textproduct: Greenville-Spartanburg

SYNOPSIS

A cold front brings rain and gusty winds today into tonight before drier conditions return behind the front early Friday morning. Gusty winds linger through Friday before diminishing Friday evening. Mostly dry conditions are expected this weekend before precipitation chances return across the North Carolina mountains early next week.

NEAR TERM /THROUGH TONIGHT/

As of 550 AM EDT Thursday:

Key Message #1: A cold front moves toward the area, bringing mostly rain and a brief burst of snow for isolated locations in the mountains.

An area of low pressure develops the northern CONUS, bringing a trailing cold front through the Ohio/TN Valley and into the CWA. Ahead of the front, moisture quickly returns throughout the night and into the morning hours. For areas of the NC Piedmont and portions of Upstate SC, this added moisture and S/SE surface winds help to develop a few rounds of pre-frontal showers. There are a few areas of the far western mountains that could also have a few initial showers during the day. Guidance places the area of greatest QPF response along and east of I-77 after sunrise, before showers spread westward. Current model soundings show little in the way of instability at the surface, with a minimal amount above a surface boundary. There is a very slight chance (15%) of a rumble of thunder in the NC Piedmont east of I-77, but confidence is low given the current guidance lacking any mentionable instability. Showers become even more widespread throughout tonight ahead of the front, expected to come move in Friday morning (next period). Total rainfall for this system through at least 7AM Friday is between 0.25"- 1.25", with the higher amounts in the upslope regions of the western NC mountains. Lastly, the exceptionally small chance of snow has been mostly shunted with the latest guidance bringing in slightly warmer temps. There still could be a quick mix of rain and snow for the highest elevations late tonight, but confidence continues to decrease. If anything were to fall, there's less than a 30% chance for any accumulations over 0.1". So, consider this a mostly rain event.

Key Message #2: Gusty winds develop this evening through tonight, especially at the higher elevations of the mountains.

Another part of this pre-frontal mess are the increased winds. As per typical for the region, the trough swinging south brings strong shear, especially with the CAA behind the front. For this, wind gusts at the highest peaks look to increase toward daybreak, with the potential for 35-45mph and 25-35mph elsewhere in the mountains. Outside the mountains, gusts pick up through tonight, with gusts of 20-25mph likely. These winds are expected to continue to increase past this forecast period and are discussed in the next section.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/

As of 1230 AM Thursday...

Key Message #1: Wind Advisory in effect from 7 AM to 7 PM Friday for Avery County as well as for elevations above 3,500 feet across the majority of the North Carolina mountains, with the exceptions being Henderson and Transylvania counties.

Gusty west/northwest winds will continue across the North Carolina mountains behind a departing cold front on Friday. With gusts expected to range from 45 to 55 mph in Avery County and above 3,500 feet in Madison, Yancey, Mitchell, Swain, Haywood, Buncombe, Graham, Macon, and Jackson counties, a Wind Advisory was issued from 7 AM Friday through 7 PM Friday. Opted to leave out Henderson and Transylvania counties for now as gusts appear to remain below advisory criteria. Winds will be gusty below 3,500 feet as well on Friday but will remain below advisory criteria (less than 45 mph). Gusts will gradually decrease late Friday afternoon into Friday evening before diminishing late Friday night.

Key Message #2: Dry conditions and mostly sunny skies return Friday and Saturday with gusty winds expected east of the mountains through early Friday evening.

High pressure builds in behind the departing cold front from the west Friday into Saturday allowing dry conditions to return area- wide. Mostly sunny skies are expected each day. Gusty west/west- northwest winds will continue east of the mountains on Friday behind the front, ranging from 20 to 30 mph. Gusts will gradually decrease late Friday afternoon, diminishing by early Friday evening. Highs will end up a few degrees below normal across the mountains on Friday, becoming a few to several degrees above normal Saturday. Highs east of the mountains will end up a few degrees normal on both Friday and Saturday. Lows Friday night will be near normal to just below normal across the mountains and near normal to just above normal east of the mountains. Lows Saturday night will end up ~4-8 degrees above normal thanks to increasing cloud cover.

LONG TERM /SUNDAY THROUGH WEDNESDAY/

As of 1245 AM Thursday...

Key Message #1: Dry conditions will continue for most locations through early next week, although some precipitation may return across the North Carolina mountains at times.

A mostly dry cold front pushes across the forecast area early Sunday morning with dry high pressure building in from the northwest behind the departing front Sunday into Monday. The southwestern periphery of the surface high appears to remain over the region Tuesday into Wednesday keeping mostly dry conditions around for most locations. However, global guidance sources depict moisture returning as it rounds the western and northern periphery of the surface ridge Tuesday into Wednesday, which would bring precipitation chances back to portions of the North Carolina mountains. Confidence on exact timing and coverage of precipitation remains low so went with NBM chance PoPs across portions of the mountains for now. Depending on the timing, some pockets of brief freezing rain may develop late Monday night into early Tuesday morning across portions of the North Carolina mountains. Confidence on freezing rain actually materializing remains low. No ice accumulation is expected at this time.

Key Message #2: Above normal high temperatures expected most of the period, with the exception of Monday when below normal highs briefly return.

Highs will run 5-10 degrees above normal east of the mountains on Sunday with temps climbing into the upper 50s to lower 60s. Highs across the mountains should end up a few degrees above normal across most locations Sunday. Much cooler temps are expected behind the cold front on Monday, with highs ending up a few degrees below normal area wide. A warming trend develops Tuesday into Wednesday, with highs ending up a few degrees above normal Tuesday, becoming 10- 15 degrees above normal Wednesday. A warming trend can be expected regarding low temperatures through the long term.

AVIATION /12Z THURSDAY THROUGH MONDAY/

At KCLT and elsewhere: VFR conditions to start with a few locations starting to decrease. A cold front approaching from the west, continues to bring restrictions in for vsby/cigs. Between 12z-16z, expect cigs to plummet into the MVFR/IFR category. -RA moves in from the south and spreads across the area. Confidence is high that showers ahead of the front will keep these restrictions in place through most of the TAF period. RA should start to taper off between 06z-08z, with restrictions slow to improve. Additionally, winds throughout the day should be light to VRB, before picking up after 00z. Gusts of 15-25kts are anticipated at most sites. Winds ahead of the front remain southerly before turning more WSW outside the mountains. KAVL should turn NW after midnight as the front reaches the area. The other concern with this strong front is LLWS. All sites could see LLWS, with KCLT starting earlier at 18z for 20040kt and lasting until 07z Friday.

Outlook: Restrictions improve into Friday night as the cold front moves out and VFR conditions return through the weekend.

GSP WATCHES/WARNINGS/ADVISORIES

GA...None. NC...Wind Advisory from 7 AM to 7 PM EST Friday for NCZ033-048>053- 058-059-062-063. SC...None.