Sugar Mountain

Forecast Discussion

Summary

SYNOPSIS

... A weak trough crossing the region today will settle along the southeast coastline Thursday through Friday. A gradual increase in easterly flow moisture is likely through the latter part of the week. Drier and stronger high pressure will settle over the region during the weekend, and likely persist through early next week, as both Jose and Maria remain off the east coast.

NEAR TERM /THROUGH TONIGHT/... As of 1030 AM: The synoptic pattern overall is rather similar to days past as broad ridging dominates across the east, and troffing prevails out west. A difference, however, is the presence of a shortwave trough now centered over West Virginia. Lobes of vorticity will round this shortwave and pass thru the CWFA this aftn, which is of interest as a potential initiation mechanism for diurnal showers and t-storms. Convective cloud temp from the morning GSO RAOB is 83F which should be reached in areas of the lower Piedmont by noon or 1 PM. Hence, it looks reasonable to buy into the latest HRRR, which shows initation southeast of I-85, with a secondary round firing over the Blue Ridge. Any convection that fires over the mtns may propagate eastward into the foothills/piedmont regions to some extent by late afternoon, perhaps aided by a vort lobe. Profiles today do exhibit slight CIN, however deep dry air supports modest lapse rates and abundant instability above the cap, upwards of 1500 J/kg albeit with very weak shear. Although general thunderstorms still will predominate, wouldn't be suprised to see a handful produce damaging wind or even hail in light of the dry profiles. Convection will wane diurnally. Temps today will be quite warm given that we're nearing the first day of fall; highs top out nearly 6-8 degrees above normal.

SHORT TERM /THURSDAY THROUGH FRIDAY/... As of 300 AM EDT Wednesday: An upper level trough axis will settle along the southeast coastline Thursday through Friday, as a 590 dm ridge axis sets up from the Great Lakes to the MS Valley. Low level easterly flow developing Thursday afternoon through Friday should help to focus the highest chance PoPs along the eastern slopes of the mountains. Thus anticipate mainly diurnal, scattered ridge top/eastern mountain convection both Thursday and Friday afternoons with weak forcing and limited moisture. SBCAPE values should steadily recover to 1000 to 1500 J/kg to support a scattered thunder mention. Minimum temperatures will remain warm - some 8 to 10 degrees above climo. Max Temps will be one to two categories above climo on Thursday and a touch cooler on Friday.

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... As of 300 AM EDT Wednesday: The upper ridge will strengthen from the north through the weekend as Tropical System Jose meanders off the mid-Atlantic coast and Hurricane Maria moves northward well east of coastal FL/GA. Much drier air will wrap southward from the ridge, with very limited precipitation chances - mainly just isolated showers Saturday afternoon in far southwest mountain sections.

The consensus solutions keep Maria far enough east off the Carolina coast Monday through Tuesday to have no impact on sensible weather across our forecast area. There are vast differences in the handling of the Jose remnants that get absorbed into the Maria circulation, but even the members with inland impacts from Jose keep any associated moisture over the mid-Atlantic coastal region and north of our area through Tuesday. Thus expect mostly northerly flow around the offshore systems and generally dry conditions with continued temperatures above climo.