the center of the country that moves overhead quickly by Thursday. This means that skies will remain mostly clear Wednesday and Thursday and temperatures will finally get back to normal if not 2-4 degrees above normal by Thursday. Looks like a nice couple of days to take off from work!
The guidance battle resumes heading towards Friday and Saturday when the models disagree about how and when the southern California closed low ejects out of the Rockies. The EC/Canadian solution is stronger/deeper and therefore, slower with the propagation of a 560dm closed low through the Rockies Friday into Saturday while the GFS more quickly ejects an open trough across the entire CONUS Friday through Saturday. Because of these differences, there are differences in how a potent northern-stream trough interacts with the southern stream energy. Because the EC/Canadian solution is slower to eject the southern closed-low, it brings the northern stream trough across our area Friday with a moisture-starved frontal passage later Friday. The GFS marches a phased system and attendant cold front across the area early Saturday with a better QPF response, but the EC/Canadian saves the more potent southern stream system for late Saturday into Sunday. At a minimum, as high pressure moves offshore, return flow sets up over the area Thursday afternoon and persists at least into the overnight hours, justifying at least slight chance PoPs over the mountains as early as Thursday evening with low-end PoPs persisting over the mountains and parts of the Piedmont through Friday. The forecast continues to blend the solutions with a nod to the EC/Canadian consensus, saving the better PoPs for later Saturday into Sunday morning as the second system approaches.
Regardless of the solution, expect another mild day on Friday with cooler, slightly below-normal conditions on Saturday because there is consensus that either weak CAA will be in place behind the EC/Canadian front or cloudy/showery conditions will persist as the front is moving through (GFS).