... An upper disturbance will move east of the area today. Dry high pressure will then briefly return through tonight. A strong low pressure system approaching from the southwest may support a threat for heavy rainfall from late Sunday into early Monday. Northwest flow snow is expected to develop across the mountains in the storm's wake from late Monday through Tuesday. Another strong low may cross the region at the end of the week.
NEAR TERM /THROUGH TONIGHT/... As of 635 AM EST: Precipitation will exit to the east quickly this morning with clearing skies shortly thereafter. A sfc high will build in through the day. Plentiful sunshine and downsloping will partially offset the cooler airmass. Highs should be near 5 to 10 degrees above normal.
High pressure continues to build into the area as the center of the high moves into VA. Low level easterly flow develops and could bring some moisture back into the area. The guidance disagrees on how much moisture moves in, and the amount of any clouds. Do show an increase in clouds over the western CWFA, but fog could be more of a concern in some locations where clouds don't develop. Of course, there's disagreement in fog development as well. Lows will be around 5 degrees above normal, but could be cooler if clouds are slow to develop and winds don't keep the atmosphere slightly mixed.
SHORT TERM /SUNDAY THROUGH MONDAY NIGHT/... As of 200 AM Saturday: The first half of Sunday will start out dry as sfc high gradually pulls offshore as our next system begins to push into the cwa around 00Z Monday. This is all in part of a cutoff low that is pushing eastward and eventually gets caught up with the southern stream energy that meanders along the Gulf Coast through the period. Both systems will carry the momentum into the Southeast with deep layer moisture and perhaps modest instability, especially in the southern fringe of the cwa. Model guidance has been spitting out 100-300 J/kg of SBCAPE and 0-6 km effective bulk shear of 40-50kts. The better environment for any strong to severe thunderstorm development is south and east of the I-85 corridor. Confidence is on the upward trend on the the overall severe threat staying confined to that area, while confidence remains steady with a low-end hydro threat over the southern Blue Ridge Escarpment due to upslope enhancement.
As the sfc low and attendant frontal boundary pushes upstream the backdoor longwave trough that eventually absorbs the cut off low, cold NW flow will push into the area and the transition to winter weather is likely over parts of the mountain community. Heaviest amounts will be at the highest peaks and TN-NC border along the spine of the Blue Ridge where the transition is likely to occur much sooner than other areas in the higher elevations. A sharp drop in thicknesses around 18Z Monday will drop snow levels overall, but the most favorable locations will be elevations at or above 3500 ft. With a lingering moisture fetch over the OH Valley and stretching into the southern Appalachians on the backside of the low. Expect the snow to stick around through the end of the forecast period for the higher peaks in NC.
Last hazard that could present weather troubles will be the tightening of the pressure gradients over the mountains once the NW component fully becomes established. CAA will enter the environment which will only increase the overall momentum at the sfc. Gusty winds and possible advisories could be considered in this scenario to go along with the expected snowfall in the mountains of NC. Near-normal temperatures are expected through Monday, but a huge dip is expected Monday night with lows in the 20s for the mountains and low 30s every where else.
LONG TERM /TUESDAY THROUGH FRIDAY/... As of 300 AM Saturday: The evolved upper low sets up shop over the eastern CONUS with the center of it just north of the area. Very cold air will be in store with thicknesses <540 dm and deep radiational cooling, expect the coldest max and min temps of the season so far with highs not getting out of the 40s anywhere and lows in the 10s across the mountains and low to mid 20s elsewhere. During this part of the medium range, temperatures will be 10+ below climo for this time of the year. Any lingering NW snow should taper off by Tuesday afternoon and dry air will filter into the cwa. Temperatures begin to rebound by the middle part of next week as upper ridging pushes higher heights into the region and the upper low ejects to the north and east. Broad sfc high controls the overall weather pattern through Thursday before more changes take place. Model guidance really diverge past Thursday due to the location and track of the next cut off low that generates over the southwestern CONUS just like the previous. Both the GFS and ECMWF show a second cut off low diving south over the High Plains while the other develops over the Southwest. The ECMWF actually phases the two together over the Southern Plains and forms a very potent upper low that moves across the southeastern CONUS by the end of the period. However, the GFS keeps the initial cut off low over the Southwest while the second cut low dives in from the High Plains and slides into the Southeast near the same time frame as the ECMWF. Not as potent, but keeps the area unsettled to say the least and kept 20 PoPs in the forecast for now due to the lack of confidence this far out. Looks as if the unsettled and amplified pattern will continue as we run through the first week of December. Outside of Tuesday, Tuesday night, and Wednesday night expect temperatures to make a return to near-normal or slightly below-normal values on the back half of next week.