... Dry but cold high pressure will begin settling in behind a departing cold front today and persist through Thursday. Another round of brief wintry weather is possible early Friday as a coastal storm brings another round of moisture, but the bulk of this precipitation should fall as a cold rain. High pressure briefly returns over the weekend, but the next storm system is expected to begin impacting the area early next week.
NEAR TERM /THROUGH TONIGHT/... As of 10:15 AM Wednesday: with the cold front pushing further south and east, precip has ended across the fcst area. We're still seeing a fair amount of scattered high clouds streaming over much of the non-mtn areas, in addition to, bkn lower clouds over a handful of the SC Upstate sites. The higher-lvl cirrus will likely linger over portions of the Upstate and Piedmont well into the afternoon.
Otherwise, dry continental high pressure will spread across the region today, and should eventually lead to clear skies throughout the area. Cold advection will continue, maintaining good mixing and fairly gusty winds in the mountains and in parts of the Piedmont downstream of gaps. However, the winds tapped by mixing will not be strong enough for gusts to approach advisory criteria. Downsloping and sunshine will partially offset the colder air in the Piedmont, but maxes still should top out a couple degrees below normal there. The mountains will be notably colder, on the order of 10 degrees below normal in many areas. Winds will diminish tonight and efficient radiational cooling will bring temps several degrees below normal throughout the area.
SHORT TERM /THURSDAY THROUGH SATURDAY NIGHT/... As of 310 am Wednesday: A progressive flow pattern will be in place across the eastern half of the country, resulting in a fairly active/unsettled short term. In the interim, the period will begin with cool and dry surface high pressure as the dominant weather feature across the western Carolinas and northeast Georgia, with temps expected to average several degrees below climo Wed night through Thu.
The first in a series of short wave troughs will eject from the southern Great Plains at the start of the period to the Mid-Atlantic by Friday morning. Height falls associated with this and a series of subsequent speed maxima will result in development of a Miller-A wave/cyclone across the Southeast coastal region. Moisture and lift associated with this cyclogenesis will overspread our forecast area Thu night into early Friday. With a 1040 mb surface high expected to be moving across southern New England Thu evening, supporting the cool/dry over our area, in-situ/hybrid cold air damming will develop as precip begins falling, and wet bulb effect is expected to result in temps falling to or just below freezing, mainly in counties bordering the eastern escarpment of the Blue Ridge, and northern Piedmont areas in North Carolina. Forecast soundings depict a robust warm nose (+5 to +8 C) quickly developing quickly above the shallow cold pool shortly after precip begins, so precip type should be pretty much exclusively freezing rain where freezing surface temps are found.
Considering the highly transient nature of the parent high (which is forecast to be in the neighborhood of Nova Scotia by 12Z Friday), advection of cool/dry surface air will be weakening throughout the morning, eventually becoming non-existent. In light of the fact that temps are only expected to drop to no more than 0-2 degrees below freezing, the self-limiting nature of freezing rain and lack of cold air maintenance is expected to result in temps warming above freezing across much of the area by late morning, allowing for the transition to a cold rain. Having said that, I wouldn't be surprised if we end up seeing a very narrow corridor of near-warning level ice accretion along the eastern escarpment, but this remains highly debatable at this juncture, and the vast majority of areas that see freezing rain should receive around .10 inch or less.
Otherwise, Friday will be cool and wet, with max temps expected to top out a solid 10 degrees below climo. Robust precip chances will linger well into Fri night, as short term guidance depicts a second region of warm advection developing across the TN Valley, southern Appalachians and vicinity in response to additional upstream speed maxima.
LONG TERM /SUNDAY THROUGH WEDNESDAY/... As of 340 am Wednesday: Improving conditions are expected throughout Saturday, as upper trough axis is forecast to sweep quickly east of the area, and only token small pops are carried during the morning. Yet more upstream height falls will significantly limit the magnitude/duration of moist northwest flow and cold advection in the wake of the trough. Thus, while some upslope shower activity is possible Sat into Sat night near the TN border, temps are expected to prove to be too warm for anything but liquid except perhaps at the highest peaks and ridgetops.
Dry and seasonably cool weather is expected Sunday into Monday, but moisture associated with the next storm system may begin to impact the forecast area by the end of Monday, and pops increase to 20-40% by that time. Global models are in good agreement in tracking a deepening cyclone from the southern Great Plains through the Mid-Miss/TN/OH Valleys late in the period, with associated well-forced frontal zone sweeping through the forecast area in the Monday night/Tue time frame. Likely pops are therefore advertised. P-type problems would not be expected based upon the current forecast cyclone track, but the potential for high shear/low CAPE convection will be something to monitor if current model trends hold. Min temps are generally expected to be above normal and maxes near-to-slightly above normal through much of the period.