... Cloudy conditions and occasional rain will persist until a cold front passes east of the region early Wednesday. Rain is forecast to briefly change to a light wintry mix before ending across the North Carolina mountains early Wednesday. Dry but cold high pressure will settle in behind the front for mid-week. 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.
NEAR TERM /THROUGH WEDNESDAY/... As of 1015 PM: The precip shield off to our west across TN and the central Gulf states continues to make very slow progress eastward. Most of the forecast area is seeing scattered to numerous light rain showers. A changeover to -FZRA and sleet is likely occuring above about 5000 ft (a little lower over Avery County). Webcams in Avery County don't look snowy yet. So overall, if anything the changeover is just a tad slower than expected. Still expect a glaze of ice and a mixture of sleet and snow accums across the Winter Weather Advisory area overnight, before the precip tapers off before daybreak. So will continue the advisory as is. Overall, only minor tweaks to temps and pops for tonight.
Cold air will move in across the mountains overnight. The guidance suggests that there will be a lingering low level warm nose even as temps near the surface cool. The entire column cools overnight. This will lead to a mixed bag of wintry precip with rain changing to freezing rain, then sleet and finally snow. That said, valley locations and counties away from the TN border will see some wintry mix, but little to no accumulations. Across the TN border counties, accumulations will be highly elevation dependent, even over the northern mountains. The recent relatively warm temps and precip will also keep accums from starting right away. The limiting factor will be that the cold air is moving in with the moisture instead of already being in place. As usual, the highest elevations will see the highest amounts. Up to 2 inches of a mix of snow and sleet and up to a tenth of an inch of ice accretion. Therefore, will issue a Winter Weather Advisory above 3500 feet for the TN border counties. Precip will end near daybreak.
Outside of the mountains, expect just showers with precip ending near or shortly after daybreak. Lows should be around 5 degrees above normal.
High pressure builds into the area Wednesday. Gusty winds will slowly diminish across the mountains. There may be some morning gusts outside of the mountains, especially in favorable gap wind locations. Skies will clear but highs will be up to 5 degrees below normal.
SHORT TERM /WEDNESDAY NIGHT THROUGH SATURDAY/... As of 245 pm Tuesday: Overall, there is little change in the general thinking for the long-anticipated late-week system. We continue to expect a fairly short (<12hr) period of freezing rain expected as moisture from Gulf Coast cyclogenesis and forcing from numerous perturbations within the SW flow aloft encounters a hybrid cold air damming surface pattern Friday morning. The current forecast is in line with previous forecasts and continues to call for light (less than 0.15") ice accumulations in climatologically favored areas of the NC Piedmont (primarily along and north of I-40), Foothills, Blue Ridge Escarpment, and central and northern mountains on Friday morning with a transition from freezing rain to rain for these areas fairly quickly late Friday morning. Fortunately, guidance continues to call for a strong (1040mb) but transient parent high-pressure to quickly move off the New England coast overnight Thursday into Friday as precip begins. The precip will have a cooling effect on the near surface airmass at least initially as it evaporates and "steals heat" from the near-surface atmosphere, allowing an in-situ damming scenario to occur early Friday while temperatures fall to near or just below freezing. However, without a parent high pressure system continually advecting in sub-freezing air from a cold source region like the Northeast US (instead we will be advecting air originating from the central Atlantic) the subsequent freezing of rain on sub-freezing surfaces will actually release "heat" into the near-surface atmosphere and work to moderate temperatures and limit accumulations. Therefore, this continues to look like a nuisance event that will complicate the Friday morning commute and require extra caution and due diligence, but should be a distant memory by Friday afternoon. Nevertheless, with cloud cover, precipitation, and in-situ wedging in place, temperatures will struggle to reach the lower 40s which is at least 8-10 degrees below normal. We will continue to highlight this event in the Hazardous Weather Outlook as there remains plenty of time for the specifics of the forecast to evolve. The aforementioned system will propagate from the GoMex to the Atlantic in classic "Miller A" fashion during the day on Friday and model guidance is in general agreement that the area will require categorical PoPs until at least Friday evening as the low-pressure system lifts up the Carolina coastline. The 12Z NAM has backed off impressive upslope flow and precipitation accumulations Friday morning and now is more in line with the 12Z ECMWF, which brings the heaviest rainfall into the area, especially along the Blue Ridge Escarpment and east, Friday afternoon into the evening hours while the 12Z GFS dry slots the area, limiting storm-total rainfall accumulations. Continued to lean on the wetter solutions for QPF with widespread 1-2" accumulations expected, though isolated higher amounts of 2-3" cannot be ruled out. Therefore, there is a marginal, low-level flood threat with this system later Friday but confidence remains very low and the threat appears to be isolated in nature. By Saturday afternoon, guidance is in agreement PoPs will be rapidly decreasing and most of the area should be dry to end the period. LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/... As of 245 pm Tuesday: Sunday night, a weak shortwave is expected to quickly follow the rapidly departing and deamplifying shortwave responsible for the short-term weather. This may allow for slight chance PoPs to linger along the NC/TN state line overnight Sunday, but temperatures at this time appear warm enough to support just light rain save for the highest peaks. Thereafter, deterministic guidance agrees that the upper-level pattern will briefly flatten out or become zonal on Sunday while the next shortwave reaches the Desert Southwest. Without a cold airmass behind the system and with westerly flow downsloping off the mountains, high temperatures on Sunday may cool off a degree or two from Saturday but remain 2-5 degrees above normal. With high pressure offshore, flow will gradually veer southeasterly and southerly across the eastern Carolinas on Monday as the next system develops to the lee of the Rockies and ejects eastward. Guidance is in agreement that with favorable southerly low-level flow originating from the GoMex, precip will break out along a warm front stretched out over the Ohio and Lower Mississippi River valleys during the day on Monday. With remnant high pressure wedging down the Blue Ridge spine, there may be some light shower activity along the favored upslope areas Monday into Monday evening and this activity may become a bit more focused Monday night as the system approaches from the west. With increased cloud cover due to weak upglide flow and the weak wedge in place, high temperatures are expected to be a degree or two cooler east of the mountains on Monday. Despite notable differences in the strength and amplitude of the responsible upper-level trough, there is general agreement that the attendant cold front will reach our area sometime on Tuesday and another healthy round of rainfall will accompany its passage, which is currently expected to occur quickly by Tuesday night. There are no notable p-type concerns with this system at this time as we remain underneath relatively warm SWly flow aloft and surface temperatures remain above freezing. However, the ECMWF and the GFS disagree as to how quickly the high-pressure wedge will erode ahead of the system, if at all, with the ECMWF keeping most of the area on the cool side of the system while the GFS brings a warm front through Tuesday morning. This makes temperatures a bit tricky and a blend was favored this far out. For now expect high temperatures to remain anywhere from near normal in the mountains and NC Piedmont and as much as 2-5 degrees above normal further south.