textproduct: Greenville-Spartanburg

WHAT HAS CHANGED

Rainfall totals have trended down Thursday through Sunday.

KEY MESSAGES

1. A summer-like pattern will continue through mid-week, with above normal temperatures. Chances for mountain diurnal convection increase Wednesday as a front approaches. 2. A cold front will bring better rain chances Thursday into the weekend but with only light rainfall amounts expected, any drought relief will be limited.

DISCUSSION

Key message 1: A summer-like pattern will continue through mid-week, with above normal temperatures. Chances for mountain diurnal convection increase Wednesday as a front approaches.

An upper level ridge will persist along the East Coast, with a Bermuda high supporting persistent southerly low level flow through mid-week. Despite the southerly flow, profiles will remain somewhat dry until later Wednesday, with surface dewpoints forecast to mix out into the 50s this afternoon and again Tue afternoon. As such, diurnal instability will be muted, and very little-to-no diurnal convection is anticipated through Tue evening. Temperatures will otherwise remain 6-8 degrees above climo through Wed.

By late Wednesday, the ridge will begin to weaken as a strong short wave trough passes through eastern Canada and New England. The leading edge of an attendant/weak frontal zone is forecast to approach the southern Appalachians by late Wed afternoon...introducing sufficient convergence and pooling moisture to enhance diurnal convective chances across the mountains. In fact...likely PoPs are forecast for much of the NC mountains by 00Z Thu. Shear parameters will remain quite weak across our area, and instability is forecast to be fairly modest, so the threat for severe storms will be very low.

Key message 2: A cold front will bring better rain chances Thursday into the weekend but with only light rainfall amounts expected, any drought relief will be limited.

A cold front will track across the forecast area Wednesday evening into early Thursday morning before stalling over the Carolinas on Friday. The front will then reactivate as a warm front and lift northward over the weekend, stalling over the Ohio Valley/Mid- Atlantic through early next week. This front will bring better rain chances than we have seen in a while but it appears that an upper ridge could build back over the Southeast faster than anticipated this weekend into early next week which could act to suppress shower and thunderstorm activity. Thus, confidence on PoPs this weekend remains low. We should get a better idea on PoPs once high-res guidance becomes available later in the week. The main change from the previous forecast is that QPF has trended lower this forecast cycle, with the NBM now showing most locations seeing 1" or less of rainfall Thursday into the weekend. There still remains the potential for some locally higher rainfall amounts >1" along the NC/TN border and along the Blue Ridge Escarpment. Although any rain will be beneficial, these amounts will not do much to improve the ongoing drought. Any severe potential continues to look low through the period. Above normal highs stick around on Thursday before below normal highs return briefly on Friday as cold air damming develops behind the front. The 06Z GFS is trending a bit stronger regarding the wedge so afternoon temps on Friday may trend cooler if this trend continues. CAD lingers through the first half of Saturday before eroding (per the 06Z GFS) so highs on Saturday should end up near normal to just above normal. Highs will end up a few degrees above normal on both Sunday and Monday. Lows each night will remain a few to several degrees above normal.

AVIATION /18Z MONDAY THROUGH SATURDAY/

At KCLT and elsewhere: While low level moisture continues to slowly increase, conditions remain fairly dry in the relative sense, and convective-free weather and VFR conditions are forecast to persist at the TAF sites through the period. Otherwise, FEW/SCT cumulus, mainly in the 035-050 range are expected this afternoon. Winds will remain S/SW at 5-10 kts through much of the period.

Outlook: VFR to persist through mid-week, except perhaps in mountain valleys, where patchy morning fog/low stratus may develop each morning. Increasing moisture will bring a more active pattern for mainly diurnal convection beginning late Wednesday, continuing through the end of the week. The potential for overnight fog/low clouds will increase as well.

GSP WATCHES/WARNINGS/ADVISORIES

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