textproduct: Greenville-Spartanburg

SYNOPSIS

Precipitation will move off to the east by the middle part of the day. After that, precipitation chances and below-normal temperatures linger through the first part of next week. Temperatures trend back toward normal by the middle of next week. Another cold front may bring precipitation back to the area late next week.

NEAR TERM /THROUGH TONIGHT/

As of 6:15 AM EST Friday...

Key Messages:

1) Wintry precip expected across portions of the NC mountains and possibly into portions of the NC Foothills this morning. A mix of snow, sleet, and freezing rain is possible in the mountains, with freezing rain possible in the Foothills.

2) A Winter Weather Advisory remains in effect this morning for portions of the NC mountains (no changes from previous fcst).

3) Precip will change over to rain and should taper off by late this morning, however cold and cloudy conditions will continue thru the day.

The center of a 1030 mb sfc high will track into Upstate NY and weaken as it reaches the New England coast later today. This high will produce a hybrid cold air damming wedge into the Carolinas. Meanwhile, cyclogenesis will occur along the central Gulf Coast and increase isentropic lift along a stalled frontal boundary draped over the Southeast. The low will quickly track east along a baro- clinic zone to the Carolina Coast overnight and into the morning. Forcing still doesn't look very strong, so QPF is expected to be light, but coverage still looks broad across our CWA. Overall, low- level thicknesses have been trending a bit warmer across most of our northern zones, so it remains to be seen if we end up getting much in the way of snow over those zones. Regardless, a warm nose will develop from the SW by daybreak and should change precip over to mostly rain and/or freezing rain. No significant changes were seen in the latest guidance wrt sfc temps or QPF, so the current Winter Wx Advisory still looks good. Low temps overnight will lock into the upper 20s to lower 30s in the high elevations and along the eastern NC Escarpment, with mid to upper 30s elsewhere.

By this afternoon, the upper shortwave will exit to our east and take the better isentropic lift with it. Sfc low pressure will begin to deepen near the Outer Banks, but a residual CAD wedge will likely linger thru the rest of the day. Precip chances taper off from NW to SE later this morning, but low clouds and fog will persist, keeping temps in the upper 30s to mid 40s for most of our fcst area this aftn. All but the highest peaks/ridges of the northern NC mtns are expected to get above freezing later today.

SHORT TERM /SATURDAY THROUGH MONDAY/

As of 1247 AM Friday:

Key Messages:

1) Some light rain possible again Saturday, mainly south of I-85.

2) Temps remain below normal.

3) Another chance of light precip Sunday night and Monday morning, with some wintry types possible, mainly over the mountains.

The latest model guidance continues a trend away from precip on Saturday as more of the region will be on the wrong side on a jet axis streaming overhead. Areas to the south of I-85 might still have enough favorable jet dynamics from a broad right entrance region to allow for some light precip to develop, but it's really only the Canadian that has the northern edge of the light precip far enough north to affect the southern parts of the forecast area. The rest of guidance, including most of the GEFS members, have the northern edge to the south. With that in mind, I expect the model blend to continue to trend toward a drier day, but still probably cloudy with lots of high jet streak cloudiness streaming overhead. Temps should stay below normal for the weekend.

Sunday poses another problem. The GFS indicates another jet streak moving out of the very broad upper trof and streaming overhead again Sunday, with additional upper divergence. Another ill-defined short wave and sfc reflection will also move along a stalled boundary well to our south. There's actually a bit more support from the synoptic scale models and especially from the GEFS to introduce another chance of light precip across the I-85 corridor and south during the day, but the NBM hasn't caught up to that idea yet. The guidance suggests a trend toward more clouds and increasing precip chances over the southeastern half, but fortunately that would be all rain as thicknesses and profiles don't support anything else.

Which brings us to Sunday night and Monday. One final (and stronger) short wave comes around the bottom of the upper trof to our west during that time and should be the agent to swing the trof axis across the region on Monday. This wave looks to track farther north and is more dynamic than the ones over the weekend. There are timing differences that come into play between the arrival of the forcing and moisture associated with the wave and a surge of cold air from the north that would influence the precip-types. As it stands right now, the wave gets here before the cold air with enough moisture to be wrung out into some light precip developing W-to-E, but wintry types are mainly limited to the high elevations and maybe the I-40 corridor east of the mtns. But, some light precip, in the form of snow, would be within the realm of possibilities if the short wave is delayed and the cold air arrives first. A few GEFS members show that scenario. Either way, in the forecast, the precip types were limited to rain/snow based on consideration of thermal profiles in the NAM and GFS. The QPF looks light, so even places that got some light snow, it would be sub-advisory.

LONG TERM /MONDAY NIGHT THROUGH THURSDAY/

As of 1253 AM Friday: A very broadly cyclonic upper flow on Tuesday looks to oscillate with brief amplification as nrn stream waves periodically pass by to our north. Confidence in the timing of these waves is weak. We should at least start out with a period of fair weather Tuesday and Wednesday with temperatures attempting a warming trend back toward normal for mid-week. The first clipper-like nrn stream wave may pass by Wednesday night and push a boundary across the region, resulting in some low-end precip chances, but outside the mtns even a slight chance looks like a stretch. In reality, probably only the TN border zones stand much of a chance for an elevation-dependent rain/snow of low amount. Another wave may dig the upper trof again Thursday night/Friday, perhaps, but this timing is even more uncertain. For that reason, we carry only unmentionable precip probs in spite of what the new GFS shows. Either way, temps remain on the cool side of normal.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: Expect restrictions to persist thru most of the 12z taf period. A broad area of sct light to moderate pre- cipitation continues to move over our eastern and southern zones as we approach sunrise this morning. The precip should move east of our area over the next few hrs, but I kept a PROB30 for RA at most terminals thru 18z. At KAVL, the PROB30 only goes thru 15z. Deeper moisture is expected to linger over the area today/tonight with cigs remaining IFR to LIFR thru most of the taf period. Visby is more likely to remain in the MVFR range today and then go IFR to possibly LIFR later tonight with light to calm winds. Otherwise, winds will be light thru the period and generally out of the NE out- side of the mtns. Expect winds to go light and VRB to calm at most sites later tonight/early Saturday. At KAVL, winds will remain light and favor a S/SE direction today, going calm later this evening.

Outlook: A brief break in restrictions is expected Saturday aftn thru early Sunday. Another storm system may bring more precip and associated restrictions Sunday into Monday. Drying high pressure is expected to spread back over the area by early Tuesday.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Winter Weather Advisory until 1 PM EST this afternoon for NCZ033-049-050-501-503-505. Winter Weather Advisory until 10 AM EST this morning for NCZ048-052-053-059-063-064. SC...None.