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FXUS62 KGSP 300616 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 116 AM EST Thu Nov 30 2023

SYNOPSIS
High pressure will linger over the region leading to continued dry weather through tonight. Moisture will return from the west beginning early Friday, with off and on rain chances through the weekend as low pressure systems move across the Eastern states.
Drier conditions will return early next week as high pressure builds into the region.

NEAR TERM /THROUGH TODAY/
As of 100 AM EST Thursday: The nighttime Microphysics satellite loops continue to show few to scattered high clouds streaming into the area from the west this morning. Cloud cover will gradually increase through daybreak becoming scattered to broken. This will limit radiational cooling somewhat, with lows only expected to fall into the 20s and lower 30s across the forecast area. Light and variable winds should develop in the next hour or two, lingering through the mid-morning hours.

Otherwise, heights will continue to rise across the area through the near term while a high pressure off the east coast churns over the Atlantic. Aloft, an area of low pressure will develop in the lee of the southern Rockies this morning before lifting northeast across the Southern Plains late this afternoon into early this evening.
This will help to set up the next round of precip for the weekend.
However, precip will remain well to the west of the forecast area through the end of the near term period. High clouds will push out of the area this morning before returning this afternoon. Winds will turn southerly by early this afternoon, with any low-end gusts limited to the higher elevations. Highs this afternoon to be ~5-10 degrees warmer than yesterday, climbing into the upper 50s and lower 60s across the lower elevations. Higher elevations will see slightly cooler temps, with highs ranging from the lower to upper 40s.

SHORT TERM /TONIGHT THROUGH SATURDAY/
As of 218 PM EST Wednesday: A compact shortwave trough will be swinging out of the Southern Plains and lifting into the Lower Mississippi Valley by tomorrow night. In advance of this feature, a dry antecedent airmass will be entrenched across the Southern Appalachians with surface high pressure centered off the Carolina coast. Weak southerly return flow on the western flank of the high will help to slowly nudge a warm front north from the coastal plain through the midlands and into the I-85 corridor by daybreak Friday morning. A slug of deep moisture emanating from the Gulf of Mexico will nudge into the region from the southwest as the upper shortwave rapidly lifts into the Ohio Valley. The synoptic pattern will become increasingly disjointed, however, as the upper wave deamplifies and becomes disconnected from an attendant trailing cold front.
Furthermore, the surface low will be filling as it translates beneath upper-level confluence. In fact, heights will actually be rising across the region Friday as sub-tropical ridging amplifies over Cuba into south Florida and the Bahamas. The result of all this will be for the highest rain chances on Friday to remain confined to the southwest mountains and western Upstate, although scattered showers cannot be ruled out at any given location. Onset of precipitation has been pushed back as initial moisture intrusion tomorrow night will be spent saturating the column before any hydrometeors can survive and make it to the surface. Despite weak southerly flow, an in-situ cold air damming airmass will likely get locked in across the foothills and portions of the Piedmont on Friday as the column becomes saturated. Temperatures will be warm enough for all liquid precipitation, but a few instances of sleet will be possible across the mountains on the nose of the surging moisture before profiles warm above freezing.

Heading into Saturday, a rather wet pattern will take shape as the region becomes sandwiched between the previously mentioned ridge over Cuba and a longwave trough axis extending through the Great Plains. This will set up a period of moist southwest flow extending from the Gulf of Mexico into the Mid-Atlantic on the warm side of a stalled cold front draped from western Tennessee through western Kentucky. Persistent warm and moist advection will eventually lead to the demise of the weak in-situ cold air damming airmass, especially without a source of sustained cold/dry air. Embedded shortwave perturbations in the southwest flow regime in concert with favorable upper jet dynamics and 1.25-1.75" PWATs will help blossom an expansive area of precipitation Friday night into Saturday.
Guidance varies as to how far north this activity will spread with the greatest rain chances across northeast Georgia and the Upstate.
50-150 J/kg of elevated MUCAPE may also prove sufficient for a few isolated lightning strikes with any deeper convective cores.

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/
As of 241 PM EST Wednesday: A perturbed southwest flow regime will continue to foster a wet pattern across much of the region Saturday night through the day Sunday and into Sunday night. Additional rounds of showers will continue to stream across the area, but rainfall amounts will generally remain light. The pattern finally begins to break down Sunday night as a potent shortwave trough dives out of the Northern Plains and into the Mississippi Valley. This will finally help progress the stagnant pattern and kick the trough axis through the area by Monday. Deep moisture will get shunted east of the area with a cooler and drier airmass filtering in behind the cold frontal passage. Global model guidance is in good agreement that another potent wave will drop out of the Northern Plains early next week, but with a lack of deep moisture this system will likely be moisture starved for much of the area. Depending on the track of the low, a period of northwest flow rain/snow showers may grace the mountains. The GFS solution depicts a deep closed upper-low with a favorable setup for a solid northwest flow snow event, but the ECMWF solution is noticeably drier less amplified with the wave. Will advertise a chance for rain/snow showers along the Tennessee border for now until guidance comes into better agreement.

AVIATION /06Z THURSDAY THROUGH MONDAY/
At KCLT and elsewhere: VFR and dry through the 06Z TAF period thanks to sfc high pressure remaining over the Southeast. FEW to SCT high clouds continue to stream in from the west this morning. Cloud cover will increase through daybreak, becoming SCT to BKN. Winds are generally light and WSW'ly east of the mountains and NW'ly at KAVL this morning. Winds will become calm to light and variable by daybreak before picking up out of the south by the early afternoon hours. Winds will gradually increase through late this afternoon, ranging from 5-8 kts. Cloud cover will decrease briefly later this morning before returning this afternoon becoming FEW to SCT. Clouds will increase in coverage late this evening into tonight becoming SCT to BKN as moisture increases from the west ahead of a low pressure system. Precip chances are expected to remain west of the terminals through the forecast period.

Outlook: Moisture and associated restrictions will return on Friday, lingering into the weekend. Drier conditions return by early next week.

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

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