Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291548 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1148 AM EDT Mon May 29 2017 .SYNOPSIS... An unsettled pattern associated with cyclonic flow aloft will persist through mid-week. && .NEAR TERM /THROUGH TONIGHT/... As of 1130 AM EDT Monday... A plume of enhanced 925-850 mb moisture advecting into central NC from the W/SW amidst strong insolation and modest mid-level lapse rates (~6.0C/km) is expected to yield 1000-1500 J/kg MLCAPE with no CINH by peak heating this afternoon. W/regard to forcing, numerous perturbations were noted in WSW flow aloft upstream of the Carolinas at 15Z. A series of the aforementioned disturbances are progged to track ENE across the Carolinas this aft/eve into tonight. In the lower levels, a developing thermal trough over the NC Piedmont this afternoon should help serve as a focus for development once CINH has eroded, particularly if a weak/broad low forms over central SC/NC as some of the latest 12Z guidance suggests. With the above in mind, expect convection to develop across the W/SW Piedmont by late afternoon. Given an environment characterized by steep low-level lapse rates (0-3km ~8c/km) and moderate DCAPE (~1000 J/kg) in a westerly flow regime, it seems likely that convection will grow upscale along outflow and propagate east across central NC by late evening (~03Z), with the relative best chance along/south of Hwy 64. Additional convection is progged to develop over southwest NC/upstate SC (upstream of the initial activity) this evening as additional disturbances in WSW flow aloft track across a moist /conditionally unstable/ airmass in place over the region. As a result, it is possible that convection could persist past midnight into the 06-09Z time-frame, primarily along/south of Hwy 64. Deep layer shear and moderate destabilization will be sufficient for supercellular organization with initial activity that develops this aft/eve, with a primary threat of damaging winds and severe hail (the latter of which may be tempered by modest mid-level lapse rates). With steep low-level lapse rates and moderate DCAPE expected this afternoon, activity is likely to grow upscale along outflow with time. This suggests the primary severe threat will transition to damaging winds late this afternoon and early evening. Expect highs ranging from the mid 80s far NW Piedmont to lower 90s Sandhills and SE Coastal Plain. Lows tonight in the 60s, coolest N/NW and warmest S/SE. -Vincent && .SHORT TERM /TUESDAY THROUGH TUESDAY NIGHT/... As of 235 AM Monday... ...Lower chance of showers/storms as moisture shifts toward the coast. Tuesday and Tuesday night: As the mid/upper trough lifts out, the main surface boundary/trough will drift SE closer to the coast Tuesday. This being a main focus for scattered storms, it will mean the highest chance of showers/storms will shift toward the coast, with limited, if any activity expected over the western areas. Some drier air will mix down from the mid levels and weak high pressure over the Appalachians will bring some drying in the low levels into the Piedmont. All this suggests a low chance of showers/storms, mainly over the Coastal Plain Tuesday afternoon/early evening, with only isolated activity elsewhere. Partly sunny skies are expected over the Piedmont, with a bit lower temperatures and humidities from previous days. Dew points should fall into the upper 50s over the NW Piedmont, but range into the upper 60s SE. Actual highs are expected in the lower to mid 80s NW, ranging into the upper 80s SE. QPF of 0.25 or less expected, generally along and east of I-95. Lows Tuesday night will be in the 60s, except some upper 50s NW. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... As of 345 AM EDT Monday... Medium range model guidance continue to advertise a weak cold front/surface trough moving across central NC late Wednesday into Wednesday night as the main mid level trough axis swings through the area. This will lead to a late day/evening chance/slight chance of seeing some showers and storms. High temps in advance of the front should generally be in the mid to upper 80s, with perhaps a few locations toughing 90 across the south. Weak high pressure will move across the area on Thursday, before a moist southerly return flow develops on Friday. Mid/upper level flow will amplify again across the Great Lakes/Northeast U.S., helping to drive a cold front south and eastward into the area late Saturday into Sunday. This will result in above normal chances for precip and a decrease in high temps. && .AVIATION /18Z MONDAY THROUGH FRIDAY/... As of 1145 AM EDT Monday... 24-HR TAF Period: VFR conditions will prevail through mid to late afternoon at all terminals. Sub-VFR conditions associated with scattered convection are expected late this afternoon and evening, primarily at southern/eastern terminals (FAY/RDU/RWI) with the relative best potential at the FAY terminal. Convection could persist past midnight (into the 06-09Z time frame), though once again it would appear that southern/eastern terminals are more likely to be affected. In areas that experience rain, a short period of IFR/LIFR ceilings or fog could develop prior to sunrise if skies clear, though whether or not this will occur remains difficult to ascertain at this time. Looking Ahead: Aside from a potential for isolated to scattered afternoon and evening convection associated with cyclonic flow aloft over the region, expect VFR conditions to generally prevail through mid to late week. -Vincent && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...Vincent NEAR TERM...Vincent SHORT TERM...Badgett LONG TERM...BSD/CBL AVIATION...Vincent is the U.S. government's official web portal to all federal, state and local government web resources and services.