Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 291550 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1150 AM EDT FRI JUL 29 2016 .SYNOPSIS... A weak upper-level trough will become centered over the eastern U.S. today through Saturday, bringing increased chances for showers and storms late Saturday through Monday, along with a trend toward more normal temperatures. && .NEAR TERM /THROUGH TONIGHT/... As of 1000 AM Friday... Little change needed to ongoing forecast. The latest surface map shows low pressure off the Northeast coast with troughing extending down through central NC, aligned closely with the 850 mb trough. The low level flow from the WNW is likely to hold down temps and dewpoints enough to limit convection, although there may still be a sufficient combination of low level mass convergence (along and east of a weak lee low that is expected to form over the western Sandhills) and higher temps/dewpoints along and east of the trough for scattered storms this afternoon into early evening. The SSEO, 3 km NAMRR, and the NCAR ensemble output all suggest a weak shower/storm cluster traversing the southern third of the forecast area late today, fitting with this scenario, and will place chance pops here with just isolated elsewhere. Despite the decent deep layer bulk shear, CAPE values should be small today, at or under 1000 J/kg of MUCAPE, limiting storm intensity. Thicknesses this morning are markedly lower than previous mornings, suggesting highs around a category below yesterday`s highs, and in fact current temps are already running 1-4 degrees below yesterday`s pace. Expect highs in the lower-mid 90s, except upper 90s SE. Will keep the heat advisory in place in the east, although a few spots may come up short, especially if dewpoints mix out more than expected in the eastern CWA. -GIH Previous discussion as of 230 AM Friday: Mostly sunny skies today with just slightly lowering heights/thicknesses will only yield subtle changes to the heat. Highs will still reach 95-100 from Fayetteville to Rocky Mount eastward to Goldsboro and Clinton. Heat indices will still reach 105 or 106 in many areas this afternoon. This will be another day to take precautions to prevent heat related issues or illnesses. Central NC will be on the back or subsidence side of the departing mid/upper trough over VA this morning. Skies were clear this morning over much of the region with partly cloudy skies near the VA border. The mean flow is a bit more westerly into the mountains and western Piedmont on the backside of the departing trough. The SW-W low level flow has aided in some dry advection from upstate SC into western NC, allowing dew points to fall into the 60s. In the east, dew points remained very oppressive, in the 70s. This lowering of dew points will eliminate the heat advisory from the Piedmont today. Heat indices will be in the 95-100 range during the mid to late afternoon in the Piedmont. However, highs will still reach the mid to upper 90s. Even though a heat advisory will not be needed, this subtle lowering of the heat indices from 105 to 95 to 100 will essentially not be that noticeable; therefore, it will be good idea to treat today just as the last few when advisories were in effect in the Piedmont. Convection is expected to be at a minimum again today with the subsidence this morning and more of a westerly flow. There will be slight chance of thunderstorms this afternoon and early evening as the surface trough develops and the low level flow begins to back to the SW then S by evening. The best chances should be in the Coastal Plain this afternoon. Dew points will again rise this evening, back into the 70s in the Piedmont and remain high in the east as the surface trough backs westward. An isolated storm is possible, but the chances remain slim without a trigger aloft. Lows generally in the 70s again. && .SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/... As of 225 AM Friday... Yet another heat advisory appears likely in the south and east on Saturday as strong heating and high humidity values will occur again. There will be more clouds over the Piedmont and northern areas, closer to the approaching mid/upper trough. This will bring some cooling, even if the showers do not become widespread. Highs should range from around 90 NW into the upper 90s in the Coastal Plain. Heat indices should reach 105 again SE, but will be in the 90s NW. As the trough aloft digs into Tennessee Valley and over the central Appalachians, a surface trough will tighten over central NC. However, the main focus for convection appears that it will be in the northern and eastern section of NC, and especially over VA due to the best lift... low level convergence... and moisture pooling to our NE. We will continue to show 40-50 POP in the NE with only 20-30 POP to the SW. This chance of showers and thunderstorms will be mainly during the afternoon and evening. Partly cloudy skies otherwise, lows Saturday night in the 70s. && .LONG TERM /Monday through Friday/...
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As of 1130 AM Friday... Stormy weather early in the work week should give way to quieter weather later in the week. The broad mid level trough axis will be oriented along the East Coast Mon, with surface troughing extending down through central NC. It still appears that the best convection chances will be across the SE half of the CWA Mon/Mon night, with lingering chances in the extreme SE Tue as the weak shear axis slides ESE through the area, although even these shower/storm chances should be largely to our east given the weak mid level flow from the WNW and NW over W and central NC and post-trough subsidence taking place. Heights aloft will continue to rise as the mid level trough shifts further out over the Atlantic with strong ridging building into and over the eastern CONUS during the mid-late week, yielding low, below-climo precip chances Wed-Fri. The 00z/29 ECMWF does favor some MCS activity riding from the OH Valley southeastward through NC late Wed/Wed night and lingering through Thu with widespread convection, however this is far from certain and lacking support from other models, so prefer to stay with a tranquil forecast for now. Models agree on low level thicknesses slipping to near to just below normal Mon through Wed, then rebounding back to near or just above normal for Thu/Fri as the surface high pressure ridge extending overhead gradually modifies with steady warming aloft. -GIH
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&& .AVIATION /18Z Friday through Wednesday/...
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As of 1150 AM Friday... VFR conditions will dominate through mid afternoon Sat, as a weak low pressure trough holds in place across central NC. There is a chance that isolated to scattered showers/storms may affect TAF sites very late this afternoon through mid evening, bringing a brief period of MVFR conditions and erratic gusty winds. Winds will be generally light through tonight, before coming from the SW at 7-12 kts starting late Sat morning. Looking beyond 18z Sat: Shower/storm chances will increase Sat afternoon through the evening, as an upper level trough gradually moves into the area from the west. There will be a better-than-usual chance for sub-VFR conditions in showers/storms Sun into Mon as the upper trough settles overhead with a series of disturbances crossing the region. MVFR or IFR fog is possible each morning as well. Storm chances will decrease Tue into Wed with VFR conditions becoming dominant once again. -GIH
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&& .RAH WATCHES/WARNINGS/ADVISORIES... Heat Advisory from noon today to 8 PM EDT this evening for NCZ011-027-028-042-043-077-078-085-086-088-089. && $$ SYNOPSIS...Hartfield NEAR TERM...Hartfield/BADGETT SHORT TERM...BADGETT LONG TERM...Hartfield AVIATION...Hartfield

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