Sunrise 6:36 AM   Sunset 8:05 PM Moonrise 9:06 PM   Moonset 6:19 AM

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FXUS62 KGSP 250731 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 331 AM EDT Thu Apr 25 2024

SYNOPSIS
A weak cold front should stall to our south tonight and Thursday as high pressure moves past to our north. The front will move back northward on Friday and wash out across our area, but giving us a cooler day because of clouds and a few showers. After that, expect a warming trend through the weekend and into next week as high pressure takes over.

NEAR TERM /THROUGH TONIGHT/
As of 315 AM EDT Thursday: The trailing cold front has completed a full fropa across the CFWA and is expected to stall south of the region throughout the daytime period with surface high pressure nosing into the region as the center of the high settles over the Great Lakes region. Weak upper troughiness will be replaced by an incoming upper ridge by the end of the period, with associated vort energy. The stalled boundary will undergo warm frontal activation at this time as a deepening low moves across the central High Plains, while the vort energy helps the warm front to gradually lift north back into the region by daybreak Friday. The aforementioned high will slide over the northeastern CONUS and allow winds to return to a east-northeasterly component overnight, which will set the stage for a wedge-like configuration to filter into the CFWA. At the same time, the favorable upslope locations along the eastern Blue Ridge Escarpment will generate a few light showers by the end of the period before showers become more widespread during the short-term, mainly across the mountains. Afternoon highs today will run at or slightly above normal with mostly sunny skies and a weak downslope component present. Increasing high clouds will filter in very late into the daytime period, but will thicken overnight and start across the eastern BR escarpment and I-40 corridor before spreading further south into the CLT metro and eastern Upstate by daybreak Friday. As a result, overnight lows are expected to run near-normal for most locations.

SHORT TERM /FRIDAY THROUGH SATURDAY NIGHT/
As of 312 AM Thursday: Friday continues to be the most troublesome part of the forecast, as guidance continues to put a sfc high somewhere off the coast of southern New England, in a good spot to support a hybrid cold air damming wedge. The problem is that the synoptic guidance continues to amplify the mid/upper ridge right overhead during the day, which limits the amount of forcing. The GFS still has some productive-looking mid-level isentropic lift, but low levels are nothing to get too excited about. The CAMs go out far enough to include Friday, but limit most of the good chances of precip production to the mtns. That being said, a trend seems to be forming that would have more clouds and probably more shower activity with a light S/SE wind at 850 mb. So, we have cut high temps another few degrees and increased the coverage of relatively modest precip probs, which points us in the direction of possibly not getting out of the 60s Friday afternoon. Light S/SE upslope flow continues into Friday night so a precip chance will be kept near the Blue Ridge Escarpment. By Saturday, the high pressure center should start to migrate south and the isentropic lift will diminish and move away, so we should be able to lose some of the cloud production and consequently see the start of a warming trend. High temps still look right around normal, with some sun in the afternoon.

LONG TERM /SUNDAY THROUGH WEDNESDAY/
As of 201 AM Thursday: The upper pattern is expected to be slowly progressive through the Medium Range, slow enough that the severe weather expected over the Plains/MS Valley region over the weekend never really makes it to us because the pattern also deamplifies and loses energy. While all that is going on to our west Sunday into Monday, the axis of the high amplitude upper ridge moves to the East Coast and supports sfc high pressure off the Southeast Coast
No big changes there
the pattern allows temps to climb maybe a category above normal Sunday and then 5-7 degrees or so above normal Monday. The upper ridge gets pushed offshore by a strong shortwave lifting out of the deamplifying and approaching trof Monday night into Tuesday. That sets us up for some forecast uncertainty with regard to the passage of a dying cold front on Tuesday. This boundary will have the mid-level support of a vort lobe moving through during the day, which should be supportive of at least scattered showers and thunderstorms, so most of the forecast area along and N/W of I-85 gets a chance, but yet the guidance blend brings the high temps up to about 10 degrees above normal. Depending on the trend of the guidance, expect some movement up or down to both. The severe storm potential looks no better than average. Even if the boundary sags through the region, the air mass change looks insignificant, so the forecast for Wednesday looks basically the same with another shot at scattered storms during peak heating, and temps still around ten degrees above normal.

AVIATION /08Z THURSDAY THROUGH MONDAY/
At KCLT and elsewhere: VFR conditions will prevail through the majority of the forecast period. The cold front has sagged south of the terminals with winds going light. Winds have shifted to a north- northeasterly component for the TAF sites, with KAVL maintaining a north-northwesterly wind. Skies are mostly clear for most locations, but mountain valley fog will be possible overnight, but should stay away from KAVL. Mostly sunny skies will be in store Thursday with winds turning the dial to a south-southeasterly component by peak heating as the direction becomes influenced by surface high over the Northeast. Model guidance maintains a northeasterly component at KCLT, which is little surprising, but decided to make winds more easterly than northerly. The front will stall south of the area and act as a wedge boundary overnight. This would set the stage for an increase in clouds overnight tonight, with possible restrictions at the NC TAF sites by or just before daybreak Friday and in all of the Upstate sites at or just after daybreak Friday. Advertising MVFR at the moment for KCLT, but could be lowered to IFR in the 12Z TAF update with a mention at all terminals. Winds will increase as a result and all TAF sites will gain an easterly component overnight as well.

Outlook: Rain and associated restrictions develop Friday as a warm front lifts north across the area. Clouds linger Saturday, along with the potential for isolated mountain convection which lingers into Monday.

GSP WATCHES/WARNINGS/ADVISORIES
GA...None.
NC...None.
SC...None.

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