textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Trending slightly warmer for highs and slightly lower for relative humidity this afternoon.

Confidence is increasing for very gusty winds and northwest flow snow showers across the mountains behind a strong cold front Sunday into Sunday night.

KEY MESSAGES

1. A cold front brings scattered showers this morning, with drier conditions developing briefly behind the front this afternoon before rain chances return this evening into tonight. Gusty winds linger through this evening before lighter winds return tonight. 2. Rain chances over the weekend with generally light amounts and minor to no impacts expected. 3. A brief return of winter with gusty NW winds, snow for portions of the mountains and below normal temperatures expected Sunday through Tuesday night.

DISCUSSION

Key message 1: A cold front brings scattered showers this morning, with drier conditions developing briefly behind the front this afternoon before rain chances return this evening into tonight. Gusty winds linger through this evening before lighter winds return tonight.

A cold front will track across the western Carolinas and northeast Georgia this morning before stalling across the southern and eastern fringe of the forecast area this afternoon into tonight. This will allow two rounds of rain to impact the area; the first round will occur this morning and the second round will occur this evening into tonight. Brief drying will develop early this afternoon into early this evening in-between the two rounds of rain. Could not rule out some rumbles of embedded thunder within showers throughout the morning hours, as the 00Z CAMs show 200-500 J/kg of SBCAPE developing ahead of the front. Occasional embedded lightning flashes have been noted within the line in east TN this morning, so a slight chance of thunder will be included over the mtns. Severe weather seems unlikely, but some strong gusts have been noted over east TN with the passage of the line. However, SBCAPE will diminish behind the front so thunder is not expected with the second round of showers tonight.

This front will also keep gusty winds around through much of today. With a 40-45 kt 850 mb jet tracking over the region this morning, blended in some the NBM 90th percentile for wind gusts. Gusts will range from 20-35 mph for elevations at/below 3,500 ft and 35-45 mph for elevations above 4,000 ft. Higher ridge tops, generally at/above 5,000 ft, could see gusts up to 50 mph. Since advisory level gusts (which are >46 mph) are mainly confined to elevations of 4,000 ft to 5,000 ft, a wind advisory will not be issued at this time. Gusts across the lower elevations will gradually taper off by the early evening hours. Gusts across the higher elevations will remain elevated through early this evening before gradually tapering off tonight.

Another round of record breaking highs are possible today, mainly east of the mountains. Both KCLT and KGSP will have the potential to break their record highs again this afternoon as rain exits to the east this morning and as cloud cover thins behind the front during peak heating hours.

Key message 2: Rain chances over the weekend with generally light amounts and minor to no impacts expected.

The general pattern going into Saturday has quasi-zonal flow aloft and an area of high pressure off the east coast. The CWA sits on the western fringe of the high pressure, leaving weak forcing for any truly mentionable weather. At this time, guidance does strike up a few showers that pass quickly over most of the area Saturday. Current model soundings show little in the way of instability for the majority of the CWA, but a rumble of thunder cannot be ruled out in the far southern zones. Best chances for rain look to be east of the mountains as PoPs continue to be higher in the 60-80% range. However, QPF response looks minimal with a 40-50% chance of areas along and south of I-85 receiving a rainfall total of at least 0.25". A few areas could receive higher amounts, especially if any instability can develop. Temperatures remain warm and well above freezing, so p-type for this system is expected to remain all rain.

Key message 3: A brief return of winter with gusty NW winds, snow for portions of the mountains and below normal temperatures expected Sunday through Tuesday night.

By Sunday, a brief pattern change is in store for the area as a strong cold front makes a run for the CWA, bringing very gusty winds and NW flow snow for the TN/NC border. Aloft, the quasi-zonal flow moves eastward in response to a developing trough and area of low pressure forming over the south. Model guidance develops the low and drives it northeast, bringing rain to most of the area, with snow at the usual peaks of the TN/NC border along the backside of the departing system Sunday night. At this time, there is a 30-40% chance of snowfall amounts exceeding 1 inch in these locations, especially for the usual areas of Avery and Swain counties. Two shots of NW flow snow are possible. The first is at the onset of the cold front late on Saturday night with a brief lull before picking up again on Sunday night. The system looks to lift out of the area by early on Monday. Aside from snow, QPF for rainfall is trending lower, with a 20-30% chance of exceeding 0.25". Overall, this system looks to bring a few rounds of NW flow snow and a small amount of rainfall, with minor impacts expected. The main impacts look to be slick roads where snow falls. Additionally, winds with this system look to be very gusty in the mountains Sunday into Monday as the trough swings across the CWA. The higher peaks have a higher probability (80-90%) of winds gusts exceeding 45 mph. A Wind Advisory may be needed.

Behind the system, a strong cP airmass spills eastward, ushering in cold temperatures and wind chills. Monday highs look to be well below normal. At this time, winds could create wind chills in the single digits across the mountains. However, temps should remain above any Cold Weather Advisory criteria. Will continue to monitor.

AVIATION /12Z FRIDAY THROUGH TUESDAY/

At KCLT and elsewhere: Watching a weakening line of showers with a few embedded storms moving over the border between TN and NC at this hour. Will extrapolate for the timing of this band relative to all the terminals. At this point, a TEMPO seems prudent for the associated restrictions, and will try to fine tune the timing down to a 2 or 3 hour window. Dry conditions will gradually return from west to east behind the front during the mid to late morning hours. Wind direction east of the mountains will remain SW through the morning before toggling more W/WSW this afternoon. Wind direction across the mountains will remain S/SW through daybreakbefore turning NW behind the front ~14-16Z. Gusty winds return late tonight and will linger through early Friday evening, ranging from 18-25+ kts.

Outlook: Rain chances and associated restrictions return this weekend. Gusty winds return Sunday into Monday night. Restrictions should end Monday for all but KAVL where low clouds may linger.

CLIMATE

RECORDS FOR 02-20

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 75 1939 26 1908 54 2018 4 2015 KCLT 77 2014 31 2015 59 1939 7 2015 1890 KGSP 75 2014 33 2015 57 1939 9 2015 1986

GSP WATCHES/WARNINGS/ADVISORIES

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