Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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000 FXUS62 KRAH 130715 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 315 AM EDT Tue Mar 13 2018 .SYNOPSIS... Low pressure will rapidly deepen as it tracks up the mid Atlantic coast tonight and Northeast coast on Tuesday. High pressure will build from the northern Plains across the Southeast states through Wednesday. && .NEAR TERM /TODAY THROUGH TONIGHT/... As of 235 AM Tuesday... 310 am update: We`re seeing slick spots on an elevated bridge here near the office, despite an air temp of 33-34F. With similar temps (or lower) around the area that saw measurable snow yesterday, will go ahead and expand the winter weather advisory for black ice for areas north of a line from Lexington to Lillington to Goldsboro. Icy bridges and overpasses are the primary concern through 10 am. -GIH Will leave as is the existing Winter Weather Advisory for Black Ice for Forsyth/Guilford/Person. Elsewhere across the northern half of the forecast area, bridges and overpasses may present a few slick spots through daybreak. Will continue handling this with SPSs, as the lack of pronounced cold air rushing into the area should minimize problems, but will monitor closely over the next few hours and watch for any deviations to these expectations. The surface low continues to deepen offshore E of the NC/VA border. A few flurries managed to breach the mountains and make their way into the Triad a few hours ago, but downslope drying effects and increasing lower level subsidence have helped these to diminish. Expect dry weather through today, with multi-layer WV imagery confirming dry low and mid level air just upstream, and surface high pressure centered over the Midwest trying to build in. High clouds should increase this afternoon as a sheared upper wave over the nations midsection approaches from the west. And residual moisture near the top of what should be a fairly deep mixed layer this afternoon should lead to scattered flat high-based cumulus. Expect well below normal highs in the mid 40s to lower 50s, with brisk NW winds today gusting up to 20-25 mph this afternoon with mixing. For tonight, models depict a lee low developing SW of CLT later today which moves SE over N SC this evening/tonight, leading to passage of a weak inverted surface trough along with an 850 mb trough axis, both shifting ESE through central NC through tonight. Meanwhile, energy dropping down the west and SW side of a deepening mid level low over NY/PA will generate impressive 140+ m height falls over NC. Forecast sounding show plentiful moisture in the 850- 700 mb depth shifting through the central and eastern forecast area, and this along with the forcing for ascent should generate a few sprinkles or flurries (as the GFS does show saturation reading into the -12C to -15C layer), however the presence of fairly dry near- surface air should keep any precip from measuring. But will certainly check later model runs to see if this scenario changes. Otherwise, expect skies to be partly cloudy, perhaps mostly cloudy for a brief time, especially from the Triangle SE toward Goldsboro/Fayetteville. Lows from the mid 20s to lower 30s. -GIH && .SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/... As of 250 AM Tuesday... The aforementioned bundle of strong vorticity dropping down the SW side of the deepening low to our north appears likely to instigate scattered to broken cloud cover over central NC, and potentially another round of sprinkles or flurries, with a greater chance that such activity may grow upscale and lead to measurable precip for a couple of hours. Both the GFS and NAM show very deep mixing Wed, but the NAM is considerably drier in the low levels than the GFS. Given the low level NW flow, the drier NAM appears more reasonable, although the dynamic lift afforded by the DPVA aloft could be enough to overcome the downslope drying. For now, will stick with partly cloudy skies and a pop under 14%, but if later model runs trend in the wetter direction, a mentioned pop may be needed. In either case, expect clearing behind the vort max passage Wed night. Highs Wed in the 40s areawide within low level cold air advection and reduced insolation. Should again see blustery and gusty NW winds. Lows Wed night 24-30 with diminishing winds. -GIH && .LONG TERM /WEDNESDAY THROUGH MONDAY/...
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As of 315 AM Tuesday... Friday will be more of the same until evening when an upper level disturbance tries to move in but the GFS is the only solution at the moment showing it. Will increase cloud cover and maintain slight chance pops on Friday evening into Saturday morning but overall a very low impact feature. Highs will continue to rise into the 60s everywhere except the northern Coastal Plain where highs will be in the upper 50s. For the weekend, a disorganized low pressure system enters from the west and provides precipitation chances beginning on Saturday afternoon and continuing through at least Sunday morning before it finally meanders east of the area. Excess cloud cover will temper forecasted highs on Saturday with 50s across the forecast area. By Sunday afternoon, things begin to clear out and temps will rise back into the 60s. Monday will be dry and seasonal with temps in the 60s before another low pressure system rolls in from the west and deepens over central NC on Tuesday. Depending on the track of the low and proximity to central NC we will have to monitor this system for the potential for any severe wx although model presentation looks fairly week and unorganized at this time. Temps near 60 in the Triad will increase to the low 70s across the extreme southern tier.
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&& .AVIATION /06Z TUESDAY THROUGH SUNDAY/... As of 115 AM Tuesday... With the exception of a deck of VFR clouds that have slipped past the mountains and into the Triad, skies have largely cleared out behind the departing storm system that impacted the region on Monday. VFR conditions are expected to hold areawide over the next 24 hours. High clouds will increase and thicken today from the WNW as a disturbance over the nation`s midsection swings ESE toward the Carolinas. With heating and mixing, we`ll also see sct-bkn clouds based above 4k ft AGL developing during the afternoon. As another disturbance drops southward around a large upper level low over NY/PA later tonight, there will be a good chance of a period of bkn- ovc clouds, and perhaps a sprinkle or flurry, mainly affecting RDU/FAY/RWI after 00z. Surface winds will be from the W or WNW today, increasing to around 10-15 kts by mid-late morning, and gusts up to around 20 kts, both diminishing toward 00z. Looking beyond 06z Wed, VFR conditions will continue, although another round of cigs and a brief sprinkle or flurry is possible Wed afternoon. Otherwise, high pressure over the upper Midwest will drift SE then E over the Southeast states through mid week. A backdoor front will approach from the north Thu before pushing southward through NC on Fri. This may bring a period of sub-VFR conditions with rain chances Fri/Sat as cool high pressure noses in from the N behind the front. A return to VFR is expected Sun. -GIH && .EQUIPMENT... Due to equipment failure, GSO upper air will be unavailable until further notice. Technicians are working to get the necessary parts so the equipment can be restored as soon as possible. && .RAH WATCHES/WARNINGS/ADVISORIES... Winter Weather Advisory until 10 AM EDT this morning for NCZ007>011- 021>028-038>043-076>078. && $$ SYNOPSIS...MWS NEAR TERM...Hartfield SHORT TERM...Hartfield LONG TERM...Ellis AVIATION...Hartfield is the U.S. government's official web portal to all federal, state and local government web resources and services.