textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Increased wind gusts and high temperatures for Wednesday.

The frontal passage Thursday morning comes in slightly slower compared to previous forecast.

KEY MESSAGES

1. Isolated showers mainly across the mountains through tonight. Record highs and gusty southwesterly winds Wednesday. 2. A strong cold front arrives Wednesday night into Thursday morning bringing widespread showers and thunderstorms, with a very low-end severe weather threat. Cooler and drier conditions will spread over the region behind the front through the rest of the workweek. 3. Dry conditions will persist the first half of the weekend before another cold front arrives Sunday into Monday, with a return of colder weather for the early part of next week.

DISCUSSION

Key message 1: Isolated showers mainly across the mountains through tonight. Record highs and gusty southwesterly winds Wednesday.

High pressure slides eastward through the evening as a weak warm frontal feature moves north across the mountains. Isolated to possibly scattered showers will move across the mountains in the weak lift associated with the warm frontal feature. Isolated showers are possible elsewhere, but will be few and far between. Can't rule out a rumble of thunder, but the chance is very low. Lows will be near the normal high temps for this time of year.

Precip chances diminish Wednesday with a weak cap in place and lack of forcing. Very gusty southwesterly winds develop across the area, but should remain below advisory level. Highs are currently forecast to break records at all three main climate sites.

Key message 2: A strong cold front arrives Wednesday night into Thursday morning bringing widespread showers and thunderstorms, with a very low-end severe weather threat. Cooler and drier conditions will spread over the region behind the front through the rest of the workweek.

Rapid height falls accompanying a central CONUS upper trough will be in the midst of propagating eastward with an attendant cold front encroaching the area Wednesday night into Thursday morning as the deepening parent low shifts across the Great Lakes into Atlantic Canada. Deep southwesterly flow ahead of the the front will pull in plenty of moisture. However, a lot of the associated synoptic forcing lifts north with the parent low and most of the models bring the front into the region during the coolest part of the diurnal cycle. Latest guidance have a narrow band of 100-200 J/kg of SBCAPE to go along with 55-65 kts of deep layer shear, which is a slight uptick from the previous forecast as a potential QLCS/disorganized line of convection moves into the region. Seems apparent that any type of organized convection will be most prominent over the immediate Tennessee border overnight Wednesday and lose its "oomph" as it progresses further east across the mountains and into the Piedmont zones by Thursday morning as it loses instability and better forcing for ascent. Can't rule out a few strong to severe storms with this line of organized convection, but confidence isn't high enough to go beyond the current Day 2 Marginal Risk for severe across the North Carolina mountains Wednesday night (before 12Z Thursday).

Post-frontal regime is expected following a complete fropa by Thursday afternoon as strong CAA spreads across the CWFA with much drier and cooler air. Gusty winds are expected across the NC mountains, with the potential for light northwest flow snow over the highest peaks and ridgetops along the NC/TN border Thursday morning as shallow low-level moisture lingers behind the front while the cold air rushes in. Any accumulations will be minimal, but temperatures will be noticeably cooler as afternoon highs will be 15-20 degrees cooler compared to Wednesday. Overnight lows Thursday night are forecast to be 5-10 degrees below normal with widespread 30s across the area and below freezing temperatures in the mountains.

Continued dry weather lingers through the end of the workweek as a transient surface high shifts across the region Thursday night and offshore the Carolina Coast by Friday, allowing for a southwesterly return flow to pick back up as temperatures warm up a few degrees Friday afternoon.

Key message 3: Dry conditions will persist the first half of the weekend before another cold front arrives Sunday into Monday, with a return of colder weather for the early part of next week.

A weak backdoor front approaches the region Friday, but only an uptick in gusts will be the main impact over the higher terrains. Guidance quickly undergoes warm frontal activation before a complete fropa occurs, leading to continued warming on Saturday as weak southwesterly flow persists. This should allow for an uptick in PoPs by Sunday afternoon as the environment will be conducive to convective development ahead of the next cold front. Rapid cyclogenesis will take place on the lee of the Rockies on Sunday as the low traverses across the lower Midwest and over the Lower Great Lakes Sunday night into Monday and the attendant cold front approaches the region. Any organized convection with this system will be dependent on the time of day it pushes through the area and whether or not the associated forcing is sufficient. Another cold snap is expected for early next week behind the front. Temperatures ahead of the front will be 6-12 degrees above normal.

AVIATION /18Z TUESDAY THROUGH SUNDAY/

At KCLT and elsewhere: VFR conditions are forecast through the period. Some spotty showers will linger across the mountains this afternoon, so VCSH in place at KAVL. Guidance showing little in the way of convection through the evening elsewhere, but still shows some around KCLT in the 00Z time frame. Have adjusted the PROB30 there to match. TS is looking unlikely at this point. Otherwise, VFR stratocu lingers across the mountains with more FEW to SCT elsewhere. BKN low altocu or high stratocu moves in overnight. Isolated showers will brush the mountains overnight or early Wednesday, but chance too low for the KAVL TAF for now. Mainly cirrus expected Wednesday, but some lower VFR may linger. Low end gusty SW winds for the SC sites with a NNW wind at KAVL this afternoon. KCLT winds are quite variable but should settle in at WNW with light and variable at KHKY. Light SW wind, NNW at AVL, expected overnight. Gusty SW winds develop on Wednesday, SSW at KAVL.

Outlook: SHRA/TSRA chances and associated restrictions return Wednesday night into early Thursday with a cold front. Gusty winds continue into Thursday. Dry conditions return Thursday night into Saturday. Another cold front may bring showers and associated restrictions Sunday.

CLIMATE

RECORDS FOR 03-11

MAX TEMPERATURE MIN TEMPERATURE STATION HIGH LOW HIGH LOW ------- ---------- ---------- ---------- ---------- KAVL 79 1967 29 1924 55 2016 14 1934 1925 KCLT 83 2015 37 1960 60 1986 22 1969 2009 1934 1990 KGSP 84 2009 34 1960 60 1986 17 1969

GSP WATCHES/WARNINGS/ADVISORIES

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