textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Updated the aviation discussion for the 00z TAF issuance.

KEY MESSAGES

1. Severe threat remains low through Tuesday morning before increasing Tuesday afternoon into Tuesday night ahead of a cold front. Storms may linger into early Wednesday. A warming trend is expected through Tuesday, with slightly cooler highs and lower humidity returning by Wednesday behind the front.

DISCUSSION

Key message 1: Severe threat remains low through Tuesday morning before increasing Tuesday afternoon into Tuesday night ahead of a cold front. Storms may linger into early Wednesday. A warming trend is expected through Tuesday, with slightly cooler highs and lower humidity returning by Wednesday behind the front.

Persistent upper troughing will continue over the eastern United States while a large upper anticyclone dominates over the central and western United States. This "Ring of Fire" pattern will allow storm complexes to round the norther/eastern periphery of the upper anticylcone, diving towards the GSP forecast area overnight tonight and again tomorrow night. Confidence on these storm complexes holding together each night/morning remains low as 06Z CAMs depict them gradually weakening as they push farther south towards the southern Appalachians. As a result, confidence on the severe threat with these complexes remains low, especially overnight tonight into early Monday morning. The SPC Day 2 Severe Weather Outlook has the northern and western tiers of the GSP CWA in a Marginal Risk for early Tuesday morning but again confidence low on whether activity will hold together well enough to lead to a damaging wind threat. Otherwise, only isolated showers and storms are expected this afternoon and early evening with the severe risk remaining low. Mostly dry conditions are expected Monday afternoon and evening but cannot entirely rule out an isolated shower or thunderstorm developing.

The severe threat ramps up Tuesday afternoon and evening ahead of a cold front. However, confidence remains low regarding the severe potential with this front as it will depend on how well the storm complex Tuesday morning holds together as it tracks southward. If the complex weakens significantly and leaves behind less debris cloudiness, then we would have more time for the atmosphere to destabilize during peak heating, allowing for severe storm development. If the complex does not weaken significantly and leaves behind more debris cloudiness, then we would have less time for the atmosphere to destabilize during peak heating as it would take longer for the debris cloudiness to lift. The SPC Day 3 Severe Weather Outlook has a Slight risk in place across western NC, the northern SC Upstate, and extreme northeast Georgia with a Marginal risk in place across a portion of the southern SC Upstate and portion of northeast Georgia for Tuesday. This appears reasonable as if we are able to destabilize enough during peak heating then strong to severe storms can be expected, especially with an abnormally high amount of deep layer shear (30-45+ kts) in place for this time of year. The severe threat could linger into late Tuesday night or even early Wednesday morning but confidence is low as 06Z CAMs do not go out far enough to capture the full event.

The cold front will stall across the Southeast Wednesday through Friday as surface high pressure builds in behind it. This will allow drier conditions to return for the rest of the workweek. Shower and thunderstorm chances look to return over the weekend as the front lifts back northward.

A warming trend is expected ahead of the front through Tuesday, with cooler and less humid conditions returning behind the front starting Wednesday and lingering through the rest of the period. Tuesday still looks to be the hottest and most humid day of the week, especially east of the mountains where heat indices could flirt with Heat Advisory criteria (which starts at 105 degrees). However, confidence on reaching heat advisory criteria is low as lingering debris cloudiness could limit both afternoon temperatures and heat indices.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Other than a few isolated showers over the eastern SC Upstate, the RADAR is clear across our area and all sites are reporting VFR conditions. Other than some overnight/morning re- strictions at our NC terminals, conditions are expected to remain VFR thru the 00z TAF period. I kept TEMPOs in place to account for MVFR/IFR visby and sct to bkn IFR to LIFR cigs at the NC terminals thru daybreak Monday. Any restrictions should sct/burn off by 13z or so. A weakening line of storms is expected to approach our area from the north overnight and into the morning, but it still appears that it will remain to our west and not impact any of our TAF sites. Otherwise, shower/t-storm chances are too low to mention in the TAFs on Monday. Winds will be mostly light and VRB to calm tonight and thru the morning, with most terminals favoring a light, N/NW direction or a WLY direction tomorrow aftn/evening.

Outlook: Showers and thunderstorms may impact our fcst area Tues morning but confidence remains fairly low. Strong to severe storms and breezy SW winds are possible Tues afternoon/evening ahead of a cold front. Storms could linger into early Wed morning, but confidence is low at this time. Low stratus and/or fog will be possible each morning, mainly in the mtn valleys.

GSP WATCHES/WARNINGS/ADVISORIES

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