textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Confidence is increasing that axis of heaviest rainfall has shifted out of the NC mountains and into the SC Upstate and NE GA.

Confidence remains low on rainfall amounts and also on any severe weather threat Thursday into Thursday night.

The aviation discussion was updated for the 12Z TAF issuance.

KEY MESSAGES

1. Rain chances increase again Thursday into Friday as the remnants of a tropical low approaches the area from the Gulf. Locally heavy rainfall and damaging winds cannot be ruled out. Drier conditions return over the weekend behind a cold front.

DISCUSSION

Key message 1: Rain chances increase again Thursday into Friday as the remnants of a tropical low approaches the area from the Gulf. Locally heavy rainfall and damaging winds cannot be ruled out. Drier conditions return over the weekend behind a cold front.

Upper shortwave trough is currently crossing the central and southern Appalachians and will exit to the east by daybreak. Flow will veer to W/NWLY in its wake this morning, helping clear out the clouds and keep dry conditions across the CWFA today. Temps will rebound under mostly sunny skies, but humidity will stay in check, as air remains relatively dry.

A vigorous shortwave will dive into the Great Lakes and help deepen a broad 500 mb longwave trough axis across the MS Valley region. While the bulk of the energy will stay well to our north, there will be enough height falls for the trough to pick up a tropical disturbance out of the NW Gulf and start steering it east across the Gulf states. Southwesterly 850 mb flow increases ahead of the deepening trough and tropical wave, making for an unusually windy day for mid-June across the region. Wind gusts of 25-35 mph look likely Thursday aftn. The latest global models are in better agreement on timing the low thru GA and the Carolinas Thursday evening thru Friday aftn. However, they still disagree on how far north it will track. The GFS continues to be weaker and further south, while the ECMWF is still on the stronger side and a little north. The Canadian is close to the ECMWF with a stronger meso-low and shows an axis of heavy rain roughly along the I-85 corridor, as it track by Thursday night. The GFS and ECMWF has a similar QPF swath, but a little south. The latest NBM QPF has trended a little south with axis of heaviest rainfall, showing 1-2" of QPF across the southern Upstate and the GA Piedmont.

As for severe weather threat: Energy from these two systems should support convection along/ahead of the tropical remnants, as leading edge environment should become fairly unstable. Shear profiles are still rather marginal for organized convection, as forecast soundings show strong low-level flow with weak mid-level flow, which may result in convection struggling to balance along outflows. The 00z CAMs show an MCV signature on the simulated reflectivity, but strongest convection remaining largely south of the CWFA. In any case, damaging wind gusts looks to be the main threat. A cold front will push in from the NW late Thursday night thru Friday morning. The latest guidance suggests the front may be about to exit the CWFA to the southeast by peak heating. But the SE edge of the area may see some redevelopment of convection Friday aftn. The new Day 3 Convective outlook has a marginal risk to our south. Temps will be at or slightly above normal Thursday, and near to slightly below normal Friday.

The weekend looks largely dry with near normal temps under a quasi-zonal flow and weak sfc high crossing the Mid-Atlantic. Could see at least scattered diurnal convection across the mountains Sunday, as moisture increases ahead of the next front. That front could bring more widespread showers and storms Monday. Temps will be near normal thru the weekend and early next week.

AVIATION /12Z WEDNESDAY THROUGH SUNDAY/

At KCLT and elsewhere: LIFR to IFR stratus has really expanded across portions of the Upstate, southern NC Piedmont and the mountain valleys. The clouds should dissipate within an hour or so after 12z. Will continue with TEMPOs for the low cigs thru 13z, where the clouds can be seen on satellite imagery. From there, VFR conditions should prevail thru this evening. Winds will pick up out of the SW by midday, with low-end gusts possible across the Upstate and KAVL late aftn. SW winds will stay up tonight, and some guidance guidance suggests gustiness continues or begins overnight. Latest guidance still not in great agreement on MVFR to IFR stratus redeveloping tonight across NE GA and into the Upstate. Confidence is highest on some MVFR cigs at KAND developing between 06-12z Thursday. Once again, KCLT will be on the edge, and will have just few015 late tonight in the 12z TAF.

Outlook: MVFR to IFR cigs are expected to scatter out again Thursday morning. Gusty SW winds expected across the area thru the day Thursday. More widespread convection is expected across the area Thursday afternoon through Friday. Dry weather returns for the weekend.

GSP WATCHES/WARNINGS/ADVISORIES

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