Area Forecast Discussion
Issued by NWS Raleigh/Durham, NC

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691 FXUS62 KRAH 220221 AFDRAH Area Forecast Discussion National Weather Service Raleigh NC 1021 PM EDT SUN AUG 21 2016 .SYNOPSIS... A cold front will progress east through our area tonight. In the wake of the front, dry high pressure will build into the region from the west through mid-week. && .NEAR TERM /TONIGHT/... As of 1015 PM Sunday... A surface cold front analyzed at 02Z from far ERN NY, SWWD across the NRN Chesapeake Bay to the NC Blue Ridge and NRN Gulf Coast states, will continue to settle SEWD and across central NC overnight. The flow just above the surface /at 925mb/ had already veered to NW at KGSO per the 00Z RAOB, and regional VWP data indicate that veering has recently occurred as far E as Raleigh. As such, some boundary layer drying may occur across the NC Piedmont even in advance of the actual surface front, and leading edge of widespread sub-70 degree surface dewpoint air, still struggling across the NC Blue Ridge. The front will pass as a dry one, however, since notable drying aloft, above a capping inversion evident around 5 k ft on the KBNA RAOB, was already also evident (to a lesser degree) on the KRNK one; and this implied subsidence is likely already overspreading west-central NC per extrapolation and RAP/HRRR forecast soundings. In addition, earlier pre-frontal convection has overturned and significantly diminished the instability that previously resided across central NC earlier Sunday. Interestingly, that earlier pre-frontal convection included a couple of different storm modes, including most notably a multi-cell cluster that thrived in a high DCAPE environment over the Sandhills, and a lone supercell that right-turned along a remnant outflow boundary from weak early afternoon convection over the NE Piedmont and NRN Coastal Plain, despite generally weak effective bulk shear. Previously forecast lows in the middle to upper 60s, to around 70 degrees in the Coastal Plain, appear on track. && .SHORT TERM /MONDAY THROUGH MONDAY NIGHT/... As of 320 PM Sunday... Parent high center over the Middle MS valley will strengthen as it builds eastward into the Mid-Atlantic States Monday-Monday night as heights increase aloft under quasi-zonal flow aloft. While daytime temperatures will only be slightly below normal, nwly flow will advect considerably drier air into the regional with PWATS well below normal, between 0.6-0.75", and bl dewpoints falling into the 50s. Capped aloft by the warm temperatures aloft a stable and dry airmass will yield mostly sunny/clear skies with strong radiational cooling will support some of the coolest temperatures we`ve since early June. Highs in the 84 to 89. Lows in the upper 50 north to lower/mid 60s south. && .LONG TERM /TUESDAY THROUGH SUNDAY/... As of 320 PM Sunday... Surface high pressure over the Mid Atlantic states on Tuesday will move off the east coast on Wednesday. Upper level ridging will build over the Southeast from Wednesday through the end of the week, leading to increasing temperatures, with highs in the low 90s by Thursday. Shortwave energy moving along the Canadian border Thursday and Friday will bring a cold front in to the the Mid Atlantic, but with most of the energy lifting northwestward the front will weaken considerably and seems unlikely to make a push in to central NC. && .AVIATION /02Z MONDAY THROUGH FRIDAY/... As of 830 PM Sunday... Showers and storms have kicked east of RWI and FAY as of 00z, leaving areas to the west in VFR conditions. A cold front moving into the mountains will cross the area after 06Z, and some patchy fog/stratus seems plausible ahead of the front and arrival of lower dewpoints, despite little support from model guidance. Northwest winds will, however, bring that drier air and prevailing VFR on Monday as high pressure builds over the region. Outlook: VFR conditions and light winds will prevail through mid- week as dry high pressure builds eastward from the OH Valley into the Mid-Atlantic. && .RAH WATCHES/WARNINGS/ADVISORIES... None. && $$ SYNOPSIS...SMITH NEAR TERM...MWS SHORT TERM...CBL LONG TERM...SEC AVIATION...SMITH/CBL

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