Sunrise 6:24 AM   Sunset 8:15 PM Moonrise 4:20 AM   Moonset 5:53 PM

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FXUS62 KGSP 060741 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 341 AM EDT Mon May 6 2024

SYNOPSIS
The weather pattern will have a summerlike look to it through Wednesday, keeping scattered thunderstorm chances around each afternoon. A strong cold front will approach out of the west on Thursday before tracking across the western Carolinas on Friday, leading to better coverage of thunderstorms towards the end of the workweek. Highs will remain above normal through most of the workweek but will climb well above normal Tuesday into Thursday.

NEAR TERM /THROUGH TONIGHT/
As of 315 am EDT Monday: Latest water vapor imagery and surface analysis indicates occluding/stacked cyclone centered over central Missouri, with remnant warm conveyor belt/deep moist plume extending from the central Gulf Coast through the TN and OH Valleys. As this plume advects over our CWA through the morning, coverage of showers is expected to increase from the SW, and an area of 40-50 PoPs overspreads the forecast area through the morning. Meanwhile, areas just to our west will become dry-slotted during the late morning and afternoon, allowing a combination of strong insolation and a plume of relatively steep mid-level lapse rates to result in strong destabilization...just as height falls are overspreading the region.
Convection will fire in this regime...with some terrain induced initiation also likely across the southern Appalachians...by early afternoon, and is expected to overspread northeast Georgia and the western Carolinas through the afternoon into the evening. Likely PoPs appear warranted across much of the CWA during this time frame.

Convection could arrive in western areas with a bit of robustness this afternoon. However, the environment is expected to be less hospitable to convection over our area owing to morning clouds/precip and relatively modest instability. While shear parameters are improved over recent days...deep layer shear of 25-30 kts (as opposed to < 20 kts the past couple of days)...this won't be enough to allow for anything more than a very isolated severe storm threat...with the upper Savannah River Valley being the most likely area to see a stray downburst and/or large hail event. As flow turns NW aloft this evening, convection-allowing guidance suggests additional waves of scattered showers and storms could drop into western NC from east TN through at least the evening hours, so PoPs remain elevated in the 40-60% range near the TN/NC border during that time, while steadily diminishing elsewhere. Max temps will be slightly above normal, while tonight's lows will again be around 10 degrees above climo.

SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/
As of 230 AM EDT Monday: Weak upper ridging will build across the Southeast on Tuesday before flattening out on Wednesday. This along with W/SW'ly 850 mb flow will lead to well above normal temps through the short term, with the mid to upper 80s expected east of the mountains and the mid 80s across the mountain valleys. Highs should end up ~8-12 above climo, with lows ~13-15 degrees above climo. Diurnal convection can be expected each afternoon and evening so have chance to likely PoPs in place each day. 0-6 km bulk shear should range from 25-35 kts each day, with SBCAPE values from 1500- 2000 J/kg on Tuesday afternoon and 2000-2500 J/kg on Wednesday afternoon. NAM and NAMnest model forecast soundings show DCAPE values from ~900-1200 J/kg each afternoon as well. Thus, strong to severe storms will be possible each day, especially on Wednesday thanks to higher SBCAPE values. The SPC Day 2 Severe Weather Outlook (Tuesday) shows a Marginal Risk for isolated severe storms across western North Carolina which makes sense considering CAMs are mainly producing convection across the NC zones on Tuesday. The SPC Day 3 Severe Weather Outlook (Wednesday) shows a Slight Risk for scattered severe storms across most of the mountain zones with a Marginal Risk for isolated severe storms across the rest of the forecast area.
This looks plausible as coverage of convection should be higher on Wednesday. Damaging wind gusts will be the primary hazard with any severe storms that develop. Some concern will still exist for locally heavy rainfall through the short term, especially for areas that received heavy rain in the days prior.

LONG TERM /THURSDAY THROUGH SUNDAY/
As of 300 AM EDT Monday: An upper trough will approach out of the west on Thursday before swinging across the Carolinas on Friday. At the sfc, a strong cold front will track east over the TN Valley on Thursday before pushing across northeast Georgia and the western Carolinas Thursday night into Friday morning. Convection is expected to develop well ahead of the main FROPA on Thursday so have likely to categorical PoPs in place. The global models have sped up the timing of the cold front compared to the last few runs, with some solutions depicting much more stable air and drier conditions for Friday. The exception is the 00Z GFS which has convection lingering through Friday afternoon. Thus, lowered PoPs to chance on Friday but PoPs may need to be lowered further in future updates if this faster trend holds. Thursday continues to look like one of the more active day of the week in regards to the severe weather potential. The approaching cold front will allow 0-6 km bulk shear values to climb to 35-45 kts, with up to 2,000 J/kg of SBCAPE in place Thursday afternoon. Forecast soundings from the GFS depict ~1,000 J/kg of DCAPE as well on Thursday afternoon, so damaging winds will be the main concern with severe storms. The locally heavy rainfall threat will return once again on Thursday thanks to 90th percentile (or greater) PWATs expected ahead of the FROPA. However, faster storm motion help offset this potential somewhat. The only kink in the severe potential at this time is that widespread cloud cover is expected to be in place on Thursday, which may limit destabilization a bit. However, with a 40 kt 850 mb jet tracking over the western Carolinas on Thursday (per the GFS), upper support should make up for the lack of insolation. Temps will remain above climo Thursday into Thursday night, but will be slightly cooler compared to Wednesday/Wednesday night thanks to convection and cloud cover.

Global models show dry high pressure building into the region out of the west behind the departing front Friday night into Saturday. The 00Z ECMWF and Canadian show another system impacting the forecast area on Sunday, but the 00Z GFS does not have this system impacting the area until after the forecast period. Thus, confidence on PoPs will be low towards the end of the forecast period. Cooler temps are expected to return this weekend, trending a few degrees below climo for both highs and lows.

AVIATION /08Z MONDAY THROUGH FRIDAY/
At KCLT and elsewhere: Spotty showers continue across the Terminal Forecast Area early this morning. Chances for a direct hit on any TAF site are remote through about daybreak. After that, increasing moisture from the west will bring increasing shower chances...with perhaps a TS or two, mainly to the upstate SC terminals. Low cigs and visby restrictions should develop across much of the area toward daybreak...although confidence in timing and magnitude of these restrictions is below average
Expect IFR cigs at most sites
with perhaps brief LIFR conditions. Cigs should improve through the daylight hours, with VFR conditions expected by early afternoon.
Convection is again expected to initiate across the mountains around mid-afternoon. Stronger steering currents today should result in convection dropping E/SE into the foothills and Piedmont during the late afternoon and evening. Additional round(s) of convection could move into the area from the northwest into the evening and early part of the overnight hours.

Outlook: Enhanced moisture will combine with a weak/stalled front through the middle of the week, resulting in a period of active/mainly diurnal convective weather each day. There will also be the potential for restrictions associated with widespread fog and/or low clouds each morning. A cold front moves in for later in the work week with continued chances of diurnal convection.

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

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