NOTE: Some of the data on this page has not been verified and should be used with that in mind. It may and occasionally will, be wrong. The tide reports are by xtide and are NOT FOR NAVIGATION. Privacy and Cookie policy

FXUS62 KGSP 100614 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 114 AM EST Sun Dec 10 2023

SYNOPSIS
Periods of rain will persist ahead of an approaching cold front today, with embedded thunderstorms developing at times. The cold front will pass through the area by early evening and gradually end the precipitation chances from the west for most of the area tonight. The main exception will be the North Carolina mountains, where colder air spilling in behind the front will produce high elevation snow and windy conditions into Monday morning. Dry high pressure then settles over the region on Monday and persists through the work week.

NEAR TERM /THROUGH TONIGHT/
As of 1250 am EST Sunday: Water vapor imagery shows a prominent upstream trough axis stretching from Lake Michigan to Arkansas this morning, with the base of the trough sharpening up near the Mississippi River Valley. An associated surface cold front was analyzed from far eastern KY through eastern TN and into northern AL around 06Z. This boundary is making slow but steady progress eastward. Regional radars show scattered shower coverage east of the Appalachians early this morning, but with a very solid band of heavy rain showers and embedded thunderstorms poised to move into the Smokies and vicinity through the early morning hours. Instability ahead of the main frontal band remains the primary limiting factor for a more widespread severe thunderstorm potential than the currently indicated marginal risk, with just 100 to 200 J/kg of SBCAPE in the southwest mountains so far. However, profiles indicate that nearly 500 J/kg of MUCAPE is available and this will likely spread east through the morning, while dewpoints recover from the southeast. In addition, surface-3km bulk shear values are on the upswing and should reach 45+ kt for most of the area as the southwesterly 850 mb jet moves in later this morning. The low-level jet will intensify further as it translates east across the foothills and then the Piedmont through late morning, with strong coverage given the deep forcing aloft from upper jet divergence, DPVA, and frontal circulations. All cells/lines developing in this regime will have to be watched closely for isolated wind/tornado potential, mainly near the escarpment areas early and then tending toward I-77 late this morning and this afternoon. In addition, a surface wave will likely ride northward along the frontal zone this afternoon, and this feature could focus both the tornado and the heavy rainfall threat nearer the I-77 corridor as the day progresses.

For now, the very low stream and river levels across the region do not support enough of a hydro threat for any Flood Watches. However, the additional 1 to 2 inch amounts expected today could still yield isolated hydro problem, especially in the increasingly worked-over southern escarpment areas and in flood prone areas nearer I-77 in any heavier rates.

The advancing upper trough should go negative tilt this evening, slightly slowing the back edge of the precipitation through the late day and the evening hours. Still anticipate most areas drying out after 06Z Monday. However, snow levels will crash down across the mountains quickly tonight behind the departing front, and even some I-40 locations could see a quick mix over to snow before the precipitation ends in the early morning hours. For now, mountain snow accumulations in the northwest flow appear sub-advisory at all but the highest peaks. In addition, a strong northwest flow gradient will set up behind the departing wave and front overnight. It will be quite windy near the Blue Ridge Mountains but, again, with advisory gusts mainly along the ridge tops.

SHORT TERM /MONDAY THROUGH TUESDAY NIGHT/
As of 135 PM Saturday...The main body of precip continues to move east of the area Sun night while upslope flow moisture lingers across the NC mtns. The upper trof axis crosses the wrn zones by 06z, which will rapidly cutoff added dyno lift, while the sfc flow backs and becomes non/orthogonal, thus a lowering snow potential is anticipated after this time. With a cold cP sfc high building in and lowering snow levels, most mtn areas will see snowfall with elevations abv 3.5 Kft receiving arnd 1-3 inches using liquid ratios, temp curves, and precip amts/timing. The latest SREF snowfall means agree well with these values and confidence continues to indicate an advisory will probably be needed abv 3.5 Kft. Will likely wrap in strong wind values with the advisory as a tightening p/grad (6 mb across the mtns) and descending CAA mixing commences thru the overnight and gusts on the order of 40-50 kts will be possible over the higher elevations. The mtn valleys/ridges will likely see a trace to a couple tenths of an inch of snow as temps drop quickly before precip fully diminishes. Some potential exists for black ice as the rate of cooling may freeze wet roads, but drying winds may limit this process. Areas east of the mtns thru the NC Piedmont could see flurries thru 12z as sub-freezing column air pushes in and possibly interacts with departing deeper moisture for a couple hrs.

A cold airmass lingers thru the day Mon with highs held abt 5 degrees below normal. Min temps Mon night drop below freezing all areas with readings ranging thru the 20s. Another dry day is in store Tue, but insol will be slow to modify the airmass and sfc winds shift more s/ly late, thus highs still below normal by a couple degrees can be expected.

LONG TERM /WEDNESDAY THROUGH SATURDAY/
As of 1230 AM Sunday...Most of the medium range remains quiet, as dry sfc high pressure dominates the region under a NWLY confluent flow aloft. A reinforcing dry cold front will drop south thru the forecast area late Wednesday, keeping temps a little below normal, despite plenty of sunshine. An upper ridge axis will begin to shift east from the Lower-MS Valley to the Southeast Friday, allowing temps to start a slow warming trend. The latest guidance is in good agreement on the fcst remaining dry thru Friday, but then diverge quickly on what's going to happen over the weekend. Given the lack of agreement in the model guidance, have gone with the NBM for next weekend's fcst. This results PoPs ramping up to chance by Saturday night, with temps mainly in the upper 30s to mid 40s. Right now going with a rain fcst, except for possibly some snow in the highest elevations.

AVIATION /06Z SUNDAY THROUGH THURSDAY/
At KCLT and elsewhere: Widespread showers and thunderstorms ahead of a cold front are poised to arrive from the west across the terminal forecast area through the rest of the morning hours, with associated IFR visibility and IFR to LIFR cigs expected. Given the potential for rogue lightning strikes just about anywhere at any time, will ride mainly on a VCTS mentions along with the prevailing SHRA for the mountains and foothills, but then feature a PROB30 window of TSRA for KCLT starting at 17Z. Foothill and Piedmont precipitation will taper off from the west this evening. Winds will increase from the south ahead of the advancing front and then shift to westerly with fropa late day, with NW flow through the evening and overnight hours. Gusts may be quite robust, above 30 kt, at KAVL tonight in the peak of the cold advection flow. KAVL could also see some snow showers mix in at times overnight before the NW flow moisture diminishes by daybreak Monday.

Outlook: Dry high pressure will return from the west on Monday and persist through the week.

GSP WATCHES/WARNINGS/ADVISORIES
GA...None.
NC...None.
SC...None.

toggle option: (graph/table)

Full Color Weather Map

Link to Loop


Other links: GEOS-West     Contential US     Full GOES-East

Greer, SC,