textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Minor adjustments to evening precip chances and revised overnight fog forecast.

Dry Friday.

KEY MESSAGES

1. Showers taper off from NW to SE this evening as a cold front crosses the area. Low clouds and patchy fog, some possibly dense overnight. Clouds slowly lift through the day Friday. 2. Dry and warm through the weekend with cooler and wetter conditions to start next week.

DISCUSSION

Key message 1: Showers taper off from NW to SE this evening as a cold front crosses the area. Low clouds and patchy fog, some possibly dense overnight. Clouds slowly lift through the day Friday.

Prefrontal convergence/baroclinic zone now near I-20 is associated with a west-east band of rain with a couple of embedded t-storms. Though drier midlevel air has reached the northern two thirds of the CWA with an ill-defined cold front, we still have not seen airmass change, and low levels remain moist, with patchy low cloud cover still present over most of the Piedmont. Scattered showers and storms, some severe, are ongoing in northern MS/AL, where the cold front is making more rapid progress as it interacts with a second shortwave embedded in the mean low-amplitude trough aloft. Will have to monitor progress of these storms as they track east, though loss of diurnal heating should weaken them and we may not have enough MUCAPE to sustain them as it is. The approach of the shortwave does still look to reactivate the front to some extent and bring stratiform precip with embedded isolated storms back north into the area overnight.

Expect the low level flow to weaken and turn northeasterly as the sfc front slowly sags southward overnight. Copious low level moisture lingers and a low level inversion develops. This will keep low clouds across the area with patchy fog, some possibly dense by morning. Expect the fog to dissipate by noon Friday, but low clouds could linger through the day, especially outside of the mountains, but the bulk of the day should be dry. Right now, have highs around 5 degrees above normal across the mountains and near normal elsewhere. That said, highs could be lower, especially outside of the mountains depending on how long the fog and low clouds last.

Key message 2: Dry and warm through the weekend with cooler and wetter conditions to start next week.

By this weekend, a mean longwave trough will be draped from the Canadian Rockies across the Northern Plains and into New England. Weak flow will extend across the southeast states in the far southern portion of the base of the trough. The trough axis will shift east of the region through the weekend with rising heights and quasi-zonal westerly flow. This will allow for temperatures to warm back to above seasonal average for late February with mid 60s to mid 70s common, especially by Sunday. A notable pattern change occurs by the start of the new week, however. A sprawling 1040mb surface high will shift from out of the Midwest into the Mid-Atlantic/New England with a resulting Cold Air Damming wedge setting up shop over the Carolinas and northeast Georgia. At the same time, a belt of weak, but perturbed, southern stream flow will reside from the Southern Plains into the Southern Appalachians. A weak lead wave will translate across the region on Monday with a return of precipitation chances. Subsequent waves may bring additional rounds of precipitation Tuesday into Wednesday, but forecast confidence rapidly wanes as global model guidance diverges with respect to the synoptic evolution. Thermal profiles may support a wintry mix across the highest mountain elevations/northern mountains, but confidence is too low to warrant much more than a brief mention in the forecast. Otherwise, temperatures elsewhere are currently forecast to be too warm for any wintry mischief. Speaking of temperatures, Monday will be a rude awakening with chilly highs in the CAD wedge that may be upwards of 20-25 degrees colder compared to Sunday.

AVIATION /00Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: Patches of both stratocu causing varying IFR to low MVFR cigs around the area, with VFR at KAVL and KAND at 00z. In general some brief improvement is possible this evening where these cigs are in place. Band of SHRA across GA and central SC could shift northward again later this evening and possibly reintroduce precip and lower cigs near KAND. Though cold front will make slow southward progress across the terminals overnight, it looks unlikely to lead to significant drying near the surface, and as higher altitude clouds advect out radiational cooling looks capable of causing widespread IFR to LIFR cigs to develop overnight. Some areas of fog/cigs at or below minima are possible. Except for KAVL, LIFR to VLIFR forecast at some point overnight. Light SW winds will turn NE behind front with some variability possible in between. Slow improvement through the morning, with MVFR cigs returning by mid-afternoon Fri. KAVL and KHKY have better access to dry air and hence see cigs scatter by 16-17z Fri.

Outlook: Restrictions could redevelop in some areas Friday night, but dry and VFR conditions should return by Saturday. Another front may bring showers and associated restrictions Monday into Tuesday.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...None. SC...None.