textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The aviation discussion was updated to reflect the 00Z TAF issuance.

KEY MESSAGES

1. Dry weather tonight, before a cold front brings scattered showers and a few embedded thunderstorms to the area on Monday. 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 into Thursday. Temperatures warm back above normal next weekend.

DISCUSSION

Key message 1: Dry weather tonight, before a cold front brings scattered showers and a few embedded thunderstorms to the area on Monday. Relatively little rain is expected with this system, and severe risk remains minimal.

Quiet weather is expected overnight.

Otherwise, several low-amplitude z500 features will phase together this evening and coalesce into a single defined trough axis over the central Great Plains, and then vigorously push eastward through tonight. Guidance agrees well on the placement of a positively-tilted and deamplifying trough axis extending from the Mississippi delta area into the central Ohio Valley by 12z Monday. The associated surface front will approach the western Carolinas tonight and cross the area through the first half of Monday, with a cooler, postfrontal air mass slipping into the area by Monday night.

The CAMs are not impressed with any severe potential associated with the front. Given the timing - with both the strongest upper forcing associated with the trough, and the frontal circulation itself both crossing the area near the diurnal minimum - ensembles depict fairly limited instability, with the most aggressive scenario featuring a slower frontal passage and destabilization across the eastern 2/3 of the forecast area by mid/late Monday morning. Even then, the probability of >500 J/kg sbCAPE is very limited. Ensembles featuring a faster FROPA depict an even bleaker scenario for convection, with less destabilization. Both the 12z GFS and recent RAP cycles depict a developing axis of low-level convergence moving from the upper Savannah River Valley into the southern Upstate on Monday afternoon...perhaps providing some marginally-better conditions for convective intiation there during the afternoon. Still think that the severe threat is minimal, however, given such a feeble convective environment. Some convective rain rates could nonetheless develop within any areas where elevated instability develops as variously featured in forecast profiles, but even then, QPF response comes to a paltry 0.1-0.15" for most of the area, barely a drop in the bucket against a remaining 3-7" of rainfall deficit across the region.

Key message 2: Another weak cold front may bring a few more showers and thunderstorms to the western Carolinas Wednesday into Thursday. Temperatures warm back above normal next weekend.

Broad upper trofing will move off the Atlantic Coast on Tuesday with the backside of the trof getting reinforced on Wednesday and Thursday. At the sfc, an elongated cold front moves east of our area Tuesday as broad high pressure spreads over the region from the north. Another weak cold front will move thru our area Wednesday into Thursday and could produce some sct showers and/or a few thunderstorms, mostly over our northern zones. Any precip amounts will likely be minimal (ie, < than 0.1 inches for most locations). Dry high pressure returns for Thursday and Friday, with the sfc high migrating offshore over the weekend. This will allow for warming SLY return flow to establish itself over the region and help push temperatures back above normal.

AVIATION /00Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: VFR expected at all terminals through the overnight hours, with only scattered high clouds once the remaining high based stratocu dissipate after sunset. Wind should go light/variable outside the mtns for the most part. The situation changes on Monday as a weak cold front pushes east across the region during the day. Moisture still looks limited with this system, so confidence in any flight restrictions is relatively low as cloud bases are expected to stay predominantly VFR. Prefer to limit the visibility restrictions due to showers to a PROB30 as the front moves thru, and we will revisit the ceiling fcst tonight. Once the front moves thru, wind should shift to N to NE in the early/mid afternoon and will probably have occasional gusts.

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.