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FXUS62 KGSP 012333 AFDGSP

Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 733 PM EDT Sat Jun 1 2024

SYNOPSIS
Dry high pressure moves off the Carolina coast on Sunday with warming temperatures and increasing moisture. A typical summer pattern will develop during the first half of the week with daily afternoon thunderstorm chances. Showers and thunderstorms will likely increase in coverage for Wednesday and Thursday as a cold front approaches our area, with drier weather expected to return by the end of the week.

NEAR TERM /THROUGH SUNDAY/
As of 730 PM EDT Saturday: The forecast remains on track as mid- to upper-level clouds continue to filter in from the west. Seeing some reflectivity splotches popping up on radar, but would be surprised if most of it is actually reaching the surface. Boundary layer will need to become more saturated before liquid droplets reach the surface. Otherwise, made adjustments based on current observations and latest model trends. Overall trends wrt the shower coverage haven't changed significantly, with coverage over our area not expected to increase substantially until overnight. Low temps early Sunday should remain near-normal due to increased cloud cover tonight/overnight and higher dewpts.

Otherwise, upper level ridging will deamplify and shift east and off the Atlantic Coast this evening and early Sunday as an upper shortwave moves over our area from the west. At the sfc, broad high pressure will continue to gradually move off the Atlantic Coast thru the near-term period as a moist frontal boundary moves into the Western Carolinas from the west. Forcing ahead of the above-mentioned upper shortwave has already reached our western zones, however more substantial moisture advection from the Atlan- tic will be slow to saturate the lower levels. The latest near-term guidance still generates the bulk of the low-level moist transport after midnight. Nonetheless, some iso to sct showers will likely materialize across the NC mtns before that. More widespread precip will spread over our fcst area overnight, but with very limited instability and meager mid-level lapse rates thru the morning hrs, thunder is unlikely until Sunday aftn, with the severe potential still looking minimal at best for Sunday. Highs should remain 1 to 2 categories below climatology.

SHORT TERM /SUNDAY NIGHT THROUGH TUESDAY/
As of 200 pm Saturday: The upper air pattern will become increasingly anticyclonic across our region early in the short term, as a weak ridge builds from the Deep South through the Great Lakes.
As a result, a deep moisture plume will gradually shunt east of the forecast area early in the period. In the interim, scattered coverage of showers along with a few storms will continue into Sunday evening before steadily tapering off. Decreasing deep layer moisture will yield less in the way of cloud cover, but also improved potential for destabilization Monday afternoon. Diurnal convection is forecast to initiate...esp across the high terrain.
While coverage is expected to be more limited than on Monday, sbCAPE of around 1500 J/kg should allow for a few stronger storms, with perhaps a stray pulse severe storm not completely out of the question. With little change in the pattern and thermodynamic profiles expected, Tuesday should be very similar to Monday, with scattered diurnal convection expected, and perhaps a slight uptick in the threat for a pulse severe storm with hotter conditions expected. The first half of the period is expected to see temps average around
or slightly above normal
while the short term is expected to end around 5 degrees above climo.

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/
As of 215 pm Saturday: An expansive/deep upper low will wobble from the Canadian Prairie at the start of the period to the Great Lakes by Thursday evening. Height falls associated with a vorticity lobe lifting ahead of the low is expected to send a frontal boundary into the region by late Wed, enhancing convective chances across the southern Appalachians and vicinity Wed into Wed night. Indications in global model guidance are that the afternoon will see at least moderate instability, albeit in a modestly sheared environment. A few strong-to-severe pulse storms and/or multicell clusters will be possible. An additional round of storms is possible Thursday, although this is a bit more uncertain, as some global model guidance suggests drier air will be filtering into the area in the wake of the frontal boundary Thu afternoon. PoPs are generally advertised in the solid chance range during that time. The latter half of the period should become more inactive as lower theta-E air advects into the region. PoPs for Fri/Sat are limited to token slight chances, mainly over the mtns. Temperatures are forecast at around 2-4 degrees above normal through the period.

AVIATION /00Z SUNDAY THROUGH THURSDAY/
At KCLT and elsewhere: VFR conditions will prevail through much of the overnight before cloud bases begin to lower with increasing moisture. Model guidance continue to place MVFR cigs across KAVL and the Upstate TAF sites after daybreak Sunday and continue through the end of the forecast period, with likely some form of scattering during portions of the daytime period. Low VFR is expected at KCLT and KHKY, but MVFR can't be fully ruled out. Shower coverage will begin to increase overnight and spread across the terminals through the end of the forecast period. Winds will toggle southeasterly and turn the dial to a south-southwesterly component by mid-morning Sunday. Placed a VCSH mention at all sites due to the scattered nature of the showers that are expected. PROB30 for shower development for when the models highlight the best overall coverage.
Instability will build in during peak heating, so included another PROB30 to highlight thunderstorm chances and associated restrictions.

Outlook: Diurnal shower and thunderstorm chances with associated restrictions will linger through the middle of next week.

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

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