textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

The aviation forecast was updated to reflect the impending 12z TAF issuance.

KEY MESSAGES

1. Breezy conditions persist into this morning, before dry and warm high pressure settles in for the beginning of the workweek. 2. Warm weather continues mid week into the weekend with rain chances gradually increasing as the pattern becomes more active.

DISCUSSION

Key message 1: Breezy conditions persist into this morning, before dry and warm high pressure settles in for the beginning of the workweek.

Skies are mostly clear across the area this morning, albeit with patchy ground fog in a few spots, mainly in the NC Piedmont. More or less as expected, coastal cyclogenesis has taken place over the Outer Banks, ushering in a weak CAA regime that's helped to scatter out some moisture and keep fog more isolated in nature. Winds remain mostly N at 5-10kts, but with fewer gusts than expected. Winds have been enough to preclude more widespread dense fog, and there are no plans to issue any dense fog at this time.

Otherwise...winds should remain elevated through late morning as 15-25kt flow just above the surface mixes down...but as the parent low begins to lift northeast into the coastal Chesapeake over the next few hours, and eventually drifts out to sea this afternoon, CAA will begin to subside, allowing winds to die down and leaving us mostly clear by noon or so. By mid-afternoon, deterministic profiles depict a deep dry layer above 900mb or so, beneath which a shallow mixed layer should develop as the day wears on. It's a bit questionable how much of this dry air will mix to the surface, given a stout a subsidence inversion just above the PBL, but also fairly breezy, turbulent winds within this inversion layer. Any dewpoint mixing that does occur should be of little impact, though, since it'd have to overcome lingering surface moisture to affect RHs, and we've received far too much rain in the last 24 hours to entertain any fire weather concerns.

Some guidance depicts a return of some patchy fog Monday night and Tuesday morning. Indeed, skies will be clear most of the night, so locations across the area could see enough radiative cooling for at least isolated fog to develop. This will be especially true along the I-77 corridor, where postfrontal CAA will have likely had the least impact on low-level moisture. Whatever fog develops should scatter out quickly Tuesday morning, giving way to a mostly cloudy day on Tuesday as progressive high pressure continues eastward, resulting in a weak southerly moisture return and associated warming trend beginning by mid-day.

Key message 2: Warm weather continues mid week into the weekend with rain chances gradually increasing as the pattern becomes more active.

By Wednesday, guidance and respective ensemble means remain in largely good agreement that flat upper riding will extend from Mexico across the Gulf and the Florida peninsula. Farther north, on the poleward side of the ridge, an extended belt of deep-layer westerlies will reside from the Desert Southwest to the Appalachians. This synoptic regime will foster continued well above average temperatures within an expansive warm sector and rising heights. Afternoon highs will climb from the low to upper 60s Wednesday to the upper 60s to upper 70s by Friday. Daily records may be challenged on Thursday and Friday depending on cloud cover and increasing rain chances. Speaking of, the pattern will become increasingly perturbed as a piece of Pacific energy drops through the Great Basin and towards the Four Corners. Ahead of this main feature of interest, several embedded shortwave perturbations will translate across the region with a surface warm front in the vicinity of the Ohio Valley. A lead surface low is progged to lift across the Midwest on Thursday with an increase in coverage of warm advection showers from isolated/stray on Wednesday to scattered on Thursday, especially across the mountains and northern foothills. By Friday into the weekend, the main trough will eject over the Southern Plains and lift through the Mississippi Valley into the Appalachians. Guidance begins to quickly diverge at this point as to timing of a potential frontal passage across the area as well as coverage of any associated showers. One camp features a faster front with a drier frontal passage, while other camps stall the front across the area and train additional rounds of precipitation. As of this writing, forecast confidence Friday into the weekend remains low and the forecast will need to be refined as guidance comes into better agreement.

AVIATION /12Z MONDAY THROUGH FRIDAY/

At KCLT and elsewhere: Seeing some spotty ground fog, ranging from MVFR to LIFR, across the terminal forecast area this morning. Most locations, however, are VFR at this point, and should remain that way going forward. Expect a steady NE wind most of the day, toggling around to the SE late in the afternoon, then becoming lighter and S/SW early tonight. Clouds should begin to build overnight also, with VFR ceilings developing after midnight for much of the area. Guidance continues to hint at potential for another round of fog before dawn Tuesday, mainly across the I-77 corridor.

Outlook: VFR and dry conditions should persist most of the week. Rain may return to the area by Thursday or Friday.

GSP WATCHES/WARNINGS/ADVISORIES

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