textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

No significant changes to the forecast with this update.

The aviation discussion was updated to reflect the 12Z TAF issuance.

KEY MESSAGES

1. A cold front crosses the area today, bringing scattered showers and a few embedded thunderstorms. Relatively little rain is expected with this system, and severe risk remains minimal. 2. Another weak cold front may bring a few more showers and thunderstorms to the western Carolinas Wednesday. Otherwise, dry weather is expected with temperatures warming back above normal next weekend.

DISCUSSION

Key message 1: A cold front crosses the area today, bringing scattered showers and a few embedded thunderstorms. Relatively little rain is expected with this system, and severe risk remains minimal.

A broad, positively tilted upper trough will cross the area today, providing some lift for clouds and precip. An associated cold front will slip thru from the north during the first half of the day, likely reaching the far southern part of the CWFA by peak heating this aftn. West-southwesterly flow ahead of the front is not advecting much moisture into the area, and model guidance is in good agreement on limited instability for convection. There is less than a 30% chance of sbCAPE >500 J/kg per the HREF and NBM probs. So while thunder cannot be ruled out, the vast majority of activity will be just showers. Given the lack of instability and elevated nature of the convection, the severe threat will remain very low. And QPF continues to look paltry, with 20% or less chance of 0.25" of rainfall today, highest along the northern tier of zones in the CWFA. The 00z CAMs are coming in showing showers entering the NC mountains from TN early this morning, then scattered showers popping up north of the sfc front across the rest of the mountains and into the Piedmont thru the aftn. Nothing looks organized, and QPF is somewhat spotty. Temps will be slightly below normal today under mostly cloudy skies and increasing N to NE wind. Showers should taper off and/or exit to our east by around sunset, with clouds lingering thru the evening. Clouds should clear out and winds become light, allowing min temps in the 40s in the mountains upper 40s to mid 50s in the Piedmont tonight.

Key message 2: Another weak cold front may bring a few more showers and thunderstorms to the western Carolinas Wednesday. Otherwise, dry weather is expected with temperatures warming back above normal next weekend.

A potent shortwave trough will dive SE through the Ohio Valley to the Mid-Atlantic Wednesday, bringing a fast-moving cold front thru the CWFA. The front will not have much moisture to work with, but models have been consistent on developing a band of convection along the boundary upstream of the Southern Appalachians and taking that activity into the NC mountains Wednesday aftn. There has been a trend in the guidance toward a thin plume of higher PWATs nosing north across the Carolinas and into the Mid-Atlantic. This may be enough moisture to support convection redeveloping along the front as it track east across the Piedmont. As a result, the NBM PoPs have trended up a bit across the I-77 corridor. CAPE still looks limited, with LREF probs still showing only a 30-40% chance of >500 J/kg of sbCAPE along the I-85 corridor Wednesday aftn/eve. But bulk shear increases to around 50-60 kt, so if instability trends up, there may be a non-zero severe threat with any convection that does manage to develop east of the mountains.

Once the shortwave ejects to the east, models are trending toward a large closed low forming over the northern Mid-Atlantic Thursday into Friday. Increased northerly flow on the back side of the low may help keep temps near normal for a couple days with dry conditions. Then the low departs and is replaced by upper ridging over the Southeast. Confidence is fairly high that temps will warm above normal next weekend, with highs possibly approaching 90 across portions of the Piedmont by Sunday.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR conditions are expected to prevail through the forecast period at all terminals. A frontal boundary will push across the area today with an associated band of high clouds overspreading much of the region early this morning. Isolated to widely scattered showers will also be possible this afternoon, but coverage should remain limited with little to no restrictions. High clouds will slowly shift east through the period, but at least some will hang on into tonight. Otherwise, calm to light winds this morning will increase into the 7-10kt range out of the north behind the front with a few instances of low-end gusts possible.

Outlook: After the front, dry conditions persist through early Wednesday. A clipper-type low may cross to our north late Wednesday, but guidance suggests rainfall will be paltry with this system, and it's questionable whether any flight restrictions will develop.

GSP WATCHES/WARNINGS/ADVISORIES

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