Area Forecast Discussion
Issued by NWS Greer, SC
Issued by NWS Greer, SC
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830 FXUS62 KGSP 011406 AFDGSP Area Forecast Discussion National Weather Service Greenville-Spartanburg SC 1006 AM EDT Mon Jul 1 2024 .SYNOPSIS... Drier and cooler conditions are expected today behind a cold front to our east. This`ll continue tomorrow, before the heat starts to build back in on Wednesday and Thursday. It`ll get increasingly hot and humid going into the weekend, and some scattered afternoon showers will be possible, especially over the mountains. && .NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Monday...The cold front has finally cleared thru the southern edge of the forecast area, with an increasing NELY flow behind it. The flow is ushering in drier air, but a pocket of lower 70s dewpts may support a few showers this aftn across the Upper Savannah Valley and southern NC mountains. Overall, the forecast looks on track, with no major changes needed with this update. The main story for today will be the more reasonable temperatures and the lower humidity, what with the front slipping southward early in the day followed by the sfc high building in from the NW. It should be noticeable. The high temp fcst is on the order of ten degrees less than what we had yesterday, and actually a few degrees below average. The lower RH will feel much nicer, though. Can`t totally rule out a stray shower in the leftover convergence zone that should set up through the afternoon in the Savannah R valley to the Blue Ridge Escarpment in SC, so a small precip chance will be kept there for the time being. Any shower activity should end by sunset. Fair weather tonight as well, with the center of high pressure moving over PA/NY. The dry air mass should allow temps to fall about a category below normal. After the last week or two, the break, no matter how brief, will be welcome. Alas, the whole time, the center of a large upper anticyclone over the srn Plains will be creeping eastward and toward us. && .SHORT TERM /TUESDAY THROUGH WEDNESDAY NIGHT/... As of 207 AM EDT Monday: By Tuesday morning, subtropical ridge will be established over the southeastern CONUS, with attendant high pressure drifting off the New England coast. The western Carolinas will be locked into NE flow for much of Tuesday, which will keep dewpoints in the mid-50s and limit afternoon high temperatures to the low- to mid-80s. A robust subsidence inversion should all but completely suppress convective activity. On the flip side...GFS and NAM profiles continue to depict a deep, bone-dry layer just above this inversion. Such a setup, while not common for June, often results in dewpoints crashing below what any model forecasts, especially at this time range. So, in keeping with the last few rounds of official forecasts...leaned toward the drier side of guidance for afternoon dewpoints. By Wednesday, low level flow in the 850-700mb layer will shift from predominantly E to predominantly S...so there`ll once again be a dry layer aloft, but it should be a modicum less impressive than Tuesday`s. The bulk of long-range ensembles also suggest that the BL-top subsidence inversion will be stronger on Wednesday, so it`ll also be harder to mix this dry air down on Wednesday. Expect diurnal dewpoint minima to be a couple categories higher on Wednesday than on Tuesday. Otherwise...temperatures will climb into the upper 80s outside the mountains...amid mostly quiet conditions. The bulk of operational guidance keeps the forecast area completely dry on Wednesday. The NBM, in contrast, continues to forecast a sliver of 15-25% rain chance across the Smokies and Balsams Wednesday afternoon...but even this may simply be an artifact resulting from the NBM taking time to "catch up" from wetter member forecasts in previous cycles. && .LONG TERM /THURSDAY THROUGH SUNDAY/... As of 223 AM EDT Monday: Little change to the medium range. Deep ridging will remain in place through the end of the week, keeping convection suppressed while increasingly potent low-level moisture flux results in higher and higher dewpoints, and increasingly small chance of mixing those dewpoints out, each afternoon. Some diurnal convective initiation over the mountains will be possible on Thursday, and especially by Friday and Saturday, may even break containment and enter the Piedmont and Upstate. But, sans any real synoptic forcing such development shouldn`t have much oomph to it. Now, by the end of the weekend, that may change to some extent. Through the entire period, wave after wave will lift out of the central Great Plains and ride up over the ridge dominating our pattern locally...having little effect here, but helping to chip away at said ridge. There`s some indication that by Sunday, the central ridge axis will be displaced enough to our east that a cold front associated with the latest upper wave could make a run across the Tennessee Valley on Sunday. As much as 1/3 of the latest LREF cycle depict such a solution...although any boundary trying to push into the Carolinas would have a tough time staying together in the increasingly unfavorable environment it`d encounter here. For now, minor tweaks to the NBM`s shotgun chance PoP seemed reasonable on Sunday and Monday. Saturday still looks like the hottest day, with temps in the upper 90s and associated heat index values well over 100 across a wide swath of the CWA. Sunday and Monday look more iffy, and will hinge on how the large-scale pattern plays out. && .AVIATION /14Z MONDAY THROUGH FRIDAY/... At KCLT and elsewhere: Prevailing VFR at all terminals through the period. The sfc cold front was moving over the western Piedmont and should move clear of the fcst area by mid-morning and bring the dry air in from the NW. Wind will continue to veer around to N and NE in response. The rest of Monday should be fair with only a few high based stratocu. Wind will be occasionally gusty at KCLT with some deeper mixing, courtesy of high pressure building in from the N. Fair again tonight. Outlook: A cold front will stall just south of the area, resulting in quiet weather thru mid-week. A return of more typical mid-summer diurnal convection is expected by Thursday into the weekend. && .GSP WATCHES/WARNINGS/ADVISORIES... GA...None. NC...None. SC...None. && $$ SYNOPSIS...MPR NEAR TERM...ARK/PM SHORT TERM...MPR LONG TERM...MPR AVIATION...PM